Bell's Palsy vs. Stroke: What Are the Differences?

Bell's palsy is the most common cause of facial droop, a term that indicates the look of a patient's face that is slack on one side from loss of muscle tone. The unaffected side of the face continues to have muscle movement and tone, which makes the affected side appear to "droop" in comparison.

Facial droop is also a hallmark trait of the asymmetrical symptoms of a stroke. Called hemiplegia, weakness or paralysis on one side of the body is the quintessential stroke symptom. In many cases, weakness of the face is how a patient's family or friends might first recognize the onset of a stroke. However, a stroke affects much more than facial muscle tone.

A stroke could possibly affect cognitive function, language, pupil tone (unequal pupils), ability to swallow, and vital signs. Both a stroke and Bell's palsy can cause a facial droop. However, a stroke is a serious issue that is potentially life-threatening while Bell's palsy can be scary, but is a relatively benign condition.

Stroke

A stroke is a brain injury caused by a sudden interruption of blood supply to the brain. The lack of blood oxygen and nutrients can cause sudden onset and ultimately lasting effects on muscle tone, speech, or cognitive ability. There are two distinct types of stroke: hemorrhagic and ischemic.

Hemorrhagic stroke is caused by a ruptured blood vessel in the brain that causes bleeding. Ischemic stroke, on the other hand, comes from a clot in a blood vessel that blocks blood flow to an area of the brain. Both types of stroke can lead to permanent disability.

Depending on the size and location of the hemorrhage, it can sometimes be treated by evacuating the bleeding. The bleeding can lead to increased pressure in the brain, which can be treated surgically as well in some cases.

Sometimes, depending on the time of presentation and other factors, an ischemic stroke can be treated with a medication or procedure to remove the clot in the blood vessel.

Besides these types of strokes, another type of sudden brain condition that mimics a stroke is called a transient ischemic attack (TIA). A TIA has a similar mechanism to an ischemic stroke, without permanent brain damage. Having a TIA increases the risk of a future stroke.

Stroke Symptoms

Stroke signs and symptoms may include:

• One-sided weakness or paralysis in the face, arm, or leg
• Sudden difficulty walking or standing
• Slurred speech or difficulty understanding speech
• Difficulty swallowing
• Cognitive impairment
• Severe headache
• High blood pressure

Bell's Palsy

Bell's palsy is a sudden-onset condition that leads to weakness of the muscles on one side of the face. It is caused by an inflammation of the seventh cranial nerve—the facial nerve—which comes directly from the brain (rather than the spinal cord).

This means a patient with Bell's palsy will not be confused or have difficulty understanding speech. There will not be any involvement of other areas of the body besides the face. Patients with Bell's palsy do not have difficulty standing, walking, or using their arms and hands.

Bell's Palsy Symptoms

Since Bell's palsy involves the facial muscles, patients can have difficulties chewing, swallowing, and speaking. All of these signs and symptoms could potentially show up in a stroke as well.

The inflammation of the facial nerve could be from an infection, but it is possible that a direct cause will not be found. Bell's palsy usually resolves within months, but there could be residual facial droop or other muscle tone issues for many years after Bell's palsy subsides.

The Difference

The biggest difference between Bell's palsy and stroke has to do with the involvement of the brain. Since Bell's palsy is not affecting actual brain tissue or brain function, there is nothing beyond the facial nerve that can be affected. If anything beyond the facial nerve is involved, it's not Bell's palsy.

Since a stroke has the potential to involve the area of the brain where the facial nerve originates, the only way to tell for sure what is causing the facial droop is to see your healthcare provider immediately or go to the emergency room at a hospital to be diagnosed.

Conditions That Mimic Stroke

A condition that mimics a stroke (like Bell's palsy) is a condition that has similar signs and symptoms as strokes, such as those described below.

Epilepsy

The seizure disorder epilepsy was the most common stroke mimic seen in one study of patients in the emergency department. Patients with epilepsy can have one-sided weakness following a seizure, called Todd's paralysis. Sometimes, seizures can cause neurological signs and symptoms that mimic strokes, without the typical convulsions.

Low Blood Sugar

Hypoglycemia (low blood sugar) was the third most common stroke mimic seen in the emergency department in the same study. Low blood sugar, particularly in patients with diabetes who are being treated with insulin, can lead to a transient loss of neurologic function.

Patients with a history of transient ischemic attacks are especially likely to show signs and symptoms indicative of strokes when experiencing hypoglycemia.

Aortic Dissection

An aneurysm in the aorta, the largest blood vessel in the body, can lead to a sudden loss of blood pressure and sudden decrease in blood flow to the brain. The decreased blood flow can cause the brain to exhibit similar signs and symptoms to a stroke.

Aortic dissection was the stroke mimic most likely to be fatal. Half of the stroke mimics that caused death in that study were from an aortic dissection.

Syncope

A sudden loss of consciousness from a drop in blood pressure is called syncope. The most common causes are cardiac conditions and vagus nerve stimulation. Due to the fact that syncope is essentially a brain malfunction, the potential for confusion between syncope and stroke can occur.

Sepsis

A systemic infection that affects multiple body systems is known as sepsis. Sepsis is a complicated condition that can mimic stroke through confusion, dizziness, loss of coordination or balance, headache, and other symptoms.

Psychiatric Condition

The second most common stroke mimic identified in the same study was a psychiatric diagnosis. This is such a broad category that it is impossible to narrow down a single type of psychiatric diagnosis as the only cause.

Identifying Strokes

Blood pressure is a good indicator of stroke when paired with other stroke symptoms like difficulty speaking, facial droop, weakness on one side, among others. A systolic blood pressure (top number) of more than 140 mm/Hg may indicate brain involvement.

Patients who were feeling sick prior to the onset of symptoms could have a different condition. The healthcare provider in the emergency department will need to rule out other potential causes in order to properly diagnose stroke.

The older a patient is, the more likely he or she is experiencing a stroke with the symptoms listed above.

When to See the Healthcare Provider

Since a stroke can happen with any or all of these symptoms discussed, it is nearly impossible to differentiate between a stroke and any of the mimic conditions, including Bell's palsy, without seeing your healthcare provider or going to the emergency room.

Patients presenting with a possible stroke will generally undergo several tests to determine if the symptoms come from a stroke or not.

A Word From Verywell

Bell's palsy and strokes are two conditions that have the potential to share similar signs and symptoms, including facial droop. If you are experiencing facial droop (or any stroke symptoms), it is best to seek help immediately for appropriate diagnosis and treatment. Strokes can cause increasing brain damage and disability the longer treatment is delayed, so it is best to seek help as soon as possible.