Primary headaches such as migraine and tension type headache are among the most common neurological disorders and frequently cause significant disability and reduced quality of life. Increasing evidence suggests that these headaches may share biological mechanisms with temporomandibular disorders, a group of conditions affecting the jaw muscles and temporomandibular joint. Both conditions are also often associated with other chronic pain disorders, suggesting that altered pain processing and sensitization of the nervous system may play an important role in their development.

Despite these observations, few studies have simultaneously evaluated local muscle tenderness around the head and neck, generalized pain sensitivity in other parts of the body, and the presence of additional chronic pain conditions in patients with primary headaches. Understanding how these factors interact may help clarify why some patients develop more severe or persistent headache disorders and may improve future diagnostic and treatment strategies.

The aim of this multicenter observational study is to compare patients with primary headaches to healthy individuals without headaches. The study will assess sensitivity of muscles around the head and neck, general pain sensitivity at distant body sites, the presence of temporomandibular disorders, and the number of other chronic pain conditions. Participants will also complete questionnaires about pain symptoms and related health conditions.

Participants will undergo a clinical examination performed by trained clinicians, including manual assessment of tenderness in head and neck muscles and measurement of pressure pain thresholds using a handheld device. Additional evaluations will include standardized questionnaires about pain intensity, pain distribution, and symptoms related to central sensitization. Cervical motor and sensorimotor function will also be evaluated using a wearable sensor system.

By comparing individuals with primary headaches and healthy controls, the study aims to better understand the relationship between headache disorders, jaw related pain conditions, and general pain sensitivity. The results may contribute to improved clinical assessment and a more comprehensive understanding of the mechanisms underlying headache and related pain disorders.

Primary headaches are among the most prevalent neurological disorders worldwide and represent a major cause of disability and reduced quality of life. Migraine and tension type headache are the most common forms and are characterized by complex pathophysiological mechanisms involving peripheral and central nervous system processes. These mechanisms include altered nociceptive processing, dysfunction of endogenous pain modulation systems, neurovascular interactions, and neuroinflammatory responses.

Temporomandibular disorders are musculoskeletal conditions affecting the temporomandibular joint, masticatory muscles, and associated structures. Previous research has shown that temporomandibular disorders frequently coexist with primary headaches. Both conditions share anatomical and neurophysiological pathways through the trigeminal system, which may contribute to overlapping clinical manifestations and mutual influence between disorders. In addition, individuals with temporomandibular disorders or headaches often present with other chronic overlapping pain conditions such as low back pain, fibromyalgia, irritable bowel syndrome, or chronic fatigue syndrome. This broader pattern of comorbidity has been associated with altered pain sensitivity and central sensitization mechanisms.

Experimental and clinical studies have demonstrated that patients with primary headaches and temporomandibular disorders often exhibit increased tenderness of pericranial and cervical muscles as well as reduced pressure pain thresholds both locally and at distant anatomical sites. These findings suggest the presence of peripheral sensitization in local tissues together with generalized hypersensitivity reflecting central sensitization processes. However, previous studies have often assessed these mechanisms separately, have used heterogeneous methodologies, and have rarely evaluated headache disorders and temporomandibular disorders simultaneously using standardized diagnostic criteria.

The present study aims to address these limitations through a multicenter observational design conducted in Spain and Germany. The study will compare individuals diagnosed with primary headache to healthy control participants without clinically relevant headache symptoms. The primary objective is to evaluate differences in pericranial muscle tenderness and generalized pressure pain sensitivity between these groups. Additional objectives include exploring the association between the number of chronic overlapping pain conditions and measures of pain sensitization, and examining the coexistence between primary headaches and temporomandibular disorders.

Participants with primary headache will be diagnosed according to the International Classification of Headache Disorders third edition by headache specialists. Temporomandibular disorders will be assessed using the Diagnostic Criteria for Temporomandibular Disorders. Pain sensitivity will be evaluated through standardized manual palpation of pericranial muscles using the Total Tenderness Score and by measuring pressure pain thresholds at extra trigeminal anatomical sites with digital algometry. Additional clinical variables will include self reported pain intensity, pain distribution, and symptoms associated with central sensitization. Cervical motor and sensorimotor function will also be assessed using a wearable sensor based measurement system that records cervical movement patterns and proprioceptive performance during standardized tests.

By integrating clinical examination, quantitative sensory testing, and standardized questionnaires within the same protocol, the study aims to provide a comprehensive characterization of pain sensitivity and comorbidity patterns in patients with primary headache. The results may improve understanding of the relationship between headache disorders, temporomandibular disorders, and generalized pain sensitization, and may contribute to the development of more comprehensive diagnostic and therapeutic approaches for individuals with complex pain presentations.

Inclusion Criteria

Adults diagnosed with primary headache disorders, including migraine or tension-type headache, according to the International Classification of Headache Disorders third edition.

Diagnosis confirmed by a headache specialist.

Stable medical treatment for headache for at least six months prior to participation.

Ability to understand and communicate in Spanish, English, or German.

Ability to provide written informed consent.

Exclusion Criteria

Presence of secondary headache disorders or clinical suspicion of secondary headache based on screening criteria.

Recent onset of undiagnosed headache or unilateral neck pain associated with neurological or neuropathic symptoms.

Severe dermatological conditions or injuries affecting the head, neck, or intraoral region that could interfere with clinical examination.

Recent fractures affecting the head or cervical region.

Previous diagnosis of uncontrolled psychiatric disorders or neurodegenerative diseases.

Pregnancy.

Participants of any self-identified gender are eligible to participate in the study. Both male and female participants, as well as individuals who identify with other gender identities, may be included provided they meet the study inclusion and exclusion criteria.

The study population will consist of adults recruited from neurology and orofacial pain clinical settings as well as from the general population. Participants with primary headache disorders will be recruited through headache specialists and clinicians working in participating centers. Eligible patients must have a confirmed diagnosis of primary headache according to the International Classification of Headache Disorders third edition and be under stable medical treatment. Healthy control participants will be recruited from the community, including students and university staff, and will be screened using a structured questionnaire to exclude individuals with clinically relevant headache disorders. All participants will be adults able to understand the study procedures and provide informed consent. Recruitment will take place at clinical and academic centers in Spain and Germany.