Transcranial Direct Current Stimulation Therapy for Central Hypersomnia Without Cataplexy

This is a randomized, sham-controlled, parallel group study. The study will last up to 5 weeks. After informed consent, subjects with idiopathic hypersomnia with an MSLT mean sleep latency of \>8 minutes will undergo actigraphy and those with an average sleep time of \>10 hours per day will continue with the study while those with \<10 hours sleep time will be excluded. In addition, OSA subjects with complaints of hypersomnia with an ESS score \<10 will also be excluded. Female subjects of child bearing age and not menopausal will have a pregnancy test performed as pregnancy is an exclusionary criteria. Subjects will be randomized to receive either active tDCS or sham stimulation for 30 minutes daily for 4 sessions. The randomization will be generated by means of a computer-generated random-number table. An unrestricted randomization scheme will be followed. Subjects will be blinded as to whether they are receiving sham or active tDCS treatments. The investigator who will conduct the analysis of all outcomes will be blinded as to subject treatment assignment. All stimulation visits will be completed within a five-consecutive day period; that is one stimulation visit may be missed provided a total of four stimulation visits are completed within a five-day period. Outcome measures will include: psychomotor vigilance test (PVT), subjective measures of sleepiness, and the Center for Epidemiologic Studies Depression (CES-D) scale. PVT will be performed pre- and post- stimulation during the first and last stimulation sessions. Subjective measures of sleepiness include the following: Epworth Sleepiness Scale (ESS), Stanford Sleepiness Scale (SSS), Functional Outcomes of Sleep Questionnaire-10 (FOSQ-10), and Visual Analogue Scale (VAS).