Evaluation of sternocleidomastoid muscle cutaneous silent period in patients with cervical dystonia

Abstract

Purpose: The aim of this study to examine the in changes inhibitory interneurons of the brainstem, which are likely to be involved in pathophysiology of cervical dystonia, using the cutaneous silent period(SP) method which is an inhibitor reflex.
 Materials and Methods: SP latency and interval values were obtained from bilateral sternocleidomastoid (SCM) muscles of individuals in 20 patients with cervical dystonia and 25 healthy volunteers using superficial electrodes. SP parameters obtained were compared within and between groups. Furthermore, intra-individual correlation analysis was performed for SP parameters from bilateral SCMs of the individuals in both groups.
 Results: The mean age of the patients participating in the study was 49.3 ± 14.7, and the control group was 48.0 ± 13.7. There was no statistically significant difference between the two groups in terms of age and gender. No significant difference was found in the comparison of SP parameters both within and between groups. There was a strong intra-individual correlation between SP latencies of bilateral SCMs of both patient and control groups. It was determined that the strongly positive intra-individual correlation between SP intervals also continued in the control group, whereas at patient group disappeared.
 Conclusion: The loss of correlation between bilateral SCM SP durations in the dystonia group indicates that the abnormality in interneuron connections, which is thought to be present in dystonia, may actually be a loss of order. This “disorganization” may explain the discrepancies in the results of cutaneous SP studies in dystonia patients.