Central disorders of hypersomnolence are categorised into narcolepsy types 1 and 2, and idiopathic hypersomnolence. The central disorders of hypersomnolence all cause severe sleepiness but can be differentiated based on ancillary symptoms, diagnostic testing, and pathophysiology.
Individuals with narcolepsy can present quite differently. Typically, they will present with at least one of the clinical tetrad of narcolepsy:
- daytime sleepiness,
- cataplexy,
- sleep paralysis and
- nocturnal hallucinations.
While most narcoleptics are sleepy during the day, they may also experience difficulties staying asleep at night. Their sleep may be disrupted by insomnia, vivid dreaming, sleep apnoea, acting out while dreaming and periodic leg movements.
Narcoleptics may not always present with cataplexy as their primary complaint. However, type 1 narcolepsy will always include a history of cataplexy syndrome. This debilitating disorder of hypersomnolence, is associated with selective loss or dysfunction of orexinergic (hypocretinergic) neurons in the hypothalamus. These patients may not always complain of daytime somnolence, often only confirming this when directly asked. Patients with type 1 narcolepsy generally feel rested after naps.
Patients with type 2 narcolepsy (approx. 10%) often present with excessive daytime somnolence with irresistible sleep attacks. Narcolepsy type 2 may be caused by less extensive injury to orexinergic neurons. These patients generally sleep well overnight, often for long periods. It’s common for patients with type 2 narcolepsy to feel extremely tired after daytime nap periods.
Central disorders of hypersomnolence do not always look “drowsy”. It can present also as memory loss, poor concentration, irritability and automatic behaviours, which can have a massive impact on your quality of life, relationships, professional and academic performance.
The International Classification of Sleep Disorders defines narcolepsy as the presence of excessive daytime sleepiness for > 3 months in association with a mean sleep latency of < 8 minutes and at least two sleep onset rapid eye movement periods on a multiple sleep latency test. On the other hand, an idiopathic hypersomnia diagnosis requires demonstration of a mean sleep latency < 8 minutes, but less than two sleep onset rapid eye movement periods.
The Wesley Hospital Sleep Disorders Center has been active in assisting patients in improving their quality of life through diagnoses, consultation with our sleep physician, and treatment as needed, with the goal of providing better management options for people suffering from central hypersomnolence.
References
Sivam S, Chamula K, Swieca J, Frenkel S, Saini B. Narcolepsy management in Australia: time to wake up. Med J Aust. 2021 Jul;215(2):62-63.e1. doi: 10.5694/mja2.51150. Epub 2021 Jun 18. PMID: 34145573.
American Academy of Sleep Medicine. International classification of sleep disorders – third edition (ICSD-3). Darien, IL: AASM, 2014.
Trotti LM. Central Disorders of Hypersomnolence. Continuum (Minneap Minn). 2020 Aug;26(4):890-907. doi: 10.1212/CON.0000000000000883. PMID: 32756227; PMCID: PMC9159677.
Mattle, Heinrich, and Marco Mumenthaler. Fundamentals of Neurology: An Illustrated Guide, Thieme Medical Publishers, Incorporated, 2016.
Understanding Narcolepsy, A resource from the Division of Sleep Medicine at Harvard Medical School http://sleepeducation.org/essentials-in-sleep/narcolepsy/overview-facts
The Diagnosis and Management of Narcolepsy Consultant. Volume 55 – Issue 8 – August 2015. Available online: https://www.consultant360.com/articles/diagnosis-and-management-narcolepsy
