malignant otitis externa
TRANSCRIPT
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