Measures of hippocampal volumes, diffusion and ¹H MRS metabolic abnormalities in temporal lobe epilepsy provide partially complementary information

Abstract

We assessed whether interictal measures of hippocampal volume, hippocampal diffusion and metabolic abnormalities yield correlated or complementary information about hippocampal pathology in patients with temporal lobe epilepsy (TLE). Volumes, apparent diffusion coefficients (ADC) and ratios of N-acetyl-aspartate (NAA) to Creatine/Phosphocreatine (Cr) and Choline (Cho) were measured from each hippocampus during one magnetic resonance imaging (MRI) session in patients with TLE. Structural MRI showed unilateral hippocampal sclerosis (HS) in 13 patients and was normal in the remaining nine patients. Pearson's correlation (two-tailed) between ADC values and NAA/(Cr + Cho) ratios was significant (P = 0.04, r = -0.45) for the hippocampus ipsilateral to the epileptogenic zone as determined on the basis of interictal and ictal scalp EEG recordings. This finding was driven by a very high correlation between the two measures in the presence of HS (P < 0.001, r = -0.96). Furthermore, ipsilateral ADC values but not NAA/(Cr + Cho) ratios were correlated with disease duration (P = 0.001, r = 0.67). Hippocampal volumes did not correlate with either ADC values, NAA/(Cr + Cho) ratios or disease duration. These data suggest that hippocampal volumes, NAA/(Cr + Cho) ratios and ADC values capture partially complementary aspects of hippocampal pathology.

Relationship between Hippocampal Structure and Memory Function in Elderly Humans

“…Data from structural imaging showed that some of these ERP changes were accounted for by our measures of hippocampal integrity. As in previous studies, there was no correlation between hippocampal volumes and hippocampal diffusion, compatible with the notion that they measure different aspects of hippocampal structure (Duzel, Kaufmann, et al, 2004;Kantarci et al, 2002). Aside from being uncorrelated, volume and diffusion changes in the hippocampus also accounted for different aspects of the ERP changes observed in the elderly.…”

“…Atrophy and increased diffusion are likely to represent complementary, uncorrelated hippocampal changes (Duzel, Kaufmann, et al, 2004;Szentkuti et al, 2004;Kantarci et al, 2002), the former probably reflecting loss of dendritic branching (neuropil) and the latter, widening of extracellular space (Schaefer, Grant, & Gonzalez, 2000). Given their complementary nature, a comprehensive study of the relationship between memory and hippocampal integrity should take into account both measures.…”

Correlation study of optimized voxel‐based morphometry and 1H MRS in patients with mesial temporal lobe epilepsy and hippocampal sclerosis

“…Whilst Cendes et al [1997b] and Sawrie et al [2001] found a significant correlation between hippocampal volumes and 1 H MRS in MTLE/HS, Kuzniecky et al [2001] and Duzel et al [2004] did not replicate earlier findings. In all the cited papers, the correlations between structural and metabolic measurements were investigated only within the hippocampal regions, and no study analyzed these correlations within the extrahippocampal GM.…”

White matter development in children with benign childhood epilepsy with centro-temporal spikes

“…Interictal DTI studies in children with epilepsy have mostly been performed in temporal lobe epilepsy, showing reduction of fractional anisotropy in the hippocampus (Kimiwada et al, 2006) and in the white matter tracts ipsilateral to left temporal foci (Govindan et al, 2008), or increased mean-, axial-and radial diffusivity in the temporal and cingulate white matter (Lee et al, 2004;Nilsson et al, 2008). Similarly, the coefficient of diffusion (ACD), which is often used interchangeably with mean diffusivity, increased interictally in the epileptogenic hippocampus of adult patients with temporal lobe epilepsy (Kantarci et al, 2002;Duzel et al, 2004). Abnormalities of fractional anisotropy and mean diffusivity have also been reported in malformations of cortical development, as well as within normal appearing epileptic tissue Rugg-Gunn et al, 2001).…”