Epilepsy remains one of the most common neurologic disorders affecting both adults and children alike. Millions of individuals in the country have a diagnosis of epilepsy, requiring treatment. Epilepsy is characterized as a seizure disorder with electro-physiologic abnormalities and is most often diagnosed by history and electroencephalography (EEG). In the majority of cases, it can be treated effectively medically with anti-epileptic drugs (AED) though approximately 10% of patients with chronic epilepsy are considered "medically intractable" meaning that they continueto have seizures despite maximal medical therapy including mono- and poly-therapy. It is in this group of patients that the seizures have the most significant impact on quality of life including psychosocial interactions, vocation and importantly driving. In these instances, it has been estimated that upwards of 10% to 15% of those patients with medically intractable epilepsy may have the potential for a surgical cure

"Medically intractable" patients by definition have failed at least two or more adequate trials of first and second line AED. Of those determined to be potential candidates for surgical intervention, an extensive evaluation including video/EEG telemetry, anatomical (MRI) and functional (positron emission tomography (PET) or (single photon emission computerized tomography (SPECT), imaging and extensive neuropsychological testing, with and without angiography or Amytal testing is performed. This initial, non-invasive/Phase I evaluation provides a comprehensive overview of the seizure syndrome. The patient's history, epileptic syndrome and complete data set are then reviewed by the members of the Epilepsy Program Team to determine the likely benefit of surgery.

Based on this review of the initial phase evaluation, a decision for proceeding directly to surgical intervention and either the type of surgical treatment or the need for further diagnostic studies, specifically, the need for invasive monitoring is decided. The majority of surgery patients require no further monitoring and go on directly to surgery. The type of surgery is based on the epileptic syndrome, imaging and electrophysiologic findings. When there is a lack of concordance of this initial evaluative data (e.g.) it is unclear as to the exact origins of the seizure focus, or there is concern of the proximity of the seizure focus to eloquent or functionally important areas of the brain, (e.g.) somatosensory cortex, speech, language, then it is recommended that the patient undergo invasive monitoring. Invasive monitoring requires the surgical implantation of EEG electrodes, either directly using stereotaxis in the parenchyma or on the surface of the brain in order to better lateralize and localize the seizure focus. By stimulating each of the contacts, one can determine the specific functional areas of speech and motor functions. Previously, the most common electrodes utilized were depth electrodes, which cross the parenchyma, and are most often used for temporal lobe epilepsy. With improvements in imaging and the diagnosis of temporal lobe epilepsy non-invasively, surface electrodes are now more commonly used due to their lower morbidity, broader range of evaluation capability, and ability for functional assessment through cortical stimulations.

Surgical intervention consists of either a resective and/or disconnected procedure. Resective procedures include the different types of lobectomy, (e.g.), temporal frontal, etc., topectomy (excision of a small area tailored to the seizure focus itself) or hemispherectomy (the "ultimate" focal resection with the removal of one-half of the brain). Resective procedures are more likely to result in a cure since they excise the seizure focus itself. Disconnective procedures include corpus callostomy and multiple pial transections and tend to be more palliative rather than curative since they do not eliminate the seizures but interrupt the propagation of the seizures, limiting their generalization. Despite that, these procedures can improve the patient's quality of life by decreasing the frequency and intensity of the seizures. One other type of surgical procedure available are the implantation of neural stimulators, more specifically, the vagal nerve stimulator (VNS).

Outcomes following surgery for the treatment of epilepsy have markedly improved over the last few decades. In a recently published article in the New England Journal of Medicine, 80 patients were randomized into a clinical trial for the efficacy and safety of surgery for temporal epilepsy, assigned to surgical treatment with temporal lobectomy or medical treatment with AED over one years time. At completion of the study, the cumulative proportion of the patients who were free of seizures was higher in the surgical group as compared to those in the medical group. Those that had surgery had a marked improvement with fewer seizures and a significantly better quality of life. The mortality was higher in the medical group since no patients died from surgery and one

patient died from his seizures in the medical group. For patients with temporal lobe epilepsy, surgery was deemed superior to prolonged medical therapy. For the disconnective procedures, a seizure free state is much less likely. A corpus callostomy, when indicated for drop attacks, can eliminate the atonic seizures, although it will have less of an impact on those patients that have multiple other seizure types such as generalized tonic-clonic and complex partial seizures. Multiple subpial transections are often used in conjunction with resective surgery for the areas of the brain where resection would cause significant neurologic injury (e.g.) speech and language or somatosensory areas. This technique though also been reported to have a marked impact on seizure frequency and intensity with good localization of the seizure focus.

The data for this remains incompletely defined and will likely continue to increase with better understanding.The future of surgical epilepsy is likely to continue to grow since the majority of patients who are potential surgical candidates have not been evaluated and treated. With improved awareness of the benefits of surgery, improvements in neuroimaging to identify lesional or abnormal areas, and improved technologies for intervention, it is likely that surgery will be the Options of choice for those patients who suffer and are affected by this disease. On the horizon and presently intense areas of research are the use of deep brain stimulation (DBS), gene transfer and cellular transplantation so as to modify or eliminate the seizure focus.

Another very promising technology in this area is the use of gamma knife radiosurgery (GKR).  This therapy has been trialed in Europe and elsewhere and, preliminarily, has been found to have similar seizure free outcomes as surgical resection of the temporal lobe focus in patients with temporal lobe epilepsy. In the future, there is the potential that GKR could actually replace the open surgery through this minimally invasive approach.
With improved awareness, and with improvements in the technology, surgery for epilepsy has become more established and readily identified as the optimal therapy for many forms of intractable seizures.