Patients with epilepsy for whom medical management has failed, may be candidates for surgical treatment. Zimmerman and Sirven review the role of surgery in the treatment of seizure disorders. The persistence of seizures after three trials of different antiepileptic drugs has been used to define medically intractable seizures. However, no consensus definition exists, and some studies indicate that refractory patients might be identified earlier.
The presence of epilepsy should be confirmed and the seizure type defined, because some disorders are not amenable to surgical correction. Patients are evaluated based on the seizure type and frequency, the amount and type of medical therapy, and the psychologic and social factors affected by epilepsy. Other considerations include seizures resulting in impaired consciousness, injury, abnormal behaviors, or unpleasant auras. Patients with frequent (at least once every one to two months) or unpredictable seizures also are potential candidates.
Antiepileptic medications do not completely control seizures in 30 to 40 percent of patients. Other reasons besides true intractability include pseudoseizures, inappropriate medications, medication noncompliance, or unreliable history. Newer agents and devices have not yet proved to be effective when conventional drugs have failed. Combination therapy often is tried before surgery, although it also has not proved to induce remission when single agents have failed.
Surgery is most commonly performed for mesial temporal lobe epilepsy, frontal lobe epilepsy, and epilepsy secondary to a lesion. Techniques may include resection of lobe sections (e.g., anterior temporal lobectomy) or lesions caused by tumors, vascular malformations, or encephalomalacia. Focal tailored resection or awake craniotomy also are options. Corpus callosotomy is sometimes used when the focus is in functional brain tissue or if seizures are nonfocal. However, this technique is typically only palliative.
Successful epilepsy surgery has led to improved quality of life and decreased mortality rates. Outcomes vary depending on the type of procedure performed and the type of epilepsy being treated. Accordingly, overall rates of seizure cure run as high as 70 percent and as low as 40 percent. Complication rates depend on the surgical team. Patients should be informed about the success rate and complications before proceeding with surgery.