EFFECT OF FOCUS LATERALIZATION ON MEMORY ASSESSMENT DURING THE INTRACAROTID AMOBARBITAL PROCEDURE

Despite the use of stimuli that can be processed by both hemispheres, a number of studies have reported lower memory scores after the left i ntracarotid amobarbital procedure (IAP) than after the right IAP. Beca use of that, failure after ipsilateral IAP is obsen ed more often in p atients with a left temporal seizure focus (LT) than in right temporal patients (RT), possibly needlessly excluding some LT patients from su rgery. In order to overcome the deleterious effects of anesthetizing t he dominant hemisphere. we designed an IAP protocol that did not promo te verbal encoding of the stimuli. For this purpose, a large number of visual and tactile stimuli (colored pictures and real objects) were p resented to be recognized later. The effect of seizure focus lateraliz ation was examined in 82 temporal lobe epileptic patients who underwen t LAP as part of their presurgical evaluation, As expected, for both R T and LT patients, long-term recognition of pictures presented under t he effect of amobarbital was highly sensitive to the presence of a con tralateral epileptic focus, However, contrary to what is generally rep orted, LT patients performed better than RT patients when their left ( ipsilateral) hemisphere was anesthetized. In RT patients, although mem ory scores were lower after the left contralateral injection, the disp arity in memory scores between the right and left injection was not as marked as in LT patients, These results are discussed in terms of the influence of type of processing required during the initial encoding on later recognition during IAP. (C) 1997 Academic Press.