MS ENT Exam Answer: Oro-Antral Fistula, Complications of Sinusitis & Management of Cavernous Sinus Thrombosis

PART 1: ORO-ANTRAL FISTULA (OAF)

Definition

Anatomy

Aetiology / Causes

1. Dental extraction - most common cause; socket fails to heal, communication epithelializes over 48-72 hours
2. Periapical or periodontal abscess - direct spread into sinus
3. Tooth implant or endodontic overfill - iatrogenic perforation
4. Caldwell-Luc procedure - wound dehiscence or failure of anterior antrostomy closure
5. Malignancy - maxillary antral carcinoma eroding the palate (an OAF presenting with a fistula should prompt biopsy to exclude malignancy)
6. Radiation necrosis / osteomyelitis of maxilla
7. Specific infections - rhinoscleroma, tuberculosis, syphilis
8. Trauma - fracture of alveolar process

Clinical Features

• History of tooth extraction or dental procedure
• Fluid (water/liquids) passing from mouth to nose
• Nasal regurgitation of food
• Foul-smelling nasal discharge (secondary sinusitis)
• Whistling sound on blowing the nose
• Unilateral maxillary sinusitis

Investigations

• OPG / dental X-ray - shows root relationship to sinus floor
• CT sinuses (coronal) - demonstrates sinus floor defect, associated sinusitis, and extent of communication; standard investigation for odontogenic sinusitis
• Endoscopy - diagnostic and pre-op assessment

Management

Surgical Techniques for OAF Closure:

PART 2: COMPLICATIONS OF SINUSITIS

Classification (Table - Scott-Brown's Vol 1)

Chandler Classification (Orbital Complications)

1. Group I - Preseptal (periorbital) cellulitis - anterior to orbital septum
2. Group II - Orbital cellulitis - diffuse oedema of orbital fat
3. Group III - Subperiosteal abscess - between periorbita and orbital wall
4. Group IV - Orbital abscess - within orbital fat
5. Group V - Cavernous sinus thrombosis

Key Orbital Complications

• Predominantly arise from ethmoid sinusitis (medial wall = lamina papyracea)
• Frontal sinusitis - abscesses form superomedially
• Signs: proptosis, periorbital oedema/erythema, ophthalmoplegia (reduced extraocular movements), chemosis, reduced visual acuity (optic nerve involvement = emergency)
• Investigation: CT orbits with contrast (defines stage); MRI if intracranial involvement suspected
• Management: IV antibiotics (cephalosporin + metronidazole); if no improvement in 24 hours or visual deterioration - surgical drainage (endoscopic medial decompression or external Lynch-Howarth approach)

Intracranial Complications

• Arise primarily from frontal sinusitis (anterior and posterior table erosion)
• Organisms: Streptococcus anginosus group (abscess tendency), S. aureus, anaerobes
• Meningitis: headache, photophobia, neck stiffness, Kernig sign
• Epidural abscess: between skull and dura - often clinically silent initially
• Subdural empyema: rapidly progressive, high mortality; between dura and arachnoid
• Intracerebral abscess: focal neurological signs, raised ICP
• Pott's Puffy Tumour: subperiosteal abscess of frontal bone with characteristic doughy frontal swelling, caused by osteomyelitis of anterior table

Microbiology of Complications

• Polymicrobial and anaerobic organisms more common in intracranial complications and in patients >15 years
• Initial IV regimen: cephalosporin + metronidazole pending culture
• Adjust based on culture sensitivity with microbiology input

General Management Principles

1. Imaging first: CT with contrast (orbital/intracranial), MRI as adjunct
2. IV antibiotics immediately - broad-spectrum
3. Surgical drainage of non-draining sinuses + abscess collections when indicated
4. Multidisciplinary approach: ENT + neurosurgery + ophthalmology + microbiology
5. Systemic steroids: not routinely recommended; may be considered for pituitary insufficiency in CST
6. Oral antibiotics continued for 14 days after IV course for orbital complications; 4-8 weeks for brain abscess

PART 3: MANAGEMENT OF CAVERNOUS SINUS THROMBOSIS (CST)

Introduction

Pathophysiology

Clinical Features

• Fever - high, spiking, "picket fence" pattern
• Bilateral ptosis (CN III palsy)
• Proptosis and chemosis - bilateral (pathognomonic when bilateral)
• Complete ophthalmoplegia - CN III, IV, VI involvement
• Ophthalmic nerve neuralgia (CN V1) - retro-ocular, periorbital pain
• Papilloedema - raised ICP
• Signs of meningeal irritation - neck stiffness
• Confusion, reduced consciousness - septic encephalopathy
• Bilateral involvement distinguishes CST from orbital cellulitis

Investigations

1. MRI brain with contrast + MR Venography (MRV) - modality of choice; shows absence of flow void in thrombosed sinus; demonstrates dural enhancement
2. CT brain with contrast - filling defects in cavernous sinus; may show "delta sign"; useful when MRI not available
3. FBC, CRP, ESR, blood cultures - microbiological workup
4. Lumbar puncture - if meningitis suspected (after CT rules out raised ICP)
5. Ophthalmology review - visual acuity, fundoscopy

Management

1. Critical Care

• Admit to ICU/neurosurgical centre
• Critical care life support - airway, breathing, circulation
• Monitoring of neurological status, visual acuity, pupillary responses

2. Antibiotics (Cornerstone of Treatment)

• Prolonged broad-spectrum IV antibiotics must be given for at least 2 weeks beyond clinical resolution - bacteria sequestered within thrombus are not killed until dural sinuses begin to recanalize
• Relapse of meningeal and ocular signs has been reported up to 6 weeks after recovery and antibiotic cessation
• Follow-up for at least 6 months is advised
• Initial regimen: IV cephalosporin (e.g., ceftriaxone) + metronidazole; add vancomycin if MRSA suspected
• Adjust based on blood/CSF cultures and local sensitivities

3. Anticoagulation (Controversial)

• No current consensus on use of anticoagulation
• Arguments FOR: prevents thrombus propagation; anti-inflammatory properties; reduces mortality and morbidity in several studies
• Arguments AGAINST: thrombus may wall off infection; risk of intracranial haemorrhage in an already inflammatory environment
• Prerequisite: imaging must exclude intracerebral haemorrhage before starting
• If used: start with unfractionated heparin (UFH) infusion targeting APTT 1.5-2x normal (rapidly reversible if bleeding occurs)
• Switch to low molecular weight heparin (LMWH) once condition improves
• Transition to oral anticoagulation (warfarin) for 3-6 months when stable

4. Steroids

• Not routinely recommended for CST
• May be considered if evidence of pituitary insufficiency (as the pituitary gland lies adjacent to the cavernous sinus)

5. Surgical Treatment

• Surgery indicated only to drain non-draining sinus infection or abscess collections
• Drain the causative paranasal sinus (FESS - sphenoidotomy/ethmoidectomy) to address source
• Neurosurgical involvement for any intracranial complications
• Direct surgical drainage of the cavernous sinus itself is not feasible

6. Ophthalmological Management

• Regular visual acuity assessment
• Treat corneal exposure (lubricants, tarsoraphy if severe lagophthalmos)
• Monitor for optic neuropathy

Prognosis

• Adult mortality: 30%
• Paediatric mortality for intracranial complications overall: 10-20%
• Survivors may have permanent neurological deficits: cranial nerve palsies, visual loss, pituitary dysfunction
• Long-term follow-up required

Summary Diagram - CST Management Algorithm

Suspected CST
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CT/MRI with contrast (MRV preferred)
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Confirm diagnosis
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ICU admission + Blood cultures
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IV broad-spectrum antibiotics (cephalosporin + metronidazole ± vancomycin)
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Exclude intracranial haemorrhage
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Consider anticoagulation (UFH → LMWH → warfarin)
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Drain causative sinus (FESS - sphenoidotomy/ethmoidectomy)
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Continue antibiotics ≥ 2 weeks post clinical resolution
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Follow-up minimum 6 months