Mohammed T. Abou-Saleh

632 PRINCIPLES AND PRACTICE OF GERIATRIC PSYCHIATRYThere are very few studies on the prevalence of RSBD. A studyin the general population by telephone interview found that 0.5%had probable RSBD 12 . Another study on a community sample ofelderly reported a rate of 0.4% 13 . RSBD tends to occurpredominantly in the elderly, and males are more affected. Ingeneral, the awareness of this condition is low among the public aswell as clinicians, and misdiagnosis is common.RSBD occurs in transient or chronic form 11 . The transient formmay be induced by drugs as well as alcohol withdrawal. Thechronic form is either idiopathic or associated with neurologicaldisorders in up to 50% of cases, such as dementia, Parkinson’sdisease, multiple system atrophy and vascular or neoplasticlesions of the central nervous system. In particular, there is astrong association with Parkinson’s disease and dementia withLewy bodies 14,15 .The exact aetiology and pathophysiology of RSBD is unclear.In normal people, there is generalized muscle paralysis duringREM sleep, sparing only the diaphragm and extraocular muscles.In RSBD there is a disruption of this pattern and patients can thusmove and act out their dreams 11 .Management of RSBD includes drug treatment with clonazepam,which is effective in up to 90% of cases, as well as safetymeasures to protect the patients from injuries 16 .PERIODIC LEG MOVEMENT IN SLEEPPreviously known as nocturnal myoclonus, PLMS consists ofstereotyped, periodic jerky movements of the lower limbs, usuallyoccurring in light sleep. Symptoms include leg jerks, insomnia,daytime sleepiness and sometimes cold feet 17 . PLMS is associatedwith restless legs syndrome (RLS), which is characterized by thepresence of unpleasant sensation in the lower limbs occurringwhen the patient lies down in bed, frequently leading to insomnia.However, PLMS can occur independently of RLS.PLMS may occur as an isolated finding, but has been observedin a number of pathological conditions, such as chronicmyelopathies and peripheral neuropathies, uraemia and sleepapnoea 18 .PLMS is very common in the elderly; studies have reportedrates up to 45% 17 . Nevertheless, the relationship of PLMS andinsomnia is still a matter of debate. It has been suggested thatPLMS may be coincidental with sleep–wake disorders, rather thanbeing a cause of it; indeed, many elderly with PLMS arecompletely asymptomatic.Mild cases of PLMS may not need any treatment. For moresevere cases, options of drug treatment include benzodiazepines(particularly clonazepam), L-dopa, bromocriptine and opiates 18 .REFERENCES1. Vitiello MV. 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REM sleep behavior disorderand degenerative dementia: an association likely reflecting Lewy bodydisease. Neurology 1998; 51: 363–70.16. Chiu HFK, Wing YK. REM sleep behaviour disorder—an overview.Int J Clin Pract 1997; 51: 451–4.17. Ancoli-Israel S, Kripke DF, Klauber MR et al. Periodic limbmovements in sleep in community-dwelling elderly. Sleep 1991; 14:496–500.18. Montplaisir J, Godbout R, Pelletier G, Warnes H. Restless legssyndrome and periodic leg movements during sleep. In Kryger MH,Roth T, Dement W, eds, Principles and Practice of Sleep Medicine,2nd edn. Philadelphia, PA: W.B. Saunders, 1994: 589–97.