REVIEW Mapping Language in Epilepsy with Functional Imaging

Surgery is an important therapeutic alternative for patients with uncontrolled epilepsy. Preoperative identifi-cation of brain regions important for language is important to reduce the risk of functional impairment after surgery. The Wada test suffers from several technical and clinical disadvantages and provides hemispheric data at best. More invasive methods such as intraoperative or chronic subdural cortical mapping have more limited application. New approaches using neuroimaging methods offer the opportunity to localize, as well as lateralize, language. In addition, normal volunteers can be studied with the same techniques, providing comparative and control data. Although most normal studies have been reported as group data, it is impor-tant for individual scans to be available for comparison with patient studies to understand the normal range of interindividual variability. Two techniques, PET with 15O-water-PET and fMRI, have been used. Both detect signal changes associated with increased regional blood flow during neuronal activity. Usually, scans performed during a language task are compared with those obtained during control conditions. It is impor-tant to choose activation tasks carefully, to make sure one is imaging activation associated with the particu-lar process of interest. PET has advantages, including a fully diffusible tracer, standardized analytic meth-ods, a more comfortable environment, and less sensitivity to movement artifact. On the other hand, it involves a cyclotron-produced tracer, radiation exposure, and is more difficult to repeat. FMRI over repre