Neuropsychological change following gamma knife surgery in patients with left temporal lobe epilepsy: a review of three cases Carrie R. McDonald a, * , Marc A. Norman a , Evelyn Tecoma b , John Alksne c , Vicente Iragui b a Department of Psychiatry, University of California, San Diego, CA, USA b Department of Neurosciences, University of California, San Diego, CA, USA c Department of Neurosurgery, University of California, San Diego, CA, USA Received 24 July 2004; revised 18 August 2004; accepted 21 August 2004 Abstract 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. Ó 2004 Elsevier Inc. All rights reserved. Keywords: Gamma knife surgery; Temporal lobe epilepsy; Neuropsychological outcome; Cognitive change 1. Introduction Anterior temporal lobectomy (ATL) remains the gold standard surgical treatment for patients with temporal lobe epilepsy (TLE), eliminating seizures in approxi- mately 70% of patients who are refractory to anticonvul- sant medications [1,2]. ATLs, however, may cause neurologic and/or neuropsychological deficits that de- pend on the side and extent of the resection [3]. In par- ticular, there is a large body of literature suggesting that patients who receive language-dominant hemisphere ATLs for treatment of their seizures suffer impairments in the acquisition and retention of verbal information [4–6]. Comparable memory deficits for complex, nonver- bal material after nondominant hemisphere temporal resections have been reported less consistently, although they exist in a small percentage of patients [7]. Postoper- ative deficits in naming and other language skills have also been reported following dominant hemisphere tem- poral lobectomies [8,9] and appear more profound for those with no early risk factor for seizure onset [10] or more extensive lateral temporal resections [11]. Recently, gamma knife surgery (GKS), a form of radiosurgery, has been used to treat TLE as an alterna- tive to surgical resection [12,13]. GKS is a noninvasive treatment in which collimated gamma rays create small, precise lesions in targeted structures without significant radiation damage to surrounding structures [13]. GKS has been used to treat a variety of neurological 1525-5050/$ - see front matter Ó 2004 Elsevier Inc. All rights reserved. doi:10.1016/j.yebeh.2004.08.014 * Corresponding author. Present address: UCSD Epilepsy Center, 9300 Campus Point Drive, La Jolla, CA 92037-7740, USA. Fax: +1 858 642 6237. E-mail address: camcdonald@ucsd.edu (C.R. McDonald). www.elsevier.com/locate/yebeh Epilepsy & Behavior 5 (2004) 949–957