Congenital Unilateral Lower Lip Palsy(Asymmetric Crying Facies)
Compassionate evaluation and specialized treatment to restore facial symmetry for children and adults.
What is Congenital Unilateral Lower Lip Palsy?
Congenital Unilateral Lower Lip Palsy (CULLP), frequently referred to clinically as Asymmetric Crying Facies (ACF), is a rare congenital condition present at birth. It is characterized by an inability to pull down one corner of the mouth, which becomes highly noticeable when the infant cries or smiles.
In most cases, ACF is caused by the underdevelopment (hypoplasia) or complete absence (agenesis) of a specific facial muscle called the depressor anguli oris. Less commonly, it may involve the depressor labii inferioris muscle. Because the rest of the facial nerve and muscles function normally—allowing the child to blink, close their eyes, and wrinkle their forehead—this condition is distinct from total facial nerve paralysis.
While the facial asymmetry itself is primarily a cosmetic concern, roughly 10% of infants with ACF may have associated congenital abnormalities, particularly structural heart defects (a condition known as Cayler cardiofacial syndrome). Therefore, a comprehensive pediatric evaluation is standard protocol upon diagnosis.
Information supported by NORD.
~0.3%
Of newborns have an asymmetric cry
At rest
The face is usually symmetric
1st line
Botox on the strong side, then surgery
A Note to Parents
Discovering your newborn has facial asymmetry can be frightening. However, it is important to know that isolated Asymmetric Crying Facies does not cause pain, does not affect brain development, and does not progress or worsen over time.
Unlike acquired nerve injuries, there is no urgent "window" where surgery must be performed immediately to save the nerve. We can carefully plan the timing of any intervention based on the severity of the asymmetry and the developmental stage of your child.
Congenital Lower Lip Palsy Signs
The visual presentation of ACF is highly characteristic, allowing experienced specialists to often diagnose it visually.
The "Crying" Asymmetry
When the baby cries, the healthy side of the lower lip pulls down normally, while the affected side remains flat or slightly elevated. This creates a distinct, lopsided appearance.
Normal Upper Face
Crucially, the upper face functions perfectly. The child can fully close both eyes tightly and wrinkle their forehead symmetrically. This distinguishes ACF from complete facial nerve paralysis.
Normal Sucking & Swallowing
Because the lips and mouth muscles required for feeding are not deeply affected, most infants with isolated ACF can breastfeed or bottle-feed without significant difficulty.
Congenital Lower Lip Palsy Treatment
Historically, children with CULLP were simply told to "live with it." Today, modern facial plastic surgery offers elegant solutions to restore a balanced smile. Treatment timing is individualized—some families choose early intervention, while others wait until adolescence.
First-line care for older children, teenagers, and adults. A small dose on the healthy side weakens the overactive depressor so the lower lip looks even when speaking or smiling. The effect lasts about four to six months and can preview what a balancing surgery would feel like. This use is off-label.
Congenital Lower Lip Palsy FAQs
What the Evidence Shows
Asymmetric crying facies is usually a lower-lip problem, not a missing smile muscle.
- The face is often symmetric at rest. The imbalance appears with crying or smiling because one depressor does not pull down.
- Infants need a heart evaluation. The pattern can travel with congenital heart disease and 22q11.2 deletion.
- First-line treatment is usually Botox to the strong side, not a free-flap smile reconstruction.
- A balancing myectomy can make that symmetry permanent after a successful Botox trial.
- The key distinction is an isolated lower-lip muscle problem versus weakness of the whole side of the face. Trouble closing the eye, a flattened forehead or nasolabial fold, feeding difficulty, or slurred speech points to facial nerve involvement instead.
- Ultrasound of the facial muscles and orofacial electrical testing can separate an absent muscle from a nerve problem. MRI or CT is reserved for suspected facial nerve or temporal-bone anomalies.
- The condition is static and benign. Asymmetry with crying usually becomes less noticeable as a child grows, but the muscle deficit itself is permanent and some imbalance with animated expression tends to persist.
- Grafting fascia to the weak side is an alternative to weakening the strong side and may improve lower-lip position and symmetry during mouth opening in selected children.
- Evidence here comes from case series and small comparative studies rather than randomized trials, and no society guideline covers this condition specifically. Treatment is elective and individualized, and botulinum toxin for this use is off-label.
Why Choose Revitalis for Congenital Lower Lip Palsy?
Dr. Nate Jowett is a facial nerve surgeon whose clinical and peer-reviewed work includes facial reanimation. His fellowship training and background span facial plastic surgery, engineering, and reconstructive microsurgery.
Whether you are days into a diagnosis or have lived with incomplete recovery for years, Dr. Jowett offers the full spectrum of care, from medical management to cutting-edge surgical reconstruction, to help you regain your smile and confidence.
Common questions
Questions Patients Ask
Is asymmetric crying facies the same as a complete facial palsy?
No. Isolated asymmetric crying facies affects lower-lip depression while forehead movement, blink, and cheek movement remain intact. Weakness in those other facial zones calls for a broader facial nerve evaluation.
Will congenital lower-lip asymmetry disappear with age?
True muscle underdevelopment is generally stable, although the asymmetry may become less noticeable as facial proportions change. Treatment is based on functional and psychosocial impact rather than age alone.
What procedures can improve lower-lip symmetry?
Options include carefully selected botulinum toxin to the stronger side, reduction of a stronger-side depressor muscle, or dynamic/static reconstruction. The best choice depends on anatomy, age, and whether asymmetry is present at rest or only with expression.
What testing confirms whether a muscle or a nerve is the problem?
Examination at rest and during crying or smiling usually settles it. When confirmation is needed, ultrasound of the facial muscles and orofacial electrical testing can separate an absent lip-depressor muscle from a nerve problem. MRI or CT is reserved for suspected facial nerve or temporal-bone anomalies.
Is botulinum toxin approved for this condition?
Its use here is off-label. Botulinum toxin to the intact side is a reversible, nonsurgical way to balance lower-lip movement, but the effect is temporary and requires repeat treatment. Because the evidence base is case series rather than randomized trials, treatment is elective and individualized.
Can the weak side be reinforced instead of weakening the strong side?
Yes, in selected children. Grafting fascia to the affected side can improve lower-lip position and add symmetry during mouth opening, and case series report improvement in most patients. Permanent options are generally deferred until facial growth is further along.
Does asymmetric crying facies affect speech?
Usually the long-term concerns are cosmetic, but articulation can occasionally be affected, and some families report improved speech clarity after balancing treatment. A speech-language assessment is reasonable if a child's clarity is a concern.
Answers are general and individualized at consultation.
Medical References & Evidence-Based Guidelines
- Dual-Vector Gracilis Muscle Transfer for Smile Reanimation with Lower Lip Depression. Ein L, Hadlock TA, Jowett N. Laryngoscope. 2021 Aug; 131(8):1758-1760. PMID: 33660858.
- Congenital Unilateral Lower Lip Palsy: A Case-Based Review. Block BR, Straka-DeMarco D, Demarest M, Mazzola CA. Childs Nerv Syst. 2023;39(1):35-40. PMID: 36198892.
- Contralateral Depressor Labii Inferioris Chemodenervation for Congenital Unilateral Lower Lip Palsy. Çam OH, Özücer B. J Craniofac Surg. 2020;31(5):e479-e481. PMID: 32487835.
- Botulinum Toxin for the Correction of Asymmetric Crying Facies. Isken T, Gunlemez A, Kara B, Izmirli H, Gercek H. Aesthet Surg J. 2009;29(6):524-527. PMID: 19944999.
- Asymmetric Crying Facies and Associated Congenital Anomalies: Prospective Study and Review of the Literature. Lahat E, Heyman E, Barkay A, Goldberg M. J Child Neurol. 2000;15(12):808-810. PMID: 11198496.
- Effect of Weakening of Ipsilateral Depressor Anguli Oris on Smile Symmetry in Postparalysis Facial Palsy. Jowett N, Malka R, Hadlock TA. JAMA Facial Plast Surg. 2017 Jan 01; 19(1):29-33. PMID: 27658020.
- A General Approach to Facial Palsy. Jowett N. A General Approach to Facial Palsy. Otolaryngol Clin North Am. 2018 Dec; 51(6):1019-1031. PMID: 30119926.
- Congenital asymmetric crying facies syndrome: A case report. Liang X, He B. Medicine (Baltimore). 2018;97(31):e11403. PMID: 30075506.
- Developmental unilateral facial palsy in a newborn: six cases and literature review. Decraene L, Boudewyns A, Venstermans C, et al. Eur J Pediatr. 2020;179(3):367-375. PMID: 31989259.
- Evaluation of Facial Symmetry in Congenital Unilateral Lower Lip Palsy Patients with Depressor Labii Inferioris Muscle Resection. Qu S, Shen S, Ji K, et al. Aesthetic Plast Surg. 2025;49(5):1205-1216. PMID: 39733048.
- Treatment of Asymmetric Crying Face by Fascia lata Grafting. Lei B, Huang Q, Li B, et al. Cleft Palate Craniofac J. 2024;61(6):917-920. PMID: 36594218.
- A simple reconstruction for congenital unilateral lower lip palsy. Udagawa A, Arikawa K, Shimizu S, et al. Plast Reconstr Surg. 2007;120(1):238-244. PMID: 17572570.
- Prognostic factors for facial nerve palsy in a pediatric population: A retrospective study and review. Wolfovitz A, Yehudai N, Luntz M. Laryngoscope. 2017;127(5):1175-1180. PMID: 27641905.