Abstracts

Rationale: Functional MRI in normal individuals shows memory processing asymmetry of verbal and nonverbal material. We investigated memory encoding of written words and of dually encodable (DE) material during the sodium amytal test, and compared performance in the normal and diseased hemispheres for both types of material in unilateral mesial temporal sclerosis (uMTS) patients undergoing preoperative sodium amytal testing (WADA). Methods: : We analyzed WADA test performance for verbal (V) (isolated typewritten words) and DE material (real objects and line drawings of common objects) in uMTS patients. An amytal dose, sufficient to cause hemiparesis, was sequentially injected in the internal carotid artery of MTS and normal hemispheres, with an approximate 30 minute interval. Eight to 14 items (objects, line drawings of objects and words) were presented during amytal effect. V and DE scores were calculated as the ratio of recalled (spontaneously + cued)/presented items. Means and standard deviations for V and DE scores were calculated for both right (R) and left (L) normal and MTS sides.Results: 39 MTS (51% L) patients were studied (56% women). Language dominance was determined by WADA. Recall scores for DE material was similar in normal L and R sides (L 0,83+/-0,25 vs. R 0,85+/-0,24). DE scores on the MTS side were 33% lower than normal side scores, without a laterality effect (L MTS 0,55+/-0,30 vs. R MTS 0,56+/-0,31). V scores were also similar in normal L and R sides (L 0,61+/-0,36 vs. R 0,63+/-0,35). A more marked disease effect was noted on both sides, with a mean 66% decrease in V scores, without a laterality effect on encoding for verbal material (L MTS 0,19+/-0,26 vs R MTS 0,20+/-0,26).Conclusions: MTS was associated with marked decrease in delayed recall in DE material and, more markedly, in V material, without hemispheric asymmetry. Processing of visually presented V and DE did not display a laterality effect in the normal or sclerotic mesial temporal structures.