Clinical features of Behcet disease. (A) Hypopyon iritis, with red eye and acute inflammatory cell sediment in the front chamber; (B) ulcer on tongue (C) multiple genital ulcers involving the labia; and (D) skin pathergy forming a pustule in response to trauma from watch strap.

tional information. Ophthalmologic examination for evidence of uveitis can be useful. Definitive diagnosis, however, requires histo-logic confirmation of noncaseating epithe-lioid cell granulomas from neural tissue (usually a meningeal biopsy), with a probable diagnosis being made in cases of a clinical syndrome consistent with neurosarcoidosis and histologic evidence of systemic sarcoid disease (via pulmonary, lymph node, or con-junctival biopsy). Response to treatment can be disappointing. First-line therapy involves corticosteroids and methotrexate. More recently, radiotherapy and infliximab (anti-TNFa) also have been used in refractory cases.

Progressive Syndromes

MS Variants

Marburg disease. This is a rapidly progressive and often fatal form of MS, progressing over a short period of time, sometimes several months. It is not thought to be a separate disease entity.

Balo concentric sclerosis. This is a histologic MS variant, referring to a lesion characterized by concentric rings of demyelination and remyelination. A similar pattern is seen on T2-weighted and T1 contrast brain MRI scans and may be distinguished from a tumour or abscess by the usual "open-ring" appearance when enhanced with gadolinium. More typical MS lesions can be seen in association. A focal progressive neurologic syndrome is the typical clinical picture, although more benign clinical phenotypes are described.

Schilder diffuse sclerosis. Originally described in 1912, the number of cases reported in the literature for which an alternative diagnosis was excluded is very small. The condition usually presents in children with progressive visual loss, hemiparesis, and cortical features such as cognitive deficits, cortical blindness, and seizures. The condition generally is more aggressive than Ms, and MRi shows one or two large white matter lesions only within the centrum semiovale. Other conditions including subacute sclerosing panencephalitis (SSPE) and the leukodystrophies should be excluded. CSF findings are not specific. Electroencephalogram (EEG) shows generalized slowing in contrast to SSPE. Histologic examination shows widespread confluent demyelination, with more typical MS lesions frequently coexisting. Frozen section samples may be mistaken for astrocytoma, with the inflammatory histiocytic features of Schilder disease most easily demonstrated in paraffin-embedded material.

Progressive Spinal Cord Syndromes The progressive spinal cord syndromes are described in the section on transverse myelitis. Vitamin B12 deficiency and compressive lesions are treatable and potentially reversible causes of myelopathy and thus should be excluded. Hereditary spastic paraplegia does not always present with a dominant family history and pes cavus, and it should be considered when the spasticity is dominant and bladder symptoms mild. An absence of CSF-specific oligoclonal bands or MRI spinal cord lesions should prompt the search for an alternative diagnosis.

HIV infection. The neurologic manifestations of HIV infection are protean. The only syndromes likely to cause confusion with MS include AIDS-related vacuolar myelopa-thy and AIDS-related dementia (although the latter tends to be more rapidly progressive than in MS). White matter lesions may occur on brain MRI. However, oligoclonal bands usually are absent. Testing for HIV antibodies should be considered where doubt exists.

HTLV-1. A progressive myelopathy due to HTLV-1 infection is seen in Afro Caribbeans and Japanese patients but is rare in Caucasians. Leg pain is common, and weakness is usually symmetrical. Brain white matter lesions do occur. Evoked potentials, if delayed, tend to be symmetrical, and CSF oligoclonal bands are matched in the serum. Antibodies to HTLV-1 are present in serum and CSF.

Infectious Disease

Lyme Disease Lyme disease occurs in the temperate, forested regions of Europe and Asia and in the northeastern and upper midwestern areas of the United States. A history of tick bite, characteristic rash (erythema chronicum migrans), and constitutional symptoms in association with a painful polyradiculopathy, facial palsy, or menin-goencephalitis allow Lyme disease to be distinguished from MS in most cases. Optic neuritis has been described. More difficulty arises with so-called tertiary Lyme disease, in which a chronic progressive neurologic disorder may develop, such as a spastic para-paresis, in association with white matter lesions on brain MRI. The diagnosis is suggested by the appropriate early history and a marked CSF lymphocytosis. Confirmation is by detection of intrathecal antibody using immunoblot, and/or polymerase chain reaction (PCR) for the antigen, where available. A prolonged course of antibiotics is advised.

Neurosyphilis Now rare in developed countries except in association with HIV, this diagnosis is considered when headache and seizures are associated with the characteristic pupillary abnormalities. However, a meningovascular hemiparesis and oculomotor palsies also may be the presenting features. Optic neuritis also is described, but is usually bilateral and associated with disc swelling and enlarged blind spots. The CSF may be pleocystic. The diagnosis is highly unlikely in the presence of a negative serum Treponema pallidum hemaglutination (TPHA) assay. A positive CSF VDRL confirms neurologic involvement in the presence of a positive serum TPHA.

Devic's Disease (Neuromyelitis Optica) Devic's disease is pathologically distinct from MS and appears to be a microvasculitis or vasculopathy, rather than a demyelinating disease. Clinically, it is characterized by acute episodes of optic neuritis (bilateral or rapidly sequential) and a subacute transverse myelitis, with no evidence of lesions outside the optic nerves or spinal cord. The brain MRI is normal, and spinal MRI usually shows elongated longitudinal spinal cords lesions (Figure 4.6) that are not typically seen in MS. CSF is usually negative for oligoclonal bands, and pleocytosis and an elevated protein level are not uncommon during an attack (Box 4.6). The optico-spinal form of MS commonly seen in Japan is probably the same disease. Recovery and prognosis is generally poor,

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