Subjective visual vertical perception and sense of smell in Parkinson disease

This article describes an open cross-sectional observational study involving 47 participants with Parkinson disease (PD) and 47 (age- and sex-matched) nondisabled controls without PD. The aim was to determine the profiles of subjective visual vertical (SVV) perception and sense of smell perception in both groups. There was a statistically significant difference (p < 0.001) between patients and controls on their smell test performance. Controls were more likely to correctly identify odors, with a median score of 10 out of 12 compared with 6.5 out of 12 for patients with PD. The median SVV error for the PD group when the frame was untilted was 0.75 degrees compared with 0.50 degrees for controls. This difference was statistically significant (p = 0.02). When the frame was tilted, the median SVV error for the PD group was 2.31 degrees compared with 2.00 degrees for controls (not statistically significant), with both groups showing similar distribution pattern of errors. There was no statistical correlation between number of correctly identified odors and an individual's SVV error. However, a statistically significant negative correlation (r = -0.45, p = 0.01) was found between Mini-Mental State Examination score and mean time taken to complete each rod and frame test in patients with PD, suggesting that SVV errors might be more correlated with cognitive function than with loss of sense of smell.