A stroke is a medical emergency caused by the sudden interruption or significant reduction of blood flow to the brain, depriving it of oxygen and nutrients. Brain cells begin to die within minutes, making the rapid recognition of physical signs paramount for a quick response. The face often provides the most immediate and visible evidence that a stroke is occurring, signaling the need for urgent action.
The Unilateral Facial Droop
The most recognizable facial sign of a stroke is a noticeable loss of muscle control, resulting in a unilateral facial droop. This appearance is caused by damage to the brain’s motor pathways, which control the muscles on the opposite side of the face. The affected side loses its resting tone, making one side of the face appear slack or lower than the other. This lack of tone often causes the nasolabial fold—the crease that runs from the side of the nose to the corner of the mouth—to flatten out. A careful visual assessment of the face at rest can reveal this sudden asymmetry, where the mouth corner on the affected side is visibly lower.
Confirming Asymmetry with Simple Actions
Asking the individual to perform an action requiring coordinated facial muscle movement, such as smiling or showing their teeth, will expose the weakness. On the side affected by the stroke, the mouth will fail to move upward or sag visibly, creating a distinctly crooked or uneven smile. If the person is asked to raise both eyebrows, the muscles on the unaffected side will contract normally, forming wrinkles across the forehead. The forehead on the stroke-affected side, however, may not wrinkle as much or at all. This disparity in movement during an active test provides concrete evidence of a neurological event impacting facial motor control.
Secondary Facial and Oral Signs
A stroke can cause several related symptoms affecting the mouth and surrounding structures beyond the visible droop. Due to weakened muscles, the individual may have difficulty containing saliva, leading to noticeable drooling from the affected corner. Difficulty with swallowing, known as dysphagia, is a frequent complication, making it hard to manage food or liquids. If asked to stick out their tongue, a person experiencing a stroke may display tongue deviation, pointing sharply toward the weakened side of the mouth. These oral signs occur because the nerves that innervate the tongue and throat muscles are compromised by the brain injury.
The Required Emergency Response
Recognizing a stroke requires an immediate emergency response, guided by the memory tool F.A.S.T. This acronym stands for Face drooping, Arm weakness, Speech difficulty, and Time to call emergency services. If the face droops, or if the individual exhibits any other sudden symptoms like slurred speech or one-sided arm weakness, dial emergency services immediately.
The “T” in F.A.S.T. represents the most important factor in determining the outcome: “Time is brain.” Every minute that passes without treatment results in the loss of millions of brain cells. Providing the time when symptoms were first observed to emergency responders is extremely helpful, as many life-saving treatments, such as clot-busting medications, are highly time-dependent. Even if the symptoms appear minor or disappear quickly—a sign of a Transient Ischemic Attack (TIA)—immediate medical attention is required.