seminar 6 MG II

8/7/2019 seminar 6 MG II

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Alzheimer Disease

Alzheimer disease (AD) is the most common cause of dementia in western civilization. Itaffects more women than men, and the clinical course generally lasts approximately fiveyears. The younger the individual is at the onset of the disease, the more severe the

deficits for the patient. One famous contemporary who suffers from the disease is former U.S. President Ronald Reagan.

The cerebral cortex and some other forebrain regions atrophy so severely that the brainmay weigh less than 1000g at death. Shrinkage is most pronounced in the frontal andtemporal lobes. The insula and the medial part of the temporal lobe tend to demonstratethe highest number of neuritic plaques. The greater the number of plaques the higher thedegree of dementia. The disease often causes vacuolization of the subpial layers of thetemporal and parietal lobes. The spongy state is associated with neuronal loss and issimilar to the effects of Creutzfeldt-Jakob disease.

Researchers continue to search for causes and cures for AD. The gene that codes for theB-amyloid protein located on chromosome 21 is implicated in the 20% of patients for whom there is a family history of AD. Head injury has been implicated in 3 to 5 % of AD cases. There is a 70 to 90% decrease in the production of the enzyme that makesacetylcholine. Other neurotransmitter abnormalities have also been implicated.

Broca Aphasia

Aphasia is defined by Websters Dictionary as a "loss or impairment of the power to useor comprehend words usually resulting from brain damage."

In most people the Broca's area is in the lower part of the left frontal lobe. It is one of the main language areas in the cerebral cortex because it controls the motor aspects of speech. Persons with a Broca aphasia can usually understand what words mean, but havetrouble performing the motor or output aspects of speech. Thus, other names for thisdisorder are 'expressive' and 'motor' aphasia. Depending on the severity of the lesion toBroca's area, the symptoms can range from the mildest type (cortical dysarthria) withintact comprehension and the ability to communicate through writing to a complete lossof speaking out loud.

Cerebello-Olivary Degeneration of Holmes

This is a rare, autosomally-inherited disease that leads to the progressive degeneration of the cerebellar cortex and the inferior olivary nucleus within the medulla. Onset isgenerally in the fourth decade. The disease results in ataxic gait, dysarthria, and tremor of the limbs.

Autopsy reveals pronounced atrophy of the cerebellum. There is almost complete loss of Pukinje cells and an associated astrocytosis. Shrinkage is not as prominent in the olives.It is thought that the disease begins in the cerebellum and that in the inferior olivary

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nucleus the neuronal loss is secondary since the Purkinje cell is the synaptic target of theinferior olivary nucleus neurons. There is some similarity pathologically between thisdisease and chronic alcoholic degeneration in that both affect the cerebellum.

Choroid Plexus Papilloma

These tumors form most commonly in the fourth ventricle and mainly affect childrenduring the first year of life. If untreated they result in hydrocephalus and symptoms of headache, lethargy, stupor and weakness of the legs. The tumor takes the form of a giantchoroid plexus and has a cellular epithelium that is closely related to the ependyma. Thisform of tumor is often accompanied by hemorrhage which increases the complications of treatment. A shunt is the most immediate form of treatment if the patient is in a conditionwhere surgical removal of the tumor cannot be performed right away. The shunt removesthe excess CSF thereby reducing the damaging affects of pressure.

Another problem that can occur with the choroid plexus is that a cyst(s) can form within

it.

Huntington Disease

This is an autosomally-inherited, dominant disorder in which the patient begins to exhibitsymptoms in the third to fourth decades. Patients with Huntington Disease (HD) initiallyhave a tendency to fidget which over months or years develops into jerky, choreiformmovements. HD usually progresses over a 10 to 25 year period. As the diseaseprogresses it leads to dementia and usually death from incurrent infection. There is ahigh incidence of suicide among patients with HD.

Pathologically, there is atrophy of certain forebrain structures including the entirecerebral cortex and even more notably of the caudate nucleus and putamen The head of the caudate is reduced to a narrow brownish band of tissue that is flattened or concave.In normal brain the ratio of small neurons to large neurons in the corpus striatum isapproximately 160:1 in Huntingtons patients the ratio is reduced to 40:1 with a markeddecrease in the number of astrocytes. The gene for this disease has been isolated to theshort arm of chromosome 4.

Locked-In Syndrome

This syndrome is due to stroke, tumor or trauma to the ventral part of the rostral pons.

Lesions there render the individual quadriplegic, unable to speak and incapable of facialmovement. One would think these individuals were in a coma except that they are able tomove their eyes and if given an eye communicating device they can communicate.

Parkinson Disease

Parkinson disease (PD) is characterized by a slowing of voluntary movements,bradykinesia, muscular rigidity and tremor at rest. These abnormalities result from a

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reduction of neurons that make dopamine in the pars compacta of the substantia nigra.The axons of these neurons normally release this neurotransmitter where they synapse, inparts of the basal ganglia called the caudate nucleus and putamen or, collectively, thecorpus striatum. Dopamine usually works as an inhibitory neurotransmitter in the corpusstriatum where it acts on cholinergic neurons.

Lewy bodies, a hyaline inclusion, are seen microscopically in the cytoplasm of residualneurons in the substantia nigra of nearly all patients with Parkinsonism. The loss of neurons results in a grossly evident depigmentation of the substantia nigra because thosedopaminergic neurons also contain the pigment neuromelanin in their cytoplasm.

There are various causes for the loss of dopaminergic neurons in the substantia nigra andthe resultant signs of PD.

Parinaud Syndrome

Also called dorsal midbrain or collicular syndrome, this disorder is characterized by anupward fixed gaze and pupils. Structures in the vicinity of the dorsal midbrain area,including cranial nerve IV, the superior and inferior colliculi, pretectal area, and pinealgland, are affected. Pineal tumors and hydocephalus are main causes of damage to thesestructures.

Pituitary Adenoma

These tumors are benign and are usually composed of secretory cells from the anterior lobe of the pituitary. Initially the tumor results in either an increase or decrease of hormone production depending on whether or not the adenoma is composed of cells

capable of producing hormone. Increased levels of hormones can lead to either Cushingdisease or acromegaly.

Secondary effects of tumor growth can lead to compression of the optic chiasm which hasa position slightly above and in front of the pituitary gland. Such damage leads to visualdifficulties.

Tourette Syndrome

This syndrome begins in childhood and manifests itself through various forms of tics.These tics include frequent, irregular movements of the head, neck, or shoulders. They

also may be more complex motor behaviors such as snorting, sniffing, and involuntaryvocalization. As the syndrome progresses repetitive behaviors such as touching others,obsessive compulsive symptoms, and explosive involuntary cursing can be morecommon. Aggressive behavior and improper sexual impulses are the rarest and mostsevere expressions of the syndrome. Most often the child is hyperactive and has beengiven some form of CNS stimulant.

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The cause of Tourette syndrome is not known, but it is believed to have a geneticcomponent. A total absence of the protein dynorphin in the striatal fibers of the globuspallidus is found in some patients. Other studies have shown a deficit in the uptake or release of dopamine and serotonin at synapses.

Wallenberg Syndrome

This syndrome is characterized by difficulty in swallowing and hoarseness due toparalysis of the ipsilateral vocal cord. In some cases taste may also be affected in theipsilateral half of the tongue. The glossopharyngeal (IX) & vagus (X) are the primarycranial nerves involved in this syndrome.

Occlusion of the posterior inferior cerebellar artery (PICA) or branches from it leads todamage to the posterior lateral region of the medulla. Thus another name for this disorder is the 'lateral medullary plate syndrome'.

Weber Syndrome

This syndrome is due to damage to the structures at the base of the midbrain including thethird cranial nerve and the corticospinal and corticobulbar fibers in the cerebralpeduncle. It is characterized by complete 3rd nerve palsy and associated withcontralateral hemipelagia.

Common causes of this syndrome are aneurysm in the posterior parts of the Circle of Willis, tumor, and occlusion in vessels supplying the anterior midbrain.

Wernicke Aphasia

There are two main components to this type of aphasia. The first is impairment in thecomprehension of written and spoken language. The second is an inability to speak substantive language; often times these patients are unable to form some words correctlyand seem to inject words in their sentences that do not fit (paraphasia). These personscannot function independently in society because they are unable to understand themeaning of written and spoken words, and they are unable to tell others what they wantor think because their own speech is devoid of content. Since there may not be anydifficulty making the sounds of language, another name for this disorder is 'fluent or sensory' aphasia.

Lesions producing this disorder can be found in the boundary region of the temporal andparietal lobes on the dorsolateral surface of the left (in most persons) cerebralhemisphere.

Wernicke-Korsakoff Syndrome

This disease, notably frequent among chronic alcoholics, is due to a deficiency of vitaminB1 or thiamine. The poor diet of alcoholics who are suffering from this syndrome leads

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to lesions and increased microhemorrhages in the mammillary bodies, thalamus andbrainstem. This syndrome can also be associated with diseases of the GI tract when thereis inadequate thiamine absorption.

Neurologic symptoms include confusion, memory loss, impaired movements and

peripheral neuropathy. Immediate administration of thiamine is usually successful intreating the symptoms, but sometimes permanent memory loss occurs.

Wilson Disease(Hepatolenticular Degeneration)

This disease is caused by the inheritance of a mutation on chromosome 13. The mutationprevents the body from eliminating excess copper. Ceruloplasmin is the protein thatbinds and removes excess copper and its levels are greatly reduced in this disorder. Toomuch copper in the system damages the cells of the liver and leads to cirrhosis.Neurological damage primarily occurs in the putamen and globus pallidus, collectively

known as the lenticular nucleus.

Symptoms of the disease include a peculiar type of tremor in the upper extremities,slowness of movement and changes in temperament. Persons may become exceptionallyargumentative, overly emotional or may experience a decrease in mental capabilities.Kayser-Fleischer rings (a rusty brown discoloration at the rims of the corneas) becomeevident as the copper begins to affect the nervous system.

The disease first affects the liver, and if treatment is administered early enough, damageto the nervous system is dramatically reduced. Treatment includes the elimination of copper containing foods such as chocolate and mushrooms. Patients are also given drugs

to chelate excess copper and eliminate it from the body.

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seminar 6 MG II