Walsh & Hoyt: Paraneoplastic Encephalomyelitis

Henson et al. first used the term encephalomyelitis with carcinoma to describe the development of progressive clinical manifestations that implicated injury to multiple levels of the nervous system in a group of patients with various malignanciesmost often small-cell lung cancer. Paraneoplastic encephalomyelitis (PEM) is characterized clinically and pathologically by patchy, multifocal involvement of any or all areas of the cerebral hemispheres, limbic system, cerebellum, brain stem, spinal cord, dorsal root ganglia, and autonomic ganglia. Neuronal loss is accompanied by mononuclear cell infiltration. In most patients with PEM, the neurologic syndrome frequently precedes the discovery of the neoplasm by several months. The most common clinical manifestation of PEM is subacute sensory neuropathy reflecting involvement of dorsal root ganglia. Early symptoms are patchy or asymmetric numbness and paresthesias, often involving the face, trunk, or proximal limbs. The symptoms eventually spread to all limbs. Patients can have difficulty walking because of pain and loss of proprioception. PEM is not as much a single disease as it is a group of disorders that share a common histopathologic appearance despite differing from each other in clinical manifestations and anatomic sites. The major disorders included under this heading are cerebral (including limbic) encephalitis, brainstem encephalitis, cerebellar encephalitis, and subacute myelitis.