MR spectroscopy in Epilepsy MRI

A normal mesial temporal lobe showing high levels of choline presumably reflects a difference in the cellular composition between the allocortex and neocortex. Thus regional metabolic variations must be considered when pathologic conditions involving the mesial temporal lobe are evaluated. There is some evidence to suggest that the distribution of N-acetyl aspartate (NAA) in the hippocampal neurons is not uniform. Mouritzen found an increase in the number of cells from the anterior to the posterior in the pyramidal cells, whereas Babb et al., did not find statistically significant difference in the number of cells between the posterior and anterior sections. According to Vermathan et al., the anteroposterior difference could be due to fewer neurons in the anterior hippocampus compared with the posterior or due to increasing thickness from the posterior to the anterior leading to different contributions from adjacent tissue.

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Proton magnetic resonance spectroscopy (1H-MRS) has been used to assess metabolite abnormalities in the seizure focus, and the reduction of NAA is a typical finding a-c. In addition, metabolite changes can also be identified outside the seizure focus in patients with HS, reflecting a widespread disorder.MRS not only helps in the diagnosis but also in the prediction of antiepileptic drug response in patients with temporal lobe epilepsy


A patient with left mesial temporal sclerosis. High-resolution (HR) T2 coronal image (a) showing T2 prolongation and atrophy involving left hippocampal head. There is also evidence of collateral white matter atrophy on the left side. Proton spectroscopy metabolic map. (b) shows reduced NAA (N-acetyl aspartate) in left hippocampal head and body. Spectroscopy map (c) from a normal subject shows similar NAA on both sides. (d–f) A young female patient with temporal lobe epilepsy and right mesial temporal sclerosis. HR T2-weighted image. (d) showing signal changes involving right hippocampal head. Atrophy is appreciated in 3D SPGR. (e) Apparent diffusion coefficient. (f) in the right hippocampus is high, secondary to gliosis (arrow)