Multiple sclerosis (MS) is a chronic
relapsing-remitting disorder of probable auto-immune origin characterized by
recurrent episodes of demyelination in the brain (including optic nerves) and
spinal cord; it results in progressive neurological deficits.
The overall prevalence of MS is 1/1,000, with higher prevalence in
Those who emigrate age >15 from areas of high prevalence to
areas of low prevalence maintain their original risk.
Women have 2x the risk of men.
Genetic and environmental
factors contribute to the pathogenesis. HLA DR 15 con-fers genetic
susceptibility. Environmental factors include viral infection, vitamin D
deficiency, and smoking.
Acute lesions on gross examination show
well-circumscribed gray lesions (plaques),
with bilateral distribution that is frequently periventricular. His-tology
shows chronic inflammation with phagocytosis of myelin by macro-phages; axons
are initially preserved.
Chronic lesions have no inflammation, with
axons showing remyelination. Remyelination
is defective because myelin sheaths are thinner with shorter internodes.
During an acute attack, nerve
conduction is entirely blocked, leading to acute neuro-logical deficits.
Chronic plaques are associated with slower nerve conduction, allowing for
partial recovery. Recurrent attacks cause progressive neurological
Clinical onset is typically
in decades 3–4. About 85% of cases show a relapsing-remitting course; a
minority of cases show primary progressive (slow deteriora-tion) or
progressive-relapsing (slow progression punctuated by acute exacerbations)
course. Recovery from each episode of demyelination occurs in weeks or months.
Early symptoms include
sensory problems, paresis, and visual dysfunction. As the disease progresses,
other symptoms include fatigue, bladder dysfunction, spasticity and ataxia.
Neuropsychological symptoms affect 40–60% of patients.
Diagnosis of MS requires the
demonstration of the dissemination of disease in space and time. Clinical
history, MRI, CSF studies and electrophysiological stud-ies are important.
Treatment is immunomodulatory drugs (e.g., interferon beta), immunosuppressive
therapies (e.g., mitoxantrone), and monoclonal antibodies (e.g., natalizumab).
The latter is used as monotherapy in cases of relapsing MS; its use is linked
Central pontine myelinolysis (CPM) is a focal demyelination of
the central area of the basis pontis. It probably
derives from rapid correction of hyponatremia, and the condition is very often
fatal. Patients at risk include the severely malnourished and alcoholics with