Cognitive decline in temporal lobe epilepsy due to unilateral hippocampal sclerosis.

OBJECTIVE

We assessed the cognitive performance of patients with temporal lobe epilepsy (TLE) caused by unilateral hippocampal sclerosis (HS), in comparison with that of matched, healthy controls. We report the relationship between cognitive measures and duration of epilepsy, correlating with hippocampal volumes, and the impact of educational level on cognitive decline.

METHODS

This study involved 61 outpatients (40 with < or = 8 years and 21 with >8 years of formal education) with unilateral HS and 61 controls. Volumetric MRI was performed on all patients and 10 controls. The results (mean, SD) of the neuropsychological tests of healthy subjects and patients were compared using the Student t and Mann-Whitney tests.

RESULTS

Patients performed worse than controls in the neuropsychological evaluation. When adjusted z scores were used to calculate the impairment index, patients had a greater percentage of abnormal tests compared with controls. The cognitive decline, assessed through the impairment index, correlated with duration of epilepsy. Higher level of education did not protect against this decline, thus not supporting the hypothesis of cerebral reserve in this population. A significant correlation between hippocampal volumetric measures and duration of epilepsy was observed only in patients with left HS.

CONCLUSION

Patients with TLE caused by HS present with cognitive morbidity that extends beyond memory deficits. Cognitive decline is associated with duration of epilepsy, and in patients with left-sided HS, duration may correlate with volumetric hippocampal loss.