Prediction of level and pattern of intelligence test performance in children with lateralized temporal lobe epilepsy

Abstract

The present study attempted to identify valid predictors of the level and pattern of Wechsler intelligence test performance in children with lateralized temporal lobe epilepsy of unknown etiology. Six seizure-related variables (seizure type, seizure frequency, number of different types of anti-convulsant medication required to control the seizures, types of EEG abnormality, age of onset of the seizure disorder, and lateralization of the epileptiform activity) were evaluated as predictors of Full-scale IQ. Three variables (lateralization, age on onset, and severity of cerebral pathology) were evaluated as predictors of the relative magnitudes of Verbal IQ and Performance IQ. The number of anti-convulsants required to control seizures was significantly related to Full-scale IQ scores. Seizure type, seizure frequency, types of EEG abnormality, age of onset, and lateralization did not contribute significantly to the amount of explained variability in Full-scale IQ. There was a nonsignificant trend towards a relationship between the lateralization of epileptiform activity and the relative magnitudes of Verbal IQ and Performance IQ. Differences between the left and right temporal groups were in the expected direction on all but one of the Verbal and Performance IQ and subtest measures. No association was found between either the age of onset or severity of cerebral pathology and the relative magnitudes of Verbal IQ and Performance IQ. Methodological problems were considered in a discussion of these results. Most of the children in the study were not significantly impaired intellectually, as evidence by the fact that only four subjects in the total sample ([lowercase underlined n]=26) demonstrated Full-scale IQ scores which were below the Average range. In the left temporal group, nine of the twelve subjects demonstrated a lower Verbal IQ while, in the right temporal group, seven subjects demonstrated a lower Verbal IQ and seven subjects demonstrated a lower Performance IQ. It was concluded that, in terms of pattern of intelligence test performance, there is a trend toward a lower Verbal IQ in children with temporal lobe epilepsy maximally involving the right hemisphere, and no trend towards a particular pattern of performance in children with temporal lobe epilepsy maximally involving the right hemisphere. The results of the present study were discussed in relation to other findings in the neuropsychological literature.