The nucleus basalis of Meynert, located in the basal forebrain substantia innominata, is a cluster of neurons that sends extensive projections to the neocortex. It is situated below the globus pallidus and contains high levels of acetylcholine esterase and choline acetyltransferase. In Alzheimer’s disease, the nucleus basalis of Meynert degenerates, leading to a decrease in acetylcholine levels.

The facial nerve is responsible for carrying taste sensation from the front two-thirds of the tongue, as well as innervating facial muscles and certain glands. The glossopharyngeal nerve receives taste signals from the back third of the tongue. The hypoglossal nerve controls the muscles of the tongue. The olfactory nerve is responsible for detecting smells. Finally, the trigeminal nerve receives sensory input from the face and controls the muscles used for chewing.

Medical Imaging Technologies

There are several medical imaging technologies used to diagnose and monitor various conditions. One such technology is the SPECT scan with ioflupane iodine injection, also known as the DAT scan. This scan helps to identify dopamine deficiency in the brain, which can rule out Parkinson’s dementia and Lewy body dementia. By using a small amount of a radioactive drug, the scan can determine how much dopamine is available in a person’s brain. In Lewy body dementia, there is a significant loss of striatal dopamine, which can be detected through this scan. This helps to differentiate between Alzheimer’s dementia, where dopaminergic activity is normal.

Another imaging technology is the CT scan, which uses x-rays and a computer to create detailed images of the inside of the body. This scan is useful in identifying injuries of growths in different parts of the body. Magnetic resonance imaging (MRI) is another technology that uses a strong magnetic field to create detailed images of the structures in the body. It is commonly used to examine organs and tissues.

PET, of positron emission tomography, is a nuclear medicine imaging technology that produces three-dimensional, color images of the functional processes within the human body. It is used to study existing conditions in the body and how they are developing.

Finally, an x-ray of the skull is mainly used to detect any bony abnormalities following trauma. However, this is now rarely requested, and if there is sufficient force, a CT scan is usually preferred. These imaging technologies play a crucial role in diagnosing and monitoring various medical conditions.

Neuropeptide Y is a neuropeptide that stimulates appetite and is a target for developing antagonists in obesity research. Angiotensin is a peptide hormone involved in controlling blood pressure through vasoconstriction. Cholecystokinin has been linked to schizophrenia, eating disorders, movement disorders, anxiety, and panic attacks. Neurotensin is hypothesized to be involved in schizophrenia due to its co-existence with dopamine in some axon terminals. Substance P is primarily associated with pain perception.

The pupils are innervated by both sides of the midbrain and respond to ambient light levels. If there is an optic nerve lesion, the non-damaged nerve becomes dominant and both pupils respond to ambient light from that nerve. A helpful mnemonic for remembering the cranial nerves and their functions is OOOTTAFVGVAH for the nerves and SSMMBMBSBBMM for their functions. To recall the innervation of the extraocular muscles, one can use SO4 LR6. The optic nerve is II, oculomotor is III and supplies all extraocular muscles except for the superior oblique and lateral rectus, trochlear is IV and innervates the superior oblique muscle for depression and intorsion, trigeminal is V and supplies sensory information and muscles of mastication, and abducens is VI and controls the lateral rectus muscle of the eye.

Parkinson’s disease is caused by the destruction of dopaminergic cells in the substantia nigra, resulting in a reduction of dopamine levels that can be detected through a DAT scan. The corpus callosum is a bundle of nerve fibers that connects the left and right cerebral hemispheres, allowing for communication between them. The dentate gyrus, located in the medial temporal lobe, plays a role in memory. Wernicke’s area, found on the left temporal lobe, is responsible for language comprehension and development. The cerebellum, located in the hindbrain, coordinates movement, muscle tone, balance, and equilibrium.

Medical Imaging Techniques

There are several medical imaging techniques used to examine the organs and tissues in the body. Magnetic resonance imaging (MRI) uses a strong magnetic field to create detailed images of the structures in the body. It is commonly used to exclude other cerebral pathologies in dementia investigation.

Positron emission tomography (PET) is a nuclear medicine imaging technique that uses radiation to produce three-dimensional, colour images of the functional processes within the human body. It is used to study existing conditions in the body and also how it is developing.

Single-photon emission computed tomography (SPECT) scan with ioflupane iodine injection, also known as DAT scan, helps to identify dopamine deficiency in the brain to rule out Parkinson’s dementia and Lewy body dementia.

Computerised tomography (CT) scan uses x-rays and a computer to create detailed images of the inside of the body. It helps to identify injuries of any growth in the different parts of the body. Although it could be used in dementia investigation, it is not the preferred modality as per NICE.

Ultrasound uses high frequency sounds to visualise soft tissues in the body. However, it is not used for investigations of the head.

A pituitary adenoma can cause compression of the optic chiasm, resulting in a bitemporal hemianopia. Other tumors, such as craniopharyngiomas, meningiomas, of gliomas, can also cause this type of visual field defect. Cerebellopontine angle tumors typically present with symptoms related to the facial, vestibulocochlear, and trigeminal nerves. A cerebrovascular event in the occipital cortex can cause visual loss, usually in the form of a homonymous hemianopia. Diabetes mellitus can cause various visual defects, including diabetic retinopathy, retinal hemorrhages of detachment, and oculomotor nerve palsy. Oculomotor nerve palsies can be caused by a variety of conditions, such as vascular events, diabetic neuropathy, intracranial aneurysms, syphilis, of raised intracranial pressure. Symptoms include ptosis, diplopia, and possible mydriasis. Laser treatment for diabetic retinopathy is unlikely to cause a well-defined homonymous hemianopia.

The abducens nerve (CN VI) controls the lateral rectus muscle, which allows for outward eye movement. If a patient has an isolated unilateral abducens nerve palsy, they may experience horizontal diplopia, where the affected eye deviates inward due to the unopposed medial rectus muscle. This results in the patient being unable to move their eye outward when looking to the affected side. If the right eye is deviated inward, it indicates right nerve palsy.

The oculomotor nerve (CN III) controls several eye muscles, including the superior rectus, inferior rectus, inferior oblique, and medial rectus muscles. It also controls the levator palpebrae superioris (LPS) muscles responsible for lifting the upper eyelid and the muscles that constrict the pupil. The presentation of an oculomotor nerve lesion can vary depending on which branch of area is affected. In a complete oculomotor nerve palsy, the affected eye may be positioned downward and outward, resulting in strabismus and diplopia. The patient may also experience mydriasis (dilated pupil) and ptosis (drooping of the eyelid).

The trochlear nerve (CN IV) controls the superior oblique muscle, which allows for downward, inward, and outward eye movement. If a patient has a trochlear nerve lesion, they may experience vertical diplopia and develop a head tilt away from the affected eye.

The hippocampal formation includes the dentate gyrus, which is located in the medial temporal lobe. The cerebrum, which is the largest part of the brain, is divided into four lobes: frontal, temporal, parietal, and occipital. The frontal lobe is situated at the front of the cerebrum, while the temporal lobes are on the sides, the parietal lobe is on the top, and the occipital lobe is at the back.

Fahr’s syndrome is a rare condition where calcium deposits accumulate in the brain’s basal ganglia, which control movement. This can lead to neuropsychiatric symptoms such as dementia, psychosis, and behavioral changes. The pituitary gland, located at the base of the brain, produces hormones that affect various parts of the body. The occipital lobe is responsible for vision, while the cerebellum controls motor coordination, balance, and muscle tone. The hippocampus, located in the medial temporal lobe, is involved in spatial navigation and memory.