The lateralizing value of IQ in mesiotemporal epilepsy: Differences between patients with unitemporal and bitemporal epileptiform discharges

Summary 

Purpose

We investigated the lateralizing ability of intelligence scores in mesial temporal lobe epilepsy (MTLE) patients according to the distribution of interictal epileptiform discharges (IEDs).

Methods

This study enrolled 82 MTLE patients. All patients had preoperative neuropsychological evaluations, including Korean Wechsler Adult Intelligence Scale. Patients were categorized as having uni- or bitemporal IEDs based on IEDs distribution (cutoff point, 90%).

Results

In patients with unitemporal IEDs, performance IQ (PIQ) was significantly lower in the right than in the left subgroup (89.6 vs. 99.4, p<0.05). Verbal IQ (VIQ)–PIQ discrepancy scores differed significantly between the left and right subgroups, being negative in the left and positive in the right subgroup. Based on multivariate analyses, two variables, right MTLE (p=0.042) and the unitemporal distribution of IEDs (p=0.030), were independently related to the VIQ–PIQ discrepancy of more than 10 points. About 47.4% of those with unitemporal IEDs had VIQ–PIQ discrepancies of greater than 10 points and the rate for correct lateralization was 77.8%. In patients with bitemporal IEDs, however, none of the intelligence scores showed evidence of correct lateralization. In patients with bitemporal IEDs, Full-scale IQ and PIQ were significantly lower in the left subgroup, and there was a significant difference in VIQ–PIQ discrepancy scores with the wrong direction.

Conclusions

We found that intelligence scores had some lateralizing ability, but only in MTLE patients with unitemporal IEDs.

Keywords: Temporal lobe epilepsy, Wechsler Adult Intelligence Scale, Laterality, Electroencephalography