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Question 1
Incorrect
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A 75-year-old man presents to the ophthalmology clinic with complaints of gradually worsening peripheral vision and a progressive headache that is worse at night. During the cranial nerve exam, a superior homonymous quadrantanopia is observed, but eye movements are intact. The rest of the cranial nerve and neurological examinations are unremarkable.
Which region of the brain is likely affected by the lesion causing these symptoms?Your Answer: Optic nerve
Correct Answer: Temporal lobe
Explanation:Superior homonymous quadrantanopias occur when there are lesions in the inferior optic radiations located in the temporal lobe. The location of the lesion can be determined by analyzing the pattern of the visual field defect. Lesions in front of the optic chiasm cause incongruous defects, while lesions at the optic chiasm cause bitemporal/binasal hemianopias. Lesions behind the optic chiasm result in homonymous hemianopias, such as the superior homonymous quadrantanopia in this case. The optic radiations carry nerve signals from the optic chiasm to the occipital lobe. Lesions in the inferior aspect of the optic radiation cause superior visual field defects, while lesions in the superior aspect of the optic radiation cause inferior visual field defects. Therefore, the lesion causing the superior homonymous quadrantanopia in this woman must be located in the inferior aspect of the optic radiation in the temporal lobe. Lesions compressing the lateral aspect of the optic chiasm cause nasal/binasal visual field defects, while lesions to the optic nerve before the optic chiasm result in an incongruous homonymous hemianopia affecting the same eye. Parietal lobe lesions can cause inferior homonymous quadrantanopias, but not superior homonymous quadrantanopias. Compression of the superior optic chiasm causes bitemporal hemianopias, not homonymous hemianopias.
Understanding Visual Field Defects
Visual field defects can occur due to various reasons, including lesions in the optic tract, optic radiation, or occipital cortex. A left homonymous hemianopia indicates a visual field defect to the left, which is caused by a lesion in the right optic tract. On the other hand, homonymous quadrantanopias can be categorized into PITS (Parietal-Inferior, Temporal-Superior) and can be caused by lesions in the inferior or superior optic radiations in the temporal or parietal lobes.
When it comes to congruous and incongruous defects, the former refers to complete or symmetrical visual field loss, while the latter indicates incomplete or asymmetric visual field loss. Incongruous defects are caused by optic tract lesions, while congruous defects are caused by optic radiation or occipital cortex lesions. In cases where there is macula sparing, it is indicative of a lesion in the occipital cortex.
Bitemporal hemianopia, on the other hand, is caused by a lesion in the optic chiasm. The type of defect can indicate the location of the compression, with an upper quadrant defect being more common in inferior chiasmal compression, such as a pituitary tumor, and a lower quadrant defect being more common in superior chiasmal compression, such as a craniopharyngioma.
Understanding visual field defects is crucial in diagnosing and treating various neurological conditions. By identifying the type and location of the defect, healthcare professionals can provide appropriate interventions to improve the patient’s quality of life.
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This question is part of the following fields:
- Neurological System
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Question 2
Incorrect
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A 24-year-old gymnast comes to see you with complaints of left wrist pain that worsens with weight bearing. She reports that this has been going on for the past month since she began intense training for her gymnastics competition. During your physical examination, you observe swelling around her left wrist and note that the pain is exacerbated by hyperextension. You suspect that this may be due to impingement of the extensor retinaculum caused by continuous pressure on wrist extension during gymnastics.
To which bone is this structure attached?Your Answer: Trapezium
Correct Answer: Triquetral
Explanation:The extensor retinaculum is a thickened fascia that secures the tendons of the extensor muscles in place. It connects to the triquetral and pisiform bones on the medial side and the end of the radius on the lateral side.
The radius bone is situated laterally to the ulna bone and articulates with the humerus proximally and the ulna distally.
The trapezium bone is a carpal bone located beneath the thumb joint, forming the carpometacarpal joint.
The capitate bone is the largest carpal bone in the hand and is positioned at the center of the distal row of carpal bones.
The scaphoid bone is located in the two rows of carpal bones and is frequently fractured during a fall on an outstretched hand.
The Extensor Retinaculum and its Related Structures
The extensor retinaculum is a thick layer of deep fascia that runs across the back of the wrist, holding the long extensor tendons in place. It attaches to the pisiform and triquetral bones medially and the end of the radius laterally. The retinaculum has six compartments that contain the extensor muscle tendons, each with its own synovial sheath.
Several structures are related to the extensor retinaculum. Superficial to the retinaculum are the basilic and cephalic veins, the dorsal cutaneous branch of the ulnar nerve, and the superficial branch of the radial nerve. Deep to the retinaculum are the tendons of the extensor carpi ulnaris, extensor digiti minimi, extensor digitorum, extensor indicis, extensor pollicis longus, extensor carpi radialis longus, extensor carpi radialis brevis, abductor pollicis longus, and extensor pollicis brevis.
The radial artery also passes between the lateral collateral ligament of the wrist joint and the tendons of the abductor pollicis longus and extensor pollicis brevis. Understanding the topography of these structures is important for diagnosing and treating wrist injuries and conditions.
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This question is part of the following fields:
- Neurological System
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Question 3
Incorrect
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A 55-year-old woman is brought to the emergency department by her family members after experiencing a funny turn at home, lasting approximately 3 minutes. She reported a metallic taste in her mouth and a metallic smell, as well as hearing her father's voice speaking to her.
What is the probable site of the pathology?Your Answer: Frontal lobe
Correct Answer: Temporal lobe
Explanation:Temporal lobe seizures can lead to hallucinations.
Localising Features of Focal Seizures in Epilepsy
Focal seizures in epilepsy can be localised based on the specific location of the brain where they occur. Temporal lobe seizures are common and may occur with or without impairment of consciousness or awareness. Most patients experience an aura, which is typically a rising epigastric sensation, along with psychic or experiential phenomena such as déjà vu or jamais vu. Less commonly, hallucinations may occur, such as auditory, gustatory, or olfactory hallucinations. These seizures typically last around one minute and are often accompanied by automatisms, such as lip smacking, grabbing, or plucking.
On the other hand, frontal lobe seizures are characterised by motor symptoms such as head or leg movements, posturing, postictal weakness, and Jacksonian march. Parietal lobe seizures, on the other hand, are sensory in nature and may cause paraesthesia. Finally, occipital lobe seizures may cause visual symptoms such as floaters or flashes. By identifying the specific location and type of seizure, doctors can better diagnose and treat epilepsy in patients.
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This question is part of the following fields:
- Neurological System
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Question 4
Incorrect
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A 58-year-old male presents to the GP with back pain. He tells you the pain started three weeks ago after helping a friend move where he was lifting lots of heavy boxes. He says the pain radiates down the lateral aspect of his right thigh and often feels a tingling sensation in this area. On clinical examination you find reduced sensation below the right knee but the knee reflex is intact. You suspect he may have damaged his sciatic nerve.
Which other feature are you most likely to find?Your Answer: Paralysis of knee extension
Correct Answer: Absent plantar reflex
Explanation:When a patient experiences a loss of ankle and plantar reflexes but retains their knee jerk reflex, it may indicate a sciatic nerve lesion. The sciatic nerve is responsible for innervating the hamstring and adductor muscles and is supplied by L4-5 and S1-3. Other symptoms of sciatic nerve damage include paralysis of knee flexion and sensory loss below the knee.
If a patient presents with a Trendelenburg sign, it may indicate an injury to the superior gluteal nerve. This nerve is responsible for thigh abduction by gluteus medius, and damage to it can cause weakness and a compensatory tilt of the body to the weakened gluteal side.
Tinel’s sign is a feature of carpel tunnel syndrome and occurs when the median nerve is tapped at the wrist, causing tingling or electric-like sensations over the distribution of the median nerve.
Damage to the obturator nerve can result in sensory loss at the medial thigh. This nerve is typically damaged in an anterior hip dislocation.
Understanding Sciatic Nerve Lesion
The sciatic nerve is a major nerve that is supplied by the L4-5, S1-3 vertebrae and divides into the tibial and common peroneal nerves. It is responsible for supplying the hamstring and adductor muscles. When the sciatic nerve is damaged, it can result in a range of symptoms that affect both motor and sensory functions.
Motor symptoms of sciatic nerve lesion include paralysis of knee flexion and all movements below the knee. Sensory symptoms include loss of sensation below the knee. Reflexes may also be affected, with ankle and plantar reflexes lost while the knee jerk reflex remains intact.
There are several causes of sciatic nerve lesion, including fractures of the neck of the femur, posterior hip dislocation, and trauma.
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This question is part of the following fields:
- Neurological System
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Question 5
Incorrect
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A 82-year-old man comes to the emergency department complaining of abdominal and bone pain. He appears confused, and his wife reports that he has been feeling down lately. After conducting blood tests, you discover that he has elevated levels of parathyroid hormone, leading you to suspect primary hyperparathyroidism.
What bone profile results would you anticipate?Your Answer: Increased levels of calcium and normal phosphate
Correct Answer: Increased levels of calcium and decreased phosphate
Explanation:PTH elevates calcium levels while reducing phosphate levels.
A single parathyroid adenoma is often responsible for primary hyperparathyroidism, which results in the release of PTH and elevated/normal calcium levels. Normally, increased calcium levels would lead to decreased PTH levels.
Vitamin D is another significant factor in calcium homeostasis, as it increases both plasma calcium and phosphate levels.
Maintaining Calcium Balance in the Body
Calcium ions are essential for various physiological processes in the body, and the largest store of calcium is found in the skeleton. The levels of calcium in the body are regulated by three hormones: parathyroid hormone (PTH), vitamin D, and calcitonin.
PTH increases calcium levels and decreases phosphate levels by increasing bone resorption and activating osteoclasts. It also stimulates osteoblasts to produce a protein signaling molecule that activates osteoclasts, leading to bone resorption. PTH increases renal tubular reabsorption of calcium and the synthesis of 1,25(OH)2D (active form of vitamin D) in the kidney, which increases bowel absorption of calcium. Additionally, PTH decreases renal phosphate reabsorption.
Vitamin D, specifically the active form 1,25-dihydroxycholecalciferol, increases plasma calcium and plasma phosphate levels. It increases renal tubular reabsorption and gut absorption of calcium, as well as osteoclastic activity. Vitamin D also increases renal phosphate reabsorption in the proximal tubule.
Calcitonin, secreted by C cells of the thyroid, inhibits osteoclast activity and renal tubular absorption of calcium.
Although growth hormone and thyroxine play a small role in calcium metabolism, the primary regulation of calcium levels in the body is through PTH, vitamin D, and calcitonin. Maintaining proper calcium balance is crucial for overall health and well-being.
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This question is part of the following fields:
- Neurological System
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Question 6
Correct
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A 45-year-old woman had an attempted central line placement in her internal jugular vein, but the doctor accidentally damaged her carotid artery, requiring surgical exploration. During the procedure, a nerve was found between the carotid artery and internal jugular vein. What is the most likely identity of this nerve?
Your Answer: Vagus
Explanation:The carotid sheath contains the vagus nerve, while the hypoglossal nerve passes through it but is not situated inside it.
The common carotid artery is a major blood vessel that supplies the head and neck with oxygenated blood. It has two branches, the left and right common carotid arteries, which arise from different locations. The left common carotid artery originates from the arch of the aorta, while the right common carotid artery arises from the brachiocephalic trunk. Both arteries terminate at the upper border of the thyroid cartilage by dividing into the internal and external carotid arteries.
The left common carotid artery runs superolaterally to the sternoclavicular joint and is in contact with various structures in the thorax, including the trachea, left recurrent laryngeal nerve, and left margin of the esophagus. In the neck, it passes deep to the sternocleidomastoid muscle and enters the carotid sheath with the vagus nerve and internal jugular vein. The right common carotid artery has a similar path to the cervical portion of the left common carotid artery, but with fewer closely related structures.
Overall, the common carotid artery is an important blood vessel with complex anatomical relationships in both the thorax and neck. Understanding its path and relations is crucial for medical professionals to diagnose and treat various conditions related to this artery.
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This question is part of the following fields:
- Neurological System
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Question 7
Correct
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Regarding the middle cranial fossa, which of the following statements about the foramina is inaccurate?
Your Answer: The foramen ovale transmits the middle meningeal artery
Explanation:The middle meningeal artery passes through the foramen spinosum, while the mandibular nerve passes through the foramen ovale. Due to the weakening of the bone at these foramina, fractures in this area are frequent.
Foramina of the Base of the Skull
The base of the skull contains several openings called foramina, which allow for the passage of nerves, blood vessels, and other structures. The foramen ovale, located in the sphenoid bone, contains the mandibular nerve, otic ganglion, accessory meningeal artery, and emissary veins. The foramen spinosum, also in the sphenoid bone, contains the middle meningeal artery and meningeal branch of the mandibular nerve. The foramen rotundum, also in the sphenoid bone, contains the maxillary nerve.
The foramen lacerum, located in the sphenoid bone, is initially occluded by a cartilaginous plug and contains the internal carotid artery, nerve and artery of the pterygoid canal, and the base of the medial pterygoid plate. The jugular foramen, located in the temporal bone, contains the inferior petrosal sinus, glossopharyngeal, vagus, and accessory nerves, sigmoid sinus, and meningeal branches from the occipital and ascending pharyngeal arteries.
The foramen magnum, located in the occipital bone, contains the anterior and posterior spinal arteries, vertebral arteries, and medulla oblongata. The stylomastoid foramen, located in the temporal bone, contains the stylomastoid artery and facial nerve. Finally, the superior orbital fissure, located in the sphenoid bone, contains the oculomotor nerve, recurrent meningeal artery, trochlear nerve, lacrimal, frontal, and nasociliary branches of the ophthalmic nerve, and abducent nerve.
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This question is part of the following fields:
- Neurological System
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Question 8
Incorrect
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A 68-year-old patient is admitted for surgery following a car accident that resulted in a fractured tibia. After 12 hours of the operation, the patient reports experiencing severe pain and tingling sensations. Upon examination, the anterior leg appears red, swollen, and feels cooler than the rest of the limb. The patient's ability to dorsiflex the foot is impaired, and there is a loss of sensation over the first and second toes. The intracompartmental pressure of the anterior leg compartment is 40mmHg. Which nerve is responsible for the patient's abnormal sensations and impaired movement?
Your Answer: Superficial peroneal nerve
Correct Answer: Deep peroneal nerve
Explanation:The deep peroneal (fibular) nerve is responsible for supplying the anterior leg compartment and runs alongside the anterior tibial artery. It enables dorsiflexion by supplying the extensor muscles of the leg, which explains why the patient is unable to perform this movement. If there is increased pressure in this leg compartment, it can compress this nerve and cause the patient’s symptoms.
The lateral plantar nerve, which is a branch of the tibial nerve, travels in the posterior leg compartment and is unlikely to be affected in this case. Additionally, it supplies the lateral part of the foot and does not contribute to dorsiflexion, so it cannot explain the patient’s symptoms.
The tibial nerve also travels in the posterior compartment of the leg and is unlikely to be affected in this case.
Answer 3 is incorrect because there is no such thing as an anterior tibial nerve; there is only an anterior tibial artery.
The superficial peroneal nerve runs in the lateral compartment of the leg and is responsible for foot eversion and sensation over the lateral dorsum of the foot. If this nerve is compromised, the patient may experience impaired foot eversion and reduced sensation in this area.
The Deep Peroneal Nerve: Origin, Course, and Actions
The deep peroneal nerve is a branch of the common peroneal nerve that originates at the lateral aspect of the fibula, deep to the peroneus longus muscle. It is composed of nerve root values L4, L5, S1, and S2. The nerve pierces the anterior intermuscular septum to enter the anterior compartment of the lower leg and passes anteriorly down to the ankle joint, midway between the two malleoli. It terminates in the dorsum of the foot.
The deep peroneal nerve innervates several muscles, including the tibialis anterior, extensor hallucis longus, extensor digitorum longus, peroneus tertius, and extensor digitorum brevis. It also provides cutaneous innervation to the web space of the first and second toes. The nerve’s actions include dorsiflexion of the ankle joint, extension of all toes (extensor hallucis longus and extensor digitorum longus), and inversion of the foot.
After its bifurcation past the ankle joint, the lateral branch of the deep peroneal nerve innervates the extensor digitorum brevis and the extensor hallucis brevis, while the medial branch supplies the web space between the first and second digits. Understanding the origin, course, and actions of the deep peroneal nerve is essential for diagnosing and treating conditions that affect this nerve, such as foot drop and nerve entrapment syndromes.
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This question is part of the following fields:
- Neurological System
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Question 9
Incorrect
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A 29-year-old male visits an acute eye clinic with a complaint of a painful eye. During the examination, the ophthalmologist observes a photophobic red eye and identifies a distinctive lesion, resulting in a quick diagnosis of herpes simplex keratitis.
What is the description of the lesion?Your Answer: Vesicular rash at the tip of the nose
Correct Answer: Dendritic corneal lesion
Explanation:Keratitis caused by herpes simplex is characterized by dendritic lesions that appear as a branched pattern on fluorescein dye. This is typically seen during slit lamp examination. While severe inflammation may be present, indicated by the presence of an inflammatory exudate of the anterior chamber (hypopyon), this is not specific to herpes simplex and may be associated with other causes of keratitis or anterior uveitis. It’s worth noting that herpes zoster ophthalmicus (HZO) is not caused by herpes simplex, but rather occurs when the dormant shingles virus in the ophthalmic nerve reactivates. Hutchinson’s sign, which is a vesicular rash at the tip of the nose in the context of an acute red eye, is suggestive of HZO. Lastly, it’s important to note that a tear dropped pupil is not a feature of keratitis and may be caused by blunt trauma.
Understanding Herpes Simplex Keratitis
Herpes simplex keratitis is a condition that primarily affects the cornea and is caused by the herpes simplex virus. The most common symptom of this condition is a dendritic corneal ulcer, which can cause a red, painful eye, photophobia, and epiphora. In some cases, visual acuity may also be decreased. Fluorescein staining may show an epithelial ulcer, which can help with diagnosis.
One common treatment for this condition is topical acyclovir, which can help to reduce the severity of symptoms and prevent further complications.
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This question is part of the following fields:
- Neurological System
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Question 10
Incorrect
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A 55-year-old male is seen in an outpatient neurology clinic after experiencing a stroke 3 weeks ago. He reports sudden, uncontrollable flailing movements in his right arm and leg. The movements are strong and involuntary, originating from the proximal sections of his limbs.
What area of the brain is likely to be impacted in this scenario?Your Answer: Temporal lobe
Correct Answer: Subthalamic nucleus of the basal ganglia
Explanation:Hemiballism is a rare hyperkinetic movement disorder that can be caused by a lesion to the subthalamic nucleus of the basal ganglia. This patient is exhibiting symptoms of hemiballism, including intense, flailing movements of the limbs that originate in the proximal area of the limb. It is important to distinguish hemiballism from chorea, which originates in the distal area of the limb.
Kluver-Bucy syndrome is associated with a lesion to the amygdala and presents with symptoms such as hypersexuality, hyperorality, hyperphagia, and visual agnosia.
Gait ataxia, characterized by an unsteady and uncoordinated gait, is associated with midline cerebellar lesions. However, this would not account for the hyperkinetic movements seen in this patient.
A stroke affecting the substantia nigra of the basal ganglia can cause Parkinson’s disease, which is characterized by bradykinesia, resting tremor, and shuffling gait.
A lesion to the temporal lobe can result in Wernicke’s aphasia, which is characterized by disorderly but fluent speech due to damage to Broca’s area.
Brain lesions can be localized based on the neurological disorders or features that are present. The gross anatomy of the brain can provide clues to the location of the lesion. For example, lesions in the parietal lobe can result in sensory inattention, apraxias, astereognosis, inferior homonymous quadrantanopia, and Gerstmann’s syndrome. Lesions in the occipital lobe can cause homonymous hemianopia, cortical blindness, and visual agnosia. Temporal lobe lesions can result in Wernicke’s aphasia, superior homonymous quadrantanopia, auditory agnosia, and prosopagnosia. Lesions in the frontal lobes can cause expressive aphasia, disinhibition, perseveration, anosmia, and an inability to generate a list. Lesions in the cerebellum can result in gait and truncal ataxia, intention tremor, past pointing, dysdiadokinesis, and nystagmus.
In addition to the gross anatomy, specific areas of the brain can also provide clues to the location of a lesion. For example, lesions in the medial thalamus and mammillary bodies of the hypothalamus can result in Wernicke and Korsakoff syndrome. Lesions in the subthalamic nucleus of the basal ganglia can cause hemiballism, while lesions in the striatum (caudate nucleus) can result in Huntington chorea. Parkinson’s disease is associated with lesions in the substantia nigra of the basal ganglia, while lesions in the amygdala can cause Kluver-Bucy syndrome, which is characterized by hypersexuality, hyperorality, hyperphagia, and visual agnosia. By identifying these specific conditions, doctors can better localize brain lesions and provide appropriate treatment.
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This question is part of the following fields:
- Neurological System
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Question 11
Incorrect
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A 63-year-old female is one day postoperative following a total thyroidectomy for thyroid cancer. The surgery was successful with no unexpected blood loss. However, the patient has observed that her voice is hoarse and soft.
During examination, the patient seems comfortable while resting and can maintain her airway without any problem. The surgical site looks normal, and there is no development of haematoma. On auscultation, her breath sounds are clear and equal in all lung fields.
What is the most likely structure to have been injured during the surgery?Your Answer:
Correct Answer: Right recurrent laryngeal nerve
Explanation:The right recurrent laryngeal nerve is at a higher risk of injury during neck surgery due to its diagonal origin under the subclavian artery. In contrast, the left recurrent laryngeal nerve is less vulnerable to injury. It is important to note that injury to the left or right subclavian artery would typically result in shock symptoms rather than hoarseness, and there were no indications of significant blood loss during the surgery.
The Recurrent Laryngeal Nerve: Anatomy and Function
The recurrent laryngeal nerve is a branch of the vagus nerve that plays a crucial role in the innervation of the larynx. It has a complex path that differs slightly between the left and right sides of the body. On the right side, it arises anterior to the subclavian artery and ascends obliquely next to the trachea, behind the common carotid artery. It may be located either anterior or posterior to the inferior thyroid artery. On the left side, it arises left to the arch of the aorta, winds below the aorta, and ascends along the side of the trachea.
Both branches pass in a groove between the trachea and oesophagus before entering the larynx behind the articulation between the thyroid cartilage and cricoid. Once inside the larynx, the recurrent laryngeal nerve is distributed to the intrinsic larynx muscles (excluding cricothyroid). It also branches to the cardiac plexus and the mucous membrane and muscular coat of the oesophagus and trachea.
Damage to the recurrent laryngeal nerve, such as during thyroid surgery, can result in hoarseness. Therefore, understanding the anatomy and function of this nerve is crucial for medical professionals who perform procedures in the neck and throat area.
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This question is part of the following fields:
- Neurological System
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Question 12
Incorrect
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A 45-year-old man is brought to the ED by his spouse, who suspects he had a stroke. The man is exhibiting signs of slurred speech and disorientation to time and space, but there is no limb weakness.
According to collateral history, the man has a history of epilepsy, although he has not had a seizure in several months. He does not smoke and did not consume any alcohol or drugs before coming to the ED. A CT scan is normal, and a focal seizure is suspected as the cause of his symptoms.
Which part of the brain is likely affected?Your Answer:
Correct Answer: Temporal lobe
Explanation:Localising features of a temporal lobe seizure include postictal dysphasia and lip smacking.
Localising Features of Focal Seizures in Epilepsy
Focal seizures in epilepsy can be localised based on the specific location of the brain where they occur. Temporal lobe seizures are common and may occur with or without impairment of consciousness or awareness. Most patients experience an aura, which is typically a rising epigastric sensation, along with psychic or experiential phenomena such as déjà vu or jamais vu. Less commonly, hallucinations may occur, such as auditory, gustatory, or olfactory hallucinations. These seizures typically last around one minute and are often accompanied by automatisms, such as lip smacking, grabbing, or plucking.
On the other hand, frontal lobe seizures are characterised by motor symptoms such as head or leg movements, posturing, postictal weakness, and Jacksonian march. Parietal lobe seizures, on the other hand, are sensory in nature and may cause paraesthesia. Finally, occipital lobe seizures may cause visual symptoms such as floaters or flashes. By identifying the specific location and type of seizure, doctors can better diagnose and treat epilepsy in patients.
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This question is part of the following fields:
- Neurological System
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Question 13
Incorrect
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A motorcyclist in his mid-thirties is in a road traffic accident and sustains a complex humeral shaft fracture that requires plating. After the surgery, he reports an inability to extend his fingers. What structure is most likely to have been damaged?
Your Answer:
Correct Answer: Radial nerve
Explanation:Mnemonic for the muscles innervated by the radial nerve: BEST
B – Brachioradialis
E – Extensors
S – Supinator
T – TricepsRemembering this acronym can help in recalling the muscles that are supplied by the radial nerve, which is responsible for the movement of the extensor compartment of the forearm.
The Radial Nerve: Anatomy, Innervation, and Patterns of Damage
The radial nerve is a continuation of the posterior cord of the brachial plexus, with root values ranging from C5 to T1. It travels through the axilla, posterior to the axillary artery, and enters the arm between the brachial artery and the long head of triceps. From there, it spirals around the posterior surface of the humerus in the groove for the radial nerve before piercing the intermuscular septum and descending in front of the lateral epicondyle. At the lateral epicondyle, it divides into a superficial and deep terminal branch, with the deep branch crossing the supinator to become the posterior interosseous nerve.
The radial nerve innervates several muscles, including triceps, anconeus, brachioradialis, and extensor carpi radialis. The posterior interosseous branch innervates supinator, extensor carpi ulnaris, extensor digitorum, and other muscles. Denervation of these muscles can lead to weakness or paralysis, with effects ranging from minor effects on shoulder stability to loss of elbow extension and weakening of supination of prone hand and elbow flexion in mid prone position.
Damage to the radial nerve can result in wrist drop and sensory loss to a small area between the dorsal aspect of the 1st and 2nd metacarpals. Axillary damage can also cause paralysis of triceps. Understanding the anatomy, innervation, and patterns of damage of the radial nerve is important for diagnosing and treating conditions that affect this nerve.
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This question is part of the following fields:
- Neurological System
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Question 14
Incorrect
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A 32-year-old woman visits her doctor complaining of a severe, pulsating headache that began last night and is concentrated at the back of her head. She experiences intense pain when coughing. Her family has a history of Type I Chiari malformation.
The doctor suspects idiopathic intracranial hypertension and conducts a fundoscopy to check for signs of papilloedema. Before using an ophthalmoscope to examine her eyes, the doctor applies a topical medication.
What is the name of the medication used?Your Answer:
Correct Answer: Tropicamide
Explanation:Tropicamide is administered before fundoscopy to enlarge the pupils. It functions as a muscarinic receptor antagonist, inhibiting parasympathetic impulses and causing the pupil constrictor response and ciliary muscle to become paralyzed. This results in pupil dilation, which is necessary for optimal visualization of the fundus.
Fluorescein stain is utilized to evaluate the cornea for damage or the presence of foreign objects in the eye.
Pilocarpine, a muscarinic receptor agonist, causes pupillary constriction and should not be used before fundoscopy as it would hinder the visualization of the fundus.
Lidocaine is a local anesthetic that works by blocking fast voltage-gated Na channels in the neuronal cell membrane responsible for signal propagation. There is no need to apply topical lidocaine before fundoscopy.
Mydriasis, which is the enlargement of the pupil, can be caused by various factors such as third nerve palsy, Holmes-Adie pupil, traumatic iridoplegia, phaeochromocytoma, and congenital conditions. Additionally, certain drugs like topical mydriatics such as tropicamide and atropine, sympathomimetic drugs like amphetamines and cocaine, and anticholinergic drugs like tricyclic antidepressants can also cause mydriasis. It is important to note that anisocoria, which is the unequal size of pupils, can also lead to apparent mydriasis when compared to the other pupil.
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This question is part of the following fields:
- Neurological System
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Question 15
Incorrect
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Which one of the following is not a content of the cavernous sinus?
Your Answer:
Correct Answer: Optic nerve
Explanation:Cavernous sinus contents mnemonic: OTOM CAT
Understanding the Cavernous Sinus
The cavernous sinuses are a pair of structures located on the sphenoid bone, running from the superior orbital fissure to the petrous temporal bone. They are situated between the pituitary fossa and the sphenoid sinus on the medial side, and the temporal lobe on the lateral side. The cavernous sinuses contain several important structures, including the oculomotor, trochlear, ophthalmic, and maxillary nerves, as well as the internal carotid artery and sympathetic plexus, and the abducens nerve.
The lateral wall components of the cavernous sinuses include the oculomotor, trochlear, ophthalmic, and maxillary nerves, while the contents of the sinus run from medial to lateral and include the internal carotid artery and sympathetic plexus, and the abducens nerve. The blood supply to the cavernous sinuses comes from the ophthalmic vein, superficial cortical veins, and basilar plexus of veins posteriorly. The cavernous sinuses drain into the internal jugular vein via the superior and inferior petrosal sinuses.
In summary, the cavernous sinuses are important structures located on the sphenoid bone that contain several vital nerves and blood vessels. Understanding their location and contents is crucial for medical professionals in diagnosing and treating various conditions that may affect these structures.
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This question is part of the following fields:
- Neurological System
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Question 16
Incorrect
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A 32-year-old man is brought to the emergency department by the paramedics. His airway is clear, and he is not experiencing any respiratory or cardiac distress. He states that he was hit by a vehicle while crossing the street.
During the examination, there is significant swelling in his knee and leg, and he has lost sensation in the plantar area of his foot. He cannot plantarflex his foot and has also lost foot inversion.
Which nerve is most likely to have been damaged?Your Answer:
Correct Answer: Tibial nerve
Explanation:When the tibial nerve is injured, the foot loses its ability to plantarflex and invert. Other nerve injuries can result in loss of sensation or motor function in specific muscles, such as the saphenous nerve causing loss of sensation in the medial leg or the femoral nerve causing loss of hip flexion and knee extension. The inferior gluteal nerve injury can lead to gluteal lurch and loss of hip extension.
The Tibial Nerve: Muscles Innervated and Termination
The tibial nerve is a branch of the sciatic nerve that begins at the upper border of the popliteal fossa. It has root values of L4, L5, S1, S2, and S3. This nerve innervates several muscles, including the popliteus, gastrocnemius, soleus, plantaris, tibialis posterior, flexor hallucis longus, and flexor digitorum brevis. These muscles are responsible for various movements in the lower leg and foot, such as plantar flexion, inversion, and flexion of the toes.
The tibial nerve terminates by dividing into the medial and lateral plantar nerves. These nerves continue to innervate muscles in the foot, such as the abductor hallucis, flexor digitorum brevis, and quadratus plantae. The tibial nerve plays a crucial role in the movement and function of the lower leg and foot, and any damage or injury to this nerve can result in significant impairments in mobility and sensation.
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This question is part of the following fields:
- Neurological System
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Question 17
Incorrect
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A 50-year-old male comes to the clinic with recent aggressive behaviour, depression, chorea and athetosis. His father had similar symptoms at the age of 70. It is suspected that he has a neurodegenerative disorder with trinucleotide repeat expansion.
What is the most likely trinucleotide repeat present in this case?Your Answer:
Correct Answer: CAG
Explanation:Huntington’s disease is a genetic disorder that causes progressive and incurable neurodegeneration. It is inherited in an autosomal dominant manner and is caused by a trinucleotide repeat expansion of CAG in the huntingtin gene on chromosome 4. This can result in the phenomenon of anticipation, where the disease presents at an earlier age in successive generations. The disease leads to the degeneration of cholinergic and GABAergic neurons in the striatum of the basal ganglia, which can cause a range of symptoms.
Typically, symptoms of Huntington’s disease develop after the age of 35 and can include chorea, personality changes such as irritability, apathy, and depression, intellectual impairment, dystonia, and saccadic eye movements. Unfortunately, there is currently no cure for Huntington’s disease, and it usually results in death around 20 years after the initial symptoms develop.
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This question is part of the following fields:
- Neurological System
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Question 18
Incorrect
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A 75-year-old man is brought to his family doctor by his wife, who reports that her husband has been misplacing items around the house, such as putting his wallet in the fridge. She also mentions that he has gotten lost on two occasions while trying to find his way home. The man has difficulty remembering recent events but can recall his childhood and early adulthood with clarity. He denies experiencing any visual or auditory hallucinations or issues with his mobility. The wife notes that her husband's behavioral changes have been gradual rather than sudden. A CT scan reveals significant widening of the brain sulci. What is the most likely diagnosis for this man, and what is the underlying pathology?
Your Answer:
Correct Answer: Extracellular amyloid plaques and intracellular fibrillary tangles
Explanation:Alzheimer’s disease is caused by the deposition of insoluble beta-amyloid protein, leading to the formation of cortical plaques, and abnormal aggregation of the tau protein, resulting in intraneuronal neurofibrillary tangles. This disease is characterized by a gradual onset of memory and behavioral problems, as well as brain atrophy visible on CT scans. Vascular dementia, on the other hand, is caused by multiple ischemic insults to the brain, resulting in a stepwise decline in cognition. Prion disease, such as Creutzfeldt-Jakob disease, is characterized by the presence of insoluble beta-pleated protein sheets. Lacunar infarcts, caused by obstruction of small penetrating arteries in the brain, can be detected by MRI or CT scans. Lewy body dementia is characterized by the presence of intracellular Lewy bodies, along with symptoms of dementia and Parkinson’s disease.
Alzheimer’s disease is a type of dementia that gradually worsens over time and is caused by the degeneration of the brain. There are several risk factors associated with Alzheimer’s disease, including increasing age, family history, and certain genetic mutations. The disease is also more common in individuals of Caucasian ethnicity and those with Down’s syndrome.
The pathological changes associated with Alzheimer’s disease include widespread cerebral atrophy, particularly in the cortex and hippocampus. Microscopically, there are cortical plaques caused by the deposition of type A-Beta-amyloid protein and intraneuronal neurofibrillary tangles caused by abnormal aggregation of the tau protein. The hyperphosphorylation of the tau protein has been linked to Alzheimer’s disease. Additionally, there is a deficit of acetylcholine due to damage to an ascending forebrain projection.
Neurofibrillary tangles are a hallmark of Alzheimer’s disease and are partly made from a protein called tau. Tau is a protein that interacts with tubulin to stabilize microtubules and promote tubulin assembly into microtubules. In Alzheimer’s disease, tau proteins are excessively phosphorylated, impairing their function.
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This question is part of the following fields:
- Neurological System
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Question 19
Incorrect
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Which of the following nerves is responsible for the cremasteric reflex?
Your Answer:
Correct Answer: Genitofemoral nerve
Explanation:The cremasteric reflex tests the motor and sensory fibers of the genitofemoral nerve, with a minor involvement from the ilioinguinal nerve. If someone has had an inguinal hernia repair, the reflex may be lost.
The Genitofemoral Nerve: Anatomy and Function
The genitofemoral nerve is responsible for supplying a small area of the upper medial thigh. It arises from the first and second lumbar nerves and passes through the psoas major muscle before emerging from its medial border. The nerve then descends on the surface of the psoas major, under the cover of the peritoneum, and divides into genital and femoral branches.
The genital branch of the genitofemoral nerve passes through the inguinal canal within the spermatic cord to supply the skin overlying the scrotum’s skin and fascia. On the other hand, the femoral branch enters the thigh posterior to the inguinal ligament, lateral to the femoral artery. It supplies an area of skin and fascia over the femoral triangle.
Injuries to the genitofemoral nerve may occur during abdominal or pelvic surgery or inguinal hernia repairs. Understanding the anatomy and function of this nerve is crucial in preventing such injuries and ensuring proper treatment.
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This question is part of the following fields:
- Neurological System
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Question 20
Incorrect
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A 67-year-old male presents 7 months after being diagnosed with Parkinson's disease. During the examination, the patient exhibits rigidity, a Parkinsonian gait, bradykinesia, and a resting tremor on one side of the body. Additionally, the patient displays hypomimia. Currently, the patient is taking levodopa and benserazide, and the neurologist has prescribed pramipexole to keep the levodopa dose low. What is a potential side effect of pramipexole that the patient should be warned about?
Your Answer:
Correct Answer: Compulsive gambling
Explanation:Dopamine agonists, which are commonly used in the treatment of Parkinson’s disease, carry a risk of causing impulse control or obsessive disorders, such as excessive gambling or hypersexuality. Patients should be informed of this potential side-effect before starting the medication, as it can have devastating financial consequences for both the patient and their family. Blurred vision is a side-effect of antimuscarinic medications, while peripheral neuropathy is a possible side-effect of several medications, including some antibiotics, cytotoxic drugs, amiodarone, and phenytoin. Weight gain is a common side-effect of certain medications, such as steroids.
Understanding the Mechanism of Action of Parkinson’s Drugs
Parkinson’s disease is a complex condition that requires specialized management. The first-line treatment for motor symptoms that affect a patient’s quality of life is levodopa, while dopamine agonists, levodopa, or monoamine oxidase B (MAO-B) inhibitors are recommended for those whose motor symptoms do not affect their quality of life. However, all drugs used to treat Parkinson’s can cause a wide variety of side effects, and it is important to be aware of these when making treatment decisions.
Levodopa is nearly always combined with a decarboxylase inhibitor to prevent the peripheral metabolism of levodopa to dopamine outside of the brain and reduce side effects. Dopamine receptor agonists, such as bromocriptine, ropinirole, cabergoline, and apomorphine, are more likely than levodopa to cause hallucinations in older patients. MAO-B inhibitors, such as selegiline, inhibit the breakdown of dopamine secreted by the dopaminergic neurons. Amantadine’s mechanism is not fully understood, but it probably increases dopamine release and inhibits its uptake at dopaminergic synapses. COMT inhibitors, such as entacapone and tolcapone, are used in conjunction with levodopa in patients with established PD. Antimuscarinics, such as procyclidine, benzotropine, and trihexyphenidyl (benzhexol), block cholinergic receptors and are now used more to treat drug-induced parkinsonism rather than idiopathic Parkinson’s disease.
It is important to note that all drugs used to treat Parkinson’s can cause adverse effects, and clinicians must be aware of these when making treatment decisions. Patients should also be warned about the potential for dopamine receptor agonists to cause impulse control disorders and excessive daytime somnolence. Understanding the mechanism of action of Parkinson’s drugs is crucial in managing the condition effectively.
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This question is part of the following fields:
- Neurological System
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Question 21
Incorrect
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A 29 week pregnant 26-year-old has been informed that her baby has hypoplasia of the cerebellar vermis, as shown by antenatal ultrasound and subsequent MRI. The baby has been diagnosed with Dandy-Walker syndrome. The neurologist explains to the mother that during embryonic development, the brain is formed from different swellings or vesicles of the neural tube, which eventually becomes the central nervous system.
What specific embryological vesicle has not developed properly in the affected baby?Your Answer:
Correct Answer: Metencephalon
Explanation:During embryonic development, the metencephalon is responsible for the formation of the pons and cerebellum.
As the prosencephalon grows, it splits into two ear-shaped structures: the telencephalon (which develops into the hemispheres) and the diencephalon (which develops into the thalamus and hypothalamus).
The mesencephalon grows slowly, and its central cavity eventually becomes the cerebral aqueduct.
The rhombencephalon divides into two parts: the metencephalon (which forms the pons and cerebellum) and the myelencephalon (which forms the medulla).
Embryonic Development of the Nervous System
The nervous system develops from the embryonic neural tube, which gives rise to the brain and spinal cord. The neural tube is divided into five regions, each of which gives rise to specific structures in the nervous system. The telencephalon gives rise to the cerebral cortex, lateral ventricles, and basal ganglia. The diencephalon gives rise to the thalamus, hypothalamus, optic nerves, and third ventricle. The mesencephalon gives rise to the midbrain and cerebral aqueduct. The metencephalon gives rise to the pons, cerebellum, and superior part of the fourth ventricle. The myelencephalon gives rise to the medulla and inferior part of the fourth ventricle.
The neural tube is also divided into two plates: the alar plate and the basal plate. The alar plate gives rise to sensory neurons, while the basal plate gives rise to motor neurons. This division of the neural tube into different regions and plates is crucial for the proper development and function of the nervous system. Understanding the embryonic development of the nervous system is important for understanding the origins of neurological disorders and for developing new treatments for these disorders.
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This question is part of the following fields:
- Neurological System
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Question 22
Incorrect
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A 45-year-old man visits a neurology clinic due to difficulty eating and wasting of the left masseter. He has been experiencing these symptoms for the past 4 months since he fell from scaffolding at work and suffered a basal skull fracture.
During the examination, the left masseter is visibly atrophied compared to the right, and the mandible deviates towards the left side. The patient also reports decreased sensation around the body of the mandible.
Which area of the skull base is likely responsible for the patient's symptoms?Your Answer:
Correct Answer: Foramen ovale
Explanation:The mandibular nerve passes through the foramen ovale, which is the correct answer. The patient’s left masseter wasting suggests a lesion of the mandibular nerve, specifically CN V3, which is responsible for the sensation and motor innervation of the lower face, mandible, temporomandibular joint, and mucous membranes. As the patient has a history of skull base trauma and new-onset masseteric wasting, it is likely that the lesion is located at the foramen ovale.
The foramen rotundum, which transmits the maxillary nerve, CN V2, is an incorrect answer as damage to this nerve would not cause the patient’s symptoms.
The foramen spinosum, which transmits the middle meningeal artery and vein, is also an incorrect answer as damage to this foramen or its contents would not cause masseteric wasting or difficulty eating.
The internal acoustic meatus, which transmits the facial and vestibulocochlear nerve, is also an incorrect answer as damage to this foramen or its contents would not cause masseteric wasting and the patient would likely have additional symptoms such as facial droop and hearing loss.
Cranial nerves are a set of 12 nerves that emerge from the brain and control various functions of the head and neck. Each nerve has a specific function, such as smell, sight, eye movement, facial sensation, and tongue movement. Some nerves are sensory, some are motor, and some are both. A useful mnemonic to remember the order of the nerves is Some Say Marry Money But My Brother Says Big Brains Matter Most, with S representing sensory, M representing motor, and B representing both.
In addition to their specific functions, cranial nerves also play a role in various reflexes. These reflexes involve an afferent limb, which carries sensory information to the brain, and an efferent limb, which carries motor information from the brain to the muscles. Examples of cranial nerve reflexes include the corneal reflex, jaw jerk, gag reflex, carotid sinus reflex, pupillary light reflex, and lacrimation reflex. Understanding the functions and reflexes of the cranial nerves is important in diagnosing and treating neurological disorders.
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This question is part of the following fields:
- Neurological System
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Question 23
Incorrect
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A 50-year-old woman comes to the Emergency Department with facial drooping and slurred speech. You perform a cranial nerves examination and find that her oculomotor nerve has been affected. What sign would you anticipate observing in this patient?
Your Answer:
Correct Answer: Ptosis
Explanation:The correct answer is ptosis. Issues with the oculomotor nerve can cause ptosis, a drooping of the eyelid, as well as a dilated, fixed pupil and a down and out eye. The oculomotor nerve is responsible for various functions, including eye movements (such as those controlled by the MR, IO, SR, and IR muscles), pupil constriction, accommodation, and eyelid opening. Arcuate scotoma is an incorrect answer. This condition is caused by damage to the optic nerve, resulting in a blind spot that appears as an arc shape in the visual field. It does not affect extraocular movements. Bitemporal hemianopia is also an incorrect answer. This visual field defect affects the outer halves of both eyes and is caused by lesions of the optic chiasm, such as those resulting from a pituitary adenoma. Horizontal diplopia is another incorrect answer. This condition is caused by problems with the abducens nerve, which controls the lateral rectus muscle responsible for eye abduction. Defective abduction leads to horizontal diplopia, or double vision.
Cranial nerves are a set of 12 nerves that emerge from the brain and control various functions of the head and neck. Each nerve has a specific function, such as smell, sight, eye movement, facial sensation, and tongue movement. Some nerves are sensory, some are motor, and some are both. A useful mnemonic to remember the order of the nerves is Some Say Marry Money But My Brother Says Big Brains Matter Most, with S representing sensory, M representing motor, and B representing both.
In addition to their specific functions, cranial nerves also play a role in various reflexes. These reflexes involve an afferent limb, which carries sensory information to the brain, and an efferent limb, which carries motor information from the brain to the muscles. Examples of cranial nerve reflexes include the corneal reflex, jaw jerk, gag reflex, carotid sinus reflex, pupillary light reflex, and lacrimation reflex. Understanding the functions and reflexes of the cranial nerves is important in diagnosing and treating neurological disorders.
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This question is part of the following fields:
- Neurological System
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Question 24
Incorrect
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A 3 week old infant has been diagnosed with hydrocephalus due to congenital spina bifida. Can you identify the location of cerebrospinal fluid (CSF) production?
Your Answer:
Correct Answer: Choroid plexuses
Explanation:The choroid plexuses, located in the ventricles of the brain, are responsible for the production of CSF. The cerebral aqueduct (or aqueduct of Sylvius) does not have a choroid plexus. The cribriform plate, which is a part of the ethmoid bone, does not produce or secrete anything but a fracture in it can cause CSF leakage into the nose and result in anosmia. The arachnoid granulations (or villi) serve as the communication between the subarachnoid space and the venous sinuses, allowing for the continuous reabsorption of CSF into the bloodstream. The pia mater, which is the innermost layer of the meninges around the brain, encloses the CSF within the subarachnoid space.
Cerebrospinal Fluid: Circulation and Composition
Cerebrospinal fluid (CSF) is a clear, colorless liquid that fills the space between the arachnoid mater and pia mater, covering the surface of the brain. The total volume of CSF in the brain is approximately 150ml, and it is produced by the ependymal cells in the choroid plexus or blood vessels. The majority of CSF is produced by the choroid plexus, accounting for 70% of the total volume. The remaining 30% is produced by blood vessels. The CSF is reabsorbed via the arachnoid granulations, which project into the venous sinuses.
The circulation of CSF starts from the lateral ventricles, which are connected to the third ventricle via the foramen of Munro. From the third ventricle, the CSF flows through the cerebral aqueduct (aqueduct of Sylvius) to reach the fourth ventricle via the foramina of Magendie and Luschka. The CSF then enters the subarachnoid space, where it circulates around the brain and spinal cord. Finally, the CSF is reabsorbed into the venous system via arachnoid granulations into the superior sagittal sinus.
The composition of CSF is essential for its proper functioning. The glucose level in CSF is between 50-80 mg/dl, while the protein level is between 15-40 mg/dl. Red blood cells are not present in CSF, and the white blood cell count is usually less than 3 cells/mm3. Understanding the circulation and composition of CSF is crucial for diagnosing and treating various neurological disorders.
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This question is part of the following fields:
- Neurological System
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Question 25
Incorrect
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A 31-year-old man visits an ophthalmology clinic with a complaint of experiencing double vision while descending stairs. He reports a recent mountain biking accident that required him to seek emergency medical attention. Although he has recuperated, he mentions that he sustained a severe frontal head injury after colliding with a tree.
During the examination, his left eye is raised and deviated medially, and he experiences vertical diplopia when looking up and down.
Which cranial nerve is most likely affected in this individual?Your Answer:
Correct Answer: Trochlear nerve
Explanation:Cranial nerves are a set of 12 nerves that emerge from the brain and control various functions of the head and neck. Each nerve has a specific function, such as smell, sight, eye movement, facial sensation, and tongue movement. Some nerves are sensory, some are motor, and some are both. A useful mnemonic to remember the order of the nerves is Some Say Marry Money But My Brother Says Big Brains Matter Most, with S representing sensory, M representing motor, and B representing both.
In addition to their specific functions, cranial nerves also play a role in various reflexes. These reflexes involve an afferent limb, which carries sensory information to the brain, and an efferent limb, which carries motor information from the brain to the muscles. Examples of cranial nerve reflexes include the corneal reflex, jaw jerk, gag reflex, carotid sinus reflex, pupillary light reflex, and lacrimation reflex. Understanding the functions and reflexes of the cranial nerves is important in diagnosing and treating neurological disorders.
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This question is part of the following fields:
- Neurological System
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Question 26
Incorrect
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A 99-year-old woman visits her GP complaining of recent facial weakness and slurred speech. The GP suspects a stroke and conducts a thorough neurological evaluation. During the cranial nerve examination, the GP observes that the glossopharyngeal nerve is unaffected. What are the roles and responsibilities of this nerve?
Your Answer:
Correct Answer: Motor, sensory and autonomic
Explanation:The jugular foramen serves as the pathway for the glossopharyngeal nerve. This nerve has autonomic functions for the parotid gland, motor functions for the stylopharyngeus muscle, and sensory functions for the posterior third of the tongue, palatine tonsils, oropharynx, middle ear mucosa, pharyngeal tympanic tube, and carotid bodies.
Cranial nerves are a set of 12 nerves that emerge from the brain and control various functions of the head and neck. Each nerve has a specific function, such as smell, sight, eye movement, facial sensation, and tongue movement. Some nerves are sensory, some are motor, and some are both. A useful mnemonic to remember the order of the nerves is Some Say Marry Money But My Brother Says Big Brains Matter Most, with S representing sensory, M representing motor, and B representing both.
In addition to their specific functions, cranial nerves also play a role in various reflexes. These reflexes involve an afferent limb, which carries sensory information to the brain, and an efferent limb, which carries motor information from the brain to the muscles. Examples of cranial nerve reflexes include the corneal reflex, jaw jerk, gag reflex, carotid sinus reflex, pupillary light reflex, and lacrimation reflex. Understanding the functions and reflexes of the cranial nerves is important in diagnosing and treating neurological disorders.
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This question is part of the following fields:
- Neurological System
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Question 27
Incorrect
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A 25-year-old man is scheduled for an open appendicectomy via a lanz incision. The surgeon plans to place the incision at the level of the anterior superior iliac spine to improve cosmesis. However, during the procedure, the appendix is found to be retrocaecal, and the incision is extended laterally. What is the nerve that is at the highest risk of injury during this surgery?
Your Answer:
Correct Answer: Ilioinguinal
Explanation:The Ilioinguinal Nerve: Anatomy and Function
The ilioinguinal nerve is a nerve that arises from the first lumbar ventral ramus along with the iliohypogastric nerve. It passes through the psoas major and quadratus lumborum muscles before piercing the internal oblique muscle and passing deep to the aponeurosis of the external oblique muscle. The nerve then enters the inguinal canal and passes through the superficial inguinal ring to reach the skin.
The ilioinguinal nerve supplies the muscles of the abdominal wall through which it passes. It also provides sensory innervation to the skin and fascia over the pubic symphysis, the superomedial part of the femoral triangle, the surface of the scrotum, and the root and dorsum of the penis or labia majora in females.
Understanding the anatomy and function of the ilioinguinal nerve is important for medical professionals, as damage to this nerve can result in pain and sensory deficits in the areas it innervates. Additionally, knowledge of the ilioinguinal nerve is relevant in surgical procedures involving the inguinal region.
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This question is part of the following fields:
- Neurological System
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Question 28
Incorrect
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A 75-year-old woman visits her GP complaining of difficulty eating and weight loss that has persisted for three months. She has a medical history of hypertension, type 2 diabetes mellitus, dyslipidemia, and osteoporosis.
During the examination, the patient's body appears cachectic. Fasciculation of the tongue is observed in the oral cavity, and when asked to stick her tongue out, it deviates to the left. The patient is unable to move her tongue towards her right side.
Based on these findings, where is the most likely location of the lesion?Your Answer:
Correct Answer: Left hypoglossal nerve
Explanation:The tongue deviates towards the side of the lesion in a hypoglossal nerve palsy, with the left hypoglossal nerve being the correct answer. Lesions of the Edinger-Westphal nucleus, left facial nerve, and right facial nerve would not cause tongue deviation as they do not control tongue movements.
Cranial nerves are a set of 12 nerves that emerge from the brain and control various functions of the head and neck. Each nerve has a specific function, such as smell, sight, eye movement, facial sensation, and tongue movement. Some nerves are sensory, some are motor, and some are both. A useful mnemonic to remember the order of the nerves is Some Say Marry Money But My Brother Says Big Brains Matter Most, with S representing sensory, M representing motor, and B representing both.
In addition to their specific functions, cranial nerves also play a role in various reflexes. These reflexes involve an afferent limb, which carries sensory information to the brain, and an efferent limb, which carries motor information from the brain to the muscles. Examples of cranial nerve reflexes include the corneal reflex, jaw jerk, gag reflex, carotid sinus reflex, pupillary light reflex, and lacrimation reflex. Understanding the functions and reflexes of the cranial nerves is important in diagnosing and treating neurological disorders.
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This question is part of the following fields:
- Neurological System
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Question 29
Incorrect
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A 25-year-old man is in a car accident and experiences initial wrist extension difficulty that gradually improves. What type of injury is probable?
Your Answer:
Correct Answer: Radial nerve neuropraxia
Explanation:Neuropraxia is the most probable injury due to the transient loss of function. The radial nerve innervates the wrist extensors, indicating that this area is the most likely site of damage.
Neuropraxia: A Temporary Nerve Injury with Full Recovery
Neuropraxia is a type of nerve injury where the nerve remains intact but its electrical conduction is affected. However, the myelin sheath that surrounds the nerve remains intact, which means that the nerve can still transmit signals. The good news is that neuropraxia is a temporary condition, and full recovery is expected. Additionally, autonomic function is preserved, which means that the body’s automatic functions such as breathing and heart rate are not affected. Unlike other types of nerve injuries, Wallerian degeneration, which is the degeneration of the nerve fibers, does not occur in neuropraxia. Overall, neuropraxia is a relatively minor nerve injury that does not cause permanent damage and can be expected to fully heal.
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This question is part of the following fields:
- Neurological System
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Question 30
Incorrect
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A 48-year-old man arrives at the Emergency Department with facial drooping and slurred speech. You perform a cranial nerves examination and find that his glossopharyngeal nerve has been affected. What sign would you anticipate observing in this patient?
Your Answer:
Correct Answer: Loss of gag reflex
Explanation:The correct answer is loss of gag reflex, which is caused by a lesion in the glossopharyngeal nerve (CN IX). This nerve is responsible for taste in the posterior 1/3 of the tongue, salivation, and swallowing. Lesions in this nerve may also result in a hypersensitive carotid sinus reflex.
Loss of taste on the anterior 2/3 of the tongue is incorrect, as this is controlled by the facial nerve (CN VII), which also controls facial movements, lacrimation, and salivation. Lesions in this nerve may result in flaccid paralysis of the upper and lower face, loss of corneal reflex, loss of taste on the anterior 2/3 of the tongue, and hyperacusis.
Paralysis of the facial muscles or mastication muscles is also incorrect. The facial nerve controls facial movements, while the trigeminal nerve (CN V) controls the muscles of mastication and facial sensation via its ophthalmic, maxillary, and mandibular branches.
Cranial nerves are a set of 12 nerves that emerge from the brain and control various functions of the head and neck. Each nerve has a specific function, such as smell, sight, eye movement, facial sensation, and tongue movement. Some nerves are sensory, some are motor, and some are both. A useful mnemonic to remember the order of the nerves is Some Say Marry Money But My Brother Says Big Brains Matter Most, with S representing sensory, M representing motor, and B representing both.
In addition to their specific functions, cranial nerves also play a role in various reflexes. These reflexes involve an afferent limb, which carries sensory information to the brain, and an efferent limb, which carries motor information from the brain to the muscles. Examples of cranial nerve reflexes include the corneal reflex, jaw jerk, gag reflex, carotid sinus reflex, pupillary light reflex, and lacrimation reflex. Understanding the functions and reflexes of the cranial nerves is important in diagnosing and treating neurological disorders.
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This question is part of the following fields:
- Neurological System
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