Prevalence and clinical features of cervical dystonia in Parkinson's disease

Objective

To study the prevalence and clinical features of cervical dystonia in Parkinson's disease (CD-PD).

Background

PD features various forms of dystonia, including CD. Yet, the prevalence and clinical features of CD in PD patients are not well-characterized.

Methods

We conducted a single site, prospective study where consecutively evaluated PD patients were examined for the presence of CD to ascertain its prevalence. For each case of CD-PD, a standardized questionnaire assessing demographic and clinical features was completed. Statistical analysis was performed to compare CD-PD characteristics to those of a previously published large idiopathic CD cohort.

Results

Of 301 consecutive PD patients evaluated, 28 (9.3 %) had CD, far surpassing estimates of CD prevalence in the general population. This CD-PD cohort was predominantly male (71 %) with a mean age of 70.9 ± 8.1 years. The mean duration of PD was 10.4 ± 6.7 years. In most cases (n = 19, 68 %), CD developed after the onset of PD. Five patients reported dystonia improvements in response to levodopa, while none reported medication-induced worsening. In contrast to CD-PD, those with ICD (n = 209) were on average younger (59.7 ± 10.1) and mostly female (74 %, p < 0.001). In addition, CD-PD was overall less severe as measured by the Global Dystonia Rating Scale (GDRS) (p = 0.002) and featured less head tremor and pain.

Conclusion

Our findings indicate CD is overrepresented in PD compared to the general population and has clinical features distinct from those of ICD. These results justify larger, more comprehensive studies of CD-PD to better understand its frequency, pathophysiology, clinical characteristics, and associated risk factors.