Polysomnographic characteristics in patients with idiopathic dystonia

Background Several aspects of the occurrence of sleep disturbances in dystonia remain unclear. Here, we assessed sleep architecture with polysomnography (PSG) and investigated the association of specific findings with mood, quality of life and severity of disease.

Methods Twelve patients with idiopathic dystonia underwent overnight PSG and findings were compared to those of a normative collective. Subjective sleep quality was evaluated with the Pittsburgh-Sleep-Quality-Index (PSQI) and the Epworth-Sleepiness-Scale (ESS). PSG findings, PSQI and ESS were correlated to motor scores of the Burke-Fahn-Marsden-Dystonia-Rating-Scale and the Torticollis-Western-Spasmodic-Rating-Scale. Further correlations were investigated between sleep assessment and mood (Beck-Depression-Inventory (BDI) and Hamilton-Depression-Rating-Scale (HDRS)), and quality of life (SF-36 subscales).

Results Patients with dystonia had impairments in REM sleep, increased N2 and arousal index. Impaired REM sleep was positively correlated with the SF-36 subscore mental health, the N1 sleep stage was associated with the HDRS score, the arousal index was negatively correlated with the SF-36 subscores social functioning and bodily pain, but positively correlated with the BDI, and daytime sleepiness according to ESS was correlated with the SF-36 subscale vitality. There were no significant correlations with motor scores.

Conclusion Our study demonstrates that sleep impairment is a fundamental characteristic in patients with idiopathic dystonia affecting both mood and quality of life. Sleep disturbances are not merely a secondary consequence of the motor disorder, but appear to be an integral and primary feature of dystonia itself.