What is Congenital Unilateral Lower Lip Palsy?
Congenital unilateral lower lip palsy is a rare birth defect affecting roughly 0.5-1% of newborns, or approximately 1 in every 160 live births. This condition happens when one side of a specific mouth muscle known as the depressor anguli oris muscle, doesn’t develop fully or at all. This muscle, shaped like a triangle, begins from the jawbone and reaches to the corner of the mouth. Two branches of the facial nerve, known as the buccal and the mandibular branch, mainly control it. This muscle’s primary function is to lower and pull to the side the lower corner of the mouth, which plays a key role in expressing sadness when we cry. If one side of this muscle doesn’t develop fully or doesn’t exist, no mouth or lip movement occurs on that side while the corner of the mouth on the normal side is pulled downwards.
What Causes Congenital Unilateral Lower Lip Palsy?
Congenital unilateral lower lip palsy has more than one cause. It can happen due to pressure on the facial nerve or if the facial nerve or muscle doesn’t develop properly. Around 80% of patients have defects in the development of the facial nerve or muscle, while about 20% experience pressure on their facial nerve.
A specific part of the facial nerve, called the marginal mandibular branch, is especially susceptible to damage from pressure injuries while the baby is still in the womb or during childbirth. However, in most cases, the root cause of this condition is the abnormal development of a facial muscle or nerve.
A number of factors contribute to this. It could be due to genetic factors, viruses infecting the female during pregnancy, or abnormalities in the structure of the brainstem, which might hinder the proper development of a muscle situated in the lower lip quadrant.
Risk Factors and Frequency for Congenital Unilateral Lower Lip Palsy
Unilateral lower lip palsy is a genetic condition where one side of the lower lip is paralyzed. About 80% of the time, this affects the left side. While this can occur on its own, in roughly 45% to 70% of cases, it is linked with other birth defects. Some instances of this condition are passed down through families, showing different severity in different people.
- Unilateral lower lip palsy is typically characterized by paralysis on one side of the lower lip.
- About 80% of the cases involve the left side.
- In some cases, this condition appears on its own, but in about 45% to 70% of cases, it is accompanied by other birth defects.
- Some cases are inherited and may vary in severity from person to person.
Signs and Symptoms of Congenital Unilateral Lower Lip Palsy
Typically, a person suffering from this condition may show one-sided drooping of the lower lip when they smile or cry. On the normal side, the lower lip drops more than usual. There’s weakness on the opposite side of the lower lip. However, when the face is at rest, it looks symmetrical. Other facial movements, such as closing the eyelids, moving the forehead, and the depth of the crease running from the side of the nose to the corner of the mouth, remain unaffected. Individuals with this condition can swallow, chew, and speak without any trouble.
Testing for Congenital Unilateral Lower Lip Palsy
Diagnosing unilateral lower lip palsy, a condition where one side of the lower lip has weakened or no muscle function, involves assessing through neurological examinations. If this condition is suspected, it’s important to also thoroughly check for other birth defects, particularly heart-related problems. This condition could potentially link with other abnormalities in areas like the brain, face, respiratory system, muscles, and urinary system.
Facial irregularities can occur on the same side as the weakened lip muscle. This condition can also be connected with specific syndromes like DiGeorge syndrome or VACTERL syndrome, which includes a combination of vertebral, heart, kidney, and limb abnormalities, and Cayler cardiofacial syndrome. Notably, it has been found that 14% of patients with unilateral lower lip palsy also had DiGeorge Syndrome. Therefore, this condition could be seen as a sign that other birth defects may be present.
Treatment Options for Congenital Unilateral Lower Lip Palsy
In simple cases of congenital unilateral lower lip palsy, where the condition is present from birth and affects one side of the lower lip with no other birth defects, the outcome is generally good. Usually, no treatment is needed. However, if there are concerns about the look of the face, reconstructive surgery can be considered.
Recent case studies show that a quick and safe method to improve an uneven face is a treatment with botulinum toxin A. This procedure involves relaxing the tense muscle on the opposite side of the face. Another option for selected cases is a less invasive surgery using both horizontal and vertical fascia grafting techniques.
Doctors can consider using ultrasound imaging of facial muscles and other tests to better understand and manage this condition. Usually, these tests reveal no anomalies in the facial nerve and muscles responsible for facial expressions.
Screening for Di George syndrome, a genetic disorder, is recommended in some studies due to its common association with lower lip palsy. This test can detect any missing piece in one specific chromosome (22q11.2).
It’s essential to have a team of health professionals overseeing these cases and providing long-term follow-up care. Such a team-based approach contributes to better care and a positive outcome.
What else can Congenital Unilateral Lower Lip Palsy be?
Doctors differentiate between Congenital Unilateral Lower Lip Palsy (CULLP) and facial nerve palsy by carefully observing the patient’s neurological signs. People with CULLP display an even distribution of wrinkles on their forehead and equal ability to close their eyes. Their smile lines or nasolabial folds, the lines running from the side of the nose to the corner of the mouth, are also similar in depth on both sides.
On the other hand, possible signs of facial nerve paralysis might include an uneven forehead with no wrinkling on one side, asymmetrical facial features, inability to fully close one eye, drooling, and issues with feeding due to unevenness of the lips.
Thorough patient history and careful clinical examination are vital for correct diagnosis. This is because the treatment plans differ for each condition. Facial nerve paralysis treatment focuses on preventing damage to the exposed eye, managing drooling, and addressing any nasal deviation, all while making allowances for the impaired function of the lips.
What to expect with Congenital Unilateral Lower Lip Palsy
The outlook is generally positive for standalone CULLP cases, and there may be no need for treatment. Over time, patients typically see improvement, especially those experiencing facial nerve pressure. However, if the issue is a result of developmental defects, symptoms may not disappear. In these cases, long-term monitoring is critical, involving a team of different healthcare professionals working together.
Possible Complications When Diagnosed with Congenital Unilateral Lower Lip Palsy
There have been no complications linked to lower lip palsy when it occurs by itself. People with this condition can eat, blink, and breathe without issues. However, if lower lip palsy is part of a group of birth defects, complications may arise based on the other systems of the body that are affected.
Preventing Congenital Unilateral Lower Lip Palsy
Congenital unilateral lower lip palsy is a small birth defect that only impacts the movement of the lower lip. This means that when a baby with this condition cries, only one side of their mouth moves downwards, while the other side stays still. Parents can rest assured knowing that this condition does not affect the child’s ability to move their eyes, feed, or breathe. It can be caused by nerve damage before or during birth, or from developmental issues with the facial nerve or affected muscles.
Although it can be a standalone condition, in some cases it may be accompanied by other birth defects like heart problems, muscle and skeleton defects (though these are less common), kidney issues, or problems with the neck or face. Parents are strongly advised to follow through with all recommended medical appointments and evaluations. If there are other underlying health issues, the child should be looked after by a team of different healthcare professionals. Parents should be reassured that the prognosis is usually positive for children with only this condition, and treatment is not typically needed. However, if parents are still worried about how it looks, minor surgeries or botox injections may be needed to improve the appearance.
