MS ENT Exam Answer (10 Marks)

PART A: Oro-Antral Fistula (OAF) as a Complication of Sinusitis

Definition

Aetiology / Causes

• Extraction of upper molar/premolar teeth (especially upper 1st and 2nd molars whose roots are in close proximity to the maxillary sinus floor)
• Periapical abscess of maxillary teeth
• Post-oral surgery infections (e.g., dental implant placement)
• Radical antral surgery (Caldwell-Luc)
• Endodontic treatment with overfilling (overfilled dental canal sealers can create an iatrogenic OAF and promote fungal colonization of the sinus)

• Chronic rhinosinusitis with odontogenic etiology
• Fungal sinusitis (fungi colonize via an OAF created during endodontic treatment)

• Maxillary antral carcinoma eroding the sinus floor, presenting through an OAF (Bailey & Love)

Pathophysiology

Clinical Features

• Passage of fluid/air from nose when drinking (regurgitation of fluid through the nose)
• Foul-smelling nasal discharge (cacosmia)
• Nasal obstruction; unilateral maxillary pain
• Food debris visible in the socket
• Valsalva test / nose-blowing test: air or saliva passes through the fistula into the nose
• CT scan: loss of maxillary sinus floor continuity; mucosal thickening or opacification of the antrum

Management of OAF

• Spontaneous closure with clot formation
• Irrigate and pack the socket; prescribe antibiotics, nasal decongestants, and advise against nose-blowing

1. Buccal advancement flap (Rehrmann flap): Most commonly used. A broad-based trapezoidal mucoperiosteal flap is elevated from the buccal sulcus and advanced to cover the defect. The periosteum is scored to allow tension-free closure.
2. Palatal rotation flap: A posteriorly based pedicled mucoperiosteal flap from the hard palate, rich in blood supply from the greater palatine artery. Useful for larger or posteriorly located defects. Leaves a raw donor area that heals by secondary intention.
3. Buccal fat pad flap: Used for moderate defects (up to 3x4 cm). The buccal fat pad is mobilized and sutured over the defect; it subsequently epithelializes.
4. For maxillary defects post-tumor ablation: Free flap reconstruction or prostheses with free tissue grafts (Sabiston Textbook; Bailey & Love).

• Functional Endoscopic Sinus Surgery (FESS) with maxillary antrostomy to drain the infected sinus
• Involvement of oral maxillofacial surgery colleagues when odontogenic etiology is suspected (Scott-Brown Vol. 1)
• Prolonged antibiotics covering anaerobes (amoxicillin-clavulanate or metronidazole combination)

PART B: Management of Cavernous Sinus Thrombosis (CST)

Definition and Significance

Pathophysiology

• Infection spreads from paranasal sinuses (ethmoid/sphenoid most implicated) or upper dentition via retrograde thrombophlebitis through the valveless ophthalmic venous system to the cavernous sinus
• Veins around the sinuses become congested and phlebitic during acute rhinosinusitis, with central propagation
• This causes septic thrombophlebitis of the cavernous sinus, leading to sepsis and multiple cranial nerve involvement (CN III, IV, V1, V2, VI)
• Common organisms: Staphylococcus aureus (most common, including MRSA), streptococci, gram-negative bacilli, and anaerobes; polymicrobial infection common in adults

Clinical Features

• Fever, lethargy, and systemic toxicity
• Retro-orbital / orbital pain (ophthalmic nerve neuralgia)
• Bilateral ptosis
• Proptosis and chemosis
• Complete ophthalmoplegia (involvement of CN III, IV, VI within the cavernous sinus)
• Dilated pupil with sluggish or absent pupillary light reflex
• Papilloedema
• Signs of meningeal irritation (neck stiffness, photophobia)
• Confusion and reduced level of consciousness (spiking fevers)

Investigations

1. MRI brain with contrast (investigation of choice): Demonstrates dural enhancement in the region of the cavernous sinus; MR venography shows absence of flow in the thrombosed sinus (most sensitive)
2. CT with IV contrast: May show filling defects equivalent to MRI; useful when MRI is not available
3. Blood cultures: Before initiating antibiotics
4. FBC, CRP, ESR, coagulation screen
5. CSF analysis if meningitis is suspected (after excluding raised ICP)
6. Microbiology liaison: Cultures and sensitivities to guide antibiotic choice

Management

1. Medical Management

• Broad-spectrum intravenous antibiotics must cover gram-positive cocci (especially S. aureus), gram-negative organisms, and anaerobes
• Recommended initial regimen: IV cephalosporin (e.g., cefotaxime or ceftriaxone) + metronidazole
• If MRSA is suspected: add vancomycin or linezolid
• Antibiotics must be continued for at least 2 weeks beyond clinical resolution because bacteria sequestered within the thrombus may not be killed until dural sinuses begin to recanalize
• Relapse of meningeal and ocular signs has been reported up to 6 weeks after cessation of antibiotics; follow-up for at least 6 months is advised (Scott-Brown Vol. 1)

• No definitive consensus exists
• Arguments for: Anticoagulants prevent thrombus propagation and have anti-inflammatory properties
• Arguments against: Thrombus may wall off the infection; anticoagulants increase risk of intracranial hemorrhage in an inflammatory environment
• When used: start with unfractionated heparin (UFH) infusion, targeting APTT of 1.5-2x control; transition to low-molecular weight heparin (LMWH) once condition improves
• For aseptic CST: systemic anticoagulation (heparin followed by warfarin) or aspirin 325 mg daily is more clearly indicated (Wills Eye Manual; Harrison's Principles)
• For septic CST complicating bacterial meningitis with progressive neurological deterioration despite antimicrobial therapy: anticoagulation recommended (Harrison's 22E)

• Not routinely recommended
• Use only if there is evidence of pituitary insufficiency complicating CST (Scott-Brown Vol. 1)

• Critical-care / ICU admission for life support and monitoring
• Intravenous fluid resuscitation
• Management of exposure keratopathy with lubricant eye drops/ointment
• Treatment of secondary glaucoma if present

2. Surgical Management

• Surgery is indicated only to drain any non-draining sinus infection or abscess collection - specifically the involved paranasal sinuses (ethmoid/sphenoid sinusotomy as relevant)
• FESS (functional endoscopic sinus surgery) with drainage of involved sinuses in a specialist neurosurgical centre
• No direct surgical decompression of the cavernous sinus is indicated
• Joint management with neurosurgeons in a specialist centre is mandatory (Scott-Brown Vol. 1 & Vol. 2)

Summary Table