Publication
Hippocampal MRS and subfield volumetry at 7T detects dysfunction not specific to seizure focus.
Publisher:
Springer Science and Business Media LLC
Date:
23-11-2017
DOI:
10.1038/S41598-017-16046-5
Abstract: Ultra high-field 7T MRI offers sensitivity to localize hippoc al pathology in temporal lobe epilepsy (TLE), but has rarely been evaluated in patients with normal-appearing clinical MRI. We applied multimodal 7T MRI to assess if focal subfield atrophy and deviations in brain metabolites characterize epileptic hippoc i. Twelve pre-surgical TLE patients (7 MRI-negative) and age-matched healthy volunteers were scanned at 7T. Hippoc al subfields were manually segmented from 600μm isotropic resolution susceptibility-weighted images. Hippoc al metabolite spectra were acquired to determine absolute concentrations of glutamate, glutamine, myo-inositol, NAA, creatine and choline. We performed case-controls analyses, using permutation testing, to identify abnormalities in hippoc al imaging measures in in idual patients, for evaluation against clinical evidence of seizure lateralisation and neuropsychological memory test scores. Volume analyses identified hippoc al subfield atrophy in 9/12 patients (75%), commonly affecting CA3. 7/8 patients had altered metabolite concentrations, most showing reduced glutamine levels (62.5%). However, neither volume nor metabolite deviations consistently lateralized the epileptogenic hippoc us. Rather, lower subiculum volumes and glutamine concentrations correlated with impaired verbal memory performance. Hippoc al subfield and metabolic abnormalities detected at 7T appear to reflect pathophysiological processes beyond epileptogenesis. Despite limited diagnostic contributions, these markers show promise to help elucidate mnemonic processing in TLE.