Hippocampal Atrophy Identified by Volumetric Measurement in Intractable Epilepsy Cases

ABSTRACT

BACKGROUND: Recurrent seizures result in brain damage, but it is usually gradual, minimal, and difficult to observe by visual inspection of magnetic resonance images (MRIs). It is well known that hippocampal structure is vulnerable to seizure-associated brain damage. We measured the hippocampal volume in patients with epilepsy to evaluate the degree of damage to the hippocampus. METHODS: We recruited 33 patients with epilepsy and 21 healthy subjects from January 2007 to December 2008. We subclassified the patients into two groups (1) 14 patients with intractable epilepsy and (2) 19 patients with drug-responsive epilepsy. In each group, the volumes of the left and right hippocampus were measured by manual drawing on brain MRIs. We compared the hippocampal volume in intractable epilepsy, drug-responsive epilepsy, and healthy subjects. The compounding effect of hippocampal sclerosis was ruled out by excluding eight patients with hippocampal sclerosis; we then compared the hippocampal volume in the two groups with epilepsy. RESULTS: The volume of the bilateral hippocampus on brain MRIs was smaller in patients with intractable epilepsy than in those with drug-responsive epilepsy and healthy subjects (left, p<0.004; right, p<0.03). After excluding the patients with hippocampal sclerosis by visual inspection, the hippocampal volumes were also found to be smaller in patients with intractable epilepsy than in those with drug-responsive epilepsy (left, p<0.04; right, p<0.05). CONCLUSIONS: While there is no definitive abnormality of the hippocampus on visual inspection of brain MRIs, we determined the degree of hippocampal atrophy and volume loss in patients with intractable epilepsy. Hippocampal volumetry will be helpful for the assessment of brain damage in patients with intractable epilepsy.