Hypersomnolence is excessive sleepiness. People with hypersomnolence, as opposed to fatigue, often fall asleep unintentionally. Once hypersomnolence has been confirmed, the first cause to be ruled out should be inadequate sleep time (chronic insufficient sleep). Most people require at least 7 hours of sleep per night and often closer to 8, men generally requiring less than women.
It is suspected that CNS hypersomnolence is related to narcolepsy. The major difference is that CNS patients do not show cataplexy or the presence of dreams (REM sleep) during nap opportunities.
Diagnosis and Tests
If lack of sleep is a problem, total sleep time should be increased before other diagnoses are considered or while other possibilities are being explored. Severe depression
and drugs causing sleepiness should also be excluded. If sleep time appears adequate, sleep disorders from the hypersomnia group should be suspected. These include:
- Sleep apnea (or sleep apnoea) syndrome
- Primary CNS hypersomnolence
- Periodic movements of the legs during sleep (PMLS), also known as nocturnal myoclonus. A condition where the legs move every 40 seconds or so, producing brief arousals. Commonly seen in the first few weeks on nasal CPAP, but it is not understood why. PMLS is another cause of daytime sleepiness.
- Rare forms of hypersomnolence such as post traumatic hypersomnolence, periodic hypersomnolence (Kleine-Levin Syndrome, idiopathic recurring stupor), or post-infectious hypersomnia.