Epilepsy & depression: the effects of comorbidity on hippocampal volume--a pilot study

Hippocampal sclerosis (HS) is one of the most common pathologies in medically intractable temporal lobe intractable epilepsy. Significant hippocampal volume loss has also been found in patients with chronic depression. Depression is common in chronic epilepsy populations, but the effects of this comorbidity on hippocampal volume are unknown. We examined the hippocampal volumes of 87 patients (n=31 right hippocampal sclerosis, RHS; n=56 left hippocampal sclerosis, LHS). Each subject completed the Hospital Anxiety and Depression Scale (HADS). In the group as a whole, 13 subjects (15%) recorded moderate or severe levels of depression. Depression was more common in the LHS group with 1 in 5 scoring in the moderate or severe range on the HADS (n=11). Depression scores were not significantly correlated with quantitative measures of hippocampal volume in the LHS group. However, higher degrees of hippocampal symmetry were associated with higher levels of depression in the RHS group. This suggests that the left hippocampus may be smaller in depressed patients with RHS, although our numbers were too small to confirm this statistically. Our results suggest that the depression may influence left hippocampal volume in patients with right hippocampal sclerosis. We conclude that the neuroradiological characteristics of patients with epilepsy and chronic depression deserve further examination.