Hippocampal Subfield Volumes in Temporal Lobe Epilepsy

ObjectiveTo study the extent of hippocampal subfield injury in temporal lobe epilepsy (TLE).BackgroundHippocampal atrophy has been well-documented in patients with TLE, but the extent of specific subfield involvement, and its functional significance, is less established.Design/MethodsTotal hippocampal and five subfield region volumes (CA1, CA2+3, CA4+DG, presubiculum, subiculum) were measured with from 1.5 or 3 T MPRAGE MRI sequences using Freesurfer 5.3.0 in 39 TLE patients referred for evaluation of drug-resistant epilepsy who had seizure foci confirmed by ictal video-EEG monitoring, and 35 healthy volunteers. Wechsler Adult Intelligence Scale III (WAIS III) and Wechsler Memory Scale III (WMS III) were obtained on patients. We performed statistical analysis with SPSS version 20 (IBM inc) using linear regression to compare subfield volumes to WAIS III and WMS III scores, and analysis of variance to compare patient and control side-to-side total hippocampal and subfield volume asymmetry. The significance level was set to P u003c 0.05 after correction for multiple comparisons.ResultsThere were no significant relations between total hippocampal or subfield volume and neuropsychological test scores, although patients with larger left hippocampi tended to have higher verbal memory and IQ scores. Total hippocampal volumes were significantly lower ipsilateral than contralateral to seizure foci, and ipsilateral / contralateral volume ratios significantly lower than control asymmetry values. In patients with both left and right TLE all ipsilateral subfields were significantly smaller than contralateral structures. In left TLE left CA1, CA4+DG, and subiculum, and in right TLE CA2+3 and CA4+DG had greater asymmetry with ipsilateral / contralateral volume ratios significantly smaller than control asymmetry values.ConclusionsOur study found hippocampal volume loss in TLE patients affecting all subfields. The extensive hippocampal injury in these patients may be related to the severity of their seizure disorder.Study supported by NINDS Division of Intramural Research Disclosure: Dr. Nielsen has nothing to disclose. Dr. Germeyan has nothing to disclose. Dr. Wiggs has nothing to disclose. Dr. Austermuehle has nothing to disclose. Dr. Theodore has nothing to disclose.