Stereotactic Surgical Treatment of Epilepsy

Abstract

In recent years, a considerable resurgence of interest in the surgical treatment of epilepsy has been evident. The reawakening of clinical and scientific interest in the surgical treatment of epilepsy has been attributable to several technical and scientific advances: improvement in the ability to image the brain, particularly with magnetic resonance and positron emission tomography; improved methods of electrophysiologic characterization of the sites of origin of seizures with closed-circuit television and scalp and intracerebral recordings; and microsurgical and stereotactic techniques for the safer surgical resection of brain lesions. In this issue of the Proceedings (pages 1053 to 1060), Cascino and colleagues provide evidence for the value of stereotactic imaging and stereotactic resection of a variety of cerebral lesions that caused seizures in a consecutive series of 30 patients (mean age, 25 years). Twenty years ago, patients with the conditions represented in this series would have been treated with anticonvulsant drugs, but no further therapeutic intervention would have been available. Many of these patients would eventually have been classified as having medically intractable seizures. The current ability to image small structural lesions of the brain, to remove them, and to have minimal associated morbidity, as demonstrated in the report by Cascino and associates, not only has brought new hope to patients with seizures but also has provided an invaluable opportunity to study the pathophysiologic features of epilepsy. The article by Cascino and colleagues addresses three important clinical issues in the assessment and treatment of patients with seizure disorders: the importance of identification of underlying structural pathologic changes whenever possible; the question of the efficacy of the resection of a structural lesion in stopping seizures; and the value of stereotactic techniques in performing the resection. Of the 30 patients studied by Cascino and colleagues, 20 had complex partial seizures and 13 had simple partial seizures. Secondary generalization of seizures occurred in 12 patients. (Of the 30 patients, 15 had multiple seizure types.) Most lesions were located in either the temporal lobe (10 patients) or the frontal lobe (9 patients). Glial tumors and vascular malformations predominated (11 cases each). Nine of the 11 patients with glial neoplasms and 10 of the 11 patients with vascular malformations had at least an 80% reduction in seizure activity after surgical resection. This result compares favorably with the efficacy of anterior temporal lobectomy for the control of complex partial seizures.1Engel Jr, J Outcome with respect to epileptic seizures.in: Engel Jr, J Surgical Treatment of the Epilepsies. Raven Press, New York1987: 553-571Google Scholar The operative morbidity was acceptably low because of the use of the stereotactic method developed by the authors, which allows computerized visualization of the trajectory to reach the lesion. Visualization of the trajectory enables the surgeon to avoid eloquent areas of the brain and important vascular structures. The most common pathologic lesion within the temporal lobe in patients who undergo a surgical procedure for the control of complex partial seizures is sclerosis of Amnion's horn (mesial temporal sclerosis)—which, as the authors indicate, cannot currently be reliably identified on imaging studies. Standard anterior temporal lobectomy has effectively produced a substantial decrease in seizures in about 80% of patients with sclerosis of Amnion's horn.1Engel Jr, J Outcome with respect to epileptic seizures.in: Engel Jr, J Surgical Treatment of the Epilepsies. Raven Press, New York1987: 553-571Google Scholar Several attempts have been made to treat complex partial seizures due to sclerosis of Amnion's horn with stereotactic surgical removal of mesial temporal structures. In patients with sclerosis of Amnion's horn, this procedure has had some success in controlling seizures, but the results have usually not been comparable to those achieved with a standard lobectomy.2Mundinger F Salomao F Gröbner E Indikationen stereotaktischer operationen und langzeitergebnisse bei konservativ therapieresistenter, insbesondere temporaler epilepsie.Arch Psychiatr Nervenkr. 1981; 231: 1-11Crossref PubMed Scopus (2) Google Scholar Most of the attempts at stereotactic surgical treatment of epilepsy, however, were made in the 1960s and 1970s, before the availability of magnetic resonance imaging of the brain. Magnetic resonance imaging-based stereotactic procedures, by providing greater accuracy to resect small portions of the mesial temporal circuitry, might produce therapeutic results equivalent to those of a standard anterior temporal lobectomy.3Kelly PJ Sharbrough FW Kall BA Goerss SJ Magnetic resonance imaging-based computer-assisted stereotactic resection of the hippocampus and amygdala in patients with temporal lobe epilepsy.Mayo Clin Proc. 1987; 62: 103-108Abstract Full Text Full Text PDF PubMed Scopus (38) Google Scholar