Facial asymmetry, where features on one side of the face do not perfectly mirror the other, is a common characteristic. While a subtle degree of facial asymmetry is normal, more noticeable differences, such as one side of the mouth appearing lower, can indicate various underlying factors. These range from everyday habits to medical conditions.
Everyday Explanations
Subtle facial asymmetry is a natural human trait, as nearly everyone possesses some degree of unevenness between the left and right sides of their face. This inherent difference often goes unnoticed and does not typically indicate a health concern. Certain habitual expressions or muscle use can contribute to a more pronounced appearance of asymmetry over time. For example, consistently favoring one side for chewing or smiling can influence facial muscle development and distribution.
The natural process of aging also plays a role in how facial symmetry evolves. Uneven changes in skin elasticity, fat distribution, and muscle tone can lead to one side of the face, including the mouth area, appearing lower. Additionally, dental or orthodontic issues can directly impact the alignment of the jaw and mouth. Missing teeth, a misaligned bite, or ill-fitting dentures can shift the jaw’s position, leading to visible asymmetry. Minor imbalances in facial muscle strength not related to nerve damage can also contribute to subtle unevenness.
Underlying Medical Conditions
A lower mouth on one side can stem from medical conditions affecting nerves or muscles. Facial nerve palsy, such as Bell’s Palsy, is a frequent cause, characterized by sudden weakness or paralysis on one side of the face. This condition results from inflammation or damage to the seventh cranial nerve, which controls facial muscles, often leading to a drooping eyebrow, eyelid, and mouth. It is sometimes linked to viral infections and typically resolves within weeks to months.
A sudden facial droop can also be a symptom of a stroke, occurring when blood flow to a part of the brain is disrupted. Unlike Bell’s Palsy, a stroke often presents with additional symptoms such as arm or leg weakness, numbness, or difficulty with speech or understanding. Other forms of nerve damage, from injury, surgical complications, or tumor compression, can also lead to facial muscle weakness and asymmetry.
Muscle disorders that affect facial muscle strength or coordination can contribute to an uneven appearance of the mouth. Temporomandibular Joint (TMJ) disorders, involving the jaw joint and surrounding muscles, can also result in facial asymmetry. Direct trauma or injury to the face or jaw can cause immediate and lasting asymmetry. Rarely, tumors or other growths can affect facial nerves or muscles, leading to noticeable asymmetry.
When to Seek Professional Guidance
Seek medical evaluation if the asymmetry appears suddenly. This is especially true if the facial droop is accompanied by other symptoms. These include weakness or numbness in an arm or leg, difficulty speaking, changes in vision, a severe headache, or trouble eating. Such accompanying symptoms can signal a more serious underlying condition like a stroke.
Any asymmetry that progressively worsens over time should also be evaluated by a healthcare professional. If the unevenness develops following a head injury or facial trauma, a medical assessment is necessary. Persistent pain or discomfort associated with the facial asymmetry is another reason to consult a doctor.
Diagnosis and Management Options
Medical professionals evaluate a lower mouth on one side with a clinical examination, patient history, and physical assessment of facial muscle movement. They may ask the individual to make various facial expressions to observe the extent and pattern of the asymmetry. Imaging studies like X-rays, CT scans, or MRIs may be used to visualize bones, soft tissues, and nerves. Nerve conduction studies, such as electromyography (EMG), can also assess nerve function and muscle response.
Management approaches vary depending on the identified cause. For benign cases, observation may be the only recommended course of action. If an underlying medical condition is diagnosed, specific treatments are available; for instance, corticosteroids and antiviral medications are prescribed for Bell’s Palsy. Physical therapy and facial exercises are recommended to improve muscle strength, coordination, and recovery from facial paralysis.
For dental or orthodontic problems, interventions include braces, clear aligners, or full mouth reconstruction to correct bite misalignments and jaw positioning. Surgical options are considered for significant structural or nerve-related causes, such as orthognathic surgery, facial implants, or fat grafting. If medical causes are ruled out or treated and the primary concern is aesthetic, cosmetic procedures like dermal fillers or botulinum toxin injections can temporarily improve facial symmetry.