SUMMARY Twelve patients with severe intractable epilepsy were treated by chronic cerebellar stimulation under double-blind conditions for six months. No reduction in seizure frequency occurred that could be attributed to stimulation, though eleven of the patients considered that the trial had helped them. One patient experienced fewer episodes of incontinence during stimulation. Cerebellar stimulation in its present form cannot be recommended for the treatment of severe intractable epilepsy.Therapeutic effects of cerebellar stimulation in severe epilepsy were first reported by Cooper.' A later report summarised the outcome in a total of 32 patients.2 Seizure frequency fell to half or less of the pre-operative rate in 18 patients and nine were regarded as therapeutic failures. One died at operation and four others died subsequently in their sleep. Two of these had not responded to stimulation, one had been free of grand mal and petit mal attacks for the six week period between implantation and death and the response of the fourth was not described. Treatment was uncontrolled and assessment open.Several other reports3-6 have since appeared which have supported the concept that cerebellar stimulation improves epilepsy, although the effect was less pronounced than in Cooper's series. Only one double-blind study7 has been performed. This involved five patients, of whom three, on the criteria recommended by Cooper et al,8 might not have been expected to respond favourably.Severe epilepsy has an appreciable morbidity. Mortality is also increased, especially in young adult males. Lennox9 quotes an overall death rate of 11-4 in the age group 25-45 compared with a rate of 3-1 in the general population. Therefore it is extremely important to establish whether or not this treatment should be recommended for occasional cases of severe intractable epilepsy. The present uncertainty

equipment was accurately calibrated. The functioning of the stimulating equipment was regularly reviewed and reasonable estimates of the charge density at the cerebellar surface and the total charge delivered to the cerebellum are therefore available. Case historyThe patient, (SB, born 8/1/55), was 24 years old at the time of his admission to the Southampton cerebellar stimulation trial. His epilepsy began at the age of seven years and there were no predisposing factors. He suffered from grand mal epilepsy, complex partial epilepsy and petit mal epilepsy. The grand mal attacks occurred rarely, but could be severe and prolonged. Complex partial attacks occuffed up to five times a day and the petit mal attacks up to forty or more in a day. Medication consisted of phenytoin 200 mg twice daily and carbamazepine 200 mg four times a day and he had been on this combination for over six months before admission. It was considered the best combination and the optimal dosage and gave serum levels of phenytoin 1-3 mg/100 ml and carbamazepine 0-7 mg/100 ml. Previously he had, at different times, been treated with these drugs in different dosages and with primidone.At operation on 20 March 1979 under general anaesthesia, two eight-button electrode pads with an electrode surface area 32 mm2 (Avery Laboratories Inc) were placed

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SUMMARY The increasing use of electrical stimulation of the brain for relief of pain, spasticity and epilepsy has introduced unfamiliar techniques into clinical neurological and neurosurgical practice. In view of the evidence that excessive levels of stimulation can damage brain tissue, it is of great importance to monitor the dose of stimulation. A review of recent clinical papers suggests that many centres do not measure the dose accurately, relying on arbitrary dial settings on external transmitters. This paper reviews the factors that affect the dose received by the patient and suggests methods of measuring them, at operation and subsequently, which should routinely be employed by clinicans implanting stimulators.In the past six years electrical stimulation has been applied to the cerebellum, periaqueductal grey matter, cerebral cortex and basal ganglia in Stimulating electrode order to treat a variety of clinical disorders. The charge transferred per second is much higher than for cardiac pacing and therefore nearly all the Z implanted stimulators to date have required an external energy source. This is provided by a Lead connecting electrode battery-powered pocket radiofrequency (RF) to receiver transmitter that transmits high-energy RF pulses ,, through the skin to an RF receiver implanted in the patient (fig 1)

A 17-year-old girl with Lafora body disease received short-term cerebellar stimulation but her epilepsy failed to improve and no changes were detected in her EEG. Neither visual nor somatosensory evoked potentials were changed by short bursts of cerebellar stimulation.