What is the management of an automastoidectomy cavity?

Management of Automastoidectomy Cavity

Automastoidectomy cavities require surveillance for fungal colonization and infection, with treatment consisting of topical antifungals for superficial mycetomas and surgical debridement with systemic antifungals for symptomatic or invasive disease.

Understanding Automastoidectomy Cavities

An automastoidectomy cavity forms when chronic infection or keratosis obturans causes spontaneous erosion of mastoid bone, creating a cavity similar to a surgical mastoidectomy 1. These cavities are prone to:

• Fungal colonization, particularly with Aspergillus species forming mycetomas (fungus balls) 2
• Chronic drainage resistant to conventional antibacterial therapy 2
• Biofilm formation on exposed bone surfaces, complicating infection management 3

Initial Assessment and Monitoring

Clinical Evaluation

• Examine for chronic otorrhea that fails to respond to standard antibacterial drops 2
• Assess cavity size and depth to determine risk of complications 1
• Obtain cultures from any drainage to identify bacterial versus fungal pathogens 2, 3
• Image with CT scan if extent of bone erosion is unclear or intracranial extension is suspected 4

Common Pathogens

The most frequently isolated organisms in chronically infected cavities include:

• Staphylococcus aureus (including MRSA) - 43% of infections 5
• Pseudomonas aeruginosa - 36% of infections 5
• Aspergillus species - most common fungal pathogen in automastoidectomy cavities 2

Treatment Algorithm

For Asymptomatic or Minimally Symptomatic Cavities

• Observation with regular cleaning is appropriate for dry, stable cavities 6
• Periodic otoscopic examination every 3-6 months to monitor for infection 2
• Patient education on keeping the cavity dry and avoiding water exposure 6

For Infected Cavities Without Fungal Involvement

• Topical antibiotics are first-line for bacterial infections, particularly fluoroquinolone drops 4
• Culture-directed systemic antibiotics if topical therapy fails after 2 weeks 4, 5
• Coverage must include Pseudomonas - use antipseudomonal agents like piperacillin-tazobactam, ceftazidime, or meropenem for severe infections 7, 5
• Add MRSA coverage with vancomycin or linezolid if cultures are positive or high clinical suspicion 5

For Fungal Mycetomas (Fungus Balls)

• Topical antifungal therapy with clotrimazole or miconazole drops for superficial colonization 2
• Oral azole antifungals (fluconazole 400 mg daily or itraconazole 200 mg twice daily) for symptomatic or invasive disease 7
• Continue treatment for at least 1 year if systemic therapy is initiated 7
• Surgical debridement is indicated for persistent symptoms despite medical therapy 7, 2

Surgical Management Indications

Consider surgical intervention when:

• Persistent infection despite 4-6 weeks of appropriate antimicrobial therapy 7
• Recurrent otorrhea requiring repeated courses of antibiotics 6
• Large cavity causing significant symptoms or cosmetic concerns 6
• Fungal mycetoma not responding to antifungal therapy 2

Surgical options include:

• Cavity debridement and cleaning to remove infected tissue and fungal debris 2
• Mastoid obliteration using autologous bone dust to reduce cavity size and eliminate dead space 6
• Coverage with temporalis fascia or periosteal flap to promote healing 6

Critical Timepoints for Reassessment

• 48 hours: If no improvement with topical antibiotics, consider systemic therapy 4
• 7 days: Repeat imaging if clinical deterioration or no improvement with antibiotics 7
• 2-4 weeks: Obtain cultures if infection persists to guide targeted therapy 7, 2
• 4-6 weeks: Repeat imaging for fungal infections to assess treatment response 7

Common Pitfalls to Avoid

• Treating with antibacterials alone when fungal infection is present - always culture drainage in chronically infected cavities 2
• Inadequate Pseudomonas coverage - this organism requires specific antipseudomonal agents and is not covered by standard prophylactic regimens 5
• Premature surgical intervention - attempt medical management for at least 4-6 weeks before considering surgery 7
• Biofilm formation on exposed bone makes infections difficult to eradicate with antibiotics alone and may require surgical debridement 3
• Stopping antifungal therapy too early - fungal infections require prolonged treatment (minimum 1 year) to prevent recurrence 7

Long-term Management

• 95% of properly managed cavities remain dry and safe with appropriate obliteration techniques 6
• Regular follow-up every 3-6 months is essential to detect early recurrence 6
• Patient compliance with keeping the cavity dry significantly reduces infection risk 6