HSC Section 8_April 2017

Otolaryngology–Head and Neck Surgery 148(6)

Presentation Initial symptoms are indistinguishable from simple otitis externa. It is usually only after multiple failed treatment attempts that MOE is suspected. The mean diagnostic delay was significantly long at 6.79 weeks, similar to the literature, which has been reported to be between 1 and 7 months. 10,11 Similar to other studies, 4,12 our results suggest that a delay in the commencement of intravenous antibiotics does not adversely affect outcome. However, this delay leads to pro- longed suffering, and physicians should always maintain a high index of suspicion in susceptible patients. Soudry et al 4 and Franco-Vidal et al 5 found that those with facial nerve palsy at presentation had a poorer out- come. This trend was noted in our series, but the number of patients with facial nerve involvement was small, and the findings did not reach statistical significance (50.0% poor outcome in the group with cranial nerve involvement vs 33.3% poor outcome in the group without; P = .603). Hematological Parameters Leukocytosis, a traditional marker of inflammation, was not prominent, and its use in monitoring activity is limited. In contrast, the usefulness of CRP and ESR as markers for activity is apparent, concurring with previous studies. 3,6 Our results showed that the absolute ESR and CRP levels could not be relied upon alone to predict outcome, but the useful- ness of these markers became evident when serial readings showed that trends were seen to correlate closely with disease activity. Patients with disease that resolved after 6 weeks of intravenous therapy showed a 21.71% reduction in mean ESR values compared with the group with persistent disease, in which ESR values remained unchanged ( Figure 1 ). A similar downward trend was also seen in CRP levels. By trending inflammatory marker levels, clinicians are able to decide more confidently which patients are suitable for anti- biotic cessation or outpatient treatment, especially when one does not have ready access to radionuclide scans. Imaging Findings Radionuclide bone and white cell–tagged scans have proven valuable in MOE. Bone scans are sensitive because the radionuclide tracer (technetium-99m methylene diphospho- nate) accumulates at areas of osteoblastic activity. However, osteoblastic activity persists long after the infective process, hence limiting the usefulness for charting progress or con- firming resolution. White cell–tagged scans using gallium citrate (Ga67) have been more useful in monitoring disease as the tracer is incorporated directly into granulocytes at sites of infection. These scans are undoubtedly valuable; however, they may not be available in all institutions deal- ing with MOE. In our experience, we have used anatomic imaging modalities such as CT and MRI to assess our patients. Computed tomography is ideal for assessing bony invol- vement. In theory, the anatomical extent of disease should be useful for prognosis. Peleg et al 13 reported that severe

who died from intracranial complications (1 = Klebsiella pneumoniae , 1 = P aeruginosa ; 1 = negative culture). Based on culture sensitivity, 52.6% (n = 10) received culture-specific therapy. Those with negative cultures received empirical intravenous ceftazidime and oral fluoro- quinolone. The mean (SD) duration of antibiotic therapy was 42.2 (15.3) days. Outpatient therapy was used in 63.2% (n = 12) to reduce inpatient stay, reducing the mean (SD) inpatient antibiotic duration to 24.3 (20.1) days. There was no statistically significant difference in out- come between those who received culture-specific therapy and those who received ceftazidime and fluoroquinolone empirically (70.0% of the directed therapy group had dis- ease that resolved vs 55.6% in the empirical therapy group; P = .650). Discussion Malignant otitis externa had associated mortality rates of 50% when it was first characterized in 1968. 1 The develop- ment of anti-pseudomonal antibiotics has since reduced mortality significantly. Studies have reviewed factors such as clinical presentation, laboratory and imaging findings, and microbiology in an attempt to identify prognostic fac- tors. However, conclusive prognostic factors have yet to be identified, and there is still no consensus on the optimal choice of antibiotics and duration of therapy. Demographic Factors The impact of age on prognosis is disputed. Franco-Vidal et al 5 reviewed 46 patients and found that age did not affect outcome. On the contrary, Soudry et al 4 studied 57 patients, and their results suggested a lower life expectancy for those aged 70 years and older. However, this was also attributed to additional risks contributed by diabetes and other atherosclerosis-related comorbidities frequently present in these patients. Our experience suggests that age is not an accurate prognostic factor. The link with diabetes is well established, 1,6 with recent studies reporting the prevalence of diabetes in MOE to be between 65% and 95%. 4,5,7 Our results concurred, with 94.7% (n = 18) having diabetes in our study. Diabetes- related microangiopathy is thought to predispose to MOE as the impaired local circulation within the EAC diminishes the ability of immunological cells to respond to invasion by P aeruginosa. 8,9 Glycemic control is linked to the severity of microangiopathy in the retina and renal circulations. Hence, we postulated that poorer glycemic control would imply more severe microangiopathy within the EAC, and this could predict severe disease. However, analysis of HbA1c levels failed to show relation to outcome. This con- curs with earlier studies that also failed to show any relation between degree of glucose intolerance and outcome. 6,9 A possible explanation could be that as most patients are elderly with longstanding diabetes, microangiopathy within the EAC is already end stage, therefore making little differ- ence in the local immune response.

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