Autonomic cardiovascular function and baroreflex sensitivity in patients with cervical dystonia receiving treatment with botulinum toxin type A

To investigate possible changes in autonomic cardiovascular regulation and cardiopulmonary baroreflex sensitivity in patients with primary cervical dystonia receiving chronic treatment with botulinum toxin type A. Short-term power spectral analysis of heart rate and systolic blood pressure variability, high-frequency and low-frequency oscillations of heart rate variability, low frequency/high frequency ratio and baroreflex sensitivity (α index) were measured in 12 patients with cervical dystonia before and 2–4 weeks after botulinum toxin type A injection and compared with nor- mative data. Results Before treat- ment, at rest, patients had signifi- cantly lower high frequency power than healthy subjects (p < 0.01), whereas no differences were found in low frequency power. Botulinum toxin injection in patients induced no changes in either power fre- quency. In patients before treat- ment and healthy subjects the low frequency oscillatory components increased similarly from rest to tilt (p < 0.01), but tilt induced lower low frequency values in patients than in healthy subjects (p < 0.01). In patients before treatment, the high frequency variations from rest to tilt remained unchanged, whereas in healthy subjects they decreased significantly (p < 0.01). Botulinum toxin type A injection in patients induced no changes in low frequency or high frequency powers. In patients before treat- ment the low frequency/high frequency ratio increased slightly from rest to tilt, but in healthy sub- jects increased significantly (p < 0.01). Botulinum toxin type A left the pretreatment low frequency/high frequency ratio un- changed. The α-index measured at rest in patients before treatment was lower than in healthy subjects (p < 0.05), whereas during tilt was similar in both groups. The α-in- dex measured after botulinum toxin injection in patients re- mained unchanged at rest and during tilt. Conclusions: Patients with cervical dystonia receiving treatment with botulinum toxin type A have mild, subclinical abnormalities in autonomic cardiovascular regulation and cardiopulmonary baroreflex sensitivity. These changes do not worsen after acute botulinum toxin type A injection.