Spectral EMG Changes in Cervical Dystonia Patients and the Influence of Botulinum Toxin Treatment

Abstract

Botulinum toxin (BoNT) injections in the dystonic muscles is the preferred treatment for Cervical Dystonia (CD), but the proper identification of the dystonic muscles remains a challenge. Previous studies showed decreased 8–14 Hz autospectral power in the electromyography (EMG) of splenius muscles in CD patients. Cumulative distribution functions (CDF’s) of dystonic muscles showed increased CDF10 values, representing increased autospectral powers between 3 and 10 Hz, relative to power between 3 and 32 Hz. In this study, we evaluated both methods and investigated the effects of botulinum toxin. Intramuscular EMG recordings were obtained from the splenius, semispinalis, and sternocleidomastoid muscles during standardized isometric tasks in 4 BoNT-naïve CD patients, 12 BoNT-treated patients, and 8 healthy controls. BoNT-treated patients were measured 4–7 weeks after their last BoNT injections and again after 11–15 weeks. We found significantly decreased 8–14 Hz autospectral power in splenius muscles, but not in the semispinalis and sternocleidomastoid muscles of CD patients when compared to healthy controls. CDF10 analysis was superior in demonstrating subtle autospectral changes, and showed increased CDF10 values in all studied muscles of CD patients. These results did not change significantly after BoNT injections. Further studies are needed to investigate the origin of these autospectral changes in dystonia patients, and to assess their potential in muscle selection for BoNT treatment.

Long-term response in clinical practice to the application of botulinum neurotoxin type A in patients with cervical dystonia

“…Regarding the proportion of patients who had previously been treated with BoNT-A, it was high, and considering an average of 7.3 months between the last treatment and enrollment, we could suggest that subjects continue to receive benefit from repeated and previous treatments. Although the proper identification of the dystonic muscles remains a challenge 11 , the principal injected muscles in this study remain similar to those most frequently described in the previous studies 12 .…”

Effects of A 3-Month Physiotherapy Intervention in Stable Cervical Dystonia As Add-On to Botulinum Toxin Therapy

“…2) [9] compared to other studies using only inspection or goniometer for ROM evaluation [16][17][18][19]. Using surface EMG we could not show significant changes which maybe related to the known vulnerability to artifacts of EMG [20] and the measurement of standardized muscles (i. e, sternocleidomastoid muscle, trapezius muscle) rather than of individually clinically involved muscles.…”

Vibro-Tactile Stimulation as a Non-Invasive Neuromodulation Therapy for Cervical Dystonia: A Case Study

“…Quantitative signatures of dystonic muscles were most clear and most significant in the cumulative density function of EMG between 3-10 Hz, which was defined as the ratio of power in the lower (3-10 Hz) band to the 3-30 Hz band (Bruijn et al, 2017a). Previous studies have shown increased CDF10 values in CD patients, representing higher signal power between 3 and 10 Hz, relative to power between 3 and 30 Hz (Nijmeijer et al, 2017) (Figure 1). Furthermore, with a cut-off value of CDF10 = 0.222, in an isometric contraction task dystonic muscles in CD patients can be identified from non-dystonic muscles in healthy controls (Nijmeijer et al, 2017).…”

“…Although no uniform electrophysiological feature was concluded as the general feature of the dystonic movement, there has been a hypothesis that a downward shift in the power of EMG signal exists in dystonic compared to non-dystonic muscles (Tijssen et al, 2000b;Nijmeijer et al, 2014Nijmeijer et al, , 2017Bruijn et al, 2017a). In line with the hypothesis, studies have shown that power of EMG between 3-10 Hz in CD patients is higher than healthy individuals during isometric contractions (Nijmeijer et al, 2014).…”