Because obstructive sleep apnea is more frequent than narcolepsy, cataplexy may be over- looked (or absent), and the individual is assumed to have obstructive sleep apnea unre- sponsive to usual therapies.
Major depressive disorder. Narcolepsy or hypersomnia may be associated or confused with depression. Cataplexy is not present in depression. The MSLT results are most often normal, and there is dissociation between subjective and objective sleepiness, as measured by the mean sleep latency during the MSLT.
Conversion disorder (functional neurological symptom disorder). Atypical features, such as long-lasting cataplexy or unusual triggers, may be present in conversion disorder (functional neurological symptom disorder). Individuals may report sleeping and dream- ing, yet the MSLT does not show the characteristic sleep-onset REM period. Full-blown, long-lasting pseudocataplexy may occur during consultation, allowing the examining physician enough time to verify reﬂexes, which remain intact.
Attention-deficit/hyperactivity disorder or other behavioral problems. In children and adolescents, sleepiness can cause behavioral problems, including aggressiveness and in- attention, leading to a misdiagnosis of attention-deficit/hyperactivity disorder.
Seizures. In young children, cataplexy can be misdiagnosed as seizures. Seizures are not commonly triggered by emotions, and when they are, the trigger is not usually laughing or joking. During a seizure, individuals are more likely to hurt themselves when falling. Sei- zures characterized by isolated atonia are rarely seen in isolation of other seizures, and they also have signatures on the electroencephalogram.
Chorea and movement disorders. In young children, cataplexy can be misdiagnosed as chorea or pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections, especially in the context of a strep throat infection and high antistreptolysin 0 antibody levels. Some children may have an overlapping movement disorder close to on— set of the cataplexy.
Schizophrenia. In the presence of ﬂorid and vivid hypnagogic hallucinations, individuals may think these experiences are real—a feature that suggests schizophrenia. Similarly, with stimulant treatment, persecutory delusions may develop. If cataplexy is present, the clinician should first assume that these symptoms are secondary to narcolepsy before con- sidering a co-occurring diagnosis of schizophrenia.
Narcolepsy can co—occur with bipolar, depressive, and anxiety disorders, and in rare cases with schizophrenia. Narcolepsy is also associated with increased body mass index or obe- sity, especially when the narcolepsy is untreated. Rapid weight gain is common in young children with a sudden disease onset. Comorbid sleep apnea should be considered if there is a sudden aggravation of preexisting narcolepsy.
Relationship to International Classification of
The International Classification of Sleep Disorders, 2nd Edition (ICSD-Z), differentiates five subtypes of narcolepsy.
The breathing-related sleep disorders category encompasses three relatively distinct dis- orders: obstructive sleep apnea hypopnea, central sleep apnea, and sleep-related hypo- ventilation.
Diagnostic Criteria 327.23 (647.33)
A. Either (1) or (2): 1. Evidence by polysomnography of at least five obstructive apneas or hypopneas per hour of sleep and either of the following sleep symptoms: a. Nocturnal breathing disturbances: snoring, snorting/gasping, or breathing pauses during sleep.
b. Daytime sleepiness, fatigue, or unrefreshing sleep despite sufficient opportuni- ties to sleep that is not better explained by another mental disorder (including a sleep disorder) and is not attributable to another medical condition.