Metabolic Patterns Associated With Non-Specific Magnetic Resonance Imaging Abnormalities in Temporal Lobe Epilepsy

We investigated the cerebral metabolic patterns associated with non-specific hyperintense T2-weighted image on Magnetic Resonance Imaging (MRI) in Temporal Lobe Epilepsy (TLE). Nineteen patients suffering from TLE with a normal CT scan underwent Positron Emission Tomography (PET) using 18F-fluorodeoxyglucose; 8 had hyperintense T2-weighted image on MRI in the epileptogenic temporal lobe and 11 had a normal MRI. Interictally, PET exhibited focal hypometabolism in all the patients with hyperintense T2-weighted image and in 8 of the 11 whose MRI was normal. The hypometabolic area was significantly more extensive in patients with hyperintense T2-weighted image in whom it always encompasses the site of the MRI abnormality. Moreover, these patients had higher metabolic asymmetry index in the temporal and parietal lobes than patients with a normal MRI. One patient with mesial temporal hyperintense T2-weighted image underwent an ictal PET, which showed that the focal hypermetabolism fitted remarkably with the site and size of the abnormal MR signal. Thus, non-specific hyperintense T2-weighted images are associated with particular interictal and ictal metabolic patterns which might suggest that these MRI abnormalities reflect an epileptogenic lesion.