Neck disability is associated with masticatory myofascial pain and regional muscle sensitivity

Objective: The primary aims of this study are to compare neck disability in masticatory myofascial pain subjects versus asymptomatic controls, and to evaluate the correlation between neck disability and muscle pain.

Design: Two groups composed this case-control study: a symptomatic group comprised of 27 subjects diagnosed with masticatory myofascial pain, as determined by the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD), and a control group comprised of 28 asymptomatic subjects. The collected variables were pain intensity (visual analogue scale), pressure pain threshold of the temporomandibular joint, anterior temporalis, masseter, sternocleidomastoid muscle, upper trapezius and Achilles tendon (digital dynamometer, kgf/cm(2)), and neck disability (Neck Disability Index). Statistical analysis included Student's t-test and the Pearson product-moment correlation coefficient (5% significance level and 95% confidence interval).

Results: The symptomatic group showed greater neck disability with a mean (SD) of 11.8 (7), as compared with 2.8 (2.4) for the asymptomatic group (p<0.05). A negative correlation was found between neck disability and pressure pain threshold of the anterior temporalis (r=-0.4, 95% CI -0.6 to -0.15, p=0.002), the sternocleidomastoid (r=-0.35, 95% CI -0.56 to -0.09, p=0.007) and the upper trapezius (r=-0.37, 95% CI -0.58 to -0.12, p=0.005).

Conclusion: Our results reinforced the clinical interconnection between masticatory and cervical structures, insofar as subjects with masticatory myofascial pain reported greater neck disability, which, in turn, was correlated with regional muscle sensitivity.