Olfactory Acuity in Chronic Migraine: A Cross-Sectional Study.

OBJECTIVE/BACKGROUND: This study aims to measure olfactory acuity in chronic migraine subjects, at baseline and on migraine days, and compare to age- and sex-matched controls. Olfactory impairment is common in neurological disorders. While smell hypersensitivity has been established with chronic migraine, olfactory acuity has not been well studied. METHODS: We recruited 50 subjects with chronic migraine from the Jefferson Headache Center and 50 age- and sex-matched controls. Using the University of Pennsylvania Smell Identification Test (UPSIT), a validated test of olfaction, olfactory acuity was measured at baseline and during a migraine for subjects, and compared to controls at baseline and at home 2 weeks later. All subjects were additionally screened for odor sensitivity and allodynia. RESULTS: The mean UPSIT score for migraine subjects was 34.5 on non-migraine days and 34.7 on migraine days (mean difference = -0.4, 95% confidence interval [CI; -1.3, 0.6] P = .45). Controls had a mean of 35.9 and 36.1 for each test day (mean difference = -0.1, 95% CI [-0.9, 0.7] P = .87). On average, migraineurs performed worse than their matched control counterparts in both test sittings (test 1: P = .047; test 2: P = .01). The great majority of subjects were allodynic (42/50) compared with only 9 of 50 controls, and the majority of subjects (41/50) found more than one listed odor to be bothersome, compared with only 10/50 controls. On non-migraine days, 18/48 chronic migraine subjects had abnormal olfaction and on migraine days 14/42 had abnormal olfaction, compared with only 9/50 controls who had abnormal olfaction on their first UPSIT. CONCLUSIONS: While chronic migraine patients do not appear to have a significant change in olfactory acuity between migrainous and non-migrainous periods, they do appear to be more likely to have abnormal olfactory acuity at baseline compared to age- and sex-matched controls