Thirty patients were tested with four dichotic speech tests before and after temporal lobectomy for control of intractable seizures. Ipsilateral ear scores improved on all tests postoperatively; these improved scores reached statistical significance for the Staggered Spondaic Word Test and for consonant-vowel syllables. This result, combined with a nonsignificant decrease for contralateral ear scores, produced postoperative increase in the ipsilateral minus contralateral ear difference scores, similar to previous literature. Preoperative tests for a larger group of patients showed significantly poorer performance than for normal subjects, for all four tests. Total correct scores, used as a measure of overall auditory processing capacity, were impaired for these patients, but unchanged or slightly improved after surgery.Since the earliest report ( 1) which documented that temporal lobe lesions altered the perception of distorted speech presented to the ear contralateral to the lesion, many investigations have shown subtle auditory effects of central nervous system lesions (2-14). Similar discriminatory effects have been shown experimentally in animals (15, 16).Dichotic auditory tasks involve the presentation of different speech or tonal signals to the two ears simultaneously, and this technique has been useful in studying auditory effects of central nervous system (CNS) lesions. These have usually shown contralateral ear deficits for temporal lobe lesions (4, 6, 7) or bilateral deficits for left temporal lobe lesions (4, 8). A larger contralateral ear deficit has been reported for total hemispherectomy ( 17), and a left ear deficit for patients who have had corpus callosum section (18, 19).A similar kind of altered perception of the contralateral ear signal has been suggested on dichotic tonal or melodic tasks. For example, after temporal lobectomy, Shankweiler (20) reported decreased ability in dichotic melody recognition for the contralateral ear; and Efron and Crandall(2 1) reported a decreased salience for the contribution from the contralateral ear tone to dichotic chord perception.Patients who have had temporal lobectomy for control of seizures have been reported to show a contralateral ear deficit using a dichotic digits task (4, 22) and also using dichotic consonant-vowel (CV) syllables (7). Oxbury and Oxbury (22), using digits, found a significant contralateral ear deficit only if Heschl's gyrus was affected by the lobectomy. Olsen (23) found that, both before and after temporal lobectomy, 40% of patients evaluated for intractable seizures had normal dichotic CV test results for both ears.These previous reports provide information for a limited number of patients with temporal lobectomy, and only the latter study compared preoperative scores to a normal control population. It seemed important to us to extend the available data for these patients, as well as to study several different tests for the same patients. Our purpose is to monitor auditory performance before and after surgery, using readily obtaine...
