MRI techniques: Bilateral findings and "normal findings"

Magnetic resonance imaging (MRI) techniques allow for significantly better imaging of the temporal lobe compared to computed tomography (CT) or other non-invasive modalities. For detection of foreign tissue lesions, MRI surpa sses CT. For the highest non-invasive yield for detection of mesial tempora l sclerosis, optimal sequences that should be employed are a heavily T1-wei ghted volumetric acquisition (to enable both volumetric calculation of hipp ocampal volume, and, if needed, intracranial volume), T2-weighted coronal s equences, with or without T2-mapping, fluid-attenuated inversion recovery ( FLAIR) and, to exclude subtle susceptibility effects from hematoma or caver noma, gradient echo scans. Magnetic resonance spectroscopy (MRS) may show a decrease in N-acetyl aspartate (NAA) concentration, or NAA: Choline + crea tine ratio. Functional MRI is a new and exciting tool that offers the promi se of accurately localizing hemispheric functions; its role in the preopera tive evaluation of temporal lobe seizures remains uncertain at present.