Any ideas why your face sags if you've had a stroke?

Facial muscles: The stroke may affect unilateral arm and leg strength, and could also affect function over the face, causing poor facial nerve function of a central type, which causes the lower face to sag secondary to weakness.

Muscle weakness: If the stroke affects the nerve that supplies the muscles of the face, these muscles are unable to contract and become lax, just as the ones in a stroke-affected arm or leg might become. It is this laxity of facial muscles that causes the sagging of the face.