Osmophobia in migraine: multifactorial investigation and population-based survey

Excerpt

The link between migraine and olfaction is well highlighted by the avoidance of smells by patients during migraine attack and by the existence of attacks induced by olfactory stimuli. The available studies are generally based on outpatients from headache centers and are mainly focused on osmophobia during attacks, but several problems remain unsolved. First of all, what’s the real prevalence of critical osmophobia in migraine and in other headaches? Is this prevalence specific of migraineurs from headache clinics or may be extended to the general population? Is repulsion for olfactory stimuli only for smells or also for perfumes? Is osmophobia necessarily associated with nausea or it may be independent? To try to answer these questions, we designed a study to assess the prevalence of osmophobia in patients with migraine and non-migraine headache, both from a headache center and from general population, and to investigate if osmophobia is usually present since the onset of the headache history or if it appears subsequently. Additionally, we focused on identifying the possible relationship between osmophobia and headache history, age of migraine onset, frequency of attacks, presence of nausea, and allodynia. The study was structured in three different sections. The first part, on outpatients from the headache center of the L. Sacco Hospital of Milan, included 1115 patients (164 males aged 36.3 ± 15.3 years and 951 females aged 39.1 ± 14.6). The second step of the study was used to validate the diagnostic questionnaire prepared for the general population. The questionnaire was filled in by 112 outpatients previously diagnosed in the headache center (12 males, mean age 41.7 ± 14.2, and 100 females, mean age 39.3 ± 12.7) and the diagnosis obtained with the questionnaire was matched with the one defined during the visit. The diagnosis of a migraine-type headache made using the questionnaire and the diagnosis of migraine previously expressed during the neurological evaluation agreed in over the 90% of cases, sustaining the possibility to investigate the general population with this tool. The third step of the study included 3112 subjects (408 males, 2697 females, and 7 non-explicated gender) investigated with the diagnostic questionnaire created in a Google Form model and distributed through social networks. Regarding our outpatients, critical osmophobia was found in the 37.5% of females and in the 23.8% of males without significant differences between genders. Mean age was not different between osmophobic and non-osmophobic migraineurs (respectively, 39.3 and 38.4 years), but migraine history was longer among osmophobic (22.4 vs 17 years, p < 0.0001 at T test). Osmophobia was more frequent among chronic migraine than in episodic forms (43.5% vs 31.5%, p < 0.0001 at chi² test) and mean frequency of attacks was higher among osmophobic patients (12.9 vs 10.7 days/month, p < 0.0001 at T test). Osmophobia was also more frequent in allodynic migraineurs (217 out of 538; 39.8%) than in non-allodynic ones (156 out of 521; 30%, p = 0.0008 at chi² test), independently by gender. Finally, osmophobia was largely more present in association with nausea, even if they are not mandatory linked; in fact, osmophobia was also found in 34 out of 1115 patients who did not feel nausea during migraine attacks. …