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Controlled Clinical Trial
. 2017 Aug 23;9(9):256.
doi: 10.3390/toxins9090256.

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

S W R Nijmeijer  1 , E de Bruijn  2 , R Verhagen  3 , P A Forbes  4 , D J Kamphuis  5 , R Happee  6 , M A J Tijssen  7 , J H T M Koelman  8
Affiliations
Controlled Clinical Trial

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

S W R Nijmeijer et al. Toxins (Basel). .

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.

Keywords: EMG; autospectral analysis; botulinum toxin; cervical dystonia; muscle selection.

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Conflict of interest statement

M.T: Funds: Nuts-Ohra, Princes Beatrix Muscle fund, Gossweiler foundation, Science Foundation Dystonia Society, Funds Mental Health, Phelps Foundation, Beatrix Children Hospital Fund, Healthy Aging Fund UMCG. M.T. received unrestricted grants from Actelion, Merz, Ipsen, Allergan Pharmaceutics & Medtronic and a Honorarium from the Merz expert meeting in Paris, January 2016. These sponsors had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, and in the decision to publish the results. J.K.: Funds: Princes Beatrix Muscle fund. The AMC movement disorder group received unrestricted educational and research grants from Ipsen and Allergan. These sponsors had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, and in the decision to publish the results.

Figures

Figure 1
Figure 1
Pooled autospectra of the rectified electromyography (EMG) between 3 and 30 Hz. Solid line: mean of the log-transformed autospectra. Dotted line: 95% confidence intervals. In BoNT-treated patients the autospectra from the second measurements are shown, when most BoNT effects are expected to have worn off. Similar autospectra were seen during the first measurement.
Figure 1
Figure 1
Pooled autospectra of the rectified electromyography (EMG) between 3 and 30 Hz. Solid line: mean of the log-transformed autospectra. Dotted line: 95% confidence intervals. In BoNT-treated patients the autospectra from the second measurements are shown, when most BoNT effects are expected to have worn off. Similar autospectra were seen during the first measurement.
Figure 2
Figure 2
Pooled autospectra of the ipsilateral splenius capitis (SPL) in BoNT-treated patients during the first and second measurement. Solid line: mean of log-transformed rectified autospectra. Dotted line: 95% confidence interval.
Figure 3
Figure 3
Plots of the CDF’s of the ipsilateral SPL muscles in Cervical Dystonia (CD) patients and the CDF’s of the SPL muscles in healthy controls during the second measurement. * CDF10 values. Individual lines: CDF plots of individual subjects. Note the deflected CDF curve of patient number 10. The corresponding autospectrum shows a high peak around 4–5 Hz responsible for this deflection and the raw EMG shows tremulous 4–5 Hz activity (data not shown). Excluding patient number 10 did not change the level of statistical significance.
Figure 4
Figure 4
ROC (receiver operating characteristic) curve for identifying muscles that belong to CD patients based on different CDF10 values. (In a ROC curve the true positive rate (sensitivity) is plotted in function of the false positive rate (1-specificity) for different cut-off values (here, CDF10 values). * point on the ROC curve corresponding to a CDF10 value of 0.222. Test variable: CDF10 values. State variable: whether the muscles belong to a patient or a healthy control. The AUC of the ROC curve was 0.887.
Figure 5
Figure 5
Number of muscles with a CDF10 above 0.222. Figure 5 illustrates the number of subjects (CD patients in red and healthy controls in blue) that have a certain number of muscles (specified on the x-axis) with CDF10 values above 0.222.
Figure 6
Figure 6
The isometric contraction device. The square represents a helmet on the subject’s head that is attached to the force/torque sensor.
See this image and copyright information in PMC

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