Treatment of Trismus (Lockjaw)
Refer patients with trismus immediately to rehabilitation specialists and dental professionals for early intervention with exercise therapy and stretching devices, while prescribing nerve-stabilizing agents (pregabalin, gabapentin, or duloxetine) to control pain and spasms that facilitate physical therapy compliance. 1, 2
Initial Assessment and Etiology
Before initiating treatment, determine the underlying cause of trismus, which critically affects management approach 2:
- Rule out malignancy first: Trismus may indicate tumor invasion into masticatory muscles (especially medial pterygoid), requiring oncologic evaluation before rehabilitation 1
- Post-treatment causes: Radiation therapy to masticatory muscles, post-surgical complications, temporomandibular joint disease 2
- Infectious causes: Odontogenic infections (periodontal or pericoronal), masticatory space infections 3
- Rare presentations: Leukemic infiltration into facial muscles (particularly in children with systemic symptoms) 4
Critical pitfall: In head and neck cancer survivors, new-onset or worsening trismus may be the first sign of recurrence rather than treatment sequelae—maintain high suspicion and low threshold for imaging 5
Primary Treatment: Conservative Management
Exercise Therapy (Cornerstone of Treatment)
Start stretching exercises as soon as trismus is diagnosed—delay worsens outcomes 1, 2:
- Gentle stretching with tongue blades and custom mouth opening devices 2
- Exercise should begin immediately after diagnosis and continue throughout radiation treatment in at-risk populations 2
- Mouth opening decreases by approximately 20% after radiotherapy if preventive exercises are not maintained 5
Pharmacologic Management
Prescribe nerve-stabilizing agents as first-line adjunct to physical therapy 1, 2:
- Pregabalin, gabapentin, or duloxetine to combat pain and muscle spasms, which facilitates compliance with stretching devices 1, 2
- Analgesics: Acetaminophen or NSAIDs (ibuprofen) for pain control 2
- Corticosteroids: Dexamethasone to reduce inflammation and associated trismus 2
The evidence strongly supports that pain control with nerve-stabilizing agents directly improves physical therapy adherence, making this combination more effective than either intervention alone 1, 2.
Specialist Interventions for Refractory Cases
When conservative measures fail, refer for botulinum toxin type A injections into affected muscles 1, 2:
- Reserved for refractory pain and spasm control 2
- Requires specialist administration (physiatrist or appropriate surgeon) 1
Prevention Strategies
For patients undergoing head and neck radiation, prevention is more effective than treatment 2, 5:
- Maintain range of motion exercises throughout and after radiation treatment 2
- Prevalence and severity of radiation-induced trismus increases with higher doses to mastication structures 5
- Intensity-modulated radiation therapy (IMRT) appears to lower the percentage and severity of trismus compared to conventional techniques 5
Special Considerations
Severity assessment: Mouth opening ≤35 mm should be regarded as trismus requiring intervention 5
Surgical context: Severe trismus may contraindicate transoral robotic surgery due to inadequate exposure—assess carefully preoperatively, as procedures may need to be aborted if exposure is insufficient under anesthesia 1
Odontogenic infections with severe trismus: Can be managed intraorally under local anesthesia using modified Akinosi technique in outpatient settings, enabling early access without general anesthesia 3