Presurgical neuropsychological assessment in epilepsy: the Wada test

37 candidates for epilepsy surgery underwent the intracarotid amytal procedure (IAP; also known as the Wada test) to determine hemispheric speech dominance and memory capacity. 31 demonstrated left hemisphere speech dominance, 2 showed evidence for bilateral language and 4 demonstrated right hemispheric language dominance. Our study supports a correlational relationship between handedness, lesion laterality and age of onset of seizures, as reported in earlier studies. Left-handed patients with a left hemisphere lesion whose seizures began to an early age had a strong tendency for reversed language dominance. Asymmetry of at least 20% in performing the memory test was taken as the cutoff score for demonstrating laterality of lesions. The asymmetry score correctly predicted laterality of lesions in all 28 patients; 6 did not have asymmetry scores and 3 were examined for language only. None of the patients who successfully passed the Wada memory test had any significant postsurgical memory deficits; 1 had transient reduction in verbal memory and 4 who did not pass the test were not operated on for this reason. Our results demonstrate the importance of the Wada test in determining cerebral speech dominance, in predicting post-surgical amnesia, and support its usefulness in predicting laterality of seizure focus in candidates for temporal lobectomy.