Facial Paralysis: Understanding Symptoms and Differences Between Peripheral and Central Types
Facial paralysis is a neurological condition that affects the facial muscles, leading to partial or complete loss of facial movement. It can be broadly categorized into two main types: peripheral facial paralysis and central facial paralysis. While both result in visible facial asymmetry, their underlying causes and clinical presentations differ significantly. Recognizing these differences is crucial for accurate diagnosis and effective treatment.
What Is Peripheral Facial Paralysis?
Peripheral facial paralysis occurs when there's damage to the facial nerve (cranial nerve VII) outside the brain, often due to infections, trauma, or idiopathic conditions like Bell's palsy. This type affects the entire side of the face and presents with distinct physical signs.
Forehead and Eye-Related Symptoms
One of the hallmark features of peripheral facial paralysis is asymmetry in the forehead. Patients may notice that the wrinkles on their forehead appear uneven, with the affected side showing diminished or completely absent forehead lines. Because the orbicularis oculi muscle is impaired, individuals often struggle to fully close the eye on the paralyzed side, resulting in incomplete eyelid closure. This can lead to dryness, irritation, and increased risk of corneal injury. Additionally, the eyebrow on the affected side typically appears lower than the unaffected side, contributing to an unbalanced facial appearance.
Nasal and Oral Manifestations
The muscles around the nose and mouth are also impacted. A noticeable flattening of the nasolabial fold—the skin crease running from the nose to the corner of the mouth—is common on the affected side. As a result, the face looks lopsided, especially when the person attempts to smile. The corner of the mouth droops downward and may pull toward the healthy side, creating a crooked expression. Simple actions such as whistling or puffing out the cheeks become difficult due to air leakage from the weakened oral muscles, further confirming motor dysfunction.
Additional Neurological Symptoms
Because the facial nerve also carries sensory and parasympathetic fibers, patients with peripheral paralysis may experience more than just motor deficits. Many report altered taste sensation over the anterior two-thirds of the tongue, caused by involvement of the chorda tympani nerve branch. Some individuals develop hyperacusis—increased sensitivity to sound—due to dysfunction of the stapedius muscle in the middle ear. Moreover, reduced tear production (lacrimal gland dysfunction) and decreased salivation (from submandibular and sublingual glands) may occur, indicating autonomic nervous system involvement.
Understanding Central Facial Paralysis
In contrast, central facial paralysis arises from brain-level issues, such as stroke, brain tumors, or traumatic brain injury affecting the motor cortex or corticobulbar tracts. Unlike peripheral cases, central paralysis primarily impacts the lower half of one side of the face, sparing the upper region—especially the forehead.
Preserved Forehead Movement: A Key Diagnostic Clue
A defining characteristic of central facial paralysis is the preservation of forehead wrinkling and eyebrow elevation. Since the upper facial muscles receive bilateral cortical input, damage on one side of the brain doesn't completely disable these muscles. Therefore, patients can still frown or raise their eyebrows symmetrically, even while showing weakness below the eyes. This distinction is vital for clinicians differentiating between central and peripheral origins during initial assessment.
Mimicking Lower-Face Weakness Without Extra Features
Below the eyes, however, symptoms resemble those seen in peripheral cases: difficulty closing the eye, shallower nasolabial folds, and a drooping mouth corner. Whistling or showing teeth may be challenging. Importantly, central facial paralysis typically does not involve sensory or autonomic disturbances. There's usually no change in taste, hearing sensitivity, or glandular secretions—key factors that help rule out peripheral nerve damage.
Why Accurate Diagnosis Matters
Distinguishing between peripheral and central facial paralysis isn't just academic—it directly influences treatment pathways. Peripheral cases may benefit from corticosteroids, antivirals, eye protection, and physical therapy, especially if diagnosed early. In contrast, central cases require urgent neuroimaging and management of underlying brain pathology, such as ischemic stroke or hemorrhage. Misdiagnosis can delay critical interventions and affect recovery outcomes.
Anyone experiencing sudden facial weakness should seek immediate medical evaluation. Early recognition of symptom patterns—such as forehead involvement, associated sensory changes, or systemic neurological signs—can guide timely and appropriate care, improving prognosis and quality of life.