Spatial extent of neuronal metabolic dysfunction measured by proton MR spectroscopic imaging in patients with localization-related epilepsy

Purpose: To assess the spatial extent of the decrease in the neuronal marke r N-acetyl-aspartate (NAA) relative to creatine (Cr) in patients with local ization-related epilepsy, and to assess clinical differences between patien ts with and without widespread NAA/Cr reduction. Methods: We studied 51 patients with localization-related epilepsy. Patient s were divided into three groups according to the EEG investigation: (a) te mporal lobe epilepsy (TLE, n = 21), (b) extratemporal lobe epilepsy (extra- TLE, n = 20), and (c) multilobar epilepsy (patients with a wider epileptoge nic zone, n = 10). We acquired proton magnetic resonance (MR) spectrocopic imaging (H-1-MRSI) of temporal and frontocentroparietal regions in separate examinations for both patients and controls. NAA/Cr values 2 standard devi ations below the mean of normal controls were considered abnormal. Results: Twenty-three (45%) patients including 12 with TLE had normal MR im aging including volumetric studies of the hippocampus. Forty-nine (96%) pat ients had low NAA/Cr, indicating neuronal dysfunction in either temporal an d/or extratemporal H-1-MRSIs; 38% of patients with TLE and 50% of patients with extra-TLE also had NAA/Cr reduction outside the clinical and EEG-defin ed primary epileptogenic area. The NAA/Cr reduction was more often widespre ad in the multilobar group [six (60%) of 10] than in temporal or extratempo ral groups [five (31%) of 16]. Nonparametric tests of (a) seizure duration, (b) seizure frequency, and (c) lifetime estimated seizures showed no stati stically significant difference (p > 0.05) for TLE and extra-TLE patients w ith or without NAA/Cr reduction outside the seizure focus. Conclusions: Of patients with localization-related epilepsy, 40-50% have ne uronal metabolic dysfunction that extends beyond the epileptogenic zone def ined by clinical-EEG and/or the structural abnormality defined by MRI.