Makindo Medical Notes.com

Necrotizing external otitis should be suspected when patients with diabetes mellitus (or another condition that compromises the immune system) complain of persistent external otitis that causes severe pain, especially at night. Malignant otitis externa refers to the presence of osteomyelitis and needs urgent ENT review and admission for IV antibiotics and possible surgery

About

• Infection of outer ear - external auditory canal
• Common often called ("swimmer's ear") seen in hot, humid climates.
• Malignant when causes osteomyelitis of the temporal bone

Microbiology

• Pseudomonas, Staph aureus, Staph epidermidis
• Strep pneumoniae, Gram negatives, Fungi

Aetiology

• Swimmers, Eczema, Minor trauma, swimming-pool water has a high concentration of halogens
• Severe: infection may extend to the cartilaginous skeleton of the ear canal and through Santorini's fissures to reach the temporal bone, causing osteitis.
• Diabetes mellitus, poor vascular supply resulting from microvascular disease is aggravated by pseudomonal vasculitis, which further restricts tissue perfusion

Clinical

• Localised Pain, erythema, itch, discharge
• Oedema, debris in the canal, tender over the tragus
• Malignant: invades bone and can cause osteomyelitis and facial nerve palsy
• Granulation tissue in the external auditory canal, especially at the bone-cartilage junction.

Investigations

• If severe then FBC, U&E, LFT, Glucose, Ca, ALP, CRP
• Malignant disease: Imaging studies may include CT, Technetium Tc 99m medronate bone scanning, and gallium citrate Ga 67 scintigraphy. The temporal bone is the first bone to be affected, with imminent involvement of the petrous apex and mastoid.

Management

• Keep the ear dry and avoid inserting anything in canal. Use Topical antibiotics, simple analgesia. Insert wick if much debris and discharge. Persists then ENT referral
• Malignant disease: Correction of immunosuppression (when possible) local treatment of the auditory canal, long-term systemic antibiotic therapy and, in selected patients, surgery.
• Antibiotics include Ciprofloxacin PO/IV, Tazocin, Gentamicin

References

• Necrotizing (Malignant) External Otitis