neurospecific polypeptide protein of the peripheral nerve, and the disease appeared to depend largely on cell-mediated immunity.

Acute Disseminated Encephalomyelitis

ADEM is characterized by acute depression of consciousness and multifocal neurologic findings that usually occur a few days or weeks following vaccine administration or virus-like disease. It is characterized pathologically by diffuse foci of perivenular inflammation and demyelination that are most prominent in the white matter of the brain and spinal cord. A definitive diagnosis of ADEM can be made only pathologically. However, recent imaging studies with enhanced magnetic resonance imagers have defined a characteristic pattern of multiple enhancing white matter lesions in patients with ADEM, and in the future, magnetic resonance imaging findings may give better data on nonfatal, nonbiopsied cases of suspected postimmunization ADEM.

Multiple Sclerosis

The establishment of a relation between acute central and peripheral nervous system demyelinating disease and infections and vaccines has opened the question of a possible relation to chronic demyelinating disease, specifically, multiple sclerosis. When mean levels of antibody to measles virus are assayed in the serum and spinal fluid of patients with multiple sclerosis, they are consistently higher than those in controls, and in some studies elevated levels of antibodies to a variety of different viruses have been found in serum and spinal fluid (Johnson et al., 1985). The persistence of these agents in patients with multiple sclerosis has not been established. In the diagnosis of multiple sclerosis, demyelinating lesions not only must occur in multiple locations within the nervous system but must also occur at different times. A prospective study of patients with multiple sclerosis showed that exacerbations appeared to be more frequent after nonspecific viral illnesses (Sibley et al., 1985). Therefore, it would be feasible that vaccines also might precipitate an exacerbation either in a patient who was predisposed to develop the disease or in a patient with already established disease. However, there is no clear-cut causal relation between any virus or vaccine and multiple sclerosis.

Focal Lesions

Both optic neuritis and transverse myelitis often are components of diffuse demyelinating diseases, both ADEM and multiple sclerosis. When they occur in isolation, their mechanisms and pathologies are usually un-



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