ESSENTIALS OF DIAGNOSIS
Episodic neurologic symptoms.
Patient usually under 55 years of age at onset.
Single pathologic lesion cannot explain clinical findings.
Multiple foci best visualized by MRI.
This common neurologic disorder, which probably has an autoimmune basis, has its greatest incidence in young adults. Epidemiologic studies indicate that multiple sclerosis is much more common in persons of western European lineage who live in temperate zones. No population with a high risk for multiple sclerosis exists between latitudes 40° N and 40° S. A genetic susceptibility to the disease is present, based on twin studies, familial cases, and an association with specific HLA antigens (HLA-DR2) and alleles of IL2RA (the interleukin-2 receptor alpha gene) and IL7RA (the interleukin-7 receptor alpha gene). Pathologically, focal—often perivenular—areas of demyelination with reactive gliosis are found scattered in the white matter of the brain and spinal cord and in the optic nerves. Axonal damage also occurs.
The common initial presentation is weakness, numbness, tingling, or unsteadiness in a limb; spastic paraparesis; retrobulbar optic neuritis; diplopia; dysequilibrium; or a sphincter disturbance such as urinary urgency or hesitancy. Symptoms may disappear after a few days or weeks, although examination often reveals a residual deficit (eFigure 24–13).
Bilateral internuclear ophthalmoplegia due to multiple sclerosis. (Reproduced, with permission, from Vaughan DG, Asbury T, Riordan-Eva P [editors]. General Ophthalmology, 15th ed. Originally published by Appleton & Lange. Copyright © 1999 by The McGraw-Hill Companies, Inc.)
Several forms of the disease are recognized. In most patients, there is an interval of months or years after the initial episode before new symptoms develop or the original ones recur (relapsing-remitting disease). Eventually, however, relapses and usually incomplete remissions lead to increasing disability, with weakness, spasticity, and ataxia of the limbs, impaired vision, and urinary incontinence. The findings on examination at this stage commonly include optic atrophy; nystagmus; dysarthria; and pyramidal, sensory, or cerebellar deficits in some or all of the limbs. In some of these patients, the clinical course changes so that a steady deterioration occurs, unrelated to acute relapses (secondary progressive disease). Less commonly, symptoms are steadily progressive from their onset, and disability develops at a relatively early stage (primary progressive disease). The diagnosis cannot be made with confidence unless the total clinical picture indicates involvement of different parts of the central nervous system at different times. Fatigue is common in all forms of the disease.
A number of factors (eg, infection) may precipitate or trigger exacerbations. Relapses are reduced in pregnancy but are more likely during the 2 or 3 months following pregnancy, possibly because of the increased demands ...