Analysis of Cortical Thickness in Narcolepsy Patients with Cataplexy

Study Objectives: To investigate differences in cortical thickness in narcolepsy patients with cataplexy and control subjects. Design: Cortical thickness was measured using a 3-D surface-based method that enables more accurate measurement in deep sulci and localized regional mapping. Setting: University hospital. Patients and Participants: We enrolled 28 patients with narcolepsy and cataplexy and 33 age-and sex-matched control subjects. Interventions: Cortical thickness was measured using a direct method for calculating the distance between corresponding vertices from inner and outer cortical surfaces. Measurements and Results: We normalized cortical surfaces using 2-D surface registration and performed diffusion smoothing to reduce the variability of folding patterns and to increase the power of the statistical analysis. Localized cortical thinning in narcolepsy patients with cataplexy was found in orbitofrontal gyri, dorsolateral and medial prefrontal cortexes, insula, cingulate gyri, middle and inferior temporal gyri, and inferior parietal lobule of the right and left hemispheres at the level of a false discovery rate P < 0.05. No significant local increases in cortical thickness were observed in narcolepsy patients. A significant negative correlation was observed between the narcolepsy patients' scores on the Epworth Sleepiness Scale and the cortical thickness of the left supramarginal gyrus. Conclusions: Cortical thinning in narcolepsy patients with cataplexy in localized anatomic brain regions may serve as a possible neuroanatomic mechanism of the disturbances in attention, memory, emotion, and sleepiness.