Masticator Space Infection

Masticator space infection is infection within the compartment enclosed by the superficial layer of the deep cervical fascia that contains the masseter, medial and lateral pterygoid and temporalis muscles with the mandibular ramus. It is a deep space infection with severe trismus, and the infection can reach the skull base.

The compartment includes the submasseteric, pterygomandibular, infratemporal and temporal spaces. The source is usually a lower third molar, and other causes are spread from adjacent spaces and mandibular osteomyelitis.

Pathophysiology. Infection spreads within the compartment along muscle planes. Upward spread along the temporalis reaches the temporal and infratemporal spaces, and from there the skull base, orbit through the inferior orbital fissure, and the cavernous sinus through the pterygoid venous plexus.

The compartment is tight, so collections develop under pressure with severe pain and spasm. Osteomyelitis of the ramus and condyle and septic arthritis of the temporomandibular joint are complications.

Severe trismus (often under 10 to 15 mm), marked pain in the cheek, ramus and temple, firm swelling over the cheek and temporal fossa, fever, malaise, dysphagia and ear pain. Facial swelling may be minimal early on.

Eye swelling, proptosis, ophthalmoplegia, reduced visual acuity, headache with meningism, altered consciousness, neck swelling and stridor suggest orbital, intracranial or airway spread and need emergency imaging and escalation.

• Airway assessment and measurement of interincisal opening.
• Contrast CT of the face, skull base and neck is the investigation of choice: collections within and around the masseter, pterygoids and temporalis, osteomyelitis, gas, thrombosis of the pterygoid plexus or cavernous sinus, and spread to the parapharyngeal space. MRI helps with skull base, intracranial and joint disease.
• Bloods: full blood count, C-reactive protein, glucose, coagulation and blood cultures when febrile.
• Culture of pus and bone, aerobic and anaerobic, and fungal culture when immunosuppression is present.
• Panoramic radiograph for the source tooth and ramus.
• Ophthalmic examination and CT or MR venography with orbital or neurological signs.

Differential diagnosis.

• Submasseteric or pterygomandibular infection confined to one space
• Temporomandibular joint septic arthritis
• Parotid abscess
• Temporal arteritis
• Orbital cellulitis
• Rhabdomyosarcoma, lymphoma or other masticator space tumour
• Tetanus
• Myositis ossificans after trauma

• Airway protection with early anaesthetic input, since trismus precludes routine laryngoscopy, using awake fibreoptic intubation or tracheostomy when airway compromise is likely.
• Antibiotics immediately after cultures: benzylpenicillin 1.2 g intravenously every 6 hours (or amoxicillin 1 g every 8 hours) with metronidazole 500 mg intravenously every 8 hours. In penicillin allergy: clindamycin 600 mg intravenously every 6 to 8 hours (maximum 2.4 g daily). With sepsis, skull base or intracranial spread, or healthcare exposure, use broader cover with an agent such as piperacillin-tazobactam 4.5 g intravenously every 8 hours (every 6 hours in severe sepsis), reduced in renal impairment, or with ceftriaxone 2 g every 12 hours and metronidazole 500 mg every 8 hours when intracranial spread is possible. Adjust to culture results.
• Duration of 2 to 6 weeks, or longer, with osteomyelitis, intracranial extension or thrombosis, and a switch to oral therapy only when the clinical response is clear.
• Source control: remove the infected tooth, drain every involved space, and perform bone debridement and sequestrectomy as needed. Multiple intraoral and extraoral incisions (including temporal and submandibular) are often needed, with drains.
• Anticoagulation for septic cavernous sinus or venous thrombosis is decided by the specialist team, as evidence is limited.
• Intensive care for sepsis, with fluid resuscitation and glucose control.
• Jaw exercises and physiotherapy once the infection is controlled to restore opening.

Special groups. Diabetes, immunosuppression, alcohol misuse and malnutrition increase severity. Children need paediatric anaesthesia and dosing by weight.

Monitoring. Hourly observation in the early phase, airway, neurological and visual checks, C-reactive protein daily, and repeat imaging if there is no improvement in 48 to 72 hours or any new deficit. Review for trismus and bone healing at 4 and 12 weeks.

Referral and escalation. Refer urgently to oral and maxillofacial surgery with ENT, critical care, ophthalmology and neurosurgery depending on spread. Emergency escalation for airway compromise, visual loss, intracranial signs or septic shock.