Pain in the temple? Headache,muscle pain or both: A retrospective analysis

Abstract

Aim

Headache attributed to temporomandibular disorders and myalgia are two diagnoses included in the diagnostic criteria for temporomandibular disorders (DC/TMD). However, it is not clear if these two diagnoses are different clinical entities given their similar presentation and way in which they are diagnosed, when the myalgia is within the temporalis muscle. The purpose of this retrospective study was to assess the overlap between headache attributed to temporomandibular disorders and myalgia of the temporalis muscle.

Methods

The charts of 671 patients seeking treatment at the Section of Orofacial Pain and Jaw Function, Aarhus University, Denmark, between January 2015 and February 2020 were screened for a diagnosis of headache attributed to temporomandibular disorders, myalgia of the temporalis muscle, or both.

Results

A total of 89 patients fulfilled the DC/TMD criteria for either headache attributed to TMD, myalgia of the temporalis or both. Of these, two had a diagnosis of headache attributed to TMD, 16 of myalgia of the temporalis, and 71 were diagnosed with both. In 97.3% of the times that headache attributed to temporomandibular disorders was diagnosed, the patient was also diagnosed with myalgia of the temporalis. The Jaccard index was 0.8, indicating a substantial overlap between the two diagnoses. Finally, the overlap of pain location between the two diagnoses was substantial, with a Jaccard index of 0.9.

Conclusions

In the present study, headache attributed to temporomandibular disorders was almost exclusively diagnosed together with myalgia of the temporalis. Therefore, we propose that headache attributed to temporomandibular disorders and myalgia of the temporalis muscle have more clinical similarities than differences and as such could be considered one single clinical entity. Further studies will be needed to address the clinical consequences of this proposal.

Introduction

The overlap between painful temporomandibular disorders (TMD) and headache in terms of prevalence and clinical characteristics has been substantially reported in the literature (1–4). Surprisingly, it has been shown to mainly occur between TMD and migraine and to a slightly lesser extent with tension-type headache (1,3,5) and it seems to be more related to myalgia than arthralgia (6). Due to this substantial overlap, diagnostic criteria for an additional TMD diagnosis; that is, headache attributed to TMD, has been proposed and is defined as a headache in the temple area that occurs secondary to the development of painful TMD (7).

Clinically, headache attributed to TMD seems to mostly co-occur with myalgia of the temporalis (8) and does not seem to hinder response to treatment when compared to patients without headache attributed to TMD (9). As such, it could be proposed that what is diagnosed as headache attributed to TMD is pain in the temporalis muscle that patients report as being a headache. No previous studies have investigated this issue, however, and there are at least three reasons that could be responsible for this overlap in diagnosis. Firstly, anatomically the affected area, the temple, overlaps substantially in both diagnoses. Secondly, the steps required to establish the headache attributed to TMD diagnosis are the same as for myalgia of the temporalis, with the exception that for headache attributed to TMD the patient must state that a familiar headache has been provoked and for myalgia of the temporalis they must state that familiar pain has been provoked (10). Thirdly, treatment targeted specifically to the temporalis muscle has been shown to decrease pain perception in the temporalis muscle in headache attributed to TMD patients (11).

One way of understanding if headache attributed to TMD and myalgia of the temporalis are the same clinical entity is by assessing the extent to which they overlap in occurrence within the same patient. It stands to reason that if the overlap is substantial, these two diagnoses most likely represent the same clinical entity.

As such, the purpose of this study was to retrospectively assess the overlap of headache attributed to TMD and myalgia of the temporalis in patients seeking care at the Section of Orofacial Pain and Jaw Function at Aarhus University, Denmark.

Materials and methods

Sample

This is a retrospective study of the medical records of consecutive patients who sought treatment at the Section of Orofacial Pain and Jaw Function, Aarhus University, between January 2015 and February 2020. The study received approval from the Danish Patient Safety Authority (3-3013-2557/1) and received a waiver of informed consent. The inclusion criteria were patients with a diagnosis of myalgia of the temporalis and/or headache attributed to TMD according to the DC/TMD (10). Included patients were allowed to have other DC/TMD diagnoses such as myalgia of the masseter muscle, arthralgia and disc displacement with reduction. Exclusion criteria were a diagnosis of a non-painful TMD or any other painful orofacial pain diagnosis that was not myalgia of the temporalis or headache attributed to TMD, as well as charts that were incorrectly filled out and as such did not allow a diagnosis of headache attributed to TMD or myalgia of the temporalis.

A posteriori we noted that a significant number of patient charts were excluded due to incomplete or incorrectly filled out DC/TMD forms. There were two main reasons for this: i) patients reporting headache in the temple area during the clinical examination that did not report this headache in the symptom questionnaire (SQ5 and/or SQ7); ii) patients reporting familiar temple pain during the clinical examination that did not report it in the first question of the examination form (E1a). To assess whether excluding these patient charts had a significant effect on our final results we decided, as a secondary outcome, to make a diagnosis of headache attribute to TMD and myalgia of the temporalis based solely on the examination form. In this way, we allowed for a higher possibility of a diagnosis of headache attributed to TMD, as most of our exclusions were because patients did not report headache in the symptom questionnaire.

Diagnosis

Patients were diagnosed with headache attributed TMD and/or myalgia of the temporalis when they fulfilled the diagnostic criteria described by Schiffman et al. (10). Patients were given a diagnosis of possible headache attributed to TMD and possible myalgia of the temporalis if they fulfilled the criteria for the alternative criteria based solely on the examination form. A possible myalgia of the temporalis diagnosis required examiner confirmation of pain location in the temporalis area (E1a) and familiar pain in the temporalis area from jaw opening, excursive movements or palpation of the temporalis muscle. A possible headache attributed to TMD diagnosis required examiner confirmation of headache location in the temporalis area (E1b) and familiar headache in the temporalis region from jaw opening or excursive movement or palpation of the temporalis muscle.

Pain location

To assess the overlap in pain location within the temporalis muscle for patients with both diagnoses, the data from the muscle palpation done during the DC/TMD examination (E9) was used. For this, the temporalis muscles of each patient were divided into three parts: Anterior, middle and posterior as per the DC/TMD clinical examination protocol (10). If a patient reported familiar pain or headache a 1 was given and if no familiar pain or headache was reported a 0 was given. This was done for both the right and the left temporalis muscles. In this way, familiar pain and headache location were described as an array of binary values for each patient. For descriptive purposes, pain frequency maps were executed to illustrate the extent of the overlap (Figure 1).

Figure 1.

Flow chart describing inclusion and exclusion criteria.

Statistical analyses

The overlap between headache attributed to TMD and myalgia of the temporalis diagnoses was investigated using the Jaccard index (12), which assessed the ratio between the overlap of the two relevant diagnoses (headache attributed to TMD ∩ myalgia of the temporalis) and the total number of patients diagnosed with either of them (headache attributed to TMD ∪ myalgia of the temporalis). The Jaccard index, which can be interpreted as the percentage of overlap, ranges from 0 to 1. A value of 1 implies a complete overlap between the two diagnoses while a value of 0 implies no overlap. In addition, prevalence rates were calculated for the included diagnoses. Finally, the Jaccard index was used to assess the overlap in pain location between the two diagnoses. This assessed the ratio between the overlap of pain location of the two diagnoses and the total number of pain locations for both diagnoses.

Results

The charts of 671 patients were screened and 89 fulfilled the inclusion criteria. In all, 582 patient charts were excluded due to the following reasons: Non-temporalis myalgia + arthralgia (67), non-temporalis myalgia (44), arthralgia (33), post-traumatic trigeminal neuropathic pain (66), trigeminal neuralgia (12), odontogenic pain (27), persistent idiopathic facial pain (10), persistent idiopathic dentoalveolar pain (6), burning mouth syndrome (2), fibromyalgia (1), paroxysmal hemicrania (1), trigeminal postherpetic neuralgia (1), juvenile idiopathic arthritis (1), non-painful diagnosis (90), incomplete or incorrectly filled out DC/TMD forms (99) and no DC/TMD forms (122) (Figure 1).

Of the 89 patients that were included in the study, two had a diagnosis of headache attributed to TMD, 16 of myalgia of the temporalis and 71 were diagnosed with both. This means that 97.3% of the time headache attributed to TMD was diagnosed, myalgia of the temporalis was also diagnosed. In addition, the Jaccard index was 0.8 for the overlap between headache attributed to TMD and myalgia of the temporalis. Of the two patients diagnosed with headache attributed to TMD, both of them were also diagnosed with masseter myalgia and arthralgia.

Of the 99 patients that had incomplete or incorrectly filled out DC/TMD forms, 54 patients were diagnosed with a possible headache attributed to TMD or myalgia of the temporalis, and the remaining 45 were excluded. Of these, three had a diagnosis of possible headache attributed to TMD, 15 of possible myalgia of the temporalis and 36 were diagnosed with both. This means that 92% of the time possible headache attributed to TMD was diagnosed, possible myalgia of the temporalis was also diagnosed.

Finally, the overlap of pain location between the two diagnoses was substantial with a Jaccard index of 0.9. The pain location data showed that the area where patients reported the most familiar pain was the anterior temporalis in 92% of patients and the area where patients reported the most familiar headache was also the anterior temporalis in 93% of the patients. Pain location drawings showing the overlap between the two diagnoses can be seen in Figure 2.

Figure 2.

Differences in familiar pain and headache location in the three different parts of the temporalis muscle. The more opaque the colour, the higher the frequency of reported familiar pain or headache. The purple colour presented for both diagnoses is an overlap of the myalgia of the temporalis (red) and headache attributed to TMD (blue) drawings. It can be seen that the overlap is substantial between familiar pain and headache in patients diagnosed with both conditions.

Discussion

The main findings of this study were that: i) a substantial overlap in diagnosis exists between headache attributed to TMD and myalgia of the temporalis and ii) a substantial overlap in pain location exists between headache attributed to TMD and myalgia of the temporalis.

The aim of the present study was to assess the overlap between headache attributed to TMD and myalgia of the temporalis. To our knowledge, no previous study has attempted to assess the overlap between these two diagnoses. The main finding was that 97% of patients diagnosed with headache attributed to TMD were also diagnosed with myalgia of the temporalis. This substantial overlap was further confirmed by the alternative criteria based solely on the DC/TMD examination form. In addition, when we assessed the areas within the temporalis muscle where patients reported pain, when they were diagnosed with both headache attributed to TMD and myalgia of the temporalis, an almost perfect overlap was shown between the two diagnoses. Taken together, this seems to indicate both diagnoses represent the same clinical condition, which is pain in the temporalis muscle.

There are several ways in which a TMD pain patient can be led to report jaw pain as a headache. The first, as described above, is if a patient has pain in the temporalis muscle and perceives this as a headache. This could also be semantics with a lack of distinction between “headache” and “jaw pain”. Further research into the semantics of pain locations seems appropriate. The second way jaw pain can be perceived as a headache is if pain refers from a masticatory structure, such as the masseter muscle or the temporomandibular joint (TMJ), to the temple region (13). The third is if a patient starts developing TMD and in consequence develops a primary headache such as migraine or tension-type headache (14). One could argue that none of these situations warrant a diagnosis of headache attributed to TMD. In the first situation, a diagnosis of myalgia of the temporalis should be given regardless of whether the patient reports it as familiar pain or familiar headache as the pain is coming from the temporalis muscle. In the second, a diagnosis of myofascial pain with referral or arthralgia should be given. In the third, the most sensible diagnosis would be to give both a diagnosis of TMD and of the primary headache the patient presents with as it has been shown that the relationship between TMD and primary headaches is bidirectional in nature (14,15).

It should be acknowledged that our study has some limitations. Firstly, the data used in this study is retrospective and as such not specifically collected to answer the present research question. The retrospective nature of the study caused many charts to be excluded due to missing data, which could have altered the results. However, the standardized way in which diagnoses were made and the small number of clinicians that examined the patients included in this study (n = 5) may have attenuated this problem slightly. Another limitation was the fact that we had many patients that were excluded from the study due to an incomplete DC/TMD form or other non-TMD pain diagnoses. In these charts, patients did not report headache and/or that the headache was not modified by jaw function in the symptom questionnaire and then during the examination the patients reported familiar headache. In these cases, the clinicians did not go back to the symptom questionnaire to check if in fact the patient had headaches that were modified by jaw function or not. As such, the charts were excluded, as we could not be sure whether they in fact had headache modified by jaw function, which is required for the headache attributed to TMD diagnosis. However, our alternative criteria did not show a considerable difference compared to our initial results. Obviously, prospective studies with larger sample sizes need to confirm the findings from this retrospective study, which nevertheless raises an important clinical question about the content validity of the headache attributed to TMD diagnosis of the DC/TMD.

Conclusion

This study showed a significant overlap between the diagnoses of headache attributed to TMD and myalgia of the temporalis as well as the location of pain for patients diagnosed with both. As such, the possibility that they represent the same clinical entity should be considered.

Article highlights

Diagnoses of headache attributed to TMD and myalgia of the temporalis overlapped substantially.

Location of pain between the two diagnoses also overlapped substantially.

This likely means that the two diagnoses represent the same clinical entity, which is pain in the temporalis muscle.