Abstracts

Risk for language impairment is a major consideration in the presurgical evaluation for medically intractable epilepsy. The Wada test has traditionally been utilized to establish language lateralization. Some epilepsy surgery centers, however, forgo Wada testing of right-handed patients being considered for right temporal lobectomy, presumably due to risks associated with the Wada procedure. While the assumption of left-hemisphere language dominance is accurate for most right-handed individuals, review of Wada and fMRI studies suggest a substantial proportion have unexpected right hemisphere language representation and possibly right hemisphere language dominance. The goal of this study was to determine the frequency of right-hemisphere language representation and dominance in right-handed epilepsy patients., Our center performs Wada tests on all patients being considered for epilepsy surgery and 120 completed bilateral testing between 2002 and early 2006. A modified version of the Loring (1992) Wada protocol was used to assess language, including measures of counting, command following, comprehension, naming, repetition, reading, and paraphasic errors. The number of correct items was divided by the total number of items administered to generate a percentage correct for each hemisphere (range 0-100). The right percentage score was then subtracted from the left percentage score to produce a lateralization index (+100 to -100), where positive scores indicate left language dominance and negative scores indicate right language dominance., Of the 120 patients included in this study, 96 described themselves as right-handed, 20 as left-handed, and 4 as ambidextrous or mixed dominant. Evidence of right hemisphere language representation was found in 46 of 96 right-handed patients (score range 3% to 100%), with 15 scoring more than 20% correct and 6 scoring more than 40% correct. Language lateralized to the right hemisphere in 7 right-handed patients (lateralization index score range -7 to -94)., While handedness predicts left hemisphere language lateralization in most right-handed individuals, a significant proportion may demonstrate right hemisphere language representation. These individuals may be at increased risk for language morbidity, possibly greater than the low incidence of complications from Wada testing. Further research is needed to quantify the relative risk for functional language change following right temporal lobectomy based upon right hemisphere language representation. Preliminary findings suggest that Wada testing should be conducted on all epilepsy surgery candidates irrespective of handedness.[table1],