RELATIONSHIP BETWEEN SLEEP, NECK MUSCLE-ACTIVITY, AND PAIN IN CERVICAL DYSTONIA

Objective: The interactions between sleep, neck muscle activity, and c ervical spinal pain were examined in a controlled study with nine pati ents suffering from idiopathic cervical dystonia (ICD; also referred t o as spasmodic torticollis), and nine gender- and age-matched controls . Methods: From each participant, two all-night polysomnograms with ad ditional electromyographic recordings from the sternocleidomastoid and upper trapezius muscles were obtained. The first night was for habitu ation to the laboratory environment; the second night for experimental data collection. Visual analogue scales were used to collect intensit y and unpleasantness ratings of cervical spinal pain before and after the second sleep recording. Results: None of the standard sleep variab les showed statistically significant differences between average value s of both groups of participants. However, a significantly larger vari ance in sleep latency was obtained for the ICD patients. In general, a bnormal cervical muscle activity decreased immediately when lying down without the intention to go to sleep. Subsequently, abnormal muscle c ontractions were gradually abolished in all ICD patients during the tr ansition from relaxed wakefulness to light NREM sleep. Following this transition phase, no more abnormal EMG activity was found in any of ou r patients. Finally, cervical-spinal pain intensity and unpleasantness were reduced by about 50% overnight. Conclusions: Both supine positio n and sleep can be associated with an improvement of symptoms of ICD, and this disorder does not induce any sleep perturbations.