Making the Narcolepsy Diagnosis
Diagnosis of patients with suspected narcolepsy usually starts with the identification of excessive daytime sleepiness (EDS), or periods of an irrepressible need to sleep during the day. However, the establishment of EDS alone is not sufficient to make the diagnosis. Additional interviewing and testing are necessary.1
The Diagnostic Process
Narcolepsy has 5 main symptoms2
Clinical Interview
A complete clinical interview, including assessment for all 5 narcolepsy symptoms (CHESS: Cataplexy, Hallucinations, Excessive daytime sleepiness, Sleep paralysis, Sleep disruption), is important to the differential diagnosis and provides clinical context when evaluating the results of sleep laboratory testing.1-4 Including the patient's spouse, bed partner, or another family member during the clinical interview can be helpful to corroborate or refute the patient’s report of sleepiness or to uncover cataplexy.5,6
Sleep Laboratory Testing
Sleep laboratory testing, consisting of overnight polysomnography (PSG) followed by a multiple sleep latency test (MSLT), should be performed if narcolepsy is suspected.1 Sleep laboratory testing should be performed under appropriate conditions using standardized techniques and should be interpreted within the clinical context of the patient’s history and symptoms.1
- Home Sleep Apnea Testing (HSAT) cannot detect narcolepsy and is not recommended if narcolepsy is suspected7,8
Hypocretin-1 Levels
Assessment of cerebrospinal fluid (CSF) hypocretin-1 levels is another objective test that can confirm a narcolepsy type 1 diagnosis.1 However, CSF hypocretin-1 levels typically are not obtained in clinical practice.9 An assay is now commercially available.
Hypocretin deficiency in patients with excessive daytime sleepiness is considered diagnostic for narcolepsy type 1 in the ICSD-31 and for narcolepsy in the DSM‑5.1,10 Hypocretin deficiency is generally defined as CSF hypocretin-1 levels ≤110 pg/mL or <1/3 (≤1/3 in DSM‑5) of mean values obtained using the same assay in healthy subjects.1,10
A complete clinical interview, including assessment for all 5 narcolepsy symptoms (CHESS: Cataplexy, Hallucinations, Excessive daytime sleepiness, Sleep paralysis, Sleep disruption), is important to the differential diagnosis and provides clinical context when evaluating the results of sleep laboratory testing.1-4 Including the patient's spouse, bed partner, or another family member during the clinical interview can be helpful to corroborate or refute the patient’s report of sleepiness or to uncover cataplexy.5,6
Sleep laboratory testing, consisting of overnight polysomnography (PSG) followed by a multiple sleep latency test (MSLT), should be performed if narcolepsy is suspected.1 Sleep laboratory testing should be performed under appropriate conditions using standardized techniques and should be interpreted within the clinical context of the patient’s history and symptoms.1
- Home Sleep Apnea Testing (HSAT) cannot detect narcolepsy and is not recommended if narcolepsy is suspected7,8
Assessment of cerebrospinal fluid (CSF) hypocretin-1 levels is another objective test that can confirm a narcolepsy type 1 diagnosis.1 However, CSF hypocretin-1 levels typically are not obtained in clinical practice.9 An assay is now commercially available.
Hypocretin deficiency in patients with excessive daytime sleepiness is considered diagnostic for narcolepsy type 1 in the ICSD-31 and for narcolepsy in the DSM‑5.1,10 Hypocretin deficiency is generally defined as CSF hypocretin-1 levels ≤110 pg/mL or <1/3 (≤1/3 in DSM‑5) of mean values obtained using the same assay in healthy subjects.1,10
A Patient’s Perspective
Watching patients describe the relief they felt when the diagnosis was made can help you discuss, recognize symptoms, and understand your patient’s life-long journey.
- American Academy of Sleep Medicine. Central disorders of hypersomnolence. In: The International Classification of Sleep Disorders – Third Edition (ICSD-3) Online Version. Darien, IL: American Academy of Sleep Medicine; 2014.
- Pelayo R, Lopes MC. Narcolepsy. In: Lee-Chiong TL, ed. Sleep: A Comprehensive Handbook. Hoboken, NJ: Wiley and Sons, Inc.; 2006:145-149.
- Thorpy MJ, Krieger AC. Delayed diagnosis of narcolepsy: characterization and impact. Sleep Med. 2014;15(5):502-507.
- Littner MR, Kushida C, Wise M, et al.; Standards of Practice Committee of the American Academy of Sleep Medicine. Practice parameters for clinical use of the multiple sleep latency test and the maintenance of wakefulness test. Sleep. 2005;28(1):113-121.
- Ahmed IM, Thorpy MJ. Clinical evaluation of the patient with excessive sleepiness. In: Thorpy MJ, Billiard M, eds. Sleepiness: Causes, Consequences and Treatment. Cambridge, United Kingdom: Cambridge University Press; 2011:36-49.
- Guilleminault C, Brooks SN. Excessive daytime sleepiness: a challenge for the practicing neurologist. Brain. 2001;124(pt 8):1482-1491.
- Collop NA, Anderson WM, Boehlecke B, et al.; Portable Monitoring Task Force of the American Academy of Sleep Medicine. Clinical guidelines for the use of unattended portable monitors in the diagnosis of obstructive sleep apnea in adult patients. Portable Monitoring Task Force of the American Academy of Sleep Medicine. J Clin Sleep Med. 2007;3(7):737-747.
- Kapur VK, Auckley DH, Chowdhuri S, et al. Clinical practice guideline for diagnostic testing for adult obstructive sleep apnea: an American Academy of Sleep Medicine clinical practice guideline. J Clin Sleep Med. 2017;13(3):479-504.
- Stanford Center for Narcolepsy. Narcolepsy Research - FAQs. Available at: http://med.stanford.edu/narcolepsy/faq1.html#3 . Accessed June 28, 2018.
- American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5). Arlington, VA: American Psychiatric Association; 2013.