Patients with idiopathic intracranial hypertension experienced significant olfactory dysfunction, according to a study published in Headache.

Researchers of this case-controlled study analyzed the olfactory functions and clinical characteristics of patients with idiopathic intracranial hypertension (n=44) and healthy controls (n=57). Idiopathic intracranial hypertension was defined as the presence of papilledema and/or measured cerebrospinal fluid opening pressure >250 mm H₂O in the same month. Olfactory function testing included the use of the Sniffin’ Sticks test to determine the threshold, discrimination, and identification scores. All study participants were assessed simultaneously. There were no significant differences in basic demographic data between the idiopathic intracranial hypertension cohort and the healthy control cohort.

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The idiopathic intracranial hypertension cohort had significant differences in the threshold score (P <.001), the total score for threshold-discrimination-identification (P =.003), and the presence of hyposmia (P =.008) when compared with the healthy controls. After completing subgroup analysis on the idiopathic intracranial hypertension cohort, patients with headaches experienced significantly higher identification scores than those without headaches (12 vs 9; P =.01), and patients with papilledema experienced significantly lower total score for threshold-discrimination-identification (29.5 vs 37; P =.006) and identification score (12 vs 15; P =.001) than patients without papilledema.

Multiple regression analyses indicated correlations between education level and the discrimination score and the total score for threshold, discrimination, and identification; disease activity and the discrimination score; cerebrospinal fluid opening pressure and all test scores; papilledema and the identification score and the total score for threshold discrimination and identification; headache and the identification score; and medication and the threshold score.

The limitations of this study include not testing during an attack period and a remission period with the same cohort to control for physiological differences. In addition, results may not be applicable to the general public due to the source population.

The researchers believe they “demonstrated clearly that there is marked impairment of olfactory function in [patients with idiopathic intracranial hypertension] compared [with] healthy controls.” They hope future studies will include larger samples to determine the potential role of olfactory testing in patients with idiopathic intracranial hypertension.

Reference

Samanci B, Samanci Y, Sen C, et al. Assessment of the olfactory function in patients with idiopathic intracranial hypertension using the Sniffin’ Sticks test: a case-control study [published online April 18, 2019]. Headache. doi:10.1111/head.13538