It's possible that a patient's complaints of headache and/or orofacial pain could be related to different overlapping pathologies or disorders, occurring at the same time, Paolo Bizzarri, PhD student at Vrije Universiteit Brussel (VUB), in Brussels, told Reuters Health by email.
"Therefore, clinicians should not rely on a single diagnosis, but consider both of them in assessment and management of these patients. Preliminary studies have shown better improvements after pharmacological and non-pharmacological therapies when based on both these conditions," said Bizzarri.
"We know that TMDs and primary headaches, still different disorders with different presentations, share several genetic, environmental, psychological and physiological factors. However, the actual relationship between them is not fully understood," he explained.
"One cohort study showed that people with migraine or mixed headache have an increased risk of developing first-onset TMD in the years following the headache diagnosis. Therefore, the hypothesis that specific headaches can 'produce' or 'facilitate' TMD appear supported," he noted.
To investigate further, Bizzarri and colleagues identified 1,405 observational studies in the literature and included 16 cross-sectional studies and one cohort study in their analysis.
The overall risk for TMDs was higher than for control groups for both migraine (odds ratio, 4.01; 95% confidence interval, 2.61 to 6.18) and TTH (OR, 4.43; 95% CI, 2.89 to 6.78) populations, the authors report in a poster at the American Headache Society (AHS) virtual annual meeting.
Bizzarri told Reuters Health the most relevant hypothesis for the relationship is that migraine or TTH induces "a progressive sensitization of neural circuits involving the trigemino-cervical complex, a neural structure processing head and orofacial information (e.g. nociception, and therefore pain). Thus, signals from craniomandibular structures, even if innocuous in healthy subjects, could find an environmental facilitation to be interpreted as pain, which is always a product of our nervous system."
The review also showed that headache patients had higher risk of myogenous TMDs, combined myogenous and arthrogenous TMDs, and painful TMDs - but not arthrogenous TMDs or non-painful TMDs.
These observations are "interesting and intriguing," Bizzarri said, "because the relationship does not appear to be related to every temporomandibular disorder. This association has been found only between muscular, and combined muscular and joint, TMDs, but not joint TMDs."
"Moreover, once we subgrouped for painful and non-painful (disc displacements or degenerations but with no pain, quite prevalent in the general population) TMDs, irrespective of muscular or joint related, only painful TMDs showed an association with primary headaches," he said.
"Therefore, the clinical management of these patients should not be based on painless radiological or clinical findings of joint disorders (disc displacement, joint 'popping' or 'clicking' at mandibular movements), nor on occlusal factors, which do not appear to be related to headaches or orofacial pain," he added.
Furthermore, "as evidence-based migraine or TTH therapies could be helpful in patients with TMD and headache comorbidity, and vice versa, treatments based on mandibular disc 'repositioning' lack scientific background and should not be considered," Bizzarri said.
The study had no commercial funding and the authors have no relevant disclosures.
SOURCE: https://bit.ly/3w78byx American Headache Society annual meeting, held June 3-6, 2021.
By Megan Brooks
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