Parkinsonism due to predominant involvement of substantia nigra in Japanese encephalitis.

OBJECTIVE: To study the clinical correlates of lesions seen predominantly in the substantia nigra in some patients with Japanese encephalitis (JE).
BACKGROUND: JE typically involves thalamus, brainstem, spinal cord, and cerebral cortex. Rarely, basal ganglia and cerebellum may be affected. Lesions are often widespread and discrete. Predominant involvement of substantia nigra in JE has not been previously reported.
METHODS: Of 52 patients with JE seen in an endemic zone, five were selected on the basis of isolated lesions in the substantia nigra on MRI; all were subjected to detailed clinical and laboratory evaluation.
RESULTS: Presenting symptoms were fever, alteration of consciousness, neck stiffness, and decreased body movements. Examination during acute illness revealed restricted eye movements, opsoclonus, upbeating nystagmus, and cogwheel rigidity. There was early and complete recovery of consciousness and eye signs. Parkinsonian features such as positive glabellar tap sign, masklike face, bradykinesia, tremors, and postural instability became apparent as these patients started walking. Reversible mutism was observed in three patients during the acute phase. Response to levodopa, amantadine, and trihexiphenedyl was partial. Three patients were followed for more than 1 year, during which time their parkinsonian features recovered completely. Substantial recovery was also observed in the two other patients 2 months after regaining consciousness.
CONCLUSIONS: Some patients with Japanese encephalitis may have lesions predominantly in the substantia nigra. After recovery from acute encephalitic illness, they manifest clinically with typical parkinsonian features. Although several viruses are known to cause parkinsonism, this is the first demonstration of a virus producing lesions predominantly in the substantia nigra and causing parkinsonism.