Facial Paralysis: Understanding Symptoms, Types, and Diagnosis

Facial paralysis is a neurological condition that affects the muscles responsible for facial expressions. It can significantly impact daily activities such as speaking, eating, and emotional expression. There are two primary classifications of facial paralysis seen in clinical practice: central (or upper motor neuron) facial palsy and peripheral (or lower motor neuron) facial palsy. Each type has distinct causes, symptoms, and diagnostic approaches, making accurate identification essential for effective treatment.

Central Facial Paralysis: Causes and Key Indicators

Central facial paralysis occurs due to damage in the brain's neural pathways—specifically, the corticobulbar tracts that control facial movement. This type of paralysis is often linked to conditions such as stroke, brain tumors, or traumatic brain injury affecting the motor cortex or internal capsule.

One of the hallmark signs of central facial palsy is weakness primarily in the lower half of one side of the face. Patients may experience drooping at the corner of the mouth, difficulty forming clear speech (dysarthria), and drooling on the affected side. Interestingly, forehead movement is usually preserved because the upper facial muscles receive bilateral brain input. This differentiates it from peripheral types where forehead involvement is common.

Peripheral Facial Paralysis: Recognizing the Signs

Peripheral facial paralysis, also known as lower motor neuron palsy, results from damage to the facial nerve (cranial nerve VII) outside the brain. The most common cause is Bell's palsy, an inflammatory condition often triggered by viral infections such as herpes simplex.

In this form, symptoms tend to be more widespread across the entire hemiface. Key indicators include:

• Loss of forehead wrinkles on the affected side
• Uneven eyebrows—one higher than the other
• Difficulty closing the eye on the paralyzed side (leading to dryness or irritation)
• Deviation of the mouth toward the unaffected side when smiling or speaking

Associated Symptoms in Peripheral Nerve Involvement

Beyond visible muscle weakness, patients with peripheral facial nerve inflammation may report additional sensory and functional disturbances. These include:

Postauricular pain—a sharp or dull ache behind the ear, often appearing before full paralysis sets in. Some individuals develop hyperacusis, an increased sensitivity to sound, due to dysfunction of the stapedius muscle innervated by the facial nerve.

Taste disturbances are also common, particularly when eating. This happens because the chorda tympani branch of the facial nerve, responsible for taste sensation on the front two-thirds of the tongue, may be compromised. As a result, food may seem bland or altered on the affected side.

Differential Diagnosis and Advanced Evaluation

While most cases of peripheral facial palsy are idiopathic (like Bell's palsy), it's crucial to rule out serious underlying causes. A small percentage of patients may have lesions affecting the facial nerve nucleus in the brainstem, which would present similarly but require different management.

To differentiate between central and peripheral origins—and to exclude structural abnormalities such as tumors, strokes, or demyelinating diseases—neurologists often recommend advanced imaging. MRI (magnetic resonance imaging) of the brain, especially focused on the brainstem and cranial nerves, plays a vital role in comprehensive evaluation.

Why Early Assessment Matters

Timely diagnosis not only helps determine the appropriate treatment—such as corticosteroids or antiviral therapy—but also prevents complications like corneal damage from incomplete eye closure. Physical therapy and facial retraining exercises can further support recovery and improve long-term outcomes.

Understanding the subtle differences between central and peripheral facial paralysis empowers both patients and healthcare providers to pursue targeted interventions. With proper medical evaluation and supportive care, many individuals experience significant improvement within weeks to months.