Teeth grinding and headache – chicken or egg?
Teeth grinding (bruxism) has been commonly linked to headache. Bruxism is not a niche phenomenon. One in five female college students and one-tenth of their male peers are aware that they clench or grind their teeth while sleeping, according to a survey of 4400 students (Finnish Student Health Survey)1. Thirty-seven percent of respondents also reported pain consistent with a condition called temporomandibular disorder (TMD or TMJ).
TMD is characterized by temporomandibular joint pain, reduced opening of the jaws ('trismus'), clicking or popping of the temporomandibular joint during movement, and tense jaw muscles. Magnetic resonance imaging (MRI) frequently shows fluid buildup in the temporomandibular joint, or displaced cartilage. Interestingly, there is significant gender disparity in symptom severity. Pain intensity and muscle tension are significantly worse in women than men with the condition. Males have an even age distribution. In women, peak onset is under the age of 25 and between 55 and 60.
The headache connection
Neurologists often see headache patients with concurrent TMD3, but the scientific evidence is inconsistent. This is often due to differences in study design and methods. In several studies, participants who were headache patients were significantly more likely to have TMD than those who were not. In a study by the Universities of Copenhagen and Aarhus, about 56% of headache patients had TMD4 compared to a reported prevalence of only 5-15% in the general population. Conversely, a controlled study in São Paulo found that 85.5% of the study population - all of whom had TMD - suffered from headache.5 More than half of these patients met the criteria for migraine. However, this is not a representative study, one reason being the small sample size.
What does other research about headache and teeth grinding say, and is there a trend? In an attempt to find out, Graziela de Luca Canto et al. reviewed 449 publications pertinent to the relationship between nocturnal bruxism (teeth clenching and grinding at night) and headaches6. The studies were screened for uniform diagnostic criteria to ensure comparability. Only 2 of the 449 studies met the criteria. Bruxism was found to be much more likely in individuals with headache disorder, with one study indicating a higher association for migraine in particular. However, causality cannot be inferred from any of the studies.
Causality moot, but...
The evidence suggests that headache and temporomandibular dysfunction probably interact and aggravate each other. Especially in migraine patients, stress due to the strain on the jaw muscles caused by bruxism can trigger an attack.
The conclusion is that treatment of TMD may be necessary to alleviate headache, but is unlikely to cure a chronic headache disorder. Moreover, not everyone knows that they have bruxism, especially if it happens at night.
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References
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1. Huhtela OS, Näpänkangas R, Joensuu T, Raustia A, Kunttu K, Sipilä K. Self-Reported Bruxism and Symptoms of Temporomandibular Disorders in Finnish University Students. J Oral Facial Pain Headache. 2016 Fall;30(4):311-317. doi: 10.11607/ofph.1674.
2. Schmid-Schwap M, Bristela M, Kundi M, Piehslinger E. Sex-specific differences in patients with temporomandibular disorders. J Orofac Pain. 2013 Winter;27(1):42-50. doi: 10.11607/jop.970.
3. Göbel, Hartmut: Die Kopfschmerzen: Ursachen, Mechanismen, Diagnostik, Therapie. 3. Auflage Berlin / Heidelberg. 2012.
4. Ballegaard V, Thede-Schmidt-Hansen P, Svensson P, Jensen R. Are headache and temporomandibular disorders related? A blinded study. Cephalalgia. 2008 Aug;28(8):832-41. doi: 10.1111/j.1468-2982.2008.01597.x. Epub 2008 May 21.
5. Franco AL, Gonçalves DA, Castanharo SM, Speciali JG, Bigal ME, Camparis CM. Migraine is the most prevalent primary headache in individuals with temporomandibular disorders. J Orofac Pain. 2010 Summer;24(3):287-92. PubMed PMID: 20664830.
6. De Luca Canto G, Singh V, Bigal ME, Major PW, Flores-Mir C. Association between tension-type headache and migraine with sleep bruxism: a systematic review. Headache. 2014 Oct;54(9):1460-9. doi: 10.1111/head.12446. Epub 2014 Sep 18. Review.
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