Comment on “Paranasal sinus opacification in headache sufferers: A population-based imaging study (the HUNT study-MRI)”

The role of various types of nasal and paranasal sinus pathology in the causation of headaches is poorly understood. The ICHD-III beta dropped the nomenclature “sinus” headache, noting that this terminology can be confusing, in favor of “headaches attributed to disorders of the nose and paranasal sinuses” (1). Both acute and chronic rhinosinusitis have been recognized as causes of headache if confirmed by careful objective criteria and temporal correlation (1). Nonetheless, attributing headaches to nasal and paranasal sinus pathology—even when imaging shows paranasal sinus opacification—is complicated for the following reasons:

Studies have suggested that people reporting “sinus” headaches invariably have primary headache disorders, with sinusitis being the etiology in perhaps only 3–5% of such patients (2,3).

Over 90% of patients with primary headache disorders may have nasal symptoms—such as rhinorrhea, congestion and postnasal drainage—even in the complete absence of any positive findings of rhinosinusitis by nasal endoscopy and paranasal sinus computed tomography scans (4).

Incidental paranasal sinus disease has been noted to be prevalent in 25–30% of asymptomatic patients (5).

In patients with sinusitis, the extent of paranasal sinus opacification may have no correlation with headache and facial pressure and pain (6).

In this issue of Cephalalgia, Hansen et al. (7) present imaging findings from a large population-based study from Norway. This cross-sectional study investigated the association between paranasal sinus opacification on magnetic resonance imaging (MRI) and headache. The present imaging study (the HUNT MRI study) is a sub-study of the well-known Nord-Trøndelag health study (HUNT study) in which the entire population of the Norwegian county of Nord-Trøndelag aged 20 years or older was invited to participate (8). Satisfactory MRI and headache information were available for 844 adults aged 50–65 years and these were the participants in this current study by Hansen et al. (7). Of the 844 participants, 302 (36%) reported having had headaches during the past 12 months. There was no significant difference in the proportion of participants with and without headache with paranasal sinus opacification above the cut-off values (sum thickness of fluid, mucosal thickening or total opacification sum). The major strengths of this ambitious study were its population-based design, the large sample size, and the use of a validated headache classification.

Several limitations should be considered when interpreting the results. First, as noted, the MRI evaluations were carried out one or two years after the headache diagnostic interview and it is possible that the headaches could have resolved, manifested, or changed type in the interim period. Furthermore, false negative MRI results may have been obtained if—for example—the imaging was performed between episodes of recurrent acute sinusitis. Second, the location of the opacification may be more relevant than the degree of mucosal thickness; discrete mucosal blockage of the paranasal ostium area that impedes ventilation and mucociliary clearance may have more clinical significance than a large cyst that is not obstructive. Third, “opacification” on MRI does not necessarily imply pathology and must be interpreted in various clinical contexts. This study did distinguish between retention cysts (which are considered incidental, not pathological) and sinonasal polyps (which are truly pathological). Fluid in the sinuses may represent pus or innocuous, recirculating mucus. Nasal findings were not addressed, and bony and mucosal nasal contact points that have been speculated to cause headaches were not studied. Fourth, the study did not utilize a validated questionnaire for sinusitis or an otolaryngic examination. Also, the study population (50–65 years) was older than a typical migraine population so the results may not extrapolate to younger patients.

Given that symptoms of rhinosinusitis overlap with migraine symptoms, and it may be difficult to attribute causation even with “positive” imaging, all imaging findings must be clinically correlated. This is, to our knowledge, the first population-based study to investigate the association between headache and paranasal sinus opacification on MRI. Those participants with headache in the general population appeared to have a similar prevalence of “opacification” than those without headache.

It is important to emphasize that the study is epidemiological and clinical situations may be different. Each patient should be individually managed, utilizing, where necessary, nasal endoscopy and computer tomography criteria for the objective confirmation of paranasal sinus disease and to treat sinonasal disease per standard of care (9). Paranasal sinus disease may exacerbate migraines (10,11), but medical treatment and surgery for rhinosinusitis may not result in the resolution of headache and facial pressure and pain in these patients (12–15). Indeed, in certain subsets of patients, the most successful management of headaches may come from addressing both the paranasal sinus pathology as well as the primary headache disorder (16). In addition, paranasal tumors and mucoceles can cause headaches and life-threatening complications. These were not found in this population-based study, but may be present in other clinical settings (16).

Further studies are needed to place the results from this strong epidemiological data into clinical context. The limitations from the current study can ideally be best addressed by a population-based case-control imaging study that utilizes validated questionnaires for sinusitis as well as headache, as well as multidisciplinary evaluation by neurologists, radiologists, and otolaryngologists.