05 Oct Periodic Limb Movements During Sleep Mimicking REM Sleep Behaviour Disorder: A New Form of Periodic Limb Movement Disorder
(Gaig et al 2016)
Rapid eye movement (REM) sleep behavior disorder (RBD) is clinically characterized by vigorous dream-enacting behaviors and unpleasant dreams. This is diagnosed during polysomnography (PSG) with video recordings and EMG activity during REM sleep. Idiopathic RBD is normally a sign Parkinson’s disease or dementia may develop. Other sleep disorders such as sleep apnoea and night terrors can sometimes cause similar behaviours. This study identified an additional condition of Periodic Limb movements, which occurred in a number of patients with similar RBD symptomatology and clinical history.
The patients were referred for abnormal sleep behaviours. Clinical and sleep history was conducted with help of the bed partners and full PSG with video monitoring was performed. Additional EMG recording montage for signals from the upper and lower limbs was included. Following diagnosis of PLMS, blood tests including iron and ferritin levels were performed. Patients were offered dopaminergic therapy and oral iron supplements when deemed necessary. Effect of treatment was assessed during follow up visits with video PSG.
17 Patients (15 men, 2 women) aged 48-77 were studied. 70% were not aware of displaying sleep behaviours however bed partners were able to describe the abnormal sleep behavior which instigated their medical investigations. Reported behaviours were usually vigorous and included kicking, punching or falling out of bed. Vocalizations were reported by all patients included talking shouting, groaning and unpleasant dreams were recalled by 10 patients.
6 Patients had Restless leg syndrome (RLS) occurring less than 3 nights per week. Neurological examination was normal in all patients with no previous diagnosis of Parkinson’s or dementia, renal failure, anaemia or iron deficiency. Two patients had OSA and successfully treated with CPAP. There was no history of other sleep disorders such as sleepwalking, confusional arousal, sleep terrors or nocturnal seizures.
Median PLM index was 61.2 and PLM Arousal index was 27.2. Movements occurred in both upper and lower limbs in all patients. Sometimes the vocalisations occurred during the arousals following the prominent PLMS during NREM sleep only. REM sleep showed normal muscle atonia and no behavioural manifestations other than PLMs so RBD was ruled out.
All patients had normal blood tests for renal function, iron and ferritin although 6 had ferritin lower than 25ng/mL but within normal range. 14 patients agreed to therapy treated with dopamine agonists such as pramipexole and 4 whose ferritin was below 25ng/mL received oral iron supplements. Clinical improvement was maintained after 3-108 months with significant decreases in frequency and severity of unpleasant dreams and abnormal behaviours.
The group of patients who presented clinically with similar symptoms to RBD were shown to be vigorous PLMS leading to arousals containing abnormal movements and vocalisations. The behaviours resembling dream enactment only occurred during NREM sleep as a result of the arousals caused by PLMS. The reported unpleasant dreams may have been triggered by sensory feedback received during a vigorous limb movement related arousal in a similar was that twitches and jerks are thought to generate dream content in RBD.
Original paper published 22 12 2016; https://academic.oup.com/sleep/article/2731733/Periodic-Limb-Movements-During-Sleep-Mimicking-REM