Right Facial Asymmetry: Arterial Localization
Right facial asymmetry (left facial droop) typically indicates ischemia in the distribution of the right internal carotid artery or right middle cerebral artery (MCA). 1
Vascular Territory and Anatomical Correlation
The right MCA is the most likely culprit vessel when right-sided facial asymmetry presents as an acute neurological finding. 1 Specifically:
- The superficial MCA territory encompasses the lateral surface of the cerebral hemisphere and is the most frequent site of MCA ischemic pathology 2
- Right MCA stroke produces contralateral (left) facial weakness affecting primarily the lower face, with relative sparing of upper facial movements 3
- The sparing of upper facial movements in MCA stroke occurs because upper face motor representation exists in both the MCA and anterior cerebral artery (ACA) territories 3
Clinical Pattern Recognition
Weakness in lip opening specifically correlates with MCA territory stroke, while eyelid closure weakness is associated with ACA stroke. 3 This distinction is critical for anatomical localization:
- Right MCA infarction produces left lower facial weakness (mouth asymmetry) 3
- The embolic mechanism remains the primary etiology for these infarcts 2
- Clinical presentation may include overlapping symptoms such as motor disturbances, language deficits, or hemianopia depending on the specific MCA branch affected 2
Critical Pitfall to Avoid
Do not assume isolated facial asymmetry is benign—this represents a focal neurological deficit requiring emergency stroke evaluation. 1 Even when facial droop is the sole manifestation, the American Heart Association recommends immediate emergency evaluation with urgent brain imaging to confirm diagnosis and determine eligibility for time-sensitive reperfusion therapies. 1
If presenting within 4.5 hours of symptom onset and imaging shows no hemorrhage, the patient should be evaluated for intravenous alteplase. 1