Management of Congenital Absence of the Depressor Anguli Oris Muscle
Overview and Significance
The management of congenital absence of the depressor anguli oris muscle (DAO) should focus primarily on thorough evaluation for associated anomalies, particularly cardiovascular malformations, as these represent the most significant morbidity and mortality risks.
Congenital absence or hypoplasia of the depressor anguli oris muscle presents as asymmetrical crying facies (ACF), where the lower lip appears asymmetric during crying but normal at rest. This condition is not merely a cosmetic concern but serves as an important clinical marker for potentially serious associated anomalies.
Initial Evaluation
Comprehensive Screening for Associated Anomalies
Cardiovascular assessment:
Other systems requiring evaluation:
Diagnostic Confirmation
- B-scan sonography can be used to confirm the diagnosis by visualizing the absence or hypoplasia of the depressor anguli oris muscle 3
- However, note that in some cases presenting with similar clinical features, the muscle may be present but dysfunctional 3
Management Approach
For Isolated DAO Absence (No Associated Anomalies)
- Observation is appropriate for isolated cases without associated anomalies
- Regular follow-up to monitor for developmental milestones and growth parameters
- Reassurance to parents that isolated ACF typically does not affect function or development
For DAO Absence with Associated Anomalies
Management of cardiovascular anomalies:
- Follow appropriate cardiac management protocols based on specific cardiac defects identified
- Regular cardiac follow-up as indicated by the severity of cardiac involvement
Developmental monitoring:
- Close monitoring for developmental delays (6% of patients develop psychomotor retardation) 1
- Early intervention services if developmental concerns arise
Growth monitoring:
- Regular assessment of growth parameters as 10% of patients experience failure to thrive 1
- Nutritional support as needed
Surgical Considerations
- Surgical correction of the facial asymmetry is generally not indicated for functional reasons
- Cosmetic surgical intervention may be considered in cases where the asymmetry causes significant psychological distress, but should be deferred until facial growth is complete
Follow-up Recommendations
- Regular follow-up during the first year of life to monitor for emergence of previously undetected anomalies
- Developmental screening at standard intervals
- Cardiac follow-up as indicated by initial cardiac evaluation
- Genetic counseling for families, particularly if multiple family members are affected 2
Prognosis
- Prognosis is primarily determined by the presence and severity of associated anomalies
- Isolated DAO absence has excellent prognosis with normal growth and development 2
- Mortality risk is primarily associated with severe cardiac or central nervous system anomalies 1
Important Considerations
- The facial asymmetry typically persists but does not worsen over time 2
- Nearly half of cases (44%) have at least 2 associated systemic anomalies, emphasizing the importance of thorough evaluation 1
- Familial occurrence has been reported, suggesting possible genetic factors 2
Clinical Pitfalls to Avoid
- Dismissing ACF as a minor cosmetic issue without screening for associated anomalies
- Focusing solely on the facial asymmetry while missing potentially life-threatening cardiac anomalies
- Failing to provide long-term follow-up, as some developmental issues may emerge later
The key to management is recognizing that while the facial asymmetry itself rarely requires intervention, the condition serves as an important marker for potentially serious associated anomalies that require prompt identification and management.