Differences Between Central and Peripheral Facial Paralysis
Understanding Facial Paralysis: Central vs. Peripheral
Facial paralysis can be a distressing condition, but understanding the underlying cause is crucial for proper diagnosis and treatment. One of the most important distinctions in neurology is between central and peripheral facial paralysis. While both affect facial muscle control, they differ significantly in origin, symptoms, and clinical presentation.
What Is Central Facial Paralysis?
Central facial paralysis occurs due to damage in the upper motor neurons located in the brain, typically as a result of stroke, brain injury, or other central nervous system disorders. A key feature of this type of paralysis is that it primarily affects the lower half of the face on the opposite side of the brain lesion.
This happens because the muscles controlling the forehead—specifically the frontalis muscle and orbicularis oculi—are bilaterally innervated by both cerebral hemispheres. As a result, even if one side of the brain is damaged, the forehead muscles often remain functional. Patients with central facial palsy can usually still raise their eyebrows and close their eyes normally.
The most noticeable symptom appears when the person tries to smile or bare their teeth—the nasolabial fold (the line from the nose to the corner of the mouth) becomes shallow, and the mouth may appear to droop on one side. This pattern is commonly seen in individuals who have experienced a cerebrovascular accident, such as an ischemic stroke.
What Defines Peripheral Facial Paralysis?
In contrast, peripheral facial paralysis stems from damage to the facial nerve (cranial nerve VII) outside the central nervous system. This form of paralysis affects all the facial muscles on the same side as the nerve injury, including those of the forehead, eye, cheek, and mouth.
Common causes include viral infections (such as herpes zoster or Bell's palsy), inflammation, trauma, or compression of the nerve as it exits the skull. The resulting swelling can impair nerve function, leading to complete facial weakness on the affected side.
Symptoms and Clinical Presentation
Individuals with peripheral facial paralysis are unable to raise their eyebrows, fully close their eyes, or control facial expressions like smiling or frowning on the affected side. In many cases, the inability to blink can lead to dryness and irritation of the eye, increasing the risk of corneal damage.
When asked to grin or show their teeth, the patient's mouth will visibly pull toward the unaffected (healthy) side, making the asymmetry more pronounced. Other possible symptoms include loss of taste on the front two-thirds of the tongue, increased sensitivity to sound (hyperacusis), and decreased tear or saliva production.
Key Differences Summarized
- Forehead Involvement: Preserved in central paralysis; impaired in peripheral.
- Eye Closure: Normal in central; weak or absent in peripheral.
- Cause: Brain-related (e.g., stroke) in central; nerve-related (e.g., infection, inflammation) in peripheral.
- Symmetry: Only lower face affected in central; entire half of the face involved in peripheral.
Accurate differentiation between central and peripheral facial paralysis is essential for timely intervention. Imaging studies like MRI or CT scans, along with neurological assessments, help clinicians determine the root cause and guide appropriate therapy—from corticosteroids and antivirals in Bell's palsy to stroke management protocols in central cases.
Early diagnosis and treatment significantly improve recovery outcomes, especially in peripheral cases where spontaneous recovery is common but not guaranteed without proper care.