Abstracts

Neuroimaging studies have correlated diminished hippocampal volumes with chronic affective and psychotic disorders. Chronic temporal lobe epilepsy (TLE) is also associated with decreased hippocampal volumes, usually in the temporal lobe responsible for seizures. Given the association of decreased hippocampal volumes with both TLE and psychiatric disorders and the common observation of psychiatric distress in patients with TLE, we predicted that there would be a correlation between decreased hippocampal volumes in TLE and increased severity of psychiatric distress that these individuals exhibit. We evaluated 39 patients with intractable, unilateral TLE. All patients completed a quantitative measure of the severity of affective, somatic, and psychotic symptoms as determined by the Symptom Checklist-90-Revised. We measured T2-weighted hippocampal volumes using our previously published protocol (Olejniczak et al 2001) and obtained the ratio of the hippocampal volume (HV) ipsilateral to the side of seizure onset divided by the contralateral HV (ie, HV epileptogenic side/HV non-epileptogenic side). We then evaluated the correlation between this ratio and the severity of psychiatric distress using a partial correlational analysis. Correlational analyses revealed that increasing severity of global psychiatric symptoms were significantly associated with decreasing volumes of the epileptogenic hippocampus as compared to the non-epileptogenic hippocampus. These results were significant after statistically removing the effects of the chronicity of seizures. Our results strongly suggest that reductions in hippocampal volumes in TLE, either by themselves or through the related limbic-cortical system, may play an important role in psychiatric distress so commonly seen in TLE. Structural pathology, rather than psychosocial factors associated with epilepsy, may play the dominant role in the psychiatric symptomatology. Conversely, hippocampal-limbic structural pathology may amplify transient psychosocial factors that ordinarily may not convert into chronic psychiatric distress.