31/07/2025
Bell’s Palsy or Stroke? How to Tell the Difference in Facial Weakness
When a patient presents with facial drooping, one of the most helpful clinical signs to distinguish a stroke from Bell’s palsy is to check forehead involvement.
In the case of a stroke, which typically causes an upper motor neuron lesion, the forehead muscles are usually spared. That’s because the upper part of the face receives input from both sides of the brain, so if one side is affected by a stroke, the other can still control the forehead. These patients are often still able to raise their eyebrows and wrinkle their forehead, even if the lower part of the face is weak.
On the other hand, Bell’s palsy affects the lower motor neuron—specifically the facial nerve itself—resulting in weakness of the entire half of the face. Patients are unable to raise the eyebrow, close the eye fully, or wrinkle the forehead on the affected side. The corner of the mouth droops, and smiling becomes difficult or impossible on that side.
In terms of onset and other signs, a stroke usually comes on suddenly and may be accompanied by additional neurological symptoms such as arm or leg weakness, slurred speech, visual problems, or difficulty walking.
In contrast, Bell’s palsy tends to develop more gradually over several hours—often noticed when a patient wakes up. It’s typically isolated to facial muscles, with no limb involvement. Patients might also mention ear pain, altered taste, or heightened sensitivity to sound on the affected side, due to involvement of the stapedius muscle.
Another clue lies in the eyes. In a stroke, patients generally can close the eye on the affected side (though it may be a bit weaker). In Bell’s palsy, incomplete eyelid closure is common, leaving the eye open and vulnerable to dryness and corneal damage.
To assess this in a clinical exam, ask the patient to:
Raise their eyebrows
Tightly close their eyes
Smile
If the forehead moves and the eye closes well, but the smile is uneven, this points toward a stroke. If there is no forehead movement, the eye stays partly open, and the mouth droops, it strongly suggests Bell’s palsy.
