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nocturnal myoclonus (periodic limb movement disorder, PLMD, periodic limb movements of sleep, PLMS)

A condition related to restless legs syndrome characterized by repetitive, periodic & stereotypical movement of the limbs, usually the legs, during quiet waking or non REM sleep. Although 85% of patients with restless legs syndrome also have nocturnal myoclonus, the reverse is not true & patients with nocturnal myoclonus may present instead with insomnia or excessive daytime sleepiness. Etiology: 1) lumbar disc disease predisposes to nocturnal myoclonus 2) autonomic (sympathetic) activation may play role [5] 3) dysfunction of dopaminergic hypothalamic A11 nucleus that synapse on preganglionic sympathetic neurons 4) idiopathic * not associated with Parkinson's disease or parkinson plus syndromes Epidemiology: 1) prevalence increases with age 2) common disorder Clinical manifestations: 1) repetitive, periodic & stereotypical movement of the limbs a) generally legs involved b) jerky & sustained components c) extension of great toe [3] d) flexing at ankle, knee & sometimes hip [3] e) repeated dorsiflexion at the ankle & great toe [5] f) movements occur during wakefulnes & sleep [5] g) duration: 0.5-5 sec h) frequency: every 20-40 sec 2) insomnia 3) excessive daytime sleepiness 4) physical examination is normal 5) patients may intermittently kick their bed partner Laboratory: 1) serum folate 2) serum ferritin (perhaps not [7]) 3) serum urea nitrogen 4) serum creatinine 5) serum bicarbonate Special laboratory: - polysomnography (required for diagnosis) Differential diagnosis: 1) hypnic jerks 2) partial seizure 3) sleep apnea 4) rapid eye movement sleep behavioral disorder - associated with Parkinson's disease & parkinson plus syndromes Management: 1) treatment only indicated if marked fragmentation of sleep [7] - therapy targeted towards improving sleep quality 2) benzodiazepines not indicated [7]* a) clonazepam (Klonopin) 0.5-2.0 mg QHS b) temazepam (Restoril) 15-30 mg QHS c) tolerance may develop 3) also see management of restless legs syndrome * used to treat rapid eye movement behavioral disorder

Related

rapid eye movement sleep behavioral disorder (RBD) restless legs syndrome; Willis-Ekbom disease (RLS)

General

sleep-related movement disorder myoclonus

References

  1. Saunders Manual of Medical Practice, Rakel (ed), WB Saunders, Philadelphia, 1996, pg 1039-40
  2. UCLA Intensive Course in Geriatric Medicine & Board Review, Marina Del Ray, CA, Sept 12-15, 2001
  3. Geriatrics Review Syllabus, American Geriatrics Society, 5th edition, 2002-2004
  4. Alessi C In: Intensive Course in Geriatric Medicine & Board Review, Marina Del Ray, CA, Sept 29-Oct 2, 2004
  5. Guggisberg AG et al, The significance of the sympathetic nervous system in the pathophysiology of periodic leg movements in sleep. Sleep 2007, 30:755 PMID: 17580597
  6. Chesson AL Jr, Wise M, Davila D et al Practice parameters for the treatment of restless legs syndrome and periodic limb movement disorder. An American Academy of Sleep Medicine Report. Standards of Practice Committee of the American Academy of Sleep Medicine. Sleep. 1999 Nov 1;22(7):961-8. PMID: 10566915
  7. Medical Knowledge Self Assessment Program (MKSAP) 18, 19. American College of Physicians, Philadelphia 2018, 2021