Neuropsychological change following gamma knife surgery in patients with left temporal lobe epilepsy: a review of three cases.

Gamma knife surgery (GKS) is a radiation procedure recently used in the treatment of temporal lobe epilepsy (TLE). Preliminary studies have shown significant seizure reductions in patients 8-26 months postprocedure; however, little is known about the effect of GKS on cognitive functioning in TLE. We report neuropsychological data on three patients with left TLE and MRI evidence of hippocampal sclerosis who underwent GKS. Two models for assessing cognitive change, reliable change indices and regression-based norms for change, were used to measure preoperative versus 13- to 27-month postoperative cognitive change. Results revealed a significantly long delayed verbal memory decline on one measure following GKS. No patient declined on measures of IQ, visual memory, or language. Radiation-induced edema was present at the time of testing in all three patients, which may have affected verbal memory performance. While preliminary, these data suggest that GKS offers a less invasive option to anterior temporal lobectomy, but may produce neuropsychological changes similar to those produced by left anterior temperol lobectomy up to 2 years post-GKS treatment.