Malignant Otitis Externa

Malignant Otitis Externa

Malignant Otitis Externa With Skullbase Osteomyllitis

Key Words: Otitis, Malignant, Osteomyelitis, skullbase.


Skull base Osteomyelitis (SBO) is one of the devastating infection with potential morbidity which warrants a high degree of suspicion when formulating a differential diagnosis for Otological skull base lesions. Malignant external Otitis (MEO) is a more localised form of SBO which usually spreads to the preauricular Soft tissues, cartilage and bone with cranial neuropathy. If untreated it may extend throughout the skull base, infra-temporal fossa, parapharyngeal space, nasopharynx along with intracranial extension. The most typical patient being an elderly, uncontrolled diabetic with pseudomonal infection and facial palsy.


Skull Base Osteomyelitis is one of the devastating infection with potential morbidity and mortality which warrants a high degree of suspicion when formulating a differential diagnosis for otologic and skull base lessions. Malignant External Otitis is a more localised form of skull base Osteomyelitis which usually spreads to peri-auricular soft tissue, cartilage and bone. If untreated it may extend throughout the skull base, infratemporal fossa, parapharyngeal space, nasopharynx and finally spreads intracranially. Other Pathologies in this area with similar symptoms and signs are wegener`s granulomatosis, Carcinoma of temporal bone, carcinoma naropharynx, metastatic lesion to clivus, pagets disease, fibrous dysplasia and basilar skull fracture. Osseous skull base is made up of tympanic ring, mastoid, petrous, maxillary, ethmoid, sphenoid, and occipital bones. Osteomyelitis of the skull base involves an infection in the diploic cancellous bone of the outer and/or inner cortical and periosteum, the dura, surrounding soft tissue, major Vessels and cranial nerves of skull base.

The original report was by Melzter and Kelemen 21 in 1959, described as a case of Pyocyaneus. Chandler 4 in 1968 was credited with coining the term malignant otitis externa. The term malignant is used to emphasize the serious nature of this infection, as in the original historical report 7 of the 13 patients died. Various alternative terms used are (synonyms) – Progressive, Fulmilnant, invasive and necrotising external Otitis.

Lucent etal 17 described the term MEO as a dangerous misnoner. But despite these misgivings the term MEO is widely used in the literature. NEO has been offered as an alternative term of MEO which is a more limited form of infection, isolated to the skin and cartilage of the EAC which may not always be associated with pseudomonas infection, but may be with others like staphylococcus.


In a comprehensive review of literature on Osteomyelitis, Waldrogel etal 31 noted three fundamentalfactors for the pathogenesis – a contageous focus of infection, haematogenous seeding and microvascular diseases. Known microangiopathy of elderly diabetic with poor glucose control compromises blood supply to the affected area which limits effective immunologic response and host resistances. The most common factor identified in the majority of the cases with MEO is the existence of elderly diabetes mellitus (90%) and majority are aged 60 years or older. Other predisposing factors are use of hearing aid, CSOM, leukemia, alcoholism, kernicterms, tuberculosis, swimmers etc., Rubin etal 25 in a retospective study found that 61.5% of patients with MEO had unsterile tap water irrigation of their ear within two weeks of onset of symptoms which is iatrogenic by physicians. Some of the other organisms have been identified with MEO and SBO in both adult and children are salmonella 28 Mycobacterium tuberculosis 14, Actionomyces 30, Aspergellous flavus 22, Aspergillons fumigatus 5. But pseudomonas is found in 99.2% of cases of MEO 15. Other organisms involved are staphylococous aureus 15 and epidermidis 2. The pathogenesis of SBO as outlined by Nado etal 24 begins in the epithelium of the EAC and extends into the retromandibular fossa through the fissure of Santorini into the parotid space or through the tympanomastoid suture. Facial palsy is typically due to soft tissue infection around the Stylomastoid foramen.

Infection spreads to mastoid tip and Jugular foramen with potentialthrombosis of the sigmoid sinus and lower cranial nerve paresis. Transvenous thrombosis and sepsis may affect lateral sinus, superior and inferior petrosal sinues with progressive osteomyelitis advancing into the petrous apex, middlefossa, base of sphenoid and clivus of the posterior fossa, contralateral temporal bone and skullbase. Posterior spread into the occipital bone elicits neural pain and potential compromise of the contents in the posterior cranial fossa. It may also spread anteriorly into the temporal fossa and facial bone.

Malignant Otitis Externa

Dr.G.C.Sahoo, Dr.N.Prataprao, Dr.Sajeeb Rangaswamy

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The diagnosis of MEO is based on clinical and laboratory evidence along with heightened suspicion of the physician. But there is no absolute diagnostic criteria. However, cohen and Friedman 6 proposed diagnostic criteria by developing obligatory and occasional caregories. The major obligatory criteria includes pain, exudate, oedema, granulation tissue, microabscess, positive technitium-99 scan or the failure of local treatment after more than 1 week and the presence of Pseudomonas auregenosa. The minor occasional criteria includes positive CTscan tomography, oldage,cranial nerve palsy, diabetes mellitus or other debilitating conditions. In the absence of otologic complaints and findings SBO may be difficult to diagnose. Isolated case reports have been published that review SBO without any history of ear infection. The clinician must be aware of any prior history of MEO despite having received successsful treatment as the classic presentation in these cases is that patient leaves the hospital completely asymptomatic only to return 4 to 7 weeks later with the onset of low grade fever, malaise and a unilateral unremitting headache that requires narcotic analgesic. It has also been reported that SBO can develop nearly one year after resolution of MEO 1MEO s not unique to elderly diabetic patients alone but few cases are reported in paediatric population also with Pseudomonas aeurogenosa 13 and Proteus mirabilis 7 infection. Disorders other than DM associated with MEO in children are anemia, malnutrition, S.J. Syndrome, lG deficiency and agranulocytosis. It is proposed that the medial location 12 of the bony cartilagenous Junction in infants and children account for earlier compromise of Facial nerve and mastoid.

Staging and Imaging

The importance of staging for OSB is to alert the clinician that certain diagnostic tests are necessary to determine the presence and extent of the disease. Baseline CT and radionucleide scans will attempt to differentiate NOE from MEO and SBO. Gallium-67 scanning identifies inflammation if immunocompetent white cells are present and functioning. The technitium – 99 bone scan reflects the increased osteoblastic activity which is indicative of Osteitis and osteomyelitis. A three level staging is proposed by Benecke 3. Stage I or NOE is limited disease in the soft tissue without bone involvement where as Stage II describes MEO in which the disease is limited to the mastoid and is the earliest form of SBO with positive gallium and technitium scan. Finally State III is extensive SBO with markedly positive gallium and technitium scan. Another staging system is proposed by Davis 9 based on clinical criteria and prognosis in three stages. A third staging system was proposed by Krum, Rehm and Kenny 16 which describe Stage – I MEO limited to the EAC and mastoid aircells, Stage – II SBO with cranial nerve palsy and Stage – III extension to the brain and meninges. Radiographic and radionucleide including Indium-III play an important role in evaluating, staging and managing MEO and SBO. Sequential imaging is critical in establishing diagnosis, demonstrating extent of the disease, monitoring the efficacy of treatment and determining the duration and end point of therapy.


The complex management of MEO and SBO consists of establishing the diagnosis, determining the extent of the disease, operating when indicated and providing appropriate antimicrobial therapy along with adjuvant therapy till the resolution of the infective process. It is also necessary to correct any metabolic abnormality and maintain glucose levels. The role of surgery is not very well defined except taking biopsy and local debridement of necrotic tissue and drianage of abscess or formal tympanomastoid procedures like MRM or Radical mastoidectomy with partial petrous apicectomy and embolectomy for Jugular vein thrombosis. Farrier 10 proposed planned surgical debridement for persistant pain or failure of the granulation tissue to heal after 2 weeks of I.V. antibiotics. Raines and schindler 26 advocated radical surgery on new onset of cranial neuropathies directly in recalcitrant MEO. Concern exists that surgery may enhance MEO and SBO by opening up facial spaces and new tissue plane with spreading infection. Prolonged anibiotic therapy with third generation cephalosporins has been the principal mean of therapy. Management of MEO and SBO significantly changed in the last decade with the availability of oral fluro-Quinolones like Ciprofloxacin and ofloxacin 29. In a report by Rubinetal 27 patients were cured of MEO with the combination of ciprolfloxacin and rifampicin for 6 to 12 weeks. Oral ciprofloxacin alone in 750 mg BID dose cured 21 out of 23 patients treated by lang 18. Ciprofloxacin given orally for a minimum of 6 weeks to 6 months was successful in patients who failed in conventional combination intravenous therapy Similar efficacy with ofloxacin (200mg) BD given to 17 patients with MEO achieved subjective improvement in all patients with in 6 days and objective improvement within 12 days of treatment 19 20 Despite the reported efficacy of prolonged systemic antibiotic therapy, treatment failure do occur due to tissue hypoperfusion and hypoxia where the use of hyperbaric oxygen (BHO) increases wound PO2 levels, enhances phagocytic oxidative killing of aerobic micro-organisms, promotes angioneogenesis and osteoneogenesis. Treatment consists of 100% O2 given for 90 minutes at 2.5 atm absolute pressure five days a week for 4 weeks as an adjuvant therapy 23.

Complications and Prognosis

Cranial nerve neuropathy is the most common non iatrogenic complication in MEO and SBO. Pseudomonas – aeroginosa produces destructive enzymes and exotoxins that promote tissue necrosis and reversible neurotoxicity 32. Other than facial palsy, the Jugular foramen syndrome affecting 9th, 10th and 11th Cranial nerves compromising phonation, swallowing and protection of the tracheobronchial tree. Other cranial nerves which may be affected are 3rd, 5th and 6th. In untreated or advanced cases death results due to meningitis, cerebritis, cerebral abscess, jugular formamen syndrome, pulmonary aspiration and pneumonia, vascular thrombosis, CVA or subarachanoid hemorrhage. The mortality rate is high with multiple cranial neuropathies despite optimal antimicrobial therapy. However recent reports with appropriate antibiotic therapy shows cure rates to be 80% – 100%. Use of hyperbaric O2 as an adjuvant therapy has also further reduced the mortality rate.


SBO is an agressive, invasive, indolent infection with potentially significant morbidity and mortality. The most common form of SBO is MEO typically seen in elderly diabetics although infections may be from other neurosurgical and cranial base sources or procedures. The diagnosis is based on detail history, clinical evaluation, culture, biopsy, blood sugar, ESR and imaging studies. Intravenous antipseudomonal antibiotic therapy, surgical debridement of granulation tissue, bony sequestration and devitalised tissue from EAC can control and cure the disease effectively. Treatment for recalcitrant infections can be supplemented with adjuvant hyperbaric oxygen (HBO) therapy. The course of antibiotic therapy varies from a short 2 to 3 weeks for MEO in children to 6 months for SBO in adults. The duration of therapy is determined by number of factors including symptomatic and clinical response and demonstration of the resolution of inflammation by monitoring treatment with sequential CT, gallium scan and ESR. The overall morbidity and mortality have significantly declined with current methods of diagnosis and treatment during the past three decades when MEO was first described.


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