Malignant otitis externa

MALIGNANT OTITIS EXTERNA

Dr Manohar SuryawanshiENT Resident, INHS Asvini

• Anatomy

• Introduction

• Microbiology

• Pathogenesis

• Diagnosis

• Investigations

• Treatment

Introduction

Definition

• Aggressive and potentially life-threatening infection

of the soft tissues of the external ear and

surrounding structures, quickly spreading to involve

the periostium and bone of the skull base.

Microbiology:

• Pseudomonas aeruginosa (95%)

• Fungus (A. Fumigatus, A. Flavus, A. Niger)

• Fungal MOE: HIV more commonly than in those who

have diabetes

• From middle ear or mastoid in contrast to

pseudomonal

• Pseudomonas infections CD4 levels < 100 cells/mm

• AspergillusCD4 counts <50 cells/mm

Predisposing factors

• Diabetes mellitus

• Immuno-compromised status

Pathophysiology:

• Cellulitis-> Chondritis-> Periostitis->

Osteitis ->Osteomyelitis

• Facial nerve (stylomastoid foramen) 60%

• IX, X and XI

• V and VI (petrous apex)

• Clivus and contralateral temporal bone can be involved

• Infection can spread anteriorly into the sphenoid and to

the carotid

• Thrombosis of sigmoid sinus, IJV -> meningitis -> cerebral abscess

• Haversian system of compact bone

• Pneumatoized portion of the temporal bone involved

late

• Otic capsule is usually spared

Clinical features:

• Long-standing otalgia (worst at night) and otorrhea

• Cranial nerve palsy

• Headaches, fever

• Neck stiffness

• Altered levels of consciousness

Hallmark finding: granulation tissue on floor of the ear canal at the bony-cartilaginous junction

Clinical and microscopic differences between bacterial and fungal malignant otitis externa

Pathogen Age Diabetes Immunosuppression

Granulationtissue

Middle ear/mastoidinvolvement

Histology

Bacterial Older Common Common + - Gram -ve rod

Fungal Younger Lesscommon

More common - + Septate hyphae,calcium oxalate crystals

Diagnosis:

• Clinical

• Biopsy

• Pseudomonas aeruginosa on culture

• Supported by a positive bone scan and/or

the presence of microabscesses at surgery

• ESR, CRP

Investigations:

• CT scan

• MRI

• Technetium-99m bone scan:

Osteoblastic activity

Highly sensitive for bony infection

• SPECT:

Good anatomic localization

Gallium scan:

• Increased uptake during infection

• Monitoring and duration of antimicrobial

therapy

technetium Tc 99m MDP bone scan

Clinicopathological classification1 Clinical evidence of malignant otitis externa with

infection of soft tissues beyond the external auditorycanal, but negative Tc-99 bone scan

2 Soft tissue infection beyond external auditory canal withpositive Tc-99 bone scan

3 As above, but with cranial nerve paralysis3a- Single3b -Multiple

4 Meningitis, empyema, sinus thrombosis or brain abscess

Treatment:

Medical

• Early infections- oral fluoroquinolone

• Advanced stages- parenteral antibiotics

may be indicated

• Monotherapy with Ceftazidime

• Tobramycin can be used with minimal toxicity if peak

level doses are closely monitored

• Implantable gentamicin

• HBOT

Surgery:

• Debridement of nonviable sequestra of bone, necrosed

and Granulation tissues

• Wide resection:

Bony skull base

Stylomastoid foramen

Jugular bulb

• Introduction of viable, vascularized tissue into the

bed

References

• Scott brown 7th edition• Ballinger 16th edition• Cummings 5th edition• OCNA 2012• Indian journal of nuclear medicine

THANK YOU