Video-based Analysis of the Blink Reflex in Parkinson’s Disease Patients

Abstract

Abstract We developed a video-based tool to quantitatively assess the Glabellar Tap Reflex (GTR) in patients with idiopathic Parkinson’s Disease (iPD) patients as well as healthy age-matched subjects. We also video-graphically assessed the effect of dopaminergic medication on the GTR in iPD patients, as well as frequency and velocity of reflex and non-reflex blinks. The Glabellar Tap Reflex is a clinical sign seen in patients e.g. suffering from iPD. Reliable tools to quantify this sign are lacking. Methods: We recorded the GTR in 11 iPD patients and 12 healthy controls (HC) with a high-speed camera and a framerate of at least 180 images/s. In these videos, reflex and non-reflex blinks were analyzed for blink count and velocity in an automated fashion. Results: With our setup, the GTR can be extracted from high-resolution cameras using landmarks of MediaPipe face algorithm. iPD patients did not habituate to the GTR; dopaminergic medication did not alter that response. iPD patients’ non-reflex blinks were higher in frequency and lower in velocity (mean width); dopaminergic medication decreased the frequency and increased the velocity – both in the direction of HC. Conclusion: We developed a quantitative, video-based tool to assess the GTR and other blinking-specific parameters in HC and iPD patients. Further studies could compare the video data to electromyogram (EMG) data for accuracy and comparability, as well as evaluate the specificity of the GTR in patients with other neurodegenerative disorders, in whom the GTR can also be present. Significance: The video-based detection of the blinking parameters allows for unobtrusive measurement in patients, a safer and more comfortable option.