Analysis of Upper Facial Weakness in Central Facial Palsy Following Acute Ischemic Stroke.

Background: Central facial palsy (CFP), resulting from upper motor neuron lesions in the corticofacial pathway, is traditionally characterized by the sparing of the upper facial muscles. However, reports of upper facial weakness in CFP due to acute ischemic stroke have challenged this long-held assumption. This study aimed to determine the prevalence of upper facial weakness in CFP and identify its associated clinical factors.

Methods: In this cross-sectional study, we evaluated consecutive patients with acute ischemic stroke admitted to a university hospital in Thailand from January 2022 to June 2023. Full-face video recordings were analyzed using the Sunnybrook Facial Grading System. Upper facial weakness was defined as asymmetry in at least one upper facial expression. Multivariable logistic regression was performed to identify factors associated with upper facial weakness.

Results: Of 108 patients with acute ischemic stroke, 92 had CFP, and among these, 70 (76%) demonstrated upper facial weakness. Tight eye closure (force and wrinkle formation, both 42%) was the most sensitive indicator for detecting upper facial weakness. Greater stroke severity, as reflected by higher NIHSS scores (adjusted odds ratio [aOR], 1.42; 95% CI 1.07-1.88) and the presence of lower facial weakness (aOR, 6.56; 95% CI 1.85-23.29) were significantly associated with upper facial involvement. Although upper facial weakness was generally milder than lower facial weakness, its severity correlated with increasing lower facial asymmetry during movement.

Conclusions: Contrary to traditional teaching, upper facial weakness is common in CFP due to acute ischemic stroke. The severity of stroke and the presence of lower facial weakness are key predictors of upper facial involvement. These findings underscore the need for clinicians to reconsider the diagnostic paradigm, recognizing that upper facial weakness can occur in CFP. Enhanced awareness may improve diagnostic accuracy, inform treatment decisions, and ultimately lead to better patient outcomes.