Figure 2.

Ultra-high field 7T hippocampal subfield volumetry. (a) Ultra-high resolution (0.6 × 0.6 × 0.6 mm) 7T hippocampal imaging in a representative TLE patient. Slices were angled perpendicular to the long axis of the hippocampus for manual subfield segmentations in the coronal plane (b). (c) Manually defined subfield volumes for CA1, CA2, CA3 and DG as well as calculated asymmetry between the left and right hemisphere, are shown for 4 patients, illustrating the range of individual patient-control volumetric results. Individual patient values (black diamond) are represented overlaid onto the range measured in controls (open circles). Red asterisks mark significant differences in volumes/asymmetries of individual patients when compared to the control group (permutation tests, p < 0.05, uncorrected). Asymmetry in volumes of subfields CA1, CA and DG were identified ipsilateral to the side of seizure onset in a patient with radiologically evident HS (Case 12). Conversely, normal asymmetry but bilateral reductions in subfield volumes were detected in a MRI-negative patient subsequently found to have bilateral seizure onset (Case 2). Discordant findings were, however, identified in Case 10, who showed marked asymmetry driven by a significant reduction in left CA3 subfield volume, contralateral to right-lateralized ictal EEG discharges and right medial temporal PET hypometabolism. This patient underwent a right temporal lobectomy with good outcome at 6 months (Class 1b). Similarly, in Case 9, significant CA1 asymmetry appeared weighted towards the contralateral hemisphere (the raw values of which were not significantly different from controls). Video-EEG in this patient was not localizing within the left temporal lobe and subsequent intracranial recordings indicated a lateral rather than hippocampal seizure onset zone.