CeH preferentially effects female headache patients (Racicki et al., 2013). CeH is classified as a secondary headache disorder because the source of the pain is thought to be a consequence of injury to, or disease of, the bony and/or soft tissues of the upper cervical spine (Kristoffersen et al., 2017). Clinical management of CeH is challenging for the physician because a pathology that would account for the pain is usually unknown.

The primary diagnostic criteria that physicians use to diagnose CeH is based upon classification according to the International Headache Society Classification IHSD 3rd Edition (HIS, 2013). CeH is characterized by unilateral head or face pain without side shift that is of moderate to severe intensity of varying duration (Antonaci et al., 2001). CeH may occasionally be bilateral, throbbing, and accompanied by nausea, vomiting, phonophobia, photophobia, and dizziness when chronic tension-type headache and chronic migraine attacks are superimposed (Biondi, 2005). If the source of CeH originates in the upper cervical spine, osteopathic physicians can use head and neck movements and pressure applied to the suboccipital and lower cervical regions (Anarte-Lazo et al., 2021) to provoke referred headache. These diagnostic techniques, along with restricted active and passive range of motion (ROM) of the head and neck (Ogince et al., 2007), provide additional credibility that the diagnosis of CeH is valid (Avijgan et al., 2020) and helps ensure that the efficacy of our treatment protocol is not weakened by applying it to subjects with a different type of headache, such as migraine, that would not be expected to respond to a treatment protocol designed for CeH patients (Bogduk N, 2014).

The largest study of conservative therapy for cervicogenic headache (Jull et al., 2002) reported that manual therapy alone was not more effective than exercises alone. The study reported that headache frequency was reduced by 50% at a 7-week follow up, but figures for reduction in pain intensity were not reported. They reported that combining manipulation and exercise was not significantly superior to either therapy alone. Hidalgo et al., (2017) have reported that combining the 2 therapies is better than either manipulation or exercise alone. The weakness of Jull et al's. (2002) study was that their treatment protocol was applied to subjects who would not have had a common etiology for their headache pain. CeH is defined by injury to, or disease of, the bony and/or soft tissues of the upper cervical spine (Bogduk N, 2014). MRI is the gold standard for diagnostic assessment of structures of the upper cervical spine (Sun et al., 2020), but Jull et, al.'s (2002) study did not include an MRI assessment of the upper cervical spine in their inclusion/exclusion criteria. The outcome of their study reported that their treatment protocol showed a positive effect, but not one that rose to a significant level. I suggest this was due to mixing headache types (CM and CeH) that have different etiologies and expecting a single treatment protocol to address both pathologies.

Since CeH results from injury to, or disease of, the bony and/or soft tissues of the upper cervical spine, it is only reasonable to exclude those patients who do not present with pathology on MRI in the upper cervical spine (Sun et al.,2020). Our study is unique in that we will test the effectiveness of specific interventions that address a specific pathology within a specific headache population. By actively restricting the study cohort to a specific headache population, we will increase our ability to detect a significant change in the outcomes of treatment by increasing the power of the statistical analysis.

This study is unique in that it proposes to investigate a mechanism responsible for referred pain in some instances of chronic CeH. The effectiveness of specific interventions to address a specific pathology within a specific headache population will be tested. It is proposed that pathology in RCPm muscles has been undervalued, primarily because of their small size and a misunderstanding of their functional significance. By actively restricting the study cohort to a specific headache population, the power of the statistical analysis will be increased. It is hypothesized that the combined use of OMT and THE will decrease headache measures of frequency, intensity and duration, will increase the CSA and reduce the percentage of fatty infiltration (FI) of RCPm muscles on MRI, and will reduce forward head posture (FHP) in female patients diagnosed with CeH.