Proton magnetic resonance spectroscopy of temporal lobe white matter in patients with histologically proven hippocampal sclerosis

The purpose of this study was to assess temporal lobe white matter changes accompanying hippocampal sclerosis on magnetic resonance (MR) imaging using single-voxel H-1 MR spectroscopy and to strengthen the hypothesis that the se white matter changes are caused by myelin alterations. In 11 patients wi th histologically proven hippocampal sclerosis, preoperative coronal fluid- attenuated inversion recovery images were visually assessed by two experien ced neuroradiologists for hippocampal signal increase and size decrease, at rophy of collateral white matter, and temporal lobe gray/white matter demar cation loss. Single-voxel H-1 MR spectroscopy of the white matter of each a nterior temporal lobe was also performed, excluding the amygdala and hippoc ampus. The N-acetyl-aspartate (NAA)/choline and NAA/creatine ratios were ca lculated. In 12 healthy volunteers both temporal lobes were spectroscopical ly examined. In all patients the excised hippocampi were histologically ass essed for the presence of sclerosis, and the excised neocortical temporal l obes were examined for gray and white matter abnormalities. MRI abnormaliti es were found on the right in six patients, on the left in four, and one sc an was normal. Hippocampal signal increase was seen in nine patients, hippo campal size decrease in ten, atrophy of collateral white matter in nine, an d gray/white matter demarcation loss in six. A significant decrease in the NAA/choline ratio was found in temporal lobe white matter ipsilateral to th e pathologic hippocampus (symptomatic side), compared with the contralatera l, asymptomatic side (P < 0.01), and also compared with controls (P < 0.001 ). The ipsilateral NAA/creatine ratio was also significantly decreased (P < 0.05) compared with the contralateral side and the control subjects (P < 0 .001). Histological examination showed hippocampal sclerosis to a different degree in all patients, Neither gliosis nor cortical dysplasia was found i n the ipsilateral, symptomatic temporal lobe, Significant decrease in the m ean of NAA/choline ratios is found in temporal lobe white matter of patient s with histologically confirmed hippocampal sclerosis, As this indicates ne uronal loss or dysfunction, the number of axons may be reduced, with associ ated decrease in myelin density. (C) 2000 Wiley-Liss, Inc.