a few times per month when the condition is untreated or in the past.
Cataplexy should not be confused with “wea kness” occurring in the context of athletic
activities (physiological) or ex clusively after unusual emotiona l triggers such as stress or
anxiety (suggesting possible psychopathology). Episodes lasting hours or days, or those not
triggered by emotions, are unlikely to be cata plexy, nor is rolling on the floor while laugh-
ing hysterically.
In children close to onset, genuine cataplexy can be atypical, affecting primarily the
face, causing grimaces or jaw opening with tongue thrusting (“cataplectic faces”). Alter-
natively, cataplexy may present as low-grad e continuous hypotonia, yielding a wobbling
walk. In these cases, Criterion B1(b) can be met in children or in individuals within 6 months
of a rapid onset.
Narcolepsy-cataplexy nearly always results from the loss of hypothalamic hypocretin
(orexin)–producing cells, causin g hypocretin deficiency (less than or equal to one-third of
control values, or 110 pg/mL in most laboratori es). Cell loss is likely autoimmune, and ap-
proximately 99% of affected individuals carry HLA-DQB1*06:02 (vs. 12%–38% of control
subjects). Thus, checking  for the presence of DQB1*06:02 pr ior to a lumbar puncture for eval-
uation of CSF hypocretin-1 immu noreactivity may be useful. Ra rely, low CSF levels of hypo-
cretin-1 occur without cataplexy, notably in youths who may develop cataplexy later. CSF