New evidence of impaired olfaction in IIH

This pilot study provides new evidence that olfaction is significantly impaired in patients with idiopathic intracranial hypertension (IIH), especially in those who have been newly diagnosed or who have experienced a recent clinical deterioration.

Subjects were 17 patients with IIH and 17 age- and sex-matched controls. Patients with a recent first diagnosis of IIH, as well as patients with a clinically significant worsening of IIH within the last three months, were classified as “acute IIH” patients. All subjects underwent the extended Sniffin’ Sticks procedure to test odor threshold, discrimination and identification (TDI).

Median TDI scores were significantly reduced in patients with IIH (29 vs. 35, P = 0.003). Scores were also reduced in patients with a recent clinical deterioration of IIH (P = 0.004).

The authors say the study’s data clearly indicate that the prevalence of a reduced sense of smell in patients with acute IIH is quite comparable to the prevalence rates of other major IIH-related symptoms. However, olfaction has received little attention in the clinical literature on IIH likely because, in the majority of cases, olfactory dysfunction in IIH is mild and most patients are unaware of it.

They would like to replicate this study’s findings within the framework of a prospective, longitudinal study. Ideally, olfactory assessment should be complemented by additional information from MRI and olfactory-evoked potentials. They say it would be interesting to probe the association between papilledema/optic atrophy and olfactory dysfunction.