Symptomatic Narcolepsy or Hypersomnolence with and Without Hypocretin (Orexin) Deficiency

The symptoms of narcolepsy can occur during the course of other neurological conditions (i.e., symptomatic narcolepsy). We define symptomatic narcolepsy as cases that meet the International Sleep Disorders Narcolepsy Criteria, which are also associated with a significant underlying neurological disorder that accounts for excessive daytime sleepiness (EDS) and temporal associations. By 2005, we have counted 116 symptomatic cases of narcolepsy reported in the literature. As several authors previously reported, inherited disorders (n = 38), tumors (n = 33), and head trauma (n = 19) are the three most frequent causes for symptomatic narcolepsy. A review of these cases (especially those with brain tumors), illustrates a clear picture that the hypothalamus is most often involved.