Abstracts

RATIONALE: Radiosurgery delivers focused radiation using stereotaxic guidance to targets within the brain. Prior studies have documented seizure reductions when vascular malformations and hypothalamic hamartomas have been treated with radiotherapy. A multicenter European trial of radiosurgery to treat temporal lobe epilepsy has demonstrated potential clinical utility. A NIH sponsored U.S. multicenter clinical trial utilizing gamma knife treatment of medically refractory medial temporal lobe epilepsy (mTLE) was started in October 2000 and the studies progress is reported here. The purpose of the study was to determine whether gamma knife radiosurgery is effective in reducing or eliminating seizures in mTLE.
METHODS: Patients with very well defined mTLE with evidence of mesial temporal sclerosis on MRI, who were otherwise excellent candidates for seizure surgery, were offered the alternative of treatment with focused radiation. After informed consent was obtained, the patients were screened and then randomized to treatment with either 20 or 24 Gy directed to the medial temporal lobe (treatment volume 5.5-7.5cc), with appropriate shielding to protect the brainstem ([lt] 10 Gy) and optic nerve ([lt]8 Gy). The patients were then followed with serial assessments including seizure counts, neurologic exams, neuropsychological testing, and neuroimaging.
RESULTS: To date 10 patients (6 right, 4 left; 7 females, 3 males) have been treated at 4 centers with the longest follow up 18 months (median 14 months). Although none are completely seizure free to date, 4 of the patients have experienced greater than 80% reductions in complex partial seizures. After a latent period of 9-15 months the patients typically reported headaches, followed by a dramatic increase in auras and then a decrease in complex partial seizures. MRIs performed when the patients were symptomatic demonstrated dramatic cerebral edema including shift of midline structures and 3 patients have required steroids to ameliorate their symptoms. One patient developed chronic papilledema, refractory to decadron and, at 14 months post radiosurgery, underwent a temporal lobectomy with resolution of symptoms.
CONCLUSIONS: A NIH sponsored, multicentered feasibility study of the use of radiotherapy to treat refractory epilepsy is underway with the preliminary findings demonstrating significant reductions in seizure frequency and severity. A single significant adverse event has been reported. The clinical features and neuroimaging results will be presented. At the end of this presentation the audience will be updated on this new treatment modality and on the role radiotherapy will potentially play in the future treatment of refractory epilepsy.
[Supported by: NIH and Elekta Corporation.]; (Disclosure: Grant - Grant support from Elekta Corporation)