Anatomy & Histology · single question
In a patient with trismus, which muscle is most directly implicated?
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Correct answer: A. Medial pterygoid
The lateral pterygoid muscle is the key muscle involved in trismus (inability to open the mouth). Trismus is most commonly caused by spasm or inflammation of the lateral pterygoid, often due to inferior alveolar nerve blocks (Vazirani-Akinosi or direct IAN), pericoronitis, or infection spreading to the pterygomandibular or infratemporal space.
- A. ✅ CORRECT – The lateral pterygoid is the primary muscle involved in trismus; spasm prevents normal mandibular opening.
- B. ❌ The medial pterygoid elevates and protrudes the mandible but is not the chief trismus muscle.
- C. ❌ The masseter elevates the mandible but is not the primary muscle in trismus.
- D. ❌ Temporalis elevates and retracts the mandible but is not the primary trismus muscle.
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