Understanding Central Facial Paralysis: Causes, Symptoms, and Differences from Peripheral Types

Central facial paralysis is a neurological condition resulting from damage to the upper motor neurons in the cerebral cortex or the nerve fibers that travel from the brain's motor cortex down to the facial nucleus in the brainstem. This type of paralysis specifically affects the pathway before it reaches the facial nerve nucleus. In contrast, peripheral facial paralysis occurs when the damage involves the facial nerve nucleus itself or the nerves extending from it into the face. Although both conditions lead to facial weakness or paralysis, they differ significantly in origin, presentation, and clinical implications.

What Is Central Facial Paralysis?

Central facial paralysis typically manifests as muscle weakness only in the lower half of one side of the face. Patients may notice a flattening of the nasolabial fold (the groove between the nose and mouth), drooping of the mouth corner, and asymmetry during facial movements such as speaking, smiling, puffing the cheeks, or whistling. Interestingly, the upper face—particularly the forehead muscles and the ability to close the eyes—is usually spared.

Why Is the Forehead Spared in Central Facial Paralysis?

This selective involvement happens because the facial nucleus in the brainstem receives motor input from both sides of the brain for the upper facial muscles (those controlling forehead wrinkling and eye closure). This bilateral innervation means that even if one side of the brain is damaged—such as from a stroke or brain tumor—the other side can still activate these muscles. However, the lower facial muscles receive primarily contralateral (opposite-side) input, making them vulnerable when one hemisphere is impaired.

Peripheral Facial Paralysis: A Different Pattern

In contrast, peripheral facial paralysis involves direct damage to the facial nerve (cranial nerve VII) or its nucleus in the brainstem. This results in complete paralysis on one side of the face, including both upper and lower regions. Common signs include loss of forehead wrinkles, inability to fully close one eye, drooping eyebrows, flattened nasolabial folds, and a crooked smile that pulls toward the unaffected side.

Clinical Features of Peripheral Nerve Damage

Because the entire facial nerve is compromised in peripheral cases, all facial expressions on the affected side are weakened or lost. Additional symptoms may include increased sensitivity to sound (hyperacusis), changes in taste, and dryness of the eye or mouth due to disrupted autonomic functions. Bell's palsy is the most common cause of acute peripheral facial paralysis, often linked to viral inflammation of the nerve.

Key Differences Between Central and Peripheral Facial Paralysis

Understanding the distinction between these two types is crucial for accurate diagnosis and treatment. The presence or absence of forehead sparing is a key diagnostic clue: central lesions usually spare the forehead, while peripheral ones do not. Imaging studies like MRI or CT scans, along with neurological assessments, help pinpoint the location of the lesion—whether in the brain (central) or along the facial nerve pathway (peripheral).

Early recognition of symptoms can lead to timely intervention, especially in central cases where underlying causes such as stroke, tumors, or multiple sclerosis must be addressed urgently. Treatment varies widely depending on the root cause but may include medications, physical therapy, and in some cases, surgical options.

Whether dealing with central or peripheral facial paralysis, prompt medical evaluation is essential. With proper care, many patients experience significant recovery, regaining facial function and improving quality of life.