Biopsy and post-mortem findings in a patient receiving cerebellar stimulation for epilepsy.

Cerebellar stimulating equipment was implanted in a 24-year-old male with severe epilepsy. He received continuous alternating stimulation for at least two months, intermittent bilateral stimulation on demand for at least two months and numerous short bursts of stimulation during preliminary testing and calibration of the apparatus. The patient died during a prolonged grand mal seizure 16 months after implantation and this paper reports the findings at necropsy. A special study was made of the degree of tissue damage in the cerebellar hemispheres resulting from implantation of the electrodes and subsequent cerebellar stimulation. There was deep grooving of the upper aspect of the cerebellum under the electrodes but only a minor degree of neuronal loss and gliosis was observed in the underlying cortex. Purkinje cell populations in the cerebellum at necropsy were similar to those in a biopsy specimen taken 16 months previously during implantation. The electrodes were covered with a thick layer of fibrous tissue but they were not adherent to the cerebellar surface. Thus, the main significant findings in the present case were the very slight structural damage to the cerebellum in contact with the electrodes and the intense fibrosis around the electrodes themselves. These features are discussed in relation to the efficacy of long-term cerebellar stimulation.