Electrophysiological evidence of persisting unilateral auditory cortex dysfunction in the late outcome of Landau and Kleffner syndrome

Objectives: In the late outcome of Landau and Kleffner syndrome (LKS), a ch ildhood-acquired epileptic aphasia, most patients show after complete recov ery of epilepsy a permanent one-ear extinction on dichotic listening rests contralateral to the temporal cortex previously affected by the epileptic f ocus. The pathophysiological significance of this dichotic extinction is no t yet understood. It may be a consequence of a permanent dysfunction in the auditory system due to epileptic activity during the maturing period of th e auditory system. Evoked potentials were used to check this hypothesis and to localize the level of the dysfunction along the auditory pathways. Methods: Early, middle latency and late auditory evoked potentials were rec orded in 5 right-handed children having recovered from LKS. They were compa red with those of 5 control children paired for age and gender. Results: In all 5 LKS patients, early and middle latency auditory evoked po tentials were normal. But the amplitude of Nle (arising from associative au ditory areas) was strongly reduced at temporal electrodes contralateral to the extinguished ear, whereas latency and amplitude of Nib (related to prim ary auditory areas) were in the normal range. Conclusions: Unilateral voltage reduction of late auditory evoked potential s over the temporal areas previously involved by epileptic discharges sugge sts a permanent dysfunction in the associative auditory cortex, the behavio ral expression of which is the unilateral dichotic extinction. (C) 2001 Els evier Science Ireland Ltd. All rights reserved.