Botulinum Toxin Injection Sites for Lockjaw Treatment
For treating lockjaw (temporomandibular disorders), botulinum toxin should be injected primarily into the masseter and temporalis muscles, with additional injections into the lateral and medial pterygoid muscles in cases of severe or refractory symptoms. 1, 2
Primary Injection Sites
Masseter Muscle
- Location: The large muscle on the side of the face that connects the mandible to the zygomatic arch
- Technique:
- Inject 30-50 units per side
- Use 3-5 injection points in a grid pattern
- Avoid the anterior third of the muscle to prevent smile asymmetry
Temporalis Muscle
- Location: Fan-shaped muscle on the side of the head
- Technique:
- Divide into 9 compartments (3×3 grid)
- Recommended injection sites: middle-anterior (Am), middle-upper (Mu), and posterior-middle (Pm) compartments
- Avoid large blood vessels and tendinous areas 3
- Inject 15-25 units per side
Secondary Injection Sites (for severe cases)
Lateral Pterygoid Muscle
- Indicated for: Jaw opening, jaw deviation, and jaw protrusion types of oromandibular dystonia
- Technique:
- Can be accessed via intraoral or extraoral approach
- For extraoral approach: insert needle below the zygomatic arch, directed medially toward the lateral pterygoid plate 4
Medial Pterygoid Muscle
- Indicated for: Jaw closing dystonia, especially after repeated injections into masseter and temporalis
- Technique:
- Access intraorally along the medial surface of the mandibular ramus
- Direct needle posteromedially 4
Dosing Considerations
- Starting dose:
- 50-100 units total (divided between muscles)
- Lower doses for first-time patients
- Duration of effect: 3-4 months on average 2
- Frequency: Repeat injections every 3-6 months as needed
Precautions and Post-Injection Care
- Remain upright for 3-4 hours after treatment
- Avoid touching, rubbing, or massaging the treated areas
- Refrain from strenuous exercise for 24 hours
- Avoid alcohol consumption for 24 hours
- Avoid drinking through straws for 24-48 hours to prevent toxin spread 5
Efficacy and Expected Outcomes
Botulinum toxin injections for temporomandibular disorders have shown significant reduction in pain and improvement in jaw movement. Studies demonstrate:
- Significant decrease in pain (p<0.0001)
- Increased mouth opening and lateral movement
- Reduced muscle tenderness in 70% of patients
- Effects lasting approximately 3 months post-injection 2
Important Considerations
- Current clinical guidelines conditionally recommend against botulinum toxin injection for chronic pain associated with temporomandibular disorders 1
- Consider botulinum toxin as part of a treatment approach after conservative therapies have failed
- Monitor for potential side effects including facial asymmetry, difficulty swallowing, or speech changes
- Accurate muscle targeting is essential for maximizing efficacy and minimizing complications
While botulinum toxin can be effective for symptom management in lockjaw, it should be considered after trying conservative approaches first, as recent guidelines from BMJ (2023) conditionally recommend against its use as a first-line treatment for chronic TMD pain 1.