Abstracts

We reviewed the long-term outcome of focal resective surgery in a large consecutive group of patients with intractable partial epilepsy from a single institution to evaluate the durability of epilepsy surgery and preoperative factors associated with improved seizure outcomes. This retrospective analysis included 491 consecutive patients who underwent epilepsy surgery at Mayo Clinic (Rochester, MN) between 1988 and 1998. The average age at surgery and seizure onset was 32 years (range, 3-69 years) and 13 years (range, 0-65 years), respectively. The mean duration of follow-up was 6.1 years (range, 5-14 years). Preoperative evaluation included a routine and video encephalogram (EEG) recordings, MRI head seizure protocol, neuropsychological testing, and sodium amobarbital study. Patients with undefined epiletogenic focus underwent an intracranial study. Cox regression analysis models were used to evaluate the risk factors associated with outcomes. Among these patients, 435 (89%) had temporal and 54 (11%) had extratemporal epilepsy. Histopathological examination of the resected specimen most commonly revealed gliosis in 222 (45%) patients, mesial temporal lobe sclerosis in 116 (24%), neoplasm in 36(7%), normal histopathology in 48 (10%) and other including developmental pathologies and vascular malformations in 32 (10%). Overall, 356 of 491 (73%) patients had an Engel Class I outcome (seizure-free, auras, or seizures only related to medication withdrawal). Almost all seizures occurred in the first year following surgery. Patients with medial temporal lobe sclerosis who were seizure free at one year remained seizure free at their last follow-up. Factors predictive of poor outcome from surgery were normal tissue pathology (p = 0.028), male gender (p = 0.03), previous surgery, and an extratemporal origin of seizures (p [lt] 0.001). The factor associated with an improved outcome was temporal origin of seizures (p [lt] 0.001). Status epilepticus was the cause of death in 13 patients during the follow-up. Epilepsy surgery offers a safe and effective long-term treatment for patients with intractable localization-related epilepsy. The response to surgery during the first follow-up year is a reliable indicator of the long-term operative outcome.