Pericranial and General Sensitivity in Patients With Primary Headache

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.