Blinking in patients with clinically probable multiple system atrophy

Background: Clinical studies in patients with MSA document facial motor abnormalities, but no studies have objectively assessed blinking abnormalities in this condition.

Methods: We enrolled patients diagnosed as having clinically probable MSA, 20 patients of the parkinsonian phenotype (MSA-P) and 10 patients of the cerebellar phenotype (MSA-C) and 20 healthy controls (HCs). Blinking was recorded with a three-dimensional optoelectronic motion system equipped with dedicated software for data analysis.

Results: During voluntary blinking, the interphase pause duration between the closing and opening phases lasted longer in MSA-P and in MSA-C patients than in HCs; the opening phase had increased duration and reduced peak velocity in MSA-P. During reflex blinking, the opening blink phase also lasted longer in MSA-P patients than in HCs. During spontaneous blinking, the rate and kinematics of the closing and opening blinking phases were lower in MSA-P and in MSA-C patients than in HCs. Blink reflex recovery was higher in patients than in HCs. No difference was found between MSA-P patients receiving or not receiving dopaminergic medication.

Conclusions: Our objective assessment of upper facial movement documents abnormalities of voluntary, spontaneous, and reflex blinking in patients with MSA-P and MSA-C, reflecting cortical-basal ganglia and brainstem dysfunction.