Variants And Related Syndromes

Dealing in appropriate depth with the potential variants of MS lies outside the scope of this chapter. However, some mention should be made of Marburg disease, Schilder disease, Balo concentric sclerosis, Devic disease, and acute disseminated encephalomyelitis (ADEM).

Marburg disease is an aggressive form of MS with a malignant course. It is multifocal, and some lesions may be associated with mass effect. It is often fatal within weeks to months of onset.

Schilder disease is a difficult concept, given that some of the initially described cases ultimately turned out to have diseases other than MS, and many were actually found to have adrenoleukodystrophy. Some cases, however, are likely to be related to MS. Usually beginning in childhood and following a progressive course, there occurs widespread, confluent or diffuse areas of demyelination involving the cerebrum, cerebellum, and brainstem, with axonal loss and often cavitation. The clinical features are similar to MS, but dementia and other cortical features are more prominent.

Balo concentric sclerosis is characterized by rings of myelin separated by rings of demyelination. Lesions may be seen in the cerebral hemispheres, cerebellum, brain-stem, spinal cord, and optic chiasm. Typically affected patients are young and present with an acute monophasic illness. Deficits may be present in higher cortical function, and signs of raised intracranial pressure are common. Although frequently fatal, some patients survive, with eventual involvement of the initially uninvolved rings of myelin.

Devic syndrome or neuromyelitis optica is a syndrome of bilateral optic neuritis and transverse myelopathy, usually occurring in quick succession. Heterogeneity is common, with some patients following a relaps-ing-remitting course and some experiencing a monophasic illness. Some patients with the syndrome undoubtedly have a form of MS, whereas others may have one of a variety of autoimmune or granulomatous disorders, such as systemic lupus erythematosus (SLE) and sarcoidosis. The term Devic disease is probably best reserved for patients with no evidence of disease outside the optic nerves and spinal cord, and who have had other potentially responsible disorders excluded.

ADEM is most commonly seen in children and young adults, although it appears to spare very young children (< 2 years). It is related to recent infection or vaccination in the majority of cases, with the number of responsible agents being considerable, but measles, rubella, and varicella being among the most common precipitants. The clinical spectrum is very broad, from a subclinical course to fulminant, rapidly progressive disease with seizures and coma. Neurologic symptoms begin 1 to 3 weeks after the onset of infection, and symptoms peak within several days. Differentiation of ADEM from MS in adults can be very difficult, and we know that 35% of adult cases with a working diagnosis of ADEM have a second episode of neurologic disturbance compatible with MS within 12 months. MRI findings are often impressive, with extensive areas of demyelination; considerable overlap with MS occurs. Basal ganglia lesions are seen in ADEM but not MS, but are only helpful discriminators in the small proportion of patients who actually exhibit these. Similarly, clinical and MRI evidence of infratentorial lesions is certainly more common in ADEM, but these occur frequently enough in MS also. Fever, meningism, and loss of consciousness usually are seen only in ADEM, and aphasia is also more common. The blood-brain barrier is more often disturbed in ADEM, showing higher cell counts, but again overlap occurs, and oligoclonal bands, more common in MS, also may not be a useful distinguishing feature.

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