Patients with tension-type headache (TTH) and migraine often experience musculoskeletal complaints, like neck pain and/or jaw pain. Earlier studies have revealed an association between different headache types and neck pain and discussed the possible role of the cervical muscles. Furthermore, patients with neck pain show a decrease in motor control of the jaw, without having any other signs of TMD. Similarly, studies in patients with TMD have only found an indication for poorer neck muscle function. Patients with TMD also show a decrease in bite force and force steadiness compared to healthy controls. It is however, unknown if bite force and force steadiness are similarly impaired in patients with headache and/or neck pain.

The current study will take a closer look at the jaw muscle function of in patients with TTH, with and without neck pain.

Tension-type headache (TTH) and migraine has been found to coincide with cervical pain, musculoskeletal dysfunction and/or temporomandibular disorders (TMD). The possible interplay between these three symptoms/disorders, headache, neck pain and TMD, have not been studied completely, only in sections. Earlier studies have revealed an association between different headache types and neck pain and discussed the possible role of the cervical muscles. Patients with TTH and (chronic) migraine exhibit lower muscle strength in the neck extensor muscles compared to healthy controls. Patients with neck pain show a decrease in motor control of the jaw, without having any other signs of TMD. Similarly, studies in patients with TMD have only found an indication for poorer neck muscle function while patients with TMD also show a decrease in bite force and force steadiness compared to healthy controls. It is however, unknown if bite force and force steadiness are similarly impaired in patients with headache and/or neck pain.

Muscle tenderness increases with increasing headache frequency and intensity in TTH while this association is not present in migraine patients. Tenderness has a significant influence on the neck muscle function in TTH patients and there is a negative correlation between Total Tenderness (TTS) and muscle force. There is currently, however, no clear understanding of the influence of tenderness on the function of jaw muscles in TTH patients.

The current project will increase the investigator's understanding of the interplay or dependency between the function of the jaw and neck muscles in TTH patients. If a comorbidity of TMD or neck pain make TTH patients more prone to dysfunction of jaw and neck muscles, this may lead to a subgrouping of these TTH patients. Together with the muscle function deficits discovered in the current case control study, this may suggest a targeted treatment for TTH to be tested in a follow up randomized control study.

Inclusion Criteria:

• Age between 18 and 55 years old.
• Diagnosed Frequent episodic TTH (1-14 headache days / month) or chronic TTH (≥15 headache days/ month) based on the ICHD-3.
• Maximum 3 days of migraine per month.
• Signed informed acceptance of participation.

Exclusion Criteria:

• medication overuse headache (ICHD-3)
• missing more than 1 molar,
• previous whiplash or head trauma,
• other major physical or neurological diseases,
• diagnosed depression, other mental illness
• unable to understand and speak Danish.
• Pregnant or lactating women.

Patients will be recruited from the Danish Headache Center. Additionally the patients and healthy controls will be included from a Danish web page for trials www.forsoegsperson.dk and from a research data base in Danish Headache Center during 2019-2020. When the participants respond through the webpage through either mail or telephone, they will receive written information through mail. They will be informed that they have the right to take a family member or close related, And that the oral information will be postponed till all can participate.

It is not yet known if there will be a plan to make IPD available.