Myelitis and peripheral neuropathy complicate many infections. The following discussion covers the major infectious etiologies of myelitis (Table 78.1), peripheral neuropathy (Table 78.2), polymorphic syndromes (Table 78.3), which typically involve the central and peripheral nervous system as well as the spinal cord, and neuropathic syndromes seen in human immunodeficiency virus (HIV) infection (Table 78.4). In addition, an algorithm (Figure 78.1) suggests an approach to the clinical and laboratory diagnosis of myelitis and peripheral neuropathy.

MYELITIS

Myelitis is an infectious or noninfectious inflammation of the spinal cord. It may be divided into processes that directly attack cord structures, primary myelitis, and those which begin in adjacent structures but progress to alter cord function, secondary myelitis. Primary myelitis can present as one of three discrete clinical patterns: (1) anterior poliomyelitis, (2) leukomyelitis, or (3) transverse myelitis. Poliomyelitis is inflammation involving the gray matter; leukomyelitis is confined to the white matter. Transverse myelitis, inflammation of an entire cross section of the spinal cord, can affect more than one spinal segment. A number of infectious agents are known to cause or to be associated with myelitis. Myelitis can also occur after an infection or a vaccination as in the acute disseminated encephalomyelitis syndrome seen in children.