Somatosensory processing is impaired in temporal lobe epilepsy

Purpose: Growing evidence suggests that temporal lobe epilepsy (TLE) is a network disease. In this view, the seizure focus may produce measurable deficits in specific cortical functions. Methods: A tactile grating orientation (GrOr) discrimination task associated with parietal lobe function was administered at the index fingertip to 15 subjects with medically intractable TLE and to 19 neurologically normal controls. TLE subjects were tested bilaterally at baseline while taking their usual antiepileptic drugs (AEDs), and off AEDs during inpatient video-EEG monitoring (n = 9). Three subjects also were tested after temporal lobectomy. t Tests were used to compare baseline performance between TLE subjects and controls, and between hands ipsi lateral and contralateral to side of seizure onset, with Bonferroni correction for multiple comparisons. TLE subjects' baseline thresholds were compared with those obtained off AEDs by using a repeated measures analysis of variance. Results: TLE subjects were severely impaired bilaterally on the GrOr task, with mean discrimination thresholds nearly twice those of controls (p ≤ 0.001 for each hand). No significant difference was found in baseline performance between hands (p = 0.37), or between baseline and off-AED testing (p = 0.42). The three subjects tested after temporal lobectomy demonstrated improved performance compared with baseline, but statistics were not performed because of the small subject number. Conclusions: Patients with medically intractable TLE have impaired tactile GrOr discrimination bilaterally that is not due to nonspecific effects of AEDs. This impaired perceptual ability may be reversible with surgical removal of the seizure focus.