The possibility of surgery should be considered in any patient whose epilepsy is not controlled by medication. Many patients whose epilepsy could be successfully treated are not referred for surgery. This under-referral is due not only to the ignorance of neurologists and paediatricians. There is a widespread feeling that such surgery is complex, daunting for the patients, and that the results are uncertain. However, modern imaging techniques have made recognizing epileptogenic but normal cortex or ‘spike chasing’ a thing of the past. Good results depend on finding and removing focal pathology; a surgical scar is not usually epileptogenic.

Patients suitable for consideration of epileptic surgery include those resistant to drug therapy, and those with a consistent type of epileptic pattern. If a seizure always follows a constant type of warning aura, the clinician should seriously consider referring the patient for specialist evaluation. Constancy of the initial phase of the seizure is suggestive of a focal origin to the seizure. Surgical treatment is also indicated if a lesion is found on imaging. Most surgery for drug resistant epilepsy is performed on the temporal lobe. Scanning in the line of the temporal horn discloses lesions not seen with conventional scans that cut through the temporal lobe. Thus ‘temporal orientated’ CT scanning is an important investigation. MRI may also reveal small epileptogenic lesions, and is being increasingly used for evaluating patients for epileptic surgery. Electroencephalography (EEG) also has a place in the investigation of patients, particularly when no lesion is seen on imaging. Specialized techniques using implanted electrodes are, however, of debatable value. They are probably applicable to only a small percentage of patients, in whom the results of surgery are less certain.

The results of surgery are best in young patients treated before schooling has ceased. Teenagers with epilepsy can become recluses; surgery renders approximately 60 to 70 per cent of patients seizure free, and allows social and scholastic rehabilitation.

Four types of procedure are carried out: temporal lobectomy (70 per cent); extratemporal cortical excisions (25 per cent); hemispherectomy (2 per cent); and callosotomy (3 per cent). Seizures arising from the temporal lobe are due either to a small indolent glioma (Fig. 3) 2291 or sclerosis of Ammon's horn. The latter is thought to arise following a prolonged (more than 30 min) febrile convulsion in a young child (up to 4 years of age). Prompt treatment of febrile convulsions is therefore important. Sclerosis of the amygdala and hippocampus (Ammon's horn) gives rise to pyschomotor or remporal lobe epilepsy several years later (about the age of 6 or 7). The amgdala and hippocampus seem to be particularly involved with the genesis of epilepsy, and excision of these structures together with any pathological areas seems to produce better seizure relief. More recently amygdalohippocampectomy has been introduced. This entails removing the structures without removing the remaining temporal lobe neocortex. Extratemporal cortical excisions must be performed under electrocorticographic guidance.

Hemispherectomy has been described as the best operation for epilepsy and is indicated for children with infantile hemiplegia epilepsy. Long-term bleeding complications curtailed its use, but the procedure has been modified and is now being performed more often.

The indications for sectioning of the corpus callosum are much less certain. This procedure, although fashionable, will probably not survive the test of time, in common with other operations for epilepsy which do not entail finding and removing focal pathology.