Post-encephalitic tremor and delayed-onset parkinsonism

Movement disorders of various types may occur in relation to viral infections of the central nervous system. They manifest themselves as obvious signs at clinical onset or during the acute phase of an encephalitis (myoclonus, tremor, or parkinsonism), or appear as later sequelae decades after the illness. We describe here a man who developed an unusual movement disorder after a probable viral encephalitis in his childhood. This consisted of a tremor (3-4Hz frequency and 100-150ms duration) of the neck, left shoulder and arm, which persisted unchanged during the ensuing years. The patient regarded this abnormal movement as annoying, but otherwise it did not impair his lifestyle. He subsequently developed the clinical picture of parkinsonism many decades after the onset of tremor, and we speculate that both tremor and parkinsonism can be considered sequelae of encephalitis, but each with a different time-course. The left-sided jerky tremor was an immediate sequela in the childhood; whereas, the rigid-akinetic parkinsonian picture represented a later sequela of the infection in old age. The injured site responsible for both the segmental tremor and the parkinsonism presumably involved the brainstem.