Myofascial trigger points in the masticatory muscles in patients with and without chronic mechanical neck pain

The purpose of this study is to describe differences in the presence of masseter and temporalis muscle trigger points (TrPs) and jaw opening between individuals with mechanical neck pain and healthy controls.

Twenty patients with mechanical neck pain (60% women) without symptoms in the orofacial region, aged 20 to 37 years old, and 20 matched controls participated. Temporalis and masseter muscles were examined for the presence of TrPs in a blinded design. Trigger points were considered active if the subject recognized the pain as a familiar symptom, whereas the TrPs was considered latent if the pain was not recognized as a symptom. Jaw opening was assessed with a ruler.

A greater number (P < .001) of TrPs in the masticatory muscles were found in patients than in controls. None of the patients or healthy controls recognized the referred pain as familiar; thus, latent rather than active TrPs were found. The distribution of TrPs between groups was different for the masseter (left odds ratio [OR], 3.4; right OR, 8.1; P < .001) and temporalis (left OR, 2.8; right OR, 5.7; P < .001) muscles. Patients with neck pain had smaller jaw opening than controls (P < .001). A negative correlation between active jaw opening and the number of TrPs within the masticatory muscles (r(s) = -0.6; P < .001) was found: the greater the number of TrPs, the smaller the jaw opening.

For the subjects in this study, those with mechanical chronic neck pain had more latent TrPs in the masticatory muscles and reduced jaw opening compared to healthy controls. These findings may suggest the spread of sensitization from the cervical segment to the trigeminal brain stem sensory nuclear complex.