Hemicranial volume deficits in patients with temporal lobe epilepsy with and without hippocampal sclerosis

Purpose: In patients with refractory temporal lobe epilepsy, studies have suggested volume deficits measured by MRT of brain structures outside the epileptogenic hippocampus. Hippocampal sclerosis (HS) is a frequent, but not obligate, finding in such patients. The present study examines the influence of the presence of HS on quantitative magnetic resonance imaging (MRI) measurements. Methods: We analyzed 47 patients and 30 controls by quantitative MRI, including intracranial volume (ICV), hemicranial volume, hippocampal volume (HCV), and T-2 relaxometry. MRT results were compared with histological findings in the resected temporal lobe. Results: Histology documented HS in 35 patients (HS group) and other findings in 12 patients (no-HS group). In both groups, the hemicranial volume ipsilateral to the epileptogenic focus was significantly smaller than on the contralateral side (p < 0.004). The HCV on both sides was smaller in the HS group compared with patients without HS (p less than or equal to 0.004). Unilateral hippocampal atrophy and increased T-2 value were found in 71% of patients with HS, and bilaterally normal HCV and T-2 value were found in 67% of patients without HS. Conclusions: The smaller hemicranial volume on the focus side, irrespective of the presence or absence of HS suggests a different pathogenic mechanism for the additional hemicranial volume deficit, compared to HS itself. The contralateral HCV deficit depends on the presence of I-IS, indicating a pathogenic connection between damage to both hippocampi.