Systematic review of the diagnosis and management of necrotising otitis externa: Highlighting the need for high-quality research

Refining necrotising otitis externa management: A follow-up study on a departmental algorithm and the role of nuclear medicine imaging

OBJECTIVE

This study evaluates the effectiveness of a departmental diagnostic and treatment algorithm for necrotising otitis externa (NOE), with a particular focus on the role of nuclear medicine imaging in improving diagnostic accuracy and patient outcomes.

METHODS

A retrospective cohort analysis was conducted on patients admitted with suspected NOE to a major UK general hospital over a two-year period. Clinical presentation, imaging modalities, and treatment outcomes were reviewed to assess the algorithm's impact, with a focus on the diagnostic yield of CT, Technetium scans, and MRI, as well as treatment success rates and recurrence.

RESULTS

Among 33 patients (mean age: 77 years), 28 were diagnosed with necrotising otitis externa (NOE). Diabetes was present in 41 %, and Pseudomonas aeruginosa was identified in 70 % of cases. CT confirmed NOE in 21 patients (64 %), including two with skull base erosion. Among 12 patients with negative CT findings, 9 underwent Technetium bone scintigraphy, with 5 (56 %) yielding positive results. Two patients underwent MRI, confirming NOE in one case. One patient was diagnosed clinically. Overall, 6 of 12 patients (50 %) with negative CT results were ultimately diagnosed with NOE following further imaging. All 28 diagnosed patients received prolonged intravenous or oral antibiotic therapy based on microbiological sensitivity. Of these, 24 had follow-up (mean: 5.6 weeks), with clinical resolution observed in 20 patients (83 %). Additional imaging was performed in 13 cases, including MRI (n = 4), CT (n = 5), Gallium scan (n = 1), PET-CT (n = 1), and combined CT/MRI (n = 2), primarily for persistent symptoms. Four patients were diagnosed with alternative conditions, including canal cholesteatoma and squamous cell carcinoma. Overall, the cure rate within the cohort was 83 %, with no NOE recurrences or NOE-related mortality recorded during the follow-up period.

CONCLUSION

This study validates the efficacy of the department's updated NOE diagnostic and treatment algorithm, reinforcing the utility of technetium bone scans in cases where CT results are inconclusive. Findings highlight the importance of combining advanced imaging with clinical assessment for optimal NOE management, ensuring high-resolution rates and preventing unnecessary interventions.

Skull base osteoradionecrosis: from pathogenesis to treatment

PURPOSE OF REVIEW

This review aims to provide a comprehensive analysis of skull base osteoradionecrosis (ORN), a severe and rare complication of radiotherapy for head and neck malignancies. It explores pathogenesis, clinical presentation, diagnostic strategies, and management approaches, emphasizing the importance of multidisciplinary care in addressing this challenging condition.

RECENT FINDINGS

Skull base ORN results from radiotherapy-induced tissue damage, characterized by hypovascularity, hypoxia, and necrosis, often compounded by secondary infections. Advances in radiotherapy techniques, such as intensity-modulated radiotherapy and heavy particles, have reduced ORN incidence, though cases persist, particularly in high-dose radiotherapy fields. Emerging treatments, including hyperbaric oxygen therapy and the pentoxifylline-tocopherol protocol, show promise but lack robust evidence for standardized use. Surgical interventions, especially those incorporating vascularized tissue reconstruction, have demonstrated favorable outcomes in refractory cases. Recent studies underscore the utility of multimodal imaging techniques, including MRI and PET/CT, for distinguishing ORN from tumor recurrence.

SUMMARY

Skull base ORN represents a complex and potentially life-threatening condition requiring tailored, multidisciplinary management. Although advancements in diagnostics and therapeutics have improved outcomes, significant challenges remain, particularly in developing standardized protocols. Further research is needed to refine treatment strategies and improve evidence-based practices for this entity.

Scedosporium Apiospermum: A Rare Cause of Necrotizing Otitis Externa. Our Experience and A Review of the Current Literature

Necrotizing otitis externa (NOE) is a severe and progressive infection of the external auditory canal that poses significant diagnostic and therapeutic challenges, particularly when caused by rare pathogens such as Scedosporium apiospermum. This case report details an 84-year-old diabetic male with NOE treated with a combination of oral and topical Voriconazole after multiple ineffective antibiotic therapies. The consequent literature review identifies and analyzes 8 cases of NOE caused by S. apiospermum, revealing significant challenges in diagnosis and management. Diagnostic delays in NOE caused by Scedosporium apiospermum were common, leading to prolonged empirical antibiotic therapy in most cases. The follow-up duration was very long, with high rates of morbidity and mortality, including serious complications. Voriconazole emerged as the most effective antifungal treatment, though its use is associated with substantial risks, necessitating careful monitoring. Our findings underscore the importance of considering fungal etiologies in persistent NOE and emphasize the need for repeated ear swabs and targeted therapy to improve patient outcomes. The results highlight a critical gap in standardized diagnostic and therapeutic protocols, advocating for more rigorous evaluation and management strategies in cases of suspected Scedosporium infections.

Diffusion-Weighted Imaging Does Not Differentiate Between Bacterial and Fungal Skull Base Osteomyelitis

OBJECTIVE

Apparent diffusion coefficient (ADC) value helps in differentiating infections from neoplasms on magnetic resonance imaging (MRI). We investigate the diffusion-weighted images in skull base osteomyelitis (SBO) to evaluate if ADC values can differentiate fungal and bacterial SBO and to analyse the microbiology of all SBO patients.

DESIGN

Retrospective observational study.

SETTING

Quaternary care referral centre.

PARTICIPANTS

A retrospective review of 142 patients diagnosed and treated for SBO patients from January 2010 to May 2023 was done.

MAIN OUTCOME MEASURE

Chi-square or Fisher's exact test was used to compare ADC values of bacterial and fungal SBO.

RESULTS

The most common pathogens isolated were Pseudomonas (42.2%), Aspergillus (30.98%), and S. aureus (23.94%). The average ADC value of affected soft tissues among patients was 1.13 ± 0.26 × 10-3 mm2/s compared to the average ADC value of normal soft tissue, 1.34 ± 0.31 × 10-3 mm2/s. There was no statistical significance when comparing the average ADC values of bacterial and fungal SBO patients (p value = 0.142).

CONCLUSION

This study suggests that though infection due to Pseudomonas was the commonest, it was detected only in 42.2% of patients. More than half of the cases had organisms other than Pseudomonas, demanding the clinician to obtain deeper biopsies early in the course of the disease for microbiological analysis. DWI does not help differentiate bacterial and fungal SBO, again emphasising the need for deeper tissue biopsies in all these patients to assist in the early identification of the pathogen.

Treatment Response Evaluation in Necrotizing Otitis Externa Using 18 F-FDG-PET Imaging

OBJECTIVE

This study aims to identify 18 F-FDG-PET imaging features for improving treatment response evaluation in patients with necrotizing otitis externa (NOE), aiding in the difficult differentiation between sterile inflammation and active infection.

STUDY DESIGN

Retrospective cohort study.

SETTING

Tertiary hospital.

PATIENTS

Patients diagnosed with NOE between 2011 and 2022. NOE criteria included otalgia, otorrhea, granulation, and radiological features consistent with osteomyelitis.

INTERVENTION

18 F-FDG-PET/computed tomography (CT) parameters were derived from manually delineated regions of interest and were evaluated on both pretreatment and end-of-treatment scans.

MAIN OUTCOME MEASURES

Recurrent disease of NOE after end-of-treatment 18 F-FDG-PET scans.

RESULTS

This study comprised 20 NOE patients, including 5 (25%) experiencing recurrent disease after the end-of-treatment scan. The end-of-treatment 18 F-FDG-PET parameters of maximal and peak standardized uptake value (SUVmax and SUVpeak) were significantly higher in recurrent cases ( p = 0.025 and p = 0.025, respectively). Both parameters demonstrated good discrimination ability in predicting recurrence, with optimal cutoffs yielding 100% sensitivity and 67% specificity. Other parameters, including mean SUV and total lesion glycolysis (TLG), did not yield significant results, neither did the calculated difference in uptake between end-of-treatment and pretreatment scans.

CONCLUSIONS

SUVpeak on 18 F-FDG-PET was the preferred parameter for treatment response evaluation of NOE at the end-of-treatment scan. A high residual SUVpeak may adequately detect patients at risk for recurrent disease, which may necessitate prolonged treatment, while low SUVpeak is found in patients with low risk for recurrent disease permitting safe treatment cessation.

Evaluation of the clinical and radiological features of patients with Malignant otitis externa (MOE)

INTRODUCTION

Malignant otitis externa (MOE) is a life-threatening infection of the external auditory canal and temporal bone.

OBJECTIVE

This study is designed to identify the clinical features, predisposing factors, radiological findings, complications, diagnoses, and management of MOE patients.

STUDY DESIGN

Retrospective cross-sectional study.

SETTING

Loghman-e-Hakim Hospital, Tehran, Iran.

METHODS

The study included 40 patients diagnosed with MOE from 2011 to 2023. The data extracted from medical records included demographic data, clinical signs and symptoms, radiological findings, laboratory data, predisposing factors, complications, treatments, and outcomes. Out of 37 patients, 21 were followed up.

RESULTS

The study found that the mean age of patients was 62.24 ± 11.44 years, with 62.2% being male. Otalgia and otorrhea were the most commonly reported symptoms, and mastoiditis was the most common radiological finding. Bone erosions and osteomyelitis were other important complications. Vascular complications were also observed in 7 patients. The study also found that most patients had underlying conditions such as diabetes mellitus, hypertension, ischemic heart disease, and renal disease. One patient passed away during hospitalization, while others improved and were discharged. Then, at follow-up, 11 patients died, mainly due to the progression of underlying disorders including cardiac, and renal manifestations.

CONCLUSION

Based on our findings, although MOE most commonly occurs in poorly-controlled diabetic or immunocompromised patients, it can also occur in individuals without known conditions. Furthermore, increasing the age and severity of DM could lead to more complications. In terms of medical therapy, coverage of gram-positive bacteria and an antipseudomonal regimen would be an effective treatment.

Diagnostic accuracy of eosinophil-to-lymphocyte ratio and eosinophil-to-neutrophil ratio as biomarkers for differentiating between fungal and bacterial infection in necrotising otitis externa

INTRODUCTION

Necrotizing otitis externa (NOE) is a serious, progressive, and potentially life-threatening infection of the external auditory canal, affecting soft tissue and bone. The most common organism causing NOE is Pseudomonas Aeruginosa and less common are Fungal infections. When managing a patient with NOE, a culture is taken from the EAC in order to tailor the appropriate antimicrobial treatment, however commonly, the culture is sterile. Inflammation biomarkers may be used as adjuncts to inform on the differential diagnosis and as prognostic markers.

AIM

To characterize and compare values and ratios of components of the complete blood count (CBC) at admission, at patients with positive swab culture.

METHODS

A retrospective study of NOE patients was conducted. We included all patients admitted between the years 2001-2023, for whom a culture swab tested positive. We compared CBC findings at hospitalization between bacteria and fungi-positive culture patients.

RESULTS

Eosinophils-to-Neutrophils Ratio (ENR) was significantly lower in the fungal group compared to the bacterial group 0.023 ± 0.02 and 0.04 ± 0.03, respectively (p-value = 0.025). Eosinophils-to-Leukocyte Ratio (ELR) was significantly lower in the fungal group compared to the bacterial group 0.058 ± 0.04 and 0.12 ± 0.1 respectively (p-value = 0.009). For definition of ELR ≤ 0.1 we found that, sensitivity was 88% (95%CI = 0.679-0.979) and NPV 90% (95%CI = 0.709-0.982). For definition of ENR ≤ 0.03 sensitivity was 88% (95%CI = 0.679-0.979) and NPV 88% (95%CI = 0.679-0.979).

CONCLUSION

Lower values of ELR and ENR in patients with NOE are associated with fungal infection and can serve as a tool in adjusting an appropriate antimicrobial therapy in cases of sterile or when no culture is available.

Epidemiology and risk factors for extension of necrotizing otitis externa

PURPOSE

Necrotizing otitis externa (OEN) is an aggressive and morbid infection of the external acoustic meatus. What are the risk factors for OEN extension?

METHODS

French monocentric retrospective study (2004-2021), including patients with OEN defined by the association of an inflamed EAM, a positive nuclear imaging, the presence of a bacteriological sample and the failure of a well-followed local and/or general antibiotic treatment. OEN was extensive if it was associated with vascular or neurological deficits, if nuclear imaging fixation and/or bone lysis extended beyond the tympanic bone.

RESULTS

Our population (n = 39) was male (74%), type 2 diabetic (72%), aged 75.2 years and pseudomonas aeruginosa was found in 88% of cases. Complications for 43% of patients were extensive fixation on nuclear imaging, for 21% of them the presence of extensive bone lysis, for 13% the appearance of facial palsy, for 5.3% the presence hypoglossal nerve palsy and for 2.5% the presence of thrombophlebitis or other nerves palsies. 59% of our population had extensive OEN. The diagnosis of the extensive OEN was made 22 days later (p = 0.04). The clinical presentation was falsely reassuring due to easier identification of the tympanic membrane (70% vs 46%, p = 0.17) but associated with periauricular oedema (42% vs 0%), bone exposure (16% vs 0%) and a temporomandibular joint pain (41% vs 12%).

CONCLUSION

Delayed treatment of OEN, identification of clinical bone lysis, especially when the tympanic membrane is easily visualized, and the presence of unbalanced diabetes are potential risk factors for extension of OEN.

A systematic review of antimicrobial treatment regimens and their outcomes in necrotising otitis externa

BACKGROUND

Necrotising otitis externa is a serious infection with minimal evidence underpinning its management. This review aims to synthesise published evidence of antimicrobial therapies and their outcomes in necrotising otitis externa.

METHODS

The review was PROSPERO registered (CRD42022353244) and conducted according to Preferred Reporting Items for Systematic Review and Meta-Analyses ('PRISMA') guidelines. A robust search strategy filtered 28 manuscripts into the final review. Antimicrobial therapy and clinical outcome data were extracted and analysed.

RESULTS

Published studies are heterogeneous, with high risk of bias and low certainty. Reporting of outcomes is poor and extremely variable. First-line therapy is most commonly in-patient (95 per cent) empiric fluoroquinolone (68 per cent) delivered intravenously (82 per cent). The lack of granular data and poor outcome reporting mean it is impossible to correlate treatment strategies with clinical outcomes.

CONCLUSION

Robust, consistent outcome reporting with reference to treatments administered is mandatory, to inform clinical management and optimise future research. Optimal antimicrobial choices and treatment strategies require clarification through prospective clinical trials.

Management and Outcomes of Necrotizing Otitis Externa: A Retrospective Cohort Study in a Tertiary Referral Center

Objectives

Necrotizing otitis externa (NOE) is a rare infection of the ear that causes osteomyelitis. We aimed to evaluate treatment outcomes and the role of imaging in diagnosing and monitoring disease resolution in a single-center study of patients with NOE.

Methods

In this retrospective cohort study, patients with NOE who were diagnosed and treated in a tertiary otology center in Utrecht, The Netherlands, between January 1, 2013 and August 1, 2022, were included. Data were retrieved from the medical records on demographics, symptoms, physical and diagnostic findings, type and duration of treatment, and course of disease.

Results

A total of 24 cases were included. Patients were often elderly (mean age = 75 years) and diabetic (88%). Pseudomonas aeruginosa was the most commonly found microorganism (63%). Twenty-two cases (92%) received intravenous antibiotic treatment, and 7 cases (29%) received additional systemic antifungal treatment. The mean duration of systemic treatment was 29 weeks. In 20 out of 22 cases (91%), imaging was used to determine the end point of treatment. None of the cases with a total resolution of disease activity (n = 5) on 18F-fluorodeoxyglucose-positron emission tomography-computed tomography imaging at the time of cessation of therapy showed clinical relapse, compared with 1 out of 4 cases on gallium single-photon emission computerized tomography.

Conclusion

Based on the experience from our center, we demonstrated that patients with NOE can successfully be treated with prolonged systemic treatment. Molecular imaging is reasonably successful for disease evaluation and decision-making on the eradication of disease.

Fungal Infections of the External Auditory Canal and Emerging Pathogens

Fungal infections of the external auditory canal can range from common (otomycosis) to life threatening (necrotizing otitis externa). Proper identification of fungal pathogens is necessary to guide appropriate therapy, and a high index of suspicion for fungal causes of ear canal disease is critical. Fungal pathogens may be an especially important cause of ear canal disease in certain populations, including patients with diabetes, patients recently treated with antibiotics, and immunosuppressed patients. Opportunistic fungal infections of the ear canal are an emerging concern.

Skull Base Osteomyelitis: Historical Perspective, Diagnosis and Management Update

SBO is a life-threatening disease that requires a high index of suspicion based on these patients complex underlying medical co-morbidities and clinician's acumen. Once a diagnosis is made, is it critical to communicate and work closely with other multidisciplinary teams (neuroradiology for appropriate choice of imaging study and interpretation; infectious disease for appropriate medical treatment and duration; internist to properly manage their underlying medical co-morbidities). Despite advances in imaging, the diagnosis is first made based on clinical judgment, appropriate culture, and tissue biopsy.

Are artificial intelligence large language models a reliable tool for difficult differential diagnosis? An a posteriori analysis of a peculiar case of necrotizing otitis externa

Key Clinical Message

Large language models have made artificial intelligence readily available to the general public and potentially have a role in healthcare; however, their use in difficult differential diagnosis is still limited, as demonstrated by a case of necrotizing otitis externa.

Abstract

This case report presents a peculiar case of necrotizing otitis externa (NOE) with skull base involvement which proved diagnostically challenging. The initial patient presentation and the imaging performed on the 78-year-old patient suggested a neoplastic rhinopharyngeal lesion and only after several unsuccessful biopsies the patient was transferred to our unit. Upon re-evaluation of the clinical picture, a clinical hypothesis of NOE with skull base erosion was made and confirmed by identifying Pseudomonas aeruginosa in biopsy specimens of skull base bone and external auditory canal skin. Upon diagnosis confirmation, the patient was treated with culture-oriented long-term antibiotics with complete resolution of the disease. Given the complex clinical presentation, we chose to submit a posteriori this NOE case to two large language models (LLM) to test their ability to handle difficult differential diagnoses. LLMs are easily approachable artificial intelligence tools that enable human-like interaction with the user relying upon large information databases for analyzing queries. The LLMs of choice were ChatGPT-3 and ChatGPT-4 and they were requested to analyze the case being provided with only objective clinical and imaging data.