Modafinil-induced hippocampal activation in narcolepsy

This study was undertaken to investigate regional metabolic abnormalities and to determine the effects of modafinil in narcoleptics on cerebral glucose metabolism using [¹⁸F] fluorodeoxyglucose positron emission tomography (FDG PET). Eight narcoleptic patients participated in the study. Two [¹⁸F] FDG PET scans were obtained before and after 2 weeks of modafinil treatment. To identify the effect of modafinil on regional cerebral abnormalities in narcoleptics, pre- and post-treatment PET scans were compared using paired t-statistics with voxel-wised manner. In narcolepsy patients, significant decreases in cerebral glucose metabolism were observed in the midbrain and upper pons, bilateral hypothalamus, posterior thalamus, hippocampus and right parahippocampus as compared with healthy subjects. After treatment, a significant increase in glucose metabolism in the left hippocampus was found in comparison with pre-treatment scan. This study demonstrated that modafinil activates the hippocampus which receives the afferents from hypothalamus, the center of sleep-wake rhythm.