The nervous system is composed of various types of cells, each with their own unique functions. Oligodendroglia cells are responsible for producing myelin in the central nervous system (CNS) and are affected in multiple sclerosis. Schwann cells, on the other hand, produce myelin in the peripheral nervous system (PNS) and are affected in Guillain-Barre syndrome. Astrocytes provide physical support, remove excess potassium ions, help form the blood-brain barrier, and aid in physical repair. Microglia are specialised CNS phagocytes, while ependymal cells provide the inner lining of the ventricles.

In summary, the nervous system is made up of different types of cells, each with their own specific roles. Oligodendroglia and Schwann cells produce myelin in the CNS and PNS, respectively, and are affected in certain diseases. Astrocytes provide physical support and aid in repair, while microglia are specialised phagocytes in the CNS. Ependymal cells line the ventricles. Understanding the functions of these cells is crucial in understanding the complex workings of the nervous system.

In adults, the level of L1 is where the spinal cord usually ends.

Lumbar Puncture Procedure

Lumbar puncture is a medical procedure that involves obtaining cerebrospinal fluid. In adults, the procedure is typically performed at the L3/L4 or L4/5 interspace, which is located below the spinal cord’s terminates at L1.

During the procedure, the needle passes through several layers. First, it penetrates the supraspinous ligament, which connects the tips of spinous processes. Then, it passes through the interspinous ligaments between adjacent borders of spinous processes. Next, the needle penetrates the ligamentum flavum, which may cause a give. Finally, the needle passes through the dura mater into the subarachnoid space, which is marked by a second give. At this point, clear cerebrospinal fluid should be obtained.

Overall, the lumbar puncture procedure is a complex process that requires careful attention to detail. By following the proper steps and guidelines, medical professionals can obtain cerebrospinal fluid safely and effectively.

The parietal pleura is located anterior to the sympathetic chain. When performing a thoracoscopic sympathetomy, it is necessary to cut through this structure. The intercostal vessels are situated at the back and should be avoided as much as possible to prevent excessive bleeding. Deliberately cutting them will not enhance surgical access.

Anatomy of the Sympathetic Nervous System

The sympathetic nervous system is responsible for the fight or flight response in the body. The preganglionic efferent neurons of this system are located in the lateral horn of the grey matter of the spinal cord in the thoraco-lumbar regions. These neurons leave the spinal cord at levels T1-L2 and pass to the sympathetic chain. The sympathetic chain lies on the vertebral column and runs from the base of the skull to the coccyx. It is connected to every spinal nerve through lateral branches, which then pass to structures that receive sympathetic innervation at the periphery.

The sympathetic ganglia are also an important part of this system. The superior cervical ganglion lies anterior to C2 and C3, while the middle cervical ganglion (if present) is located at C6. The stellate ganglion is found anterior to the transverse process of C7 and lies posterior to the subclavian artery, vertebral artery, and cervical pleura. The thoracic ganglia are segmentally arranged, and there are usually four lumbar ganglia.

Interruption of the head and neck supply of the sympathetic nerves can result in an ipsilateral Horners syndrome. For the treatment of hyperhidrosis, sympathetic denervation can be achieved by removing the second and third thoracic ganglia with their rami. However, removal of T1 is not performed as it can cause a Horners syndrome. In patients with vascular disease of the lower limbs, a lumbar sympathetomy may be performed either radiologically or surgically. The ganglia of L2 and below are disrupted, but if L1 is removed, ejaculation may be compromised, and little additional benefit is conferred as the preganglionic fibres do not arise below L2.

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.

The arachnoid villi are responsible for absorbing cerebrospinal fluid into the venous sinuses of the brain. On the other hand, the choroid plexus produces and releases cerebrospinal fluid. The inferior colliculus is involved in the auditory pathway, while the corpus callosum allows communication between the left and right hemispheres of the brain. The pia mater is the innermost layer of the meninges and is impermeable to fluid. Normal pressure hydrocephalus is a condition that presents with gait abnormality, urinary incontinence, and dementia, and is characterized by dilation of the ventricular system on imaging.

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.

The definition of a TIA has been updated to be based on tissue rather than time. It now refers to a temporary episode of neurological dysfunction caused by focal brain, spinal cord, or retinal ischemia, without resulting in acute infarction. Both TIAs and strokes can affect the spinal cord, brain, and retina, and both can cause symptoms that may require hospitalization. However, neither condition typically results in a significant troponin rise, which is more commonly associated with cardiac events.

A transient ischaemic attack (TIA) is a brief period of neurological deficit caused by a vascular issue, lasting less than an hour. The original definition of a TIA was based on time, but it is now recognized that even short periods of ischaemia can result in pathological changes to the brain. Therefore, a new ’tissue-based’ definition is now used. The clinical features of a TIA are similar to those of a stroke, but the symptoms resolve within an hour. Possible features include unilateral weakness or sensory loss, aphasia or dysarthria, ataxia, vertigo, or loss of balance, visual problems, sudden transient loss of vision in one eye (amaurosis fugax), diplopia, and homonymous hemianopia.

NICE recommends immediate antithrombotic therapy, giving aspirin 300 mg immediately unless the patient has a bleeding disorder or is taking an anticoagulant. If aspirin is contraindicated, management should be discussed urgently with the specialist team. Specialist review is necessary if the patient has had more than one TIA or has a suspected cardioembolic source or severe carotid stenosis. Urgent assessment within 24 hours by a specialist stroke physician is required if the patient has had a suspected TIA in the last 7 days. Referral for specialist assessment should be made as soon as possible within 7 days if the patient has had a suspected TIA more than a week previously. The person should be advised not to drive until they have been seen by a specialist.

Neuroimaging should be done on the same day as specialist assessment if possible. MRI is preferred to determine the territory of ischaemia or to detect haemorrhage or alternative pathologies. Carotid imaging is necessary as atherosclerosis in the carotid artery may be a source of emboli in some patients. All patients should have an urgent carotid doppler unless they are not a candidate for carotid endarterectomy.

Antithrombotic therapy is recommended, with clopidogrel being the first-line treatment. Aspirin + dipyridamole should be given to patients who cannot tolerate clopidogrel. Carotid artery endarterectomy should only be considered if the patient has suffered a stroke or TIA in the carotid territory and is not severely disabled. It should only be recommended if carotid stenosis is greater

The superior orbital fissure is the pathway for the ophthalmic branch of the trigeminal nerve.

The optic canal is the route for the optic nerve.

The zygomaticofacial foramen is a tiny opening that accommodates the zygomaticofacial nerve and vessels.

The jugular foramen is the passage for cranial nerves IX, X, and XI.

The supraorbital nerve and vessels traverse through the supraorbital foramen, which is situated directly beneath the eyebrow.

Foramina of the Skull

The foramina of the skull are small openings in the bones that allow for the passage of nerves and blood vessels. These foramina are important for the proper functioning of the body and can be tested on exams. Some of the major foramina include the optic canal, superior and inferior orbital fissures, foramen rotundum, foramen ovale, and jugular foramen. Each of these foramina has specific vessels and nerves that pass through them, such as the ophthalmic artery and optic nerve in the optic canal, and the mandibular nerve in the foramen ovale. It is important to have a basic understanding of these foramina and their contents in order to understand the anatomy and physiology of the head and neck.

The correct answer is the anterior inferior cerebellar artery. This artery can cause sudden onset vertigo and vomiting, as well as ipsilateral facial paralysis and deafness, which are all symptoms mentioned in the question. The fact that the patient has right-sided facial paralysis indicates that the right anterior inferior cerebellar artery is affected.

The anterior cerebral artery is not the correct answer. This artery can cause contralateral hemiparesis and sensory loss, but the patient in the question has intact motor function in all four limbs.

The basilar artery is also not the correct answer. Strokes affecting this artery can cause ‘locked-in’ syndrome, which is characterized by complete paralysis of voluntary muscles except for those controlling eye movement. However, the patient in the question has intact motor function in all limbs.

The posterior cerebral artery is also not the correct answer. Strokes affecting this artery can cause contralateral homonymous hemianopia with macular sparing and visual agnosia, but the patient in the question has intact vision.

Stroke can affect different parts of the brain depending on which artery is affected. If the anterior cerebral artery is affected, the person may experience weakness and loss of sensation on the opposite side of the body, with the lower extremities being more affected than the upper. If the middle cerebral artery is affected, the person may experience weakness and loss of sensation on the opposite side of the body, with the upper extremities being more affected than the lower. They may also experience vision loss and difficulty with language. If the posterior cerebral artery is affected, the person may experience vision loss and difficulty recognizing objects.

Lacunar strokes are a type of stroke that are strongly associated with hypertension. They typically present with isolated weakness or loss of sensation on one side of the body, or weakness with difficulty coordinating movements. They often occur in the basal ganglia, thalamus, or internal capsule.

Subarachnoid haemorrhage is a potential complication for individuals with Ehlers-Danlos syndrome, a group of connective tissue disorders characterized by joint hypermobility, hyper-extensive skin, and easy bruising. It should be noted that acute kidney injury is not a risk factor, but adult polycystic kidney disease may increase the likelihood of subarachnoid haemorrhage.

Understanding Subarachnoid Haemorrhage

Subarachnoid haemorrhage (SAH) is a type of intracranial haemorrhage where blood is present in the subarachnoid space, which is located deep to the subarachnoid layer of the meninges. Spontaneous SAH is caused by various factors such as intracranial aneurysm, arteriovenous malformation, pituitary apoplexy, arterial dissection, mycotic aneurysms, and perimesencephalic. The most common symptom of SAH is a sudden-onset headache, which is severe and occipital. Other symptoms include nausea, vomiting, meningism, coma, seizures, and sudden death. SAH can be confirmed through a CT head scan or lumbar puncture. Treatment for SAH depends on the underlying cause, and most intracranial aneurysms are treated with a coil by interventional neuroradiologists. Complications of aneurysmal SAH include re-bleeding, vasospasm, hyponatraemia, seizures, hydrocephalus, and death. Predictive factors for SAH include conscious level on admission, age, and the amount of blood visible on CT head.

The ventromedial nucleus of the hypothalamus is responsible for regulating satiety, and therefore, damage to this area can result in hyperphagia.

The posterior nucleus plays a role in stimulating the sympathetic nervous system and body heat, and lesions in this area can lead to autonomic dysfunction and poikilothermia.

The lateral nucleus is responsible for stimulating appetite, and damage to this area can cause a decrease in appetite and anorexia.

The paraventricular nucleus produces oxytocin and ADH, and lesions in this area can result in diabetes insipidus.

The dorsomedial nucleus is responsible for stimulating aggressive behavior and can lead to savage behavior if damaged.

The hypothalamus is a part of the brain that plays a crucial role in maintaining the body’s internal balance, or homeostasis. It is located in the diencephalon and is responsible for regulating various bodily functions. The hypothalamus is composed of several nuclei, each with its own specific function. The anterior nucleus, for example, is involved in cooling the body by stimulating the parasympathetic nervous system. The lateral nucleus, on the other hand, is responsible for stimulating appetite, while lesions in this area can lead to anorexia. The posterior nucleus is involved in heating the body and stimulating the sympathetic nervous system, and damage to this area can result in poikilothermia. Other nuclei include the septal nucleus, which regulates sexual desire, the suprachiasmatic nucleus, which regulates circadian rhythm, and the ventromedial nucleus, which is responsible for satiety. Lesions in the paraventricular nucleus can lead to diabetes insipidus, while lesions in the dorsomedial nucleus can result in savage behavior.