Submental Space Infection

Submental space infection is infection of the space between the anterior bellies of the digastric muscles, below the mylohyoid and above the investing fascia of the chin. It arises from mandibular incisors and canines and may spread to the submandibular space (and bilaterally to Ludwig angina).

• Mixed oral flora is responsible.
• Risk factors: untreated caries or periapical infection of the anterior mandibular teeth, diabetes, HIV.

Painful, firm swelling beneath the chin, loss of the chin contour and the cervicomental angle, fever, with an anterior mandibular tooth that is tender; trismus is minimal.

• Pus may point in the skin below the chin.
• Differential diagnosis: submental lymphadenitis, thyroglossal duct cyst (infected), dermoid cyst, Ludwig angina, ranula, sublingual gland infection, sialadenitis, lipoma, tumour, cellulitis.
• Complications: spread to submandibular and sublingual spaces, Ludwig angina with airway obstruction, necrotising infection, mediastinitis, sepsis.

Clinical with dental assessment.

• Dental examination and orthopantomogram; ultrasound or CT with contrast for abscess and extension.
• Full blood count, CRP, glucose, blood cultures if febrile; pus culture; HIV test.
• Airway assessment for floor of mouth elevation.

Antibiotics, drainage and removal of the dental source.

• Supportive: analgesia (paracetamol 1 g, ibuprofen 400 mg), hydration, soft diet, chlorhexidine 0.2 percent rinses, upright position, warm compress.
• Pharmacological: amoxicillin 500 mg three times daily with metronidazole 400 mg three times daily for 5 to 7 days (or amoxicillin clavulanate 625 mg three times daily; clindamycin 300 mg four times daily if allergic); children, amoxicillin 25 mg/kg/day in three doses with metronidazole 7.5 mg/kg three times daily. Moderate, severe or bilateral: benzylpenicillin 2.4 g IV every 6 hours with metronidazole 500 mg IV every 8 hours (or ceftriaxone 2 g IV daily with metronidazole), switching to oral therapy after 48 hours of improvement to complete 10 to 14 days.
• Procedures: extraoral incision and drainage through a skin incision below the chin (about 1 cm below the border of the mandible), or intraoral approach; extraction of the source tooth; airway management in Ludwig angina.
• Special groups: pregnancy, penicillin and metronidazole after the first trimester; children, weight based doses; diabetes and HIV, IV therapy and admission.
• Red flags: tongue elevation, bilateral swelling, drooling, stridor, trismus, neck swelling beyond the submental region, toxicity.
• Follow-up: review at 24 to 48 hours; dental treatment; wound review at 1 week.