The Erroneous Appearance of Silver Nitrate on CT Imaging in Patients with Severe Otitis Externa; A Case Series

Abstract

Introduction Silver nitrate is commonly used within otolaryngology to treat granulation tissue in severe otitis externa. It appears radio-opaque on CT (computed tomography) imaging and therefore can mimic bony fragments and foreign bodies. This is particularly cumbersome when the phenomena correlates to the clinical complaint. Discussion We report two cases of 73-year-old and 75-year-old males who presented with chronic otalgia and discharge. Granulation tissue in the external auditory canal was identified and chemically cauterised with silver nitrate. Subsequent CT petrous bones demonstrated an unidentified foreign body in the canal with extensive soft tissue swelling giving an impression of a wick in situ and “minor bony erosion in the left external acoustic canal” respectively. An additional CT of a 57-year-old female who had been treated with silver nitrate for granulomatous tissue reported “multiple highly radiopaque foci in the external auditory canal, suggestive of foreign body”. Though relatively unknown, this phenomenon has been reported in literature. However, there are few reports of silver nitrate artefacts in CT images of the head no cases in the context of otitis externa. Our patients avoided further imaging or surgery following clarification with the radiologists and symptomatic improvement with long-term intravenous antibiotics. Conclusion Given the prevalence of CT imaging and cauterization in otolaryngology, we recommend contemporaneously documenting the use of silver nitrate and highlighting this on request forms to avoid alarming erroneous reports, unnecessary investigation and surgical procedures. We also recommend, where clinically acceptable, to use silver nitrate prior to imaging.