Depressed mood and memory impairment in temporal lobe epilepsy as a function of focus lateralization and localization.

Objective: Memory disorders and depressed mood are prominent psychological symptoms of temporal lobe epilepsies (TLEs). We examined the interaction of depressive mood and memory as a function of focus localization.

Methods: One hundred fifty-two TLE patients with right mesial (n=37, RTLE-AHS), right lateral (n=31, RTLE-LAT), left mesial (n=42, LTLE-AHS), and left lateral (n=42, LTLE-LAT) lesions and epilepsies underwent comprehensive presurgical evaluation and neuropsychological assessment of mood and memory. Univariate and multivariate analyses of covariance (ANCOVAs) and partial correlation analyses were performed to reveal interactions of depression and memory as a function of focus localization.

Results: No differences between the study groups were revealed for depression, indicating a general risk of 30% for depressed mood (BDI>12) in patients with TLE. ANCOVAs revealed significant main effects of focus side (left: verbal learning deficits; right: figural learning deficits) and site (mesial at disadvantage) on learning and memory scores. Correlation analyses revealed interactions between memory and mood only in LTLE-LAT patients.

Conclusions: Although the data provide evidence that side and site of the epileptogenic region differentially affect material specific memory performance, there was no evidence of a specific temporal target region for depressive mood. In the majority of the patients, depressed mood and memory impairment appeared as independent rather than as related symptoms of TLE. In LTLE-LAT, however, mood was significantly related to verbal and figural memory performance. Epilepsy-driven pathological left temporofrontal circuits are discussed as a prerequisite for the coupling of mood disorders and memory impairment in this specific patient subgroup which is also known from the psychiatric major depression syndrome.