The Difference Between Bell's Palsy and Stroke

How to Tell the Difference

Bell's Palsy is an impairment of the facial nerve that causes weakness or paralysis on one side of the face. It is the most common cause of facial droop, which is 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 brain function, speech recognition, pupil tone (unequal pupils), ability to swallow, and vital signs. The difference between a stroke and Bell's palsy is the difference between a potentially life-threatening medical condition and a relatively benign, but often scary, condition.

Stroke

A stroke is a medical brain injury marked by a sudden onset and residual deficits in muscle tone, speech, or cognitive ability. It is caused by a problem in the blood vessels of the brain, and its medical name is a cerebrovascular accident (CVA). There are two distinct types of stroke: hemorrhagic and ischemic.

Hemorrhagic stroke comes from a broken blood vessel in the brain that leads to bleeding and a hematoma. 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.

Hemorrhagic stroke can be treated by draining pressure out of the brain through a hole drilled by a surgeon. Ischemic stroke can be treated with clot-dissolving medication or a procedure to remove the clot.

Besides a cerebrovascular accident, another type of sudden brain condition that mimics a stroke without permanent damage is called a transient ischemic attack (TIA). A TIA, sometimes called a mini-stroke, is usually the result of restricted blood flow to a portion of the brain and could be a warning signal of the more severe CVA.

Stroke Symptoms

Because the brain is divided into hemispheres, an injury to one side of the brain will only show up on one side of the body. Stroke signs and symptoms 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 7th cranial nerve—the facial nerve—which comes directly from the brain (rather than the spinal cord).

Unlike strokes, Bell's palsy will not directly involve the brain.

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 there is anything beyond the facial nerve involved, it's not Bell's palsy.

While Bell's palsy does not involve brain function, it is totally possible for a stroke to only involve facial nerve function.

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 doctor 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

A 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. They can also have other neurological signs and symptoms that mimic strokes, which are technically seizures, but they do not have the typical convulsions.

Low Blood Sugar

Hypoglycemia (low blood sugar) is 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.

In one study, 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.

If a patient was not already feeling sick prior to the onset of symptoms, there is a higher probability that the sudden symptoms indicate a stroke.

Patients who were feeling sick prior to the onset of symptoms could have a different condition.

The physician 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 Doctor

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 doctor 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. Patients who are experiencing a stroke will need to be diagnosed there, and it is best to seek help as soon as possible.

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