Late-life action tremor in a southern sea otter (enhydris lutris nereis).

Although tremor is highly prevalent in human beings, there are few reports of tremor occurring in other mammals. Such tremor can further our insight into the mechanisms and anatomical basis of human tremor disorders. We report on a southern sea otter with a slowly progressive 6.5 to 8.5 Hz action tremor of late life that shared several clinical characteristics with essential tremor. The main pathological finding was in the cerebellum, where there was extensive vacuolation of Purkinje cells.