- A condition in which sleep periods are excessively long, but the person responds normally in the intervals; distinguished from somnolence. [hyper- + L. somnus, sleep]
* * *hy·per·som·nia -'säm-nē-ə n1) sleep of excessive depth or duration2) the condition of sleeping for excessive periods at intervals with intervening periods of normal duration of sleeping and waking compare NARCOLEPSY
* * *n.sleep lasting for exceptionally long periods, as occurs in some cases of brain inflammation.
* * *hy·per·som·nia (hi″pər-somґne-ə) [hyper- + somn- + -ia] excessive sleeping or sleepiness, as in any of a group of sleep disorders with a variety of physical and psychogenic causes.
Medical dictionary. 2011.