How not to miss malignant otitis externa: The secrets of radiological diagnosis

Transcription

1 How not to miss malignant otitis externa: The secrets of radiological diagnosis Poster No.: C-1788 Congress: ECR 2010 Type: Educational Exhibit Topic: Head and Neck Authors: A. Romsauerova, J. Brunton; Dundee/UK Keywords: malignant otitis externa, diagnosis, imaging findings DOI: /ecr2010/C-1788 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 11

2 Learning objectives To describe and illustrate the spectrum of imaging characteristics of malignant otitis externa in order to avoid missing that diagnosis. Background Malignant otitis externa (MOE) is a potentially life-threatening and debilitating disorder that involves inflammation and damage of the bone and soft tissues of the skull base. MOE is a recognised complication of a progressive otitis externa and it is caused by the invasive spread of bacterial, or rarely, fungal infection. MOE most commonly occurs in elderly diabetics. Furthermore the MOE is increasingly seen in immunocompromised patients suffering from HIV or after chemotherapy. Most commonly the underlying micro-organism is Pseudomonas aeruginosa. Other bacteria that are known to cause malignant external otitis include Staphylococcus aureus, Staphylococcus epidermidis and Klebsiella sp. In some cases MOE can also be caused by fungal organisms like Aspergillus sp. or Candida species. This potentially deadly disease therefore needs an early diagnosis in order to be successfully managed. MOE was first recognised by Meltzer in 1959 and thoroughly depicted in a series of 13 patients with MOE in the late sixties. Since then the imaging techniques have improved considerably so that the anatomic extent, follow-up and resolution of the disease can be assessed. Bone scanning has proved to be a valuable imaging modality for the diagnosis and follow up of MOE but interpretation can be difficult as the scan can remain positive indefinitely and this limits its use in following disease progression or resolution. Gallium or Gallium-SPECT scans have been shown to be more specific as the tracer is incorporated into the bacteria and granulocytes. However, in some cases Gallium scanning can be normal in disease recurrence which resulted in a false negative scan. PET with FDG-labelled leucocytes was reported in only one case of suspected MOE. Its use resulted in a false positive case since the patient was suffering from simple otitis externa rather than MOE. Page 2 of 11

3 CT and MRI are imaging modalities which allow anatomic localisation of the disease enabling the radiologist to make the diagnosis and observe the resolution or progression of the disease. CT is an ideal imaging modality to look for bony erosions but it is limited by the slow rate of bone remineralisation that can be used to assess response to therapy. MRI does not use radiation and provides the most anatomically detailed information about the disease extent and soft tissue involvement including bone marrow changes. MOE is an entity that is sometimes not recognised by general radiologists. We describe the diagnostic features which are found in this condition. From our recent experience of cases with MOE half of them were diagnosed late. We have therefore reviewed the literature and together with the analysis of the CT imaging in our recent cases developed a strategy on how to best evaluate the imaging studies of patients with suspected MOE. We have used CT in diagnosis of our cases. The population of patients presenting with MOE often have multiple co-morbidities and are poor subjects for MRI. Imaging findings OR Procedure details The imaging features of MOE are illustrated on CT images using soft tissue and the bone window reconstructions. Images for this section: Page 3 of 11

4 Fig. 1: Frequency of diagnostic CT and MRI imaging findings in malignant otitis externa Page 4 of 11

5 Fig. 2: 87 yrs old male diabetic with six-week history of right ear discharge. A-abnormal soft tissue is seen in the external auditory canal with destruction of the lateral aspect of the anterior wall. Inflammatory soft tissue is seen extending into the base of the pinna and the right temporomandibular joint. B-there is opacification of the middle ear cavity and mastoid air cells. The auditory ossicles are not eroded. C-inflammation extends into the right temporomandibular joint space and parotid space. D- There is erosion of scutum. Page 5 of 11

6 Fig. 3: 48 yrs old immunocompromised female with long standing left ear discharge and eardrum perforation. A- Abnormal soft tissue is noted within the bony external auditory canal causing patchy destruction of the anterior, posterior and inferior walls. B- Soft tissue thickening and bony destruction is seen extending postero-inferiorly to involve the anterior wall of the mastoid and the mastoid air cells in the anterior aspect. C- Mild soft tissue thickening and fluid with air fluid levels are noted in the middle ear cavity and the mastoid air cells. There is no evidence of erosion of the auditory ossicles. D- The abnormal soft tissue extends anteriorly into the left temporomandibular joint. Page 6 of 11

7 Fig. 4: 74 yrs old diabetic male severe right otitis externa with swollen external auditory canal and persistent pain. A, B- there is a soft tissue thickening in the right external auditory canal with adjacent subperiosteal bony erosion. C- minor blunting and erosion of the scutum on the right is suspected. The tegmen tympani is intact. Page 7 of 11

8 Fig. 5: 93 yrs old diabetic male with left otalgia and ear discharge. A- extensive abnormal soft tissue occupying the left external auditory canal and extending as far as the tympanic membrane although there is no involvement of the left middle ear B- the inflammatory process involves the cartilaginous external auditory canal and extends into the left parotid Page 8 of 11

9 space C- there is early TMJ involvement with an effusion affecting the left TMJ but no focal bone destruction Page 9 of 11

10 Conclusion Malignant otitis externa cases are relatively rare and most radiologists are at risk of not appreciating early cases. We share our experience on how to improve the radiological diagnostic accuracy of malignant otitis externa. We used CT instead of MRI as the CT is easily accessible out of hours, it is quick and it doesn't require the patient to lie still for a long time and shows bony involvement better than MRI. Therefore CT is preferred as initial diagnostic tool, contrast enhanced CT or MRI can be used to follow-up soft tissue infection. Personal Information Dr. Andrea Romsauerova, MD Department of Radiology Ninewells Hospital and Medical School Dundee Scotland UK a.romsauerova@nhs.net References 1. J. R. Chandler. Malignant external otitis. Laryngoscope 78 (8): , B. Z. Joshua, J. Sulkes, E. Raveh, J. Bishara, and B. I. Nageris. Predicting outcome of malignant external otitis. Otol.Neurotol. 29 (3): , J. Rubin, H. D. Curtin, V. L. Yu, and D. B. Kamerer. Malignant external otitis: utility of CT in diagnosis and follow-up. Radiology 174 (2): , Page 10 of 11

11 4. H. D. Curtin, P. Wolfe, and M. May. Malignant external otitis: CT evaluation. Radiology 145 (2): , A. M. Strashun, M. Nejatheim, and S. J. Goldsmith. Malignant external otitis: early scintigraphic detection. Radiology 150 (2): , H. Ismail, W. P. Hellier, and V. Batty. Use of magnetic resonance imaging as the primary imaging modality in the diagnosis and follow-up of malignant external otitis. J.Laryngol.Otol. 118 (7): , S. G. Gherini, D. E. Brackmann, and W. G. Bradley. Magnetic resonance imaging and computerized tomography in malignant external otitis. Laryngoscope 96 (5): , Grandis J. Rubin, B. F. Branstetter, and V. L. Yu. The changing face of malignant (necrotising) external otitis: clinical, radiological, and anatomic correlations. Lancet Infect.Dis. 4 (1):34-39, Page 11 of 11