Are Two Head(ache)s Better Than One

Migraine is a common and debilitating condition that virtually all neurology clinicians see regardless of specialty. In a recent systematic review of the US adult population, 20.7% of women and 9.7% of men experience a migraine attack over a 3-month period. Migraine also disproportionately affects those with limited access to health care including the unemployed and those with lower family incomes.¹ The World Health Organization studies global burden of disease (GBD) to inform health decision making. In 2016, the GBD for all diseases worldwide found that tension-type headache was the third most prevalent and migraine the sixth. In terms of years of life lived with disability, migraine ranked second globally.² Given these statistics, it is not surprising that migraine is costly. A 2018 study found that patients with migraine had total annual direct costs (health care) plus indirect costs (missed work and short- and long-term disability) that were $8924 higher than those of demographically similar individuals without evidence of migraine.³ What these data do not capture is the impact on career trajectory, family involvement, interpersonal relationships, and identity, which is likely to be much greater.

In this issue of Neurology: Clinical Practice, Mathew et al. present a study of the prevalence of occipital neuralgia (ON) in patients who present with headache to an outpatient headache clinic. This retrospective chart review found that 195 of 800 individuals—nearly 25%—presenting with headache had occipital neuralgia (based on their application of ICHD3 criteria).⁴ Only 15% of those studied had isolated ON. Of the 85% who had another headache disorder, the most common was migraine (chronic or episodic migraine with or without aura) occurring in 70% of study patients. Of note, the risk factors for ON were very similar to the risk factors for increased disability associated with migraine including elevated body mass index, longer duration of symptoms, and higher frequency of migraine. As part of the diagnostic criteria, all patients with ON received occipital nerve blocks (ONB) with bupivacaine and triamcinolone either unilaterally or bilaterally depending on the presentation. Although it is presumed that all patients derived temporary relief from ONB, no data are presented regarding the durability of this response or its effect on headache management long term. The study design raises concern for bias related to the retrospective nature of the study using chart review (where documentation can often justify the procedure) and having only 1 clinician examine and treat the patients. More concerning is the fact that the prevalence of ON in this study is much higher than previously reported. In the Bruneck population-based study cited by the authors, the prevalence of all cranial neuralgias was only 1.6%.⁵ A Dutch study found that the incidence of ON was 3.2 per 100,000.⁶ So why the discrepancy of incidence/prevalence of ON between this study and previous studies? It may be related to the definition of ON in ICHD3,⁷ which provides a descriptive but not biologically based diagnosis. Specifically, many of the criteria for ON are seen in other headache disorders (especially migraine) including severe, sharp occipital pain, associated with allodynia, tenderness, or trigger points over the occipital nerve. The study did not present the temporal sequence of migraine and ON, although age at presentation was an associated risk factor; the later development of ON in patients who already have migraine may suggest that ON is simply a peripheral sensitization phenomenon in patients known to occur in migraine with time. In addition, a preponderance of evidence now suggests that migraine itself responds to ONB,⁸ which limits diagnostic specificity for such a treatment. This also raises the possibility that many features of ON are consistent with the diagnosis of migraine. Our clinical experience is inconsistent with the study findings that no occipital Tinel sign was found in several hundred patients without ON. This zero “false-positive rate” implies that the diagnosis of ON did not take into consideration criterion E (not better accounted for by another ICHD-3 diagnosis) where judgment of the entire clinical context should carry the most weight, rather than a single physical examination finding driving diagnostic classification.

This study could have unintended consequences. Based on the results of this study, ONB would be indicated in up to 25% of patients presenting with headache, which would substantially add to the cost of care without clear evidence of improved outcomes by using such a treatment so broadly. Coverage for ONB is quite limited with large commercial insurers who consider this procedure “experimental” for the diagnoses of migraine and ON. Given current limited insurance coverage for ONB, expanding the indications for ONB could potentially jeopardize coverage for indications that have evidence to support therapeutic benefit, particularly in short-term prophylaxis of cluster headache and migraine, status migrainosus, and intractable migraine in pregnancy.^9,10 In conclusion, we commend the authors for this observational study highlighting the potential overlap between migraine and occipital neuralgia, the need for careful history and examination of patients with headache, and highlighting ONB which is an important and likely underused treatment for many patients with headache disorders. However, we caution that critical interpretation of the results is warranted to drive appropriate therapeutic choices. Further research is needed for refinement and prospective field testing of the ICHD3 diagnostic criteria for ON using identifiable clinical, biological, and therapeutic markers.

Author Contributions

H.B. Schwarz and M.S. Robbins: drafting/revising the manuscript.

Study Funding

No targeted funding reported.

Disclosure

H.B. Schwarz and M.S. Robbins perform occipital nerve blocks routinely in their practice of headache medicine. Full disclosure form information provided by the authors is available with the full text of this article at Neurology.org/cp.