Is facial droop contralateral or ipsilateral to the side of a stroke?

Facial Droop Occurs Contralateral to the Stroke Lesion

Facial droop in stroke is contralateral (opposite side) to the brain lesion in the vast majority of cases, because the corticobulbar fibers that control the lower face cross (decussate) before reaching the facial nucleus in the pons. 1

Anatomical Basis

• The motor cortex sends corticobulbar fibers down through the brainstem to control facial movement 2
• Fibers controlling the lower face (including the mouth and ability to smile) cross to the opposite side at or above the level of the facial nucleus in the pons 2, 3
• Therefore, a stroke in the left hemisphere produces weakness of the right lower face, and vice versa 4, 2
• This results in the classic finding: the patient cannot smile symmetrically on the side opposite the brain lesion 1

Clinical Correlation with Carotid Disease

• In patients with both carotid stenosis and stroke, the cerebral infarct is typically ipsilateral (same side) as the carotid lesion, meaning the facial droop appears on the side opposite the diseased carotid artery 1
• For example: right carotid stenosis → right hemisphere stroke → left facial droop 1

Important Exceptions (Rare Brainstem Strokes)

While the standard rule applies to >95% of strokes, rare brainstem infarctions can produce atypical patterns:

• Pontine lesions above the facial nucleus may cause contralateral facial weakness that mimics cortical stroke 4, 2
• Medullary infarctions involving aberrant fiber pathways can rarely produce ipsilateral facial weakness 5, 3
• These exceptions occur when the stroke directly affects the facial nucleus itself or aberrant corticobulbar fiber pathways in the brainstem 5, 4, 3

Practical Clinical Application

• When evaluating acute stroke, expect facial droop on the opposite side from the brain lesion 1
• The presence of facial droop helps localize the stroke to the contralateral hemisphere in typical presentations 2
• If imaging shows a carotid lesion, look for stroke symptoms (including facial droop) on the opposite side of the body but same side as the vascular lesion 1

Monitoring for Deterioration

• In patients at risk for malignant cerebral edema, monitor for ipsilateral pupillary dilation (which indicates herniation), not facial changes 6
• Progressive neurological deterioration from swelling presents with altered consciousness and pupillary changes rather than evolving facial weakness 6