Comparison of mechanical properties of masticatory muscles and oculomotor control in individuals with and without chronic mechanical neck pain: A cross- sectional study

Abstract Background: Chronic mechanical neck pain (CMNP) is often associated with visual impairments, headaches, and temporomandibular dysfunctions. The plethora of symptoms associated with neck pain results from the densification of the deep cervical fascia and its myofascial continuum. Although there exists an anatomical myofascial link between the neck, the head, and Tenon's capsule of the eye, their functional interrelationship remains unclear. This study compares the mechanical properties of masticatory and neck muscles and oculomotor control in individuals with and without CMNP. Methods: A comparative cross-sectional study was performed involving 26 participants with chronic mechanical neck pain and 26 healthy individuals matched for age and gender, aged between 18 and 45 years. The outcome includes the biomechanical properties (stiffness, frequency, and decrement) of the head and neck muscles using myotonpro and the oculomotor control, evaluated through the smooth pursuit neck torsion (SPNT) test using videonystagmography. Results: Independent t-test revealed that there were statistically significant differences in the frequency Hz (p= 0.001) and stiffness N/m (p= 0.01) of the temporalis and masseter muscles, suggesting increased tonus and stiffness in the neck pain group compared to the healthy individuals. In addition, a significant reduction in vertical downward gain of the right eye during right trunk torsion was observed in the CMNP group (mean difference = 0.13, p = 0.032, effect size = 0.35), whereas vertical upward gains and horizontal gains showed no statistically significant differences between participants with and without neck pain. Conclusion: Individuals with CMNP demonstrate modifications in the mechanical properties of masticatory muscles, along with noticeable impairments in oculomotor control. The findings underscore the importance of implementing comprehensive assessment and management strategies that specifically address both myofascial and sensorimotor dysfunctions in CMNP. Trial registration:The trial registration number for this study is IEC 828-2021. The trial was registered with the Clinical Trials Registry, India CTRI/2022/02/040383. Registration date: 17/02/2022.