What is the added value of surgical treatment, compared to medical treatment only, for necrotizing otitis externa?

Balance between desired and undesired effects

The systematic literature search yielded conflicting results in the few selected articles. Only one RCT was identified, which favored surgery for treatment response in patients with refractory necrotizing otitis externa who were unsuccessfully treated with antibiotics for 6 weeks. However, the methodological and statistical approaches were questionable (Singh, 2018). An observational study on the primary treatment of necrotizing otitis externa found no clinically relevant improvement in remission rates favoring surgical treatment over antibiotics alone (RR 1.15, 95% CI: 0.84 to 1.55) (Lambor, 2013).

Current literature cannot provide a clear answer regarding the role of surgery in necrotizing otitis externa. This is partly due to the rarity of the condition and partly because the cornerstone of treatment is medical. Recent trends also show a sharp decline in the use of extensive surgical therapy for the disease (which included mastoidectomy, facial nerve decompression, and/or middle ear exploration), with 13.3% of patients undergoing extensive surgery before 2009 compared to 3.7% after 2009 (Byun, 2020).

A variety of surgical options are described in the literature, ranging from nettoyage of the ear canal to lateral temporal bone resection. Based on the literature search, it is evident that no clear surgical indication exists. However, specific procedures could be considered for different indications. This list is explicitly not a hierarchical ste-by-step enumeration of treatment options; it is a list of treatment options that is opted for in literature in specific conditions.

• Nettoyage of the ear canal: This can be performed in combination with obtaining culture material or tissue biopsy for diagnostic purposes. Cleaning the ear canal of debris might not be considered a surgical intervention, but it is mentioned because it is reported in literature as (part of) a treatment.
• Other studies describe more extensive surgical interventions of the ear canal, including sequestrectomy and smoothing of bony irregularities / canalplasty. In our opinion, it is important not to confuse NOE with osteitis of the temporal bone for this indication. Osteitis due to a localized infection and/or inflammation can be a major cause of sequestra and epithelial defects in the ear canal, leading to granulation tissue and loss of the canal's migratory capacity. Moreover, prior radiotherapy of the parotid gland or nasopharynx can cause avascular necrosis or osteoradionecrosis of the temporal bone, leading to tissue defects as mentioned earlier, which can mimic NOE. Again, this should not be confused with NOE, especially because the nature of this problem is not primarily infectious.
• Mastoidectomy: The guideline panel believes that the main incentive for this procedure would be diagnostic, as local treatment of the ear canal might not reveal pathogens. Local epithelialization in the ear canal may be restored due to local treatment, whereas the infectious process can progress in deeper tissues. Mastoidectomy solely to reduce infectious load has been described but is considered obsolete.
• (Sub)total petrosectomy/lateral temporal bone resection: The most invasive type of surgery consists of (sub)total petrosectomy or lateral temporal bone resection. No evidence supports the indication for these procedures. These types of surgery could be considered as salvage surgery if all other treatments fail, potentially aiding in reducing disease burden. However, morbidity and mortality rates are high, making these procedures generally discouraged (Peleg, 2007; Omran, 2012).
• Facial nerve decompression: Facial nerve decompression in cases of facial nerve palsy is described as an indication for surgical intervention, with one study reporting its positive effects (Freeman, 2023). Facial nerve decompression is automatically performed in combination with mastoidectomy due to the surgical approach.

The extent of surgical intervention, if any, depends on multiple factors. Moreover, a combination of procedures can be chosen if indicated. The most obvious surgical indication is the search for a causative pathogen, especially in cases of failed initial medical treatment. Imaging can guide the determination of the anatomical area to approach for tissue sampling. The ear canal, mastoid, and skull base can be areas of interest, and occasionally the nasopharynx, if affected, is easily accessible.

Given the sparse literature available, it is difficult to provide clear recommendations. If no pathogen is identified, antibiotic treatment cannot be optimized, surgical intervention should be considered. The type of surgery will be determined on an individual basis and depends on multiple factors. Imaging reveals which areas are affected, guiding the choice of surgery. The clinical state of the patient, as well as cranial nerve involvement, is weighed in the decision to perform surgery. If there is a suspicion of malignancy tissue samples need to be obtained, and more invasive surgery might be necessary to collect relevant tissue samples. Unequivocally, antibiotic treatment will remain the primary treatment modality in case of NOE. Studies to determine the benefit of surgical interventions will continue to be challenging, as necrotizing otitis externa is rare and indications are unclear. However, a large multicenter study with clear indications might provide more insight into the role of surgery in the treatment of necrotizing otitis externa.

Quality of the evidence

The overall quality of evidence is very low. This means that the estimated effect of the critical outcomes that were found are very uncertain. There was a downgrade due to the following:

• Risk of Bias: methodological limitations.
• Inconsistency: inconsistency of the results.
• Indirectness: indirectness of the evidence, due to differences in the use of surrogate outcomes.
• Imprecision: inaccuracy, due to a very small number of events in a small sample size.

Moreover, the inconsistent terminology used in surgical approaches and the doubtful use of correct diagnoses might give a distorted image of literature, with a high risk of publication bias.

Values and preferences of patients (and possibly their caregivers)

Since studies describing surgery for necrotizing otitis externa are rare, it can be difficult to decide when to opt for surgery. Moreover, available reports are unclear and inconsistent regarding the type and extent of surgery. Patients should be informed about the goal of the procedure and the associated risks. The uncertainty of the outcome should also be addressed. The alternative to surgical intervention depends on the indication for the procedure. If the causative pathogen is unknown, surgery to obtain tissue samples is a reasonable indication. In cases of cranial nerve palsy, the indication and outcome are more uncertain, and both physicians and patients should be aware of this. If (optimal) conservative treatment does not result in clinical improvement, similar considerations must be made, and specialized (tertiary) centers should be consulted regarding further treatment.

Costs (resources)

Since surgery for NOE is rare, costs for this kind of treatment are negligible considering total treatment costs. However, no studies have been performed to show cost-effectiveness of the treatment, let alone for the surgery done in a small percentage of cases.

Equity ((health) equity/equitable)

The guideline panel expects no problems with health equity with regard to medical treatment of necrotizing otitis externa.

Acceptability

The guideline panel expects no problems with ethical acceptability or sustainability with regard to medical treatment of necrotizing otitis externa.

Feasibility

Regardless of the eventual recommendation, surgical intervention is feasible. The intervention is a treatment option for some clinicians. Even though the surgical procedure is feasible, the indication is complex, if existent, as mentioned before. Given this complexity the advice is to consult a specialist in NOE when surgery is considered in patients that do not seem to respond to conservative treatment. No specialized equipment is needed for surgical procedures.

Rationale of the recommendation: weighing arguments for and against the interventions

The literature on outcome or effect of surgical intervention as a standard treatment is of insufficient certainty and different studies all use different outcome measures. Therefore, the recommendations are expert opinions.

The available literature for surgical treatment in NOE suggests that surgery has a very limited role. The main indication for surgical exploration is in case of failing conservative treatment in case of an unknown causative pathogen.

There is insufficient available evidence on the effect of facial nerve decompression in case of facial nerve palsy in NOE.

Final judgment:

Weak recommendation against surgical intervention in patients with necrotizing otitis externa.