Assessment of visual misperceptions in patients with Parkinson's disease using single and bistable percepts as testing tools.

BACKGROUND

Visual misperceptions (VMs) and hallucinations (VHs) often go unreported in patients with Parkinson's disease (PD). We assessed the utility of single and bistable visual percepts as testing tools for visual perceptual abnormalities in PD.

AIM

To assess VM in patients with PD using single and bistable percepts as testing tools.

SETTINGS AND DESIGN

This was a case-control study conducted at a movement disorders clinic.

MATERIALS AND METHODS

Thirty patients with PD and 30 age and sex-matched controls were assessed for motor severity and stage using Unified Parkinson's Disease Rating Scale-III (UPDRS-III) and modified Hoehn and Yahr scale. Higher mental functions were assessed by Mini-Mental State Examination (MMSE), Frontal Assessment Battery (FAB), and Trail making tests (TMT-A and B) scores. The participants were presented with monochromatic images representing either "single" or "bistable percepts" and the misperceptions were recorded. VM scores of patients and controls were compared. The correlation between disease duration, treatment period, motor severity, frontal executive functions, and VMs were determined.

RESULTS

Twenty-six patients had mild-to-moderate PD. Patients with PD had higher mean VM scores (P < 0.0005). None of the patients reported VHs. TMT-A, TMT-B, TMT-B - A scores were significantly lower in the control group (P < 0.0005). Cases showed significant positive correlation of VM with disease duration, treatment duration, UPDRS-III score, H and Y stage, and TMT A and B and an inverse correlation with MMSE and FAB scores. The patients with VM score greater than the upper limit of normal (Mean + 1.5 standard deviation [SD]), calculated from the control group, showed similar correlation of VM with motor and cognitive parameters.

CONCLUSIONS

VMs are frequent in patients with PD when assessed using single and bistable visual percepts. VM correlates with frontal executive dysfunction, disease duration, and severity.