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J Am Dent Assoc, Vol 137, No 9, 1267-1274.
© 2006 American Dental Association
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RESEARCH

JADA Continuing Education

Headache impact in patients with orofacial pain



Somsak Mitrirattanakul, DDS, PhD and Robert L. Merrill, DDS, MS


   ABSTRACT
TOP
 ABSTRACT
OROFACIAL PAIN DISORDERS
 SUBJECTS AND METHODS
 RESULTS
 DISCUSSION
 CONCLUSIONS
 REFERENCES
 
Background. The authors conducted a cross-sectional survey to assess headache disability in patients with orofacial pain.

Methods. The authors administered a Migraine Disability Assessment (MIDAS) questionnaire to 337 university-based clinic patients with OFP and 367 general dental (GD) patients, who served as controls. They made primary and secondary diagnoses in patients with OFP according to standard diagnostic criteria. The authors classified the patients into three major categories: primary headache (PH), musculoskeletal disorders (MS) and neuropathic pain (NP). They categorized the MIDAS score into four severity grades (I, the lowest, through IV, the highest). The authors analyzed the data using {chi}2, t test, one-way analysis of variance and logistic regression for calculated odds ratios.

Results. Patients with OFP had a greater prevalence of headache than did patients in the GD group (72.7 percent versus 31.9 percent, respectively; P < .001), with a higher total MIDAS score, number of headache days in the previous three months and headache severity (P < .001). Within the OFP group, the diagnostic prevalence of PH, MS and NP was 7.1 percent, 79.8 percent and 13.1 percent, respectively (P < .001). The authors categorized 56 percent of patients with OFP and headache into the high-impact headache group (MIDAS grades III and IV; P < .001).

Conclusions. Patients with OFP had a higher prevalence of headache with greater disability impact than did control subjects. The degree of disability was related strongly to the MS diagnosis.

Clinical Implications. The coexistence of PH and MS disorders can lead to higher headache disability. Clinicians need to treat both disorders concomitantly, which will result in improved treatment outcomes.

Key Words: Orofacial pain; headache disability; MIDAS; musculoskeletal disorders

Chronic orofacial pain (OFP) conditions include musculoskeletal disorders, oral cancer, glossodynia and neuropathies such as trigeminal, traumatic and postherpetic neuralgias, as well as primary headache (PH) disorders such as migraine, tension-type and cluster headaches. Among these conditions, the most prevalent are musculoskeletal in origin (for example, temporomandibular disorders [TMDs]).


   OROFACIAL PAIN DISORDERS
TOP
 ABSTRACT
 OROFACIAL PAIN DISORDERS
SUBJECTS AND METHODS
 RESULTS
 DISCUSSION
 CONCLUSIONS
 REFERENCES
 
As with headache, OFP disorders, including TMD, are highly prevalent conditions in the general population.1,2 These disorders represent a real contemporary health problem, particularly as they become interrelated.3–6 Not surprisingly, self-reported headache is one of the most common symptoms in patients with TMD.7–16 The diagnosis of these headaches using standardized criteria has not been explored critically in the OFP population.

Some studies have demonstrated that treating various TMD symptoms can significantly decrease headache, indicating a close relationship between these two disorders.15,17–24 Typically, patients with TMD have myofascial trigger points in the masticatory and cervical muscles that, when palpated, replicate or exacerbate some self-reported headache complaints.25 While tension-type headache may be associated more readily with TMD, other PH disorders, such as migraine or autonomic cephalalgias, arise from nonmasticatory structures. However, the presence of painful TMD symptoms also may have an excitatory influence on these headaches, because both meningeal nociceptors and nociceptive inputs from masticatory structures, as well as upper cervical nociceptors, converge in the medullary trigeminal nucleus for their connections with second-order neurons.26

The impact of headache in patients with OFP has not been studied widely. Disability, as defined by the World Health Organization, is a consequence of illness or inability to work or function.27 In this study, we used the Migraine Disability Assessment (MIDAS) questionnaire to determine headache disability in patients with OFP. MIDAS is a validated and reliable tool for assessing disability resulting not only from migraine, but from other headache disorders as well.28–30 MIDAS is designed to measure headache-related disability in the workplace, in the household and in nonwork activities (such as family and other social activities) via a simple five-item self-administered questionnaire. The MIDAS score is simply a sum of the number of lost days from five items in these three domains.

Although previous studies have shown that headache disorders result in both work and non-work disability,31–33 there are also direct and indirect costs related to the attendant disability.34 We focused on disability because it is the major determinant of the cost of illness.35 In addition, while clinicians often fail to ask patients about disability, information regarding disability is an important determinant of treatment needs when it is obtained or made available.

We designed this study to describe the prevalence of headache, its associated disability and its relationship to major OFP diagnoses of musculoskeletal disorders (MS) and neuropathic pain (NP).


   SUBJECTS AND METHODS
TOP
 ABSTRACT
 OROFACIAL PAIN DISORDERS
 SUBJECTS AND METHODS
RESULTS
 DISCUSSION
 CONCLUSIONS
 REFERENCES
 
We conducted a cross-sectional study of patients with OFP and general dental (GD) patients seeking care from July 2001 to June 2002 at the University of California, Los Angeles School of Dentistry. Research assistants distributed a self-administered MIDAS questionnaire to 350 consecutively seen patients who were seen first in the OFP graduate clinic and 380 new GD patients who served as controls. Owing to incomplete data, we included only 337 patients with OFP and 367 GD patients in this study. This university-based OFP clinic is a tertiary care provider for patients referred by their general or specialty dentists, family physicians and specialists in head and neck pain problems. We obtained demographic data, including age and sex, from both groups.

We made primary and secondary diagnoses for the patients with OFP, according to the 1996 diagnostic guidelines of the American Academy of Orofacial Pain36 and the International Classification of Headache Disorders (ICHD II) criteria.37 We further categorized the primary diagnoses (for example, capsulitis, myofascial pain) of patients with OFP (that is, their chief complaint) into three diagnostic categories: PH, MS and NP.

Diagnoses. For the PH category, the diagnoses included migraine with or without an aura, tension-type headaches with or without peri-cranial tenderness, cluster headache, chronic migraine or other PHs. Where necessary, we ruled out secondary headaches via appropriate comprehensive diagnostic testing and/or referral for neurological evaluation. Diagnoses in the MS category included myofascial pain, temporomandibular joint disk displacement with or without reduction, limited opening, arthralgia, arthritis and arthrosis. For the NP category, the diagnoses included trigeminal neuralgia, glossopharyngeal neuralgia and other cranial neuralgias, as well as peripheral and central trigeminal neuropathy. Where applicable, we examined patients further to rule out dental or soft-tissue disease.

The questionnaire asked all subjects whether they had experienced any headache during the previous three months. If the answer was "yes," we then asked them to complete the MIDAS questionnaire. We placed the patients who did not report having any headaches during the previous three months in the "no headache" group. The total MIDAS score is derived from the sum of the scores from five questions about missed time from work (or school) and household work (one question each about missed days and days with at least 50 percent reduced productivity) and missed days of nonwork activities (such as social events) for a three-month period before the initial visit.

In addition to the five items used to calculate the MIDAS scores, we recorded two items: average severity of headache pain and number of days with headache in the previous three months. We recorded the average severity of headache pain on a visual analog scale (VAS) from 0 to 10. We categorized the total MIDAS score into one of four grades (I to IV) of increasing severity of disability, and then subcategorized these groups into low- or high-impact headache according to the MIDAS grade. We considered MIDAS grades I and II to represent low impact and grades III and IV high impact.

Statistical analyses. We used a {chi}2 test to show the frequency differences in categorical variables such as sex, diagnostic category and headache impact category. We used a one-way analysis of variance (ANOVA) and t test to assess differences between groups regarding variables such as age, MIDAS score, headache days and VAS score. We used logistic regression analyses to calculate odds ratios (ORs) for the likelihood of the MS diagnostic category being included in the high-impact group. We considered a P value of less than .05 to be statistically significant.


   RESULTS
TOP
 ABSTRACT
 OROFACIAL PAIN DISORDERS
 SUBJECTS AND METHODS
 RESULTS
DISCUSSION
 CONCLUSIONS
 REFERENCES
 
Table 1Go shows demographic and other information for subjects in the GD and OFP groups. For patients in each group who reported experiencing headache, the {chi}2 test showed that more patients in the OFP group than in the GD group were in the high-impact group and, conversely, that more patients in the GD group than in the OFP group were in the low-impact group.


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  		TABLE 1 General characteristics of study groups.

 
For patients with headache in each group, Table 2Go shows MIDAS scores for each item. The t test revealed that each MIDAS item’s score was statistically higher in the OFP group than in the GD group. We noted that for patients with OFP and headache, the average number of days missed in household work (item 3), productivity reduced by one-half or more in household work (item 4) or missed nonwork and social activities (item 5) were greater than those for school or work time (items 1 and 2). In addition, a t test revealed that patients in the OFP group had higher total MIDAS scores, more headache days in the previous three months and higher average headache severity than did patients in the GD group with headache (P < .001).


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  		TABLE 2 MIDAS* scores for both groups with headache in previous three months.

 
Table 3Go (page 1271) shows the headache impact and disability among three groups of patients with OFP. One-way ANOVA with a post hoc analysis (Tukey test) revealed significant differences in age among the no headache, low-impact headache and high-impact headache groups (P < .001). A {chi}2 test revealed that a significantly greater percentage of subjects with OFP in the high-impact group were in the MS diagnostic category than in either of the other two diagnostic categories. The combined percentages of subjects in the low- and high-impact headache groups also were highest for the MS diagnostic category.


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  		TABLE 3 Headache impact and disability in patients with OFP* in previous three months.

 
In addition, a t-test analysis revealed that the number of headache days and headache severity were significantly higher in the high-impact groups than in the low-impact groups in all three diagnostic categories. Only the number of headache days for the NP category did not reach a statistically significant difference.

Finally, we evaluated the effect of MS, the most common OFP diagnostic category, when it coexisted with other diagnoses, either as a primary or secondary diagnosis. We found that when PH was the primary diagnosis, the presence of MS as a secondary diagnosis amplified the mean MIDAS score, number of headache days in the previous three months and headache severity, and it resulted in an OR of 3 for a likelihood of being included in the high-impact group (Table 4Go, page 1272). However, this did not reach statistical significance, possibly owing to the small sample size in this group.


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  		TABLE 4 Primary and secondary diagnoses of patients with OFP* and headache in previous three months.

 
When MS was the primary diagnosis and PH was the secondary diagnosis, the combination amplified significantly the mean MIDAS score, the number of headache days in the previous three months and the headache severity, and it resulted in a significant OR of 1.51 for being included in the high-impact group. However, the coexistence of MS and NP did not result in a significant OR for the likelihood of being in the high-impact headache group. This also may have been due to the small sample size in each subgroup.


   DISCUSSION
TOP
 ABSTRACT
 OROFACIAL PAIN DISORDERS
 SUBJECTS AND METHODS
 RESULTS
 DISCUSSION
CONCLUSIONS
 REFERENCES
 
These study results show that the majority of patients with OFP were female. This finding coincides with other clinical epidemiologic studies of OFP/TMD,38,39 general pain40 and headache populations.41,42 These results also showed a similar trend of higher headache prevalence in the OFP group than in the GD group. The prevalence of headache in TMD populations was reported previously in a range of 48 to 77 percent.7,18,43,44

The impact of TMD has been shown to resemble that of other chronic pain conditions.45 In 1992, Research Diagnostic Criteria were developed to classify TMD with a dual-axis approach.46 Axis I is devoted to clinical diagnosis, whereas Axis II is devoted to psychosocial classification, including a graded chronic pain scale. However, no studies, to our knowledge, have evaluated the impact of headache in this population, despite the fact that headache is one of the most prevalent symptoms in the population with TMD.

MIDAS questionnaire. Although there is no specifically designed tool to measure headache disability in patients with OFP, this study has shown that the MIDAS questionnaire could assess headache disability readily and appropriately in this population. When we compared the MIDAS scores (Table 2Go), we found a distinctive difference between GD patients and patients with OFP (the total mean score for the GD group was only 9.38, whereas the total mean score for patients with OFP was 37.0). Clearly, headache has a higher impact on patients with OFP, and the degree of disability affecting patients’ functioning in their personal and professional lives is immense.

We subdivided patients with OFP into three main diagnostic categories (PH, MS and NP) on the basis of their primary diagnosis. As shown in Table 3Go, the highest prevalence of PH was in the high-impact headache group. This might be explained by the fact that chronic daily headaches are associated commonly with a high degree of disability.47,48

These data demonstrate an interesting correlation between OFP and headache, leading us to consider a causal or exacerbating relationship. As shown in Table 4Go, the coexistence of a primary diagnosis of PH with a secondary diagnosis of MS or, conversely, a primary diagnosis of MS with a secondary diagnosis of PH significantly amplifies the degree of disability in each diagnostic category alone, possibly indicating a synergistic relationship between these two disorders.

Headache mechanisms. The current theories regarding headache mechanisms relate to cortical spreading depression, unstable inhibitory brainstem modulation and the development of central secondary sensitization in migraine-susceptible patients.49–52 Clearly, secondary sensitization leads to peripheral allodynia, which is noted often in tender masticatory and cervical muscles during the ictal phase of headache. Our study findings suggest that other events (for example, nociception in the masticatory muscles) commonly seen in patients with MS disorders also may induce or increase central sensitization in patients with headache, resulting in induction (kindling) or worsening of headache in an already sensitized brainstem.53–57

If a patient with OFP experiences masticatory muscle pain only as an epiphenomenon of secondary sensitization, one would expect that treating the headache itself would resolve the muscle pain. Reports are found in the literature regarding the resolution of MS symptoms after administering dihydroergotamine-45 or a triptan to these patients.58 However, in the OFP population, with ongoing musculoskeletal pain, the frequency and intensity of the headache have been reported to improve by reducing the nociceptive input from the masticatory muscles and joints through physical therapeutic modalities.21,59 Furthermore, several authors60–62 have suggested that it is uncommon to see the muscle pain resolve in these patients with use of abortive migraine medications (such as triptans). This suggests that nociceptive activity around the pericranial blood vessels not only can induce a neurogenic inflammatory response, kindling a migraine and inducing pericranial allodynia, but also that nociceptive activity in other trigeminal afferents, such as muscle and joint, may kindle and/or exacerbate headache.

Although this study compared the relationship between MS and PH, the MS diagnosis did not clearly separate muscle disorders from joint disorders. Future studies are needed to clarify this issue by separating muscle disorders from joint disorders. In addition, patients in a tertiary care center commonly have more psychological issues than other patients that affect their pain and disability, because typically they have been shunted from clinician to clinician without benefit before being referred to a comprehensive-care university clinic.63–65 It would be helpful to obtain standardized comparative psychological data, in addition to the disability data that we evaluated in this study, to determine the impact of psychological issues.


   CONCLUSIONS
TOP
 ABSTRACT
 OROFACIAL PAIN DISORDERS
 SUBJECTS AND METHODS
 RESULTS
 DISCUSSION
 CONCLUSIONS
REFERENCES
 
Our findings show that the prevalence of headache is significantly higher in patients in the OFP group compared with that in GD patients serving as controls. In addition, the degree of disability associated with the headache was higher in the OFP group, and the association of MS with PH significantly increased the severity of reported pain and disability in the OFP group with headache compared with that in the individual PH or MS diagnostic categories. Finally, as suggested by the data, it is important to address both MS and PH when treating patients with OFP to optimize outcomes. These data suggest that treating only one of the disorders will result in suboptimal therapeutic outcomes.


   FOOTNOTES
 

Dr. Mitrirattanakul is an instructor, Occlusion Unit, Faculty of Dentistry, Mahidol University, Bangkok, 6 Yothi Street, Ratchatevi, Bangkok, 10400 Thailand, e-mail "sammu99{at}gmail.com". Address reprint requests to Dr. Mitrirattanakul.


Dr. Merrill is an adjunct professor, Division of Oral Biology and Medicine, University of California, Los Angeles, School of Dentistry.


   REFERENCES
TOP
 ABSTRACT
 OROFACIAL PAIN DISORDERS
 SUBJECTS AND METHODS
 RESULTS
 DISCUSSION
 CONCLUSIONS
 REFERENCES
 

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