SAN DIEGO — Gamma knife radiosurgery may be a viable alternative to standard open surgery for patients with mesial temporal lobe epilepsy, preliminary results from a multicenter study suggest.
“Anterior temporal lobectomy is the gold standard for the treatment of mesial temporal lobe epilepsy, so why consider an alternative therapy such as gamma knife radiosurgery?” Dr. Mark Quigg asked at the annual meetings of the American Epilepsy Society and the Canadian League Against Epilepsy. “Well, nothing's perfect. There's a small but significant morbidity with open surgery. Traditional surgery with its obligate ICU time and inpatient stay costs money. Many patients and some referring physicians have an unrealistic look as to what epilepsy surgery entails.”
In a 3-year multicenter study, Dr. Quigg and his associates performed gamma knife radiosurgery on 30 patients with mesial temporal lobe epilepsy. The treatment target was the temporal portion of the amygdala, the anterior 2 cm of the hippocampal gyrus, and the adjacent parahippocampal gyrus. Of the 30 patients, 17 were randomized to 20 Gy (low dose) and 13 were randomized to 24 Gy (high dose), comprising 5.0–7.5 mL at the 50% isodose volume.
The mean age of patients was 34 years and more than half (18) were female, said Dr. Quigg of the department of neurology at the University of Virginia, Charlottesville. After surgery, patients were followed for 18 months at 3-month intervals. They also were evaluated again at 24 months and 36 months.
Patients were considered seizure free if no seizures (excluding auras) occurred between the 18− and 24-month visits. At the meeting, Dr. Quigg limited his data presentation to outcomes at 24 months.
Dr. Quigg reported that overall, 67% of patients who underwent gamma knife surgery were seizure free at 24 months. A greater proportion of those who underwent high-dose gamma knife surgery were seizure free, compared with those who underwent low-dose surgery (85% vs. 56%, respectively), but the differences were not statistically significant because of the small sample size. By 24 months, one patient was lost to follow-up and another patient experienced papilledema that responded partially to dexamethasone and underwent anterior temporal lobectomy. Some patients required the supplementary use of antiepileptic drugs for auras and almost half required steroids for edema/headaches.
“The strength of the study is that the actual Gy of surgical target is very uniform amongst all of the centers,” Dr. Quigg commented.
“The rates of seizure remission are comparable to what's published for anterior lobectomy. The safety profile of these patients is within bounds of standard open surgery. It's going to take more time and perhaps a prospective comparison to sort out the relative merits of one procedure over another,” he said.
The study was supported by the National Institutes of Health and Elekta AB, maker of the Leksell Gamma Knife.
Participating sites included the University of Virginia; Columbia University, New York; Indiana University, Indianapolis; the State University of New York, Syracuse; the University of California, San Francisco; the University of Pittsburgh; the University of Southern California, Los Angeles; and the University of Washington, Seattle.