Cerebellar degeneration following long-term phenytoin therapy.

Diffuse loss of cerebellar Purkinje cells and to some extent, of granule cells occurred in a 78-year-old woman who had been continually treated with phenytoin for more than 20 years and in whom progressive cerebellar deficits developed in the later years of life. In the absence of other demonstrable cause, the selective morphologic changes in the cerebellum are attributed to long-term administration of phenytoin.