Multiple Sclerosis
The Common Vein
Definition
Multiple sclerosis is a disease in which there is demyelination of the nerves. It is caused by an autoimmune response which results in the production of abnormal immunoglobulins that target myelin. Hence, it is a chronic, relapsing and disabling disease affecting more than a 250.000 people in the United States. It affects mostly young adults. Interestingly, there is an association with higher geographic latitudes and incidence of the disease.
Functionally, demyelination prevents saltatory electrical conduction from happening. In other words, that particular nerve track is blocked.
Typically, bouts of acute attacks (demyelination) occur. The disease is mainly intermittent; after each attach a sequelae can occur. Moreover, between each attack, damage may also progress indolently. Several types of multiple sclerosis exist, being classified according to the damages resulting from each attack and between attacks.
Structurally, areas of demyelination with reactive gliosis are seen in white matter of brain and spinal cord, sometimes also in the optic nerves.
Clinically, weakness or numbness, in one or more extremities is the initial symptom in 50% of patients. Because the disease can affect any part of the CNS, the symptoms are extremely variable. As such, there can be symptoms as distinct as those resulting from optic nerve neuritis, ataxia resulting from cerebellar lesions, brainstem symptoms (vertigo, dysarthria, diplopia), loss of sphincter control. The main clue is the presence of temporally spaced lesions of distinct focal losses.
The diagnosis can be supported through electrocerebral responses evoked by monocular visual stimulation studies and by electrical stimulation of a sensory or mixed peripheral nerve. The immunoelectrophoresis of the CSF shows increased levels of IgG, oligoclonal banding and presence of myelin basic protein.
In terms of imaging, MR remains the most sensitive test. T2 weighted images demonstrate multiple hyperintense white matter lesions, usually not contrast enhanced. Periventricular lesions are very suggestive of multiple sclerosis, but are nonspecific. The lesions that occur, termed plaques, are typically ovoid, usually located near the ventriculi or having a subcortical location, but, as described above, these plaques can also be present in the cerebellum, mesencephalon, corpus callosum, medulla oblongata , and spinal cord.
In acute attacks, corticosteroids can reduce the symptoms. Chronic therapy differs according to the subtype of MS, and can involve ß-interferon, glatiramer acetate or immunosuppressive therapy.