Radiosurgery or Open Surgery for Epilepsy Trial

Inclusion and Exclusion Criteria: Adults (18 years and older) of either gender who would otherwise be eligible for temporal lobe resection will be offered enrollment for randomization to RS or ATL. 1. Seizure type: Patients must have simple and/or complex partial seizures with or without secondary generalization. 2. Seizure Frequency: Patients must have at least 3 complex partial seizures during the 3 month (12 week) baseline seizure diary period with at least 1 of 3 seizures occurring within the last 2 months (8 weeks). 3. Patients with electrographic evidence of seizures arising from one temporal lobe, with radiographic evidence of mesial temporal sclerosis in the same temporal lobe will be included. Patients with normal MRIs, bilateral hippocampal damage, or cortical lesion will be excluded. 4. Subjects should be on stable doses of antiepileptic medications for at least 3 months prior to treatment. 5. All female patients of childbearing age will have documented that they are using a safe and effective means of birth control and will have a negative urine pregnancy test completed within 1 week prior to their treatment. 6. Patients should be able to understand the potential benefits and risks of this therapy and be able to understand the protocol and sign their own consent forms. For these reasons, only patients 18 years and older and with I.Q. greater than or equal to 70 will be included. 7. Patients with any focal neurologic deficit that would make it difficult to detect a new radiation-associated injury will be excluded. All patients will receive formal visual field testing (Humphrey) and patients with visual field deficits will be excluded. 8. Patients with radiographic evidence of other pathologies such as vascular malformations or tumors will be excluded. 9. Patients with diabetes mellitus or hypertension will be excluded from this study because radiation injury to the brain is more common in these patients. 10. Subjects should not have significant psychiatric conditions that would make accurate assessment of seizure frequency difficult, as judged by the principal investigator. Such conditions include a history of non-epileptic seizures, psychosis (other than post-ictal psychosis) and severe mood disorders including suicide attempt within past 12 months or noncompliance with psychotropic medications. 11. Patients with a history of significant past or present medical disorders determined severe enough to prevent participation in a surgical trial by the principal investigator are excluded. 12. Patients with any progressive neurological disorder (such as multiple sclerosis or systemic lupus erythematosis) are excluded. 13. Patients with a history of poor compliance with past antiepileptic drug therapy as judged by the principal investigator are excluded. 14. Patients with a recent history of abusing drugs or alcohol with significance as judged by the principal investigator are excluded. 15. Patients who are receiving any investigational drugs at the time of enrollment are excluded. 16. Patients with current use of vigabatrin are excluded. Past use does not exclude a patient pending a normal formal visual field test. 17. Patients with currently functioning vagal nerve stimulators (VNS) are excluded. Past use does not exclude a patient as long as the device is explanted. Indwelling VNS electrodes are permitted in agreement with each center's policies on brain MRI imaging. 18. Patients who can not be anticipated to participate for the full 36 months of the trial will be excluded. 19. Native English speakers from the U.S. or other English speaking countries or patients who learned English before age 5 and were educated in English. Spanish speaking patients can be included as long as the study site can provide an officially translated (IRB approved) consent form in Spanish. Non-Spanish speaking patients with English as a second language (ESL) and/or non-English and non-Spanish speaking patients can be included only under the following conditions: 1) the study site must be able to have the consent form translated into the patient's native language using an official translator, and 2) the study site's neuropsychologist must be willing and able to assess the patient at baseline and post-treatment at 12, 24, and 36 months in that patient's native language to ensure the patient's safety.