3 body of the auricle -elastic fibrocartilage and is a continuous plate except for anarrow gap between the tragus and the anterior crus of the helix-incisura terminalis. lateral surface of the auricle prominences and depressions. Curved rim of helix-Darwins tubercle-small prominence, Concha devided by descending limb of helix. Cymba conchae-suprameatal triangle. Below the crus of the helix -tragus, Opposite the tragus, at the inferior limit of the antihelix, is the antitragus.
4 Eac-2.4cm, carti-8mm and bony-1.6mm. Fissures of santorini
7 DefinitionAggressive 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.Term coined by Chandeler in 1968
8 Microbiology: Pseudomonas aeruginosa (95%) Fungus (A. Fumigatus, A. Flavus, A. Niger)
9 Fungal MOE: HIV more commonly than in those who have diabetes From middle ear or mastoid in contrast to pseudomonalPseudomonas infections CD4 levels < 100 cells/mmAspergillusCD4 counts <50 cells/mm
10 Predisposing factors Diabetes mellitus Immuno-compromised status endarteritis, small vessel obliteration,which, coupled with the ability of Pseudomonas to invade vessel wallsand cause a vasculitis with thrombosis and coagulation necrosis of surrounding tissue, underlies the pathophysiology of this disease Microangiopathy, impaired phagocytosis, Cerumen of high PH in DM
11 Pathophysiology: Cellulitis-> Chondritis-> Periostitis-> Osteitis ->OsteomyelitisFissures of santorini,
12 Facial nerve (stylomastoid foramen) 60% IX, X and XIV and VI (petrous apex)Clivus and contralateral temporal bone can be involvedInfection can spread anteriorly into the sphenoid and to the carotid
13 Haversian system of compact bone Thrombosis of sigmoid sinus, IJV -> meningitis -> cerebral abscessHaversian system of compact bonePneumatoized portion of the temporal bone involved lateOtic capsule is usually sparedComplications in children include necrosis of TM, stenosis of the EAC, auricular deformity, and sensorineural and conductive hearing loss
14 Clinical features:Long-standing otalgia (worst at night) and otorrhea
15 Cranial nerve palsyHeadaches, feverNeck stiffnessAltered levels of consciousness
16 Hallmark finding: granulation tissue on floor of the ear canal at the bony-cartilaginous junction
17 Clinical and microscopic differences between bacterial and fungal malignant otitis externa PathogenAgeDiabetesImmunosuppressionGranulationtissueMiddle ear/mastoidinvolvementHistologyBacterialOlderCommon+-Gram -ve rodFungalYoungerLesscommonMore commonSeptate hyphae,calcium oxalate crystals
18 Diagnosis: Clinical Biopsy Pseudomonas aeruginosa on culture Supported by a positive bone scan and/orthe presence of microabscesses at surgeryESR, CRPcombination of pain,granulations, otorrhea and resistance to local therapy for at least eight to ten days are highly sensitive for making adiagnosis of malignant otitis externa. Diabetes or other immunocompromised state, Silver stain for fungal
19 Technetium-99m bone scan: Osteoblastic activity Investigations:CT scanMRITechnetium-99m bone scan:Osteoblastic activityHighly sensitive for bony infectionSPECT:Good anatomic localization1. CT scan shows even small cortical erosion of the tympanic bone and is a useful first-line test. Disadvantages of CT :under appreciation of thesoft tissue and intracranial extent of disease2. Tc99 MDP detects as little as 10% demineralization3. Involvement of the retrocondylar fat pad on MRI has been proposed as an early diagnostic
20 Gallium scan: Increased uptake during infection Monitoring and duration of antimicrobialtherapy1. Ga scan every 4wk, -ve when infection clears2. Diagnostic accuracy (and expense) may be afforded by the simultaneous acquisition of a SPECT technetium-99m bone scan and indium-111–labeled leukocyte scan.
21 CT scan showing the soft tissue obliterating left external auditory canal left mastoid, infra-temporal fossa, skull base and involving the left TMJ
22 (a) increased signal beneath the skull base that reflects the inflammatory process (arrowed). (b) Indium-labelled white cellscan of the same patient showing increased uptake in the temporal bone
23 SPECT-CT images provide greater definition of the pathological uptake in the right mastoid and petrous bone with no extension beyond the midline.
25 Clinicopathological classification 1Clinical evidence of malignant otitis externa withinfection of soft tissues beyond the external auditorycanal, but negative Tc-99 bone scan2Soft tissue infection beyond external auditory canal withpositive Tc-99 bone scan3As above, but with cranial nerve paralysis3a- Single3b -Multiple4Meningitis, empyema, sinus thrombosis or brain abscess
26 Treatment: Medical Early infections- oral fluoroquinolone Advanced stages- parenteral antibioticsmay be indicatedDuration of treatment: 06wks or as indicated by the results of radiologic studies and clinical response.
27 Monotherapy with Ceftazidime Tobramycin can be used with minimal toxicity if peak level doses are closely monitoredImplantable gentamicinHBOTGentamicin incorporated polymethyl-methacrylate beads were implanted, following surgical debridement, removed after 2 mths.
28 Surgery:Debridement of nonviable sequestra of bone, necrosed and Granulation tissuesWide resection:Bony skull baseStylomastoid foramenJugular bulb1.Surgical resection-resistant to therapy traditional mastoidectomy should theoretically not be effective indébriding the infection. facial nerve is involved in the region of the stylomastoid foramen, facial nerve decompression
29 Introduction of viable, vascularized tissue into the bed e.g. temporalis muscle flapor microvascular free tissue transfer
30 References Scott brown 7th edition Ballinger 16th edition Cummings 5th editionOCNA 2012Indian journal of nuclear medicine