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narcolepsy

Etiology: 1) cataplexy 2) altered sleep rapid-eye movement patterns 3) defects in noradrenergic or dopamine receptors is suggested from research in dogs [2] Epidemiology: 1) HLA linkage: HLA DR-2 & Dqw1 2) onset in adolescence or young adulthood 3) effects both sexes equally 4) occurs in 0.05% of US population Genetics: 1) 60-fold increased incidence in children of narcoleptics, but no clear Mendelian pattern of inheritance 2) association with HLA-DR2, DQw1 & Dw2 Clinical manifestations: 1) sleepiness a) sleep attacks (generally initial manifestation) b) total sleep in 24 hour period is not increased - patients tend to sleep 7-8 hours/night & awake refreshed [9] c) daytime naps 15-20 minutes usually refreshing d) automatic behaviors 1] microsleep periods invading awakened activities 2] patient with diminished awareness 2) cataplexy (80%) a) pathognomonic for narcolepsy b) may develop several years after initial sleep attacks 3) sleep paralysis 4) hypnagogic hallucinations (68%) a) vivid dream-like experiences which the patient cannot distinguish from reality b) may occur during daytime naps c) may occur as patient is falling off to sleep 5) disturbed nocturnal sleep (87%) - > 2 sleep-onset REM periods [9] 6) memory impairment (50%) Laboratory: 1) HLA typing indicated only in cases that do not fit standard pattern 2) thyroid function tests 3) narcolepsy-associated Ag in serum/plasma 4) see ARUP consult [2] Special laboratory: 1) overnight sleep study (polysomnography) - may be evidence of REM sleep disorder - > 2 sleep-onset REM periods [9] 2) multiple sleep latency test (MSLT) Radiology: - computed tomography (CT) of head Differential diagnosis: 1) sleep apnea 2) nocturnal myoclonus 3) idiopathic hypersomnolence (hypersomnolence disorder) - tend to take naps longer than 15-20 minutes, have trouble waking from naps, & do not feel alert afterward [9] - may sleep longer than 7-8 hours/night 4) psychiatric disorder 5) antisocial personality disorder 6) hypothyroidism 7) hydrocephalus 8) absence seizures 9) vertebrobasilar insufficiency Complications: - stroke (RR=2.5) - myocardial infarction (RR=1.6) - cardiac arrest (RR=1.6) - heart failure (RR=2.6) - comorbidities (metabolic syndrome) common - hypertension - obesity - diabetes - hypercholesterolemia [8] Management: 1) general recommendations a) brief daytime naps as needed b) avoid sleep deprivation 2) analeptics a) modafinil (drug of choice) [5] b) pemoline (Cylert) 37.5-150 mg QD or divided BID c) methylphenidate (Ritalin) 20-60 mg QD divided BID/TID d) dextroamphetamine or methamphetamine 20-60 mg QD or divided BID 3) symptoms of cataplexy a) tricyclic antidepressants 1] clomipramine (Anafranil) 25-75 mg QD 2] protriptyline (Vivactil) 5-20 mg QD 3] imipramine (Tofranil) 50-75 mg QHS - may be synergistic with protriptyline b) fluoxetine (Prozac) 20-80 mg QD 4) experimental agents a) zimeldine b) gamma hydroxybutyrate (sodium oxybate) 5) prognosis a) generally a lifetime condition b) symptoms may abate in old age

Related

cataplexy hypersomnia (hypersomnolence, excessive sleepiness) multiple sleep latency test (MSLT) sleep paralysis

General

sleep disorder

References

  1. Saunders Manual of Medical Practice, Rakel (ed), WB Saunders, Philadelphia, 1996, pg 1038-39
  2. Medical Knowledge Self Assessment Program (MKSAP) 11, American College of Physicians, Philadelphia 1998
  3. Harrison's Principles of Internal Medicine, 14th ed. Fauci et al (eds), McGraw-Hill Inc. NY, 1998, pg 155
  4. Nightingale S, Orgill JC, Ebrahim IO, de Lacy SF, Agrawal S, Williams AJ. The association between narcolepsy and REM behavior disorder (RBD). Sleep Med. 2005 May;6(3):253-8. PMID: 15854856
  5. Morgenthaler TI et al, Practice parameters for the treatment of narcolepsy and other hypersomnias of central origin. Sleep 2007, 30:1705 PMID: 18246980
  6. ARUP Consult: Narcolepsy The Physician's Guide to Laboratory Test Selection & Interpretation https://www.arupconsult.com/content/narcolepsy
  7. Scammell TE Narcolepsy. N Engl J Med 2015; 373:2654-2662. December 31, 2015. PMID: 26716917
  8. WebMD Professional Clinical Update. Nov 3, 2020 Narcolepsy and Prevalence of Comorbidities. - Ohayon MM. Narcolepsy is complicated by high medical and psychiatric comorbidities: a comparison with the general population. Sleep Med. 2013;14(6):488-492. PMID: 23643648 - Black J, Reaven NL, Funk SE, et al. Medical comorbidity in narcolepsy: findings from the Burden of Narcolepsy Disease (BOND) study. Sleep Med. 2017;33:13-18. PMID: 28449892 - Cohen A, Mandrekar J, St Louis EK, Silber MH, Kotagal S. Comorbidities in a community sample of narcolepsy. Sleep Med. 2018;43:14-18. PMID: 29482805 Free PMC article.
  9. DSM-5-TR
  10. Facts about Narcolepy http://www.nhlbi.nih.gov/health/public/sleep/narcolep.htm - NINDS Narcolepsy Information Page https://www.ninds.nih.gov/Disorders/All-Disorders/Narcolepsy-Information-Page