Transcranial Direct Current Stimulation Therapy for Central Hypersomnia Without Cataplexy

1. To determine the effects of transcranial direct current stimulation (tDCS) on vigilance in subjects with central hypersomnia without cataplexy.
2. To determine the effects of tDCS on subjective measures of sleepiness and alertness in subjects with 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).

Eligibility Criteria:
Inclusion Criteria:

* Age 18 - 70 years
* Epworth Sleepiness scale score \>10
* Stable medication dosage over previous 4 weeks
* Able to understand English and read and write at the 8th grade level and give a written informed consent document.
* Stable sleep/wake schedule (that is, no rotating shift work)
* Clinical diagnosis of any of the following:

  1. Idiopathic Hypersomnia
  2. Narcolepsy without Cataplexy
  3. Hypersomnia in OSA patients adequately treated with PAP therapy or dental device
  4. Posttraumatic hypersomnia
  5. Hypersomnia, unspecified
* Multiple sleep latency test (MSLT) shows fewer than two sleep onset REM periods and a mean sleep latency of ≤ 8 minutes. An MSLT is not required for inclusion of OSA patients provided their Epworth Sleepiness Scale (ESS) score is \>10. Adequately treated OSA patients will be defined as: i) an average PAP usage of \> 4 hours per night and a residual apnea-hypopnea index (AHI) of \<10/hour based on PAP machine download during at least a 30-day period, or ii) regular use of dental device during sleep based on self-report and a prior sleep study showing an AHI \<10/hour while using the dental device.
* Subjects with idiopathic hypersomnia with an MSLT mean sleep latency of \> 8 minutes will be included provided they have hypersomnia symptoms and habitually long sleep times (average of \>10 hours per day) documented by actigraphy for at least 7 days.18

Exclusion Criteria:

* Self-reported habitual sleep period of \< 7 hours/night
* History of automobile accident due to falling asleep while driving
* Currently taking stimulant medications such as Modafinil, Armodafinil, Methylphenidate, or Dextroamphetamnie.
* Inability to understand or read English
* Clear history of cataplexy
* Moderate or severe sleep apnea defined as an apnea-hypopnea index (AHI) of \> 15/hour based on a previous sleep study and non-compliant with treatment.
* Self-reported Substance abuse (current)
* Excessive alcohol consumption defined as:
* More than 3 glasses of wine a day
* More than 3 beers a day
* More than 60 mL of hard liquor a day
* Presence of cardiac pacemaker or automatic implantable cardioverter-defibrillator (AICD).
* Pregnancy, lactation
* Recent hospitalization for major surgery/major illness (within past 1 month)
* Non-removable metal or tattoos around head
* Use of implantable birth control device such as Implanon
* History of severe and frequent headaches
* Known coronary artery disease
* Seizure disorder
* Uncontrolled hypertension
* Congestive heart failure