Phantosmias and Parkinson disease

Background: Impaired olfaction is a common, nonmotor manifestation of Parkinson disease (PD). However, to our knowledge, qualitative olfactory disturbances, such as odor distortions, have not been extensively reported in this condition. Objective: To describe 2 patients who reported positive olfactory symptoms preceding typical PD, which were consistent with olfactory hallucinations (phantosmias) in the absence of major smell deficit. Design: Case series. Setting: University hospital. Patients: We describe 2 patients, both seen in 2007, who reported pleasant olfactory hallucinations for several years. Main Outcome Measures: Iodine I 123-labeled ioflupane single-photon emission computed tomography and olfactometric testing results. Results: The (123)I-labeled ioflupane single-photon emission computed tomography showed reduced radiotracer uptake in both striatum more marked in the putamen and on the left side in patient 1 and reduced radiotracer uptake in both putamen more marked on the right side in patient 2. Olfactometric testing showed mild hyposmia in patient 1 and normal function in patient 2. The disappearance of the phantosmias in both patients coincided with the development of typical PD. Conclusion: We propose phantosmia as a new premotor manifestation of PD and suggest that qualitative abnormalities of olfaction, rather than the typical smell loss demonstrated in this condition, should be more carefully examined in the prodromal phase of PD.