Efficacy of botulinum toxin type A in correcting the tremor component in patients with cervical dystonia

Head tremor is observed in a significant proportion of patients with cervical dystonia (CD) and aggravates the condition; however, evidence regarding the efficacy of botulinum toxin type A specifically in relation to the tremor component, as opposed to the dystonic posture, remains limited. Objective: to evaluate the efficacy of botulinum toxin A (Xeomin) in treating the tremor component of cervical dystonia, based on changes in clinical, instrumental and socio-psychological indicators. Material and methods. A prospective, observational, single-group 'before-after' study was conducted in 33 patients with idiopathic CD and head tremor who received incobotulinumtoxin A (Xeomin) under electromyographic guidance. Parameters were recorded at baseline and after 3 weeks. The diagnosis of CD with a tremor component was established on the basis of the presence of a pathological posture, localization of the tremor in the area affected by dystonia, a jerky component and positional dependence. Tremor was assessed using accelerometry (frequency and amplitude in three head positions) and by the angle of head deviation; the severity of dystonia was assessed using the TWSTRS severity subscale (0–35 points); functional status was assessed using Fahn's torticollis disability scale; quality of life was assessed using the SF-36; anxiety was assessed using the Integrative Anxiety Test; and stigmatization was assessed using the self-stigmatization scale. Results. The amplitude of the tremor decreased significantly in all positions: at rest by 64%, contralaterally by 57%, and ipsilaterally by 43% (p<0.001), whilst the frequency remained unchanged. The angle of head deviation decreased from 15.0° to 5.0° (p<0.001), and the TWSTRS severity subscale score fell from 10.0 to 8.0 (p=0.001). There was an improvement in functional status on the Fahn scale (from 86 to 95%; p<0.001) and in quality of life (SF-36, both components; p<0.001; particularly in the mental health component). Self-stigmatization decreased slightly, whilst anxiety remained largely unchanged. Conclusion. Incobotulinumtoxin A significantly reduces the amplitude of the tremor component in patients with CD without affecting its frequency, reflecting the drug's peripheral mechanism of action, and improves functional status and quality of life. The reduction in motor symptoms was not accompanied by a corresponding change in anxiety or self-stigmatization, indicating that the psychosocial burden persists even after the motor symptoms have been alleviated.