Hypersomnia due to medical condition may
be diagnosed when sleepiness is thought to be the
direct result of a medical or neurologic condition
but the patient does not meet clinical or laboratory
criteria for a diagnosis of narcolepsy. The severity
of daytime somnolence and length of nighttime
sleep vary considerably among patients.
A variety of conditions may underlie this disorder.
Associated neurologic disorders may include
encephalitis, cerebrovascular accidents, brain
tumor, head trauma, and Parkinson disease.22–24
Common genetic conditions associated with
ACCP Sleep Medicine Board Review Course 2008 39
sleepiness include Prader-Willi syndrome and
myotonic dystrophy.25,26 Associated endocrinopathies
such as hypothyroidism and hypoadrenalism
and toxic-metabolic disorders such as hepatic
encephalopathy and renal failure have been implicated.
Drug-induced and psychiatric causes are
classifi ed elsewhere.