A 58-year-old man with carcinoma of the left maxillary sinus develops progressive difficulty opening his mouth over three months. Examination shows limitation of jaw opening with deviation of the mandible toward the left side. This symptom indicates tumour invasion of which structure?

• A Masseter muscle
• B Medial pterygoid muscle ✓
• C Temporomandibular joint
• D Inferior alveolar nerve

Explanation

Trismus in maxillary sinus carcinoma signals posterolateral spread through the posterior wall of the antrum into the pterygoid muscles, most often the medial pterygoid, and upstages disease to T4. The masseter lies lateral to the ramus and is not reached by direct antral extension. TMJ involvement and inferior alveolar nerve palsy are late, rare events and do not explain early progressive trismus with ipsilateral deviation.

Reference: Scott-Brown's Otorhinolaryngology Head and Neck Surgery, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.