Kleine in 1925 and Levin in 1936 described an episodic disorder characterized by somnolence and overeating. For days or weeks, the patients, mostly adolescent boys, sleep 18 h or more a day, awakening only long enough to eat and attend to toilet needs. They appeared dull, often confused, and restless, and were sometimes troubled by hallucinations. In the series of 11 cases collected by Critchley, the age range of onset was from late teenage years to mid-1920s, with few exceptions. There may be a brief prodromal period of inertia and drowsiness. The duration of nocturnal sleep may be greatly prolonged, or, as in our patients referred to below, they may sleep for days on end. Food intake during and around the period of hypersomnia may exceed three times the normal (bulimia) and occurs almost compulsively during brief periods of semiwakefulness; to a variable extent, there are other behavioral changes such as social withdrawal, negativism, slowness of thinking, incoherence, inattentiveness, and disturbances of memory. The somnolence has been well studied by modern laboratory methods; except for the total duration of sleep, the individual components of the NREM and REM cycles are normal. Between episodes these patients are behaviorally and cognitively normal.
The basis of this condition has never been clarified. A psychogenic mechanism has been proposed, without foundation in our opinion. The syndrome usually disappears during adulthood, and there is limited pathologic material (see further discussion in the context of hypothalamic syndromes in Chap. 26). A series of 108 cases reviewed by Arnulf and colleagues frame the clinical features; a predominance of males, higher C-reactive protein than controls, and a history of early childhood developmental problems. There was no human leukocyte antigen (HLA) clustering, but children of Jewish heritage were overrepresented. Another large sample reported by Lavault and colleagues, is more recent but makes largely the same points. We have cared for a sibling pair who had the illness into young adulthood (Katz and Ropper). In some patients with this disorder, schizophrenic and sociopathic symptoms have been recorded between attacks, raising doubt as to whether all the reported cases are of the same type. We have seen variants of this syndrome manifesting as drowsiness and extreme inactivity lasting for a few weeks, then with a complete return to normalcy.
No consistent change in the level of hypocretin (orexin) has been found in the spinal fluid, as occurs in narcolepsy (see further on), and the two disorders are distinct. Imaging studies have shown various areas of reduced metabolism during episodes, including but not isolated to the hypothalamus, and between attacks; the interpretation of these findings is unclear (Portilla et al and Haba-Rubio et al).
Many treatments have been tried and there is only tentative evidence from an open label, prospective e trial reported by Leu-Semenescu and colleagues that lithium may reduce the rate of relapse and duration of episodes. Other medications have not been consistently effective (e.g., antidepressant drugs), but some of the stimulants that are used for the treatment of narcolepsy may be useful (see further on).
Finally, it should be mentioned that sleep laboratories now recognize a form of idiopathic hypersomnia in which there are repeated episodes of drowsiness throughout the day. This condition is discussed further on, in relation to the diagnosis of narcolepsy, with which it is most often confused. A related disorder has been described of “menstrual related hypersomnia” that has a cyclic catamenial nature.