Sleep-related head jerks: toward a new movement disorder.

Sleep-related head jerks (SRHJ) are often considered as a physiological motor phenomenon, occurring mainly during rapid eye movement (REM) sleep. Their clinical relevance and links with other sleep parameters are unclear. We characterized the clinical and polysomnographic features of patients with excessive SRHJ and compare them with healthy controls and patients with isolated REM sleep behavior disorder (iRBD). A total of 30 patients (19 males, 27.5 y.o., 16.0-51.0) with a REM-HJ index >30/h were identified over a period of 5 years. All had a video-polysomnographic (PSG) recording to characterize the SRHJ, to assess associations with other sleep parameters and to quantify phasic and tonic electromyographic activity during REM sleep, compared with 30 healthy controls and 30 patients with iRBD. Five among the 30 patients had a primary complaint of involuntary nighttime head movements associated with sleepiness or non-restorative sleep. The mean REM-HJ index was 57.22/h ± 24.42, a nonperiodic pattern, stable across the sleep cycles, and with a low between-test variability (for the nine patients with two PSG assessments in untreated condition). REM-HJs were often associated with arousals (65.2%) and leg movements (38.1%) and less with respiratory events (9.6%), without association with increased phasic and tonic electromyographic activities. SRHJ were also found in 36.7% of controls and 56.7% of iRBD patients, but with a lower index in REM sleep (0.79/h ± 1.59 and 2.76/h ± 4.57). Although SRHJ are frequent in the general population and with uncertain clinical significance, rare severe symptomatic forms should be individualized and eventually be categorized as a new sleep-related movement disorder, distinct from RBD and periodic leg movements.

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