Malignant otitis externa is an unusual but potentially life threatening invasive infection of the external auditory canal and the temporal bone. It is a misnomer as it is not a neoplastic process, but the term best describes its propensity to cause devastating complications and high morbidity and mortality. Though first reported in the year 1838 by Toulmouche, MOE was identified as a unique clinical entity as late as 1968 by Chandler et al who described it as a rare disease , which occurs exclusively in elderly diabetics, caused by Pseudomonas Aeroginosa with poor response to treatment and high mortality. The ever increasing advancements in diagnosis and treatment and changing demographics warrant a review of the management of malignant otitis externa. In this article, we have retrospectively reviewed all the cases diagnosed and managed by us for MOE along with the review of literature.
Malignant otitis externa is a severe invasive infection that originates at the junction of cartilaginous and bony part of the external auditory canal. It starts as cellulitis of the deep peri- auricular tissue which successively progresses through periosteitis , osteitis, chondritis , osteomyelitis and eventually intracranially causing multiple cranial nerve palsies. The pathophysiology is not completely understood .However a number of factors are thought to contribute such as microangiopathy, hypoperfusion and diminished host resistance. Infection, which is usually introduced by minor trauma or aural irrigation eventually spreads to the skull base through fissures of Santorini. Microabscesses are found throughout the haversian system of the compact bone.Involvement of the pneumatized portion of the temporal bone is usually late.
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The disease is more common in humid and warm climates. Increased sweating and itching in this temperature can attribute to the higher incidence of MOE. The incidence of this condition has increased due to increase in geriatric and diabetic population, the diagnosis is also being made in young immunocompromised patients such as those with malignancy, malnutrition and HIV.
Diabetics are more susceptible to this condition irrespective of the type (insulin dependent and non-insulin dependent, well or poorly controlled). Studies have also shown that cerumen of diabetic patients has a higher pH(normal- 6.1)and reduced concentration of lysozyme, which could impair local antibacterial activity.
Atypical presentation such as middle ear involvement , fungal infection, Hstiocytosis X are more common in non-diabetic patients.
Pseudomonas Aeruginosa , a gram negative aerobic bacteria is the commonest organism causing MOE.  The pathogenicity of this organism is attributed to its ability to secrete exotoxin and various enzymes like lecithinase, lipase, esterases, proteases. It is also covered by a mucoid layer which is resistant to digestion by macrophages. Recently, resistant strains of pseudomonas have been reported following treatment with ciprofloxacin.Staphylococcus aureus has also been identified as a another causative organism , particularly MRSA, and rarely staphylococcus epidermidis.Proteus species and klebsiella are other reported organisms.
Fungal MOE is mostly due to Aspergillus Fumigatus  and Candida. Other unusual organism reported to cause MOE are Sciediosporum Apiospermum and Malassezia Sympodialis. A mixed infection involving both bacterial and fungal infection is possible particularly in the immunocompromised debilitated elderly in the tropical countries.
Diagnosis of MOE requires a high index of suspicion, since there is no widely acceptable specific criteria .It is usually made clinically and supported by positive bone scan and /or presence of micro abscesses at surgery.
Presence of pain out of proportion to changes seen at otoscopy, purulent otorrhea with granulations and resistance to local therapy for at least 8 to 10 days are highly sensitive for making a diagnosis of MOE. Other important features include pseudomonas aeuroginosa growth on culture, lower cranial nerve palsy and an elevated ESR more than 100mm/hr.
Radionuclide bone scans, High resolution CT and MRI has added much to the diagnosis and management of this condition in recent years. Multiple staging systems are available in the literature but there is no consensus on stage specific treatment guidelines.
Total Count is often normal or only mildly raised despite the aggressive nature of this infection. All patients not known to be diabetic should be tested for this condition and the possibility of underlying immunodeficiencies.
Ear swabs are essential to guide the choice of antimicrobial therapy and should ideally be taken prior to commencing antibiotics, either topical or systemic.
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A CT scan defines the anatomical extent of the disease and remains the initial investigation of choice. Subtle changes in bone density can be picked up, along with swelling in the nasopharynx and parapharyngeal space. Serial CT scanning helps identify the extent of soft tissue swelling, however it is not useful for monitoring resolution of skull base
osteomyelitis; significant bone re-mineralization requires time.
MRI scanning is useful for assessing the initial severity of the disease and is excellent at delineating the extent of soft tissue disease present and intracranial complications.
Radioisotope scans (technetium 99 / gallium 67) have an increasing role in assessing malignant otitis externa.
Gallium 67 is a very sensitive but non-specific test, detecting and binding to actively dividing cell. A base line gallium scan is obtained for comparison followed by serial scans to monitor treatment response. Scanning the affected side and comparing to the non-affected side often improves interpretation of the scan. Gallium scans are useful for comparing radiological improvement to clinical improvement and guiding the length of antibiotic treatment required.
Single Photon Emission Computed Tomogrophy (SPECT) technology has improved poor spatial resolution, an initial concern with this scan. Radioactive labelled white cell scans have a role in assessing the presence and degree of osteomyelitis. A study on the various radiological and radionuclide investigations for malignant otitis externa concluded that CT and/or MRI should be supported by routine SPECT bone imaging for initial diagnosis of malignant otitis externa. Routine SPECT bone imaging further supplemented by gallium scintigraphy should be the investigation of choice in the follow up for assessing response to treatment and disease. But it is not available easily in most centres.
Dual In-WBC/T c-99m MDP bone SPECT scintigraphy provides an accurate imaging modality for diagnosis and follow-up of temporal and facial osteomyelitis when existing clinical or postoperative bone changes make it difficult to detect active osteomyelitis .
The mainstay of treatment for malignant otitis externa has been stringent diabetic control , prolonged antibiotic therapy, aural toileting and debridement of granulation tissue and most importantly aggressive treatment with suitable antimicrobial agent. Hyberbaric oxygen is gradually gaining recognition as an beneficial adjuant therapy. A good analgesia is also required for a complete managment of MOE.
The general condition of the patient including nutrition, electrolyte imbalance, should be optimized simultaneously.
Systemic antipseudomonal antibiotics are the primary therapy for malignant external otitis. The introduction of parenteral semisynthetic penicillins has ever since reduced mortality .However, prolonged combination parenteral therapy with aminoglycosides and antipseudomonal ôÂÂ°â€¦beta lactam antibiotics was associated with long-term hospitalisation and renal and vestibular toxicity, in addition to the morbidity of the disease itself. The excellent antipsuedomonal activity of fluroquinolones has made them the treatment of choice in malignant otitis externa.Oral quinolones, especially ciprofloxacin, have revolutionised the treatment of malignant external otitis and replaced combination intravenous therapy. The advantages of quinolones include its low toxicity profile, and excellent penetration into bone. The dosing of ciprofloxacin does not require adjustment in the elderly patient with renal dysfunction. Despite the rapid relief of symptoms (pain and otorrhoea), prolonged treatment for 6ââ‚¬"8 weeks is still recommended, as indicated for an osteomyelitis.
Cefaperazone sulbactum and pipercillin tazobactam are two very effective anti pseudomonal antibiotics. Cefaperazone is a broad spectrum antibiotic against most of the gram positive and gram negative pathogens, Sulbactum is a beta lactamase inhibitor, which in combination with cefoperazone not only protects it from beta lactamases but also increases the bactericidal activity by a synergistic action. Piperacillin tazobactam is highly active against gram positive bacteria, including strains that produce beta lactamase, and inhibits a wide spectrum of both fastidious and non fastidious gram negative bacilli, including Pseudomonas aeruginosa. Piperacillin tazobactam also inhibits a broader spectrum of anaerobes than does ampicillin/sulbactam or ticarcillin/clavulanate
In earlier years, surgical debridement had a role in the treatment of malignant external otitis, but with the advent of quinolone therapy, we have seen decline in indication for surgical management other than diagnostic and in recalcitrant cases.
Hyperbaric oxygen has been used on occasion. with mixed results and may be considered as an adjuvant treatment.
Sri Ramachandra Hospital study
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A retrospective case sheet audit and case records of 15 cases of MOE mananged in our tertiary referral hospital from a January 2006 to May 2010 has been carried out .
Patients were diagnosed based on the criteria mentioned in Table 1 (Modified from Cohen & Friedman). Demographic data, symptoms, investigations, treatment and the final outcome of treatment were analysed.
The average age in these patients was 63.2 years (50 ââ‚¬" 83 years), 12 of the patients were male (Table II). All 15 patients were diabetic for an average period of 12 years (5 to 28 years) with random blood glucose level at admission varying from 164 to 275 mg/dl (average ââ‚¬" 212.2 mg/dl) (Table III). Symptoms of ear pain and discharge was present for an average of 46 days (range 10 to 180 days) prior to admission and was present in all 15 patients. Based on classification of Malignant Otitis Externa by Chandler , 3 patients had stage I disease, 9 patients were stage II and 3 patients were stage III (Table IV). On admission, all patients were administered intravenous antibiotics in hospital for an average duration of 10 days (Table II). Culture swab from affected ear taken at time of admission grew Pseudomonas Aeruginosa in 5 patients, Staphylococcus Aureus in 2, Acitenobacter, Candida Albicans and Enterococcus Faecalis in 1 patient each. 9 among these patients had lower motor neuron type of facial palsy of which 8 patients presented with grade III facial palsy (House-Brackmann grade). 1 patient who had grade II facial palsy at presentation recovered completely. Ipsilateral Hypoglossal nerve palsy was seen in 2 of the above 15 patients. One patient had IX, X, XI and XII cranial nerve palsy on the affected side. 1 patient who expired had developed ipsilateral internal carotid artery aneurysm and contralateral V, VII, IX, X, XI, XII cranial nerve palsy (Table III). 7 patients received intravenous Piperacillin and Tazobactam (4.5 gram 8th hourly) for an average period of 8 days (5 days to 14 days) of which 6 patients showed signs of improvement after the third day of treatment (Table II). Intravenous Cefaperazone and Sulbactam (1.5 gram 8th hourly) was used in 3 patients for an average period of 10 days (9 to 12 days). All 3 recovered (Table II). A Combination of Piperacillin with Tazobactam and Cefaperazone was used in 2 patients. Both patients recovered. (Table II). Patients who did not respond to the above combinations were given one of the following intravenous antibiotic Linezolid or Imepenem and Amikacin were used in one patient each in addition to the above (Table II). Out of the 15 patients, 4 patients received supplemental antifungal medication, as they did not show adequate response to intravenous antibiotics and their ear swab showed fungal elements. 2 of them received intravenous Amphotericin to a cumulative dose of 4gm over a period of 6 weeks and 2 received antifungal ear drops. 2 of the 15 patients succumbed to the disease during the course of treatment which accounts for 13.33% mortality in this series. Other patients were followed up every three months for at least one year.
Patient was considered to be treated successfully when the following criteria were met:
a) Absence of ear pain,
b) absence of ear discharge,
c) absence of granulation in the external auditory canal and/or
d) Recovery of cranial nerve palsy.