[Effects of unilateral temporal lobectomy on verbal dichotic listening test]

Verbal dichotic listening test was conducted before and after anterior temporal lobectomy on 25 patients who underwent the operation because of their medication-resistant epileptic seizures. Their speech dominance by Wada test was all left sided. 1. Preoperatively, patients having the epileptogenic focus in the right temporal lobe (R-TLE) and those having the focus in the left (L-TLE) were, as expected, all right-ear dominant. The mean number of correct responses was fewer in L-TLE than in R-TLE group. 2. Postoperatively, no detrimental effects for recognition of verbal auditory stimuli by the ear contralateral to the focus was observed both in L-TLE and in R-TLE group. 3. Postoperatively, the ear-dominance shifted: to the left in patients with L-TLE, and to the right more conspicuously in patients with R-TLE compared to the preoperative scores. In other words, the recognition ability by the ears ipsilateral to the side of focus, or of resected temporal lobe, was ameliorated. Summarizing, the unilateral anterior temporal lobectomy did not cause "lesion effect" but yielded improvement of verbal auditory recognition by ears ipsilateral to the epileptogenic focus. Diminished epileptic bombardment resulted in by the resection surgery may be a possible explanation.