Submasseteric space infection with severe trismus

§Chief complaint

Unable to open the mouth, painful swelling at the angle of the jaw for 5 days

§Medical & dental history

• 01Fit and well
• 02No allergies
• 03Partially erupted 48 with recurrent pericoronitis

§Clinical examination

• 01Firm, tender swelling over the right mandibular ramus obliterating the angle
• 02Severe trismus — interincisal opening 12 mm
• 03Temperature 38.4 C, pulse 104
• 04Floor of mouth soft, no dysphagia, airway patent

§Figures

§Differential diagnosis

§Final diagnosis

Right submasseteric space infection secondary to pericoronitis of 48

Disproportionate trismus with tenderness over the ramus and a deep collection between the masseter and the lateral ramus on contrast CT localises the submasseteric space; the partially erupted third molar is the source.

§Investigations

• 01Contrast-enhanced CT of face and neck
• 02Full blood count, CRP, blood cultures if febrile
• 03Pus for culture and sensitivity at drainage

§Radiology

• 01OPG — distoangular impacted 48 with pericoronal bone loss
• 02Contrast CT — rim-enhancing collection 20 mm deep to masseter with fat stranding; airway not displaced

§Treatment plan

• 01Admission, intravenous fluids and antibiotics
• 02Extraoral or intraoral incision and drainage under general anaesthesia
• 03Extraction of 48 at the same sitting
• 04Nasoendoscopic airway assessment given trismus

§Surgical procedure

• 01Awake fibreoptic intubation because of trismus
• 02Intraoral incision along the anterior border of the ramus, blunt dissection into the submasseteric space, 20 mL pus released
• 03Extraction of 48; corrugated drain placed

§Follow-up & outcome

• 01Day 2 — pyrexia settled, opening 22 mm, drain removed day 3
• 02Day 10 — opening 38 mm with jaw exercises
• 036 weeks — full function restored

Outcome: Full recovery with normal mouth opening after physiotherapy; no recurrence.

§Discussion

• 01Trismus disproportionate to visible swelling points to a masticator space (submasseteric or pterygomandibular) collection.
• 02Airway management is the first decision in deep space infection; awake fibreoptic intubation is the safe default with significant trismus.

§Clinical pearls / learning points

• 01Trismus severity is a severity score, not just a symptom.
• 02Drain the space and remove the tooth in the same anaesthetic whenever safe.

§Viva questions

§MCQs

§Related diseases

§Similar cases