Complications of DAO Botox Injections
Botulinum toxin injections for the Depressor Anguli Oris (DAO) muscle can cause several complications including diffusion to adjacent muscles leading to asymmetrical smiles, dysphagia, facial paresis, and in rare cases, more serious systemic effects. While generally safe when performed correctly, proper technique and anatomical knowledge are essential to minimize adverse events.
Common Complications
- Asymmetrical smile: The most frequent complication occurs when botulinum toxin spreads to adjacent muscles, particularly the depressor labii inferioris (DLI), causing lip asymmetry during facial expressions 1, 2
- Facial weakness or paresis: Temporary weakness in nearby facial muscles can occur due to toxin diffusion beyond the intended target area 3
- Injection site reactions: Local effects such as pain, erythema, or bruising at the injection site 4
- Dry mouth: Can occur due to effects on salivary production 5
Serious but Rare Complications
- Dysphagia (difficulty swallowing): Can occur if toxin diffuses to muscles involved in swallowing 3, 5
- Aspiration risk: Related to dysphagia, particularly in patients with pre-existing neuromuscular disorders 5
- Systemic spread of toxin: In very rare cases, botulinum toxin can spread beyond the local area, causing generalized weakness 3
- Botulism-like syndrome: Extremely rare but potentially serious complication with symptoms of widespread muscle weakness 3
Anatomical Considerations
The risk of complications is directly related to anatomical factors:
- Muscle overlap: The DAO partially overlaps with the DLI medially and borders the risorius, zygomaticus major, and platysma muscles laterally 1
- Injection depth: The average soft tissue thickness at the DAO point is approximately 6.7 mm, requiring precise depth control 6
- Proximity to important structures: Nearby facial nerves and blood vessels can be affected if injection technique is improper 2
Risk Factors for Complications
- Pre-existing neuromuscular disorders: Patients with conditions like myasthenia gravis have increased risk of adverse effects 4
- Improper technique: Incorrect injection sites or depths significantly increase complication risk 1, 2
- Excessive dosing: Higher doses increase risk of diffusion to adjacent structures 3
- Multiple treatment sites: Receiving botulinum toxin injections in multiple facial areas simultaneously may increase systemic absorption risk 3
Prevention of Complications
To minimize adverse events:
- Use precise anatomical landmarks: Target the upper half of the DAO muscle using the three-point injection technique to avoid the DLI 2
- Optimal injection points: Use facial landmarks such as the cheilion and pupil to accurately locate the DAO point (P5) without requiring palpation of the modiolus 6
- Appropriate dosing: Use the minimum effective dose to achieve the desired effect 1
- Proper technique: Ensure correct depth of injection (approximately 6-7 mm) 6
- Avoid high-risk patients: Exercise caution in patients with pre-existing neuromuscular disorders 4
Management of Complications
If complications occur:
- Patient education: Inform patients that most side effects are temporary and will resolve as the toxin effect diminishes (typically 3-6 months) 5
- Supportive care: For dysphagia or other functional issues, provide supportive measures until resolution 5
- Monitor respiratory function: In rare cases of significant toxin spread, respiratory monitoring may be necessary 5
- Psychological support: Address patient concerns about facial asymmetry or other visible effects 5
Special Considerations
- Off-label use: DAO treatment with botulinum toxin is considered off-label use 2
- Patient selection: Careful assessment of facial anatomy before treatment is essential 1
- Informed consent: Patients should be made aware of the potential complications and their temporary nature 5
By understanding these potential complications and following proper injection techniques based on precise anatomical knowledge, clinicians can minimize adverse events while achieving the desired aesthetic improvement in patients seeking correction of drooping mouth corners.