When a seizure disorder persists despite optimum drug therapy and significantly affects quality of life, surgical treatment should be considered. Many patients with severe refractory epilepsy can benefit from appropriate surgery and should be given this option by timely referral and investigation. Extrapolating US studies,1 there are probably several thousand eligible people in Australia. In the past, operations were confined to removal of obvious structural causes of seizure, such as tumours or post-traumatic scars. Over the past 50 years, it has become increasingly apparent that there are many patients with persisting epilepsy who could benefit from surgical resection of foci previously difficult to define. The development of increasingly precise methods of anatomical and functional seizure localisation has expanded this group.

The evidence for effectiveness of surgery for epilepsy can be seen by outcome studies comparing patients who have had surgery with patients who have had long-term medical therapy. An important recent Canadian study2 of 80 patients refractory to at least two anticonvulsants who were randomly assigned to either undergo temporal lobe surgery or receive further drug treatment showed clear statistical evidence of the success of surgery. At one year, 58% of patients in the surgical group and 8% in the medical group were free of seizures. It should be noted that four patients had adverse effects of surgery, including one small thalamic infarct, one wound infection, and reduced verbal memory in two cases. One patient in the medical group died.

Not all patients with refractory epilepsy can be treated surgically. A prerequisite for successful surgery for epilepsy is the precise definition of a discrete seizure focus involving an area of cortex amenable to safe excision. Psychiatric and social factors must also be taken into account. The sequence of events leading to surgery will usually include a period of video electroencephalography (EEG) to define and localise the seizure syndrome, magnetic resonance imaging (MRI), and localisation of eloquent cortex (ie, functional [speech or motor] cortex) by neuropsychological or functional testing. Intraictal single-photon emission computed tomography (SPECT) scanning of regional blood-flow changes is an extremely useful tool for confirmation of a seizure focus. Where available, positron emission tomography is helpful to correlate abnormal glucose metabolism with areas of anatomical abnormality.

Anterior temporal lobectomy with hippocampectomy is the most commonly performed surgical procedure for treating epilepsy (see Box). This is because the procedure has a high rate of cure or significant reduction of seizures in patients with complex partial seizures due to hippocampal sclerosis, the largest group of suitable patients. The long-term result of this operation, performed on appropriately selected patients, is that about 70% of patients will become seizure-free.3 Resection of areas of cortical dysplasia has been performed more frequently in recent years, as this condition can now usually be defined with MRI. Where cortical dysplasia occurs close to motor or language areas of the cortex, surgery is often performed under local anaesthesia so that motor function or speech can be monitored by cortical stimulation, reducing the risks of postoperative paresis or dysphasia. In addition, electrocorticography (EEG recorded directly from the cortex), performed either acutely, during surgery, or electively, after placement of subdural electrodes, can further define the boundary between functional and non-functional cortex. Image-guided surgery linked to MRI has enhanced the accuracy and safety of cortical excision.

Hemispherectomy is the most successful form of excisional surgery. This major procedure is occasionally indicated for young patients with developmental or acquired affections of one hemisphere leading to catastrophic and continued seizure patterns, although it constitutes a high-risk procedure. Many of these patients make a good recovery once their seizures are eliminated.

Corpus callostomy or vagotomy are palliative procedures that may benefit some patients with severe generalised seizure patterns. The former may also be helpful (although rarely curative) in some patients with atonic seizures or drop attacks. Chronic stimulation of the left vagal nerve via a subcutaneous stimulator linked to electrodes placed in the cervical region is a low-risk, albeit expensive, procedure that reduces seizure frequency in about 50% of patients with otherwise untreatable severe epilepsy.

A small group of patients with hypothalamic hamartomas leading to the syndrome of gelastic ("laughing") epilepsy may now be treated successfully surgically using an image-guided technique via the third ventricle.4

Postoperatively, adequate support systems are extremely important. Most patients will require ongoing anticonvulsant treatment for two or more years. Mortality and major morbidity after surgery for epilepsy are nowadays low: mortality is less than 0.5% and hemiparesis and hemianopia occur in less than 2% of cases.5 Devastating memory disorders following temporal lobectomy can be avoided by appropriate patient selection and preoperative neuropsychological testing. For example, verbal memory deficits suggesting a left or dominant hippocampal lesion would contraindicate a right hippocampal resection.

Considering the poor long-term prognosis for patients with refractory seizures, appropriate surgery has unequivocal advantages. In addition to the social and psychological benefits to the individual, cost–benefit analysis has demonstrated the advantages of surgical treatment compared with life-long medical management.6

The requirements for input from various specialists and the need for particular investigative techniques means that such patients should be assessed in Comprehensive Epilepsy Centres. Some notable contributions to the development of surgery for epilepsy have come from Australia and New Zealand.7-9 There are many more Australians who could benefit from surgical treatment, and this option should be considered by those caring for patients whose seizures continue to be disabling despite best medical treatment.