The utility of magnetic resonance imaging in the diagnostic evaluation of idiopathic olfactory loss.

OBJECTIVES/HYPOTHESIS To report the utilization and cost effectiveness of magnetic resonance imaging (MRI) in the evaluation of patients with idiopathic olfactory loss. STUDY DESIGN Case series with chart review. METHODS A retrospective review of patients presenting with olfactory disorders at a university-based taste and smell center from July 1998 through October 2011 was performed to determine the diagnostic utility of MRI in the evaluation of patients with idiopathic olfactory loss. RESULTS In a cohort of 839 patients with olfactory loss, idiopathic olfactory loss was most common, accounting for 247 patients-or 29% of this cohort. MRI was used in the evaluation of idiopathic olfactory loss 54.9% of the time, and abnormalities were identified in 4.6% of these patients. However, only 0.8% of these patients had olfactory loss attributable to imaging abnormalities. Therefore, the estimated cost per attributable abnormal finding was $325,000, given an average hospital charge of $2,500 per MRI. CONCLUSION In this cohort of patients with olfactory loss, the etiology most commonly remained idiopathic. Brain MRI, though frequently performed, demonstrated a very low diagnostic yield, with a rate of abnormal findings similar to that seen in the normal population. Based on these data, the routine use of MRI in patients presenting with isolated idiopathic olfactory loss may be unwarranted. Selection bias may contribute to the low yield of MRI among this cohort; further studies are needed to characterize those patients most likely to benefit from MRI evaluation. LEVEL OF EVIDENCE 4.