Presurgical multimodality neuroimaging in electroencephalographic lateralized temporal lobe epilepsy

The purpose of this study was to compare 2hyphen;[18F]fluoro‐2‐deoxy−D−glucose positron emission tomography (FDG‐PET), hippocampal volumetry (HV), T2 relaxometry, and proton magnetic resonance spectroscopic imaging (1H‐MRSI) in the presurgical neuroimaging lateralization of patients with nonlesional, electroencephalogram (EEG)‐defined unilateral temporal lobe epilepsy (TLE). Twenty‐five patients were prospectively studied, along with age‐matched controls. T2 relaxometry examinations were performed in 13 patients. Comparison of FDG‐PET, HV, and 1H‐MRSI was possible in 23 patients. FDG‐PET lateralized 87% of patients, HV 65%, N‐acetyl aspartate (NAA)/(choline [Cho] + creatine [Cr]) 61% and [NAA] 57%. Combined HV and NAA/(Cho + Cr) results lateralized 83% of the patients, a value similar to PET. Of 10 patients with normal magnetic resonance imaging (MRI) scans, 2 were lateralized with HV, 6 with FDG‐PET, 4 with NAA/(Cho + Cr), and 3 with [NAA]. T2 relaxometry lateralized no patients without hippocampal atrophy. Bilateral abnormality was present in 29 to 33% of patients with 1H‐MRSI measures and 17% with HV. Only hippocampal atrophy correlated with postoperative seizure‐free outcome. FDG‐PET remains the most sensitive imaging method to correlate with EEG‐lateralized TLE. Both FDG‐PET and 1H‐MRSI can lateralize patients with normal MRI, but only the presence of relative unilateral hippocampal atrophy is predictive of seizure‐free outcome. Bilaterally abnorma; MRI and 1H‐MRSI measures do not preclude good surgical outcome.