Chronic temporal lobe epilepsy: spatial extent and degree of metabolic dysfunction studied with magnetic resonance spectroscopy (MRS)

Abstract Introduction: Proton magnetic resonance spectroscopy ( 1 H MRS) has been proposed as a lateralizing method for the presurgical evaluation of patients with medically intractable temporal lobe epilepsy (TLE). Studies have shown correlations between temporal lobe (TL) NAA and seizure frequency, and TL NAA/Cr and the duration of epilepsy in patients with TLE. This latter finding may suggest that progressive neuronal dysfunction may occur in both temporal lobes in patients with TLE, even when the seizures originate in only one temporal lobe. We analyzed our data in an attempt to find a possible correlation between extension of neuronal dysfunction based on NAA measures and duration of epilepsy. Methods: We studied 45 consecutive patients with the diagnosis of TLE, who were referred for presurgical evaluation. Duration of epilepsy was defined as the interval between the age of seizure onset and the time of the MRS examination. All studies were performed in the inter-ictal state, prior to intracranial monitoring or resection. We performed two-tailed Pearson correlation analysis between ipsilateral NAA/Cr and extension of the abnormality (voxels involved) and the duration of the seizure disorder in years. Results: The average duration of epilepsy in this group was 20 years. No significant correlation was found between duration of epilepsy and mean hippocampal NAA/Cr ( r  = −.131, p  = .390); nor was a correlation found between duration of epilepsy in years or the extent of metabolic lesion (voxels involved) ( r  = −.264, p  = .079). Conclusions: Hippocampal NAA/Cr does not correlate with duration of epilepsy in TLE. Our findings suggest that cross-sectional group measures of hippocampal neuronal function do not suggest damage progression.