Pediatric Narcolepsy Is Under-Diagnosed

Many physicians are unfamiliar with narcolepsy and cataplexy, and thus they remain under-diagnosed. For children, the problem is compounded by the fact that pediatric presentation of narcolepsy can differ from adult presentation. Even pediatric neurologists can misdiagnose narcolepsy as epilepsy or another neuromuscular disorder. Narcolepsy typically begins in childhood (between the ages of 10 and 20 years), and can have a complex effect on neurobehavioral and cognitive functioning in children; therefore, it is important that narcolepsy be diagnosed and managed as early as possible. This is especially the case for children with neurological or neurodevelopmental diseases who are more likely to have narcolepsy.

Narcolepsy is a chronic disorder characterized by excessive daytime sleepiness (persisting ≥ 3 months), quick entry into rapid eye movement (REM) sleep and, in some patients, sudden loss of muscle tone (cataplexy). There are two diagnostic criteria for narcolepsy. In 2014, the American Academy of Sleep Medicine (AASM) released the International Classification of Sleep Disorders – Third Edition (ICSD-3). The AASM notes that, alternatively, in young children, narcolepsy may sometimes present as excessively long night sleep or as resumption of previously discontinued daytime napping. In 2013, the American Psychiatric Association (APA) published the Diagnostic and Statistical Manual of Mental Disorders – Fifth Edition (DSM-5), which contains diagnostic criteria for sleep-wake disorders, including narcolepsy, and is designed for use by mental health and medical clinicians who are not experts in sleep medicine. While the ICSD-3 criteria require results from a sleep study, the DSM-5 criteria do not. They also note that, in children, cataplexy can present as spontaneous grimaces or jaw-opening episodes with tongue thrusting or global hypotonia, without any obvious emotional triggers.

Childhood narcolepsy is associated with several other characteristics. Children can have profound facial hypotonia and some patients experience motor tics. Obesity is also common in children with narcolepsy. More than half of children who first present with signs of narcolepsy are obese. In addition, approximately one third of children with narcolepsy also have symptoms of attention deficit hyperactivity disorder (ADHD).

Interestingly, researchers have found that migraines in children (the symptoms of which may differ from adult migraines) are also an independent risk factor for narcolepsy development in children. One study on the subject was prompted by the investigators’ clinical observation that approximately half of children diagnosed with narcolepsy reported migraines. Narcolepsy appears to be the result of dysfunctional hypothalamic activity and the association between narcolepsy and migraines may be another clue to the underlying pathophysiology of narcolepsy.

Typically, when diagnosing narcolepsy, physicians take down a detailed clinical history and have the patient fill out several questionnaires which might include the pediatric modified Epworth Sleepiness Scale, the Pediatric Daytime Sleepiness Scale, and the Cleveland Adolescent Sleepiness Scale. Patients likely will also need to have an overnight polysomnography as well as the daytime multiple sleep latency test (MSLT). Researchers in Sweden have recently developed a health-related quality-of-life instrument for young people with narcolepsy (NARQoL-21) which may also be helpful in evaluating the effects of narcolepsy on the child. It encompasses an assessment of the young person’s concern for the long-term future. Using this tool, investigators have found that even patients with a relatively low burden of narcolepsy can experience a decrease in their health-related quality of life because of the negative effects of narcolepsy on the occupational, career, and social aspects of life. As more treatment options become available for narcolepsy, it should be possible to relieve these concerns and allow these children to have the careers and social life that they desire.

References

1. Chaplin, JE, Szakacs, A, Hallbook, T, et al. The Development of a Health-related Quality-of-life Instrument for Young People with Narcolepsy: NARQoL-21. Health Qual Life Outcomes. 2017. 15:135.

2. Maski, K and Owens, JA. Insomnias, Parasomnias, and Narcolepsy in Children: Clinical Features, Diagnosis, and Management. Lancet Neurol. 2016. 15:1170.

3. Pillen, S, Pizza, F, Dhondt, K, et al. Cataplexy and Its Mimics: Clinical Recognition and Management. Curr Treat Options Neurol. 2017. 19:23.

4. Yan, C-P, Hsieh, M-L, Chiang, J-H, et al. Migraine and Risk of Narcolepsy in Children: A Nationwide Longitudinal Study. PLOS One. 2017. 12:e0189231.