CT assessment of acute coalescent mastoiditis.

Transcription

1 CT assessment of acute coalescent mastoiditis. Poster No.: C-1794 Congress: ECR 2010 Type: Educational Exhibit Topic: Head and Neck Authors: A. Thomson, S. J. Thomas, A. Hutchings, E. Tilley; Portsmouth/UK Keywords: CT, Mastoiditis, Complications DOI: /ecr2010/C-1794 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 18

2 Learning objectives 1. To define acute coalescent mastoiditis 2. To briefly review the relevant anatomy with respect to CT assessment of the complications of acute mastoiditis 3. To review the major complications that occur relating to acute coalescent mastoiditis 4. To review CT cases of patients with complications of acute coalescent mastoiditis. Background NORMAL APPEARANCES Page 2 of 18

3 Fig.: 1.Normal appearances of the mastoid. Note the clear middle ear cavities. The narrow aditus opens into an unopacified mastoid antrum and air cells. Note also the thin sigmoid sinus plate (posterior wall of mastoid)and the lateral mastoid cortex (lateral wall of mastoid). These areas should be carefully reviewed for subtle bone destruction in cases of acute coalescent mastoiditis. Page 3 of 18

4 Fig.: 2. Normal coronal petrous temporal bones. Note the superior wall of the middle ear cavity - the tegmen. Note also the lateral mastoid cortex (lateral mastoid wall). In the imaging of acute coalescent mastoiditis, bone destruction should be assessed for on multiplanar reformats. WHAT IS ACUTE COALESCENT MASTOIDITIS? If infection in the middle ear cavity is uncontrolled swelling of the mucosa in the narrow mastoid aditus can block the drainage from the mastoid, trapping secretions in the mastoid resulting in acute mastoiditis. The inflamed and oedematous tissues are under pressure resulting in local acidosis and bony resorption of the walls of the mastoid air cells. The air cells coalesce and an empyema can form. This is acute coalescent mastoiditis. Fig.: 3. Acute coalescent mastoiditis. Note the destruction of the mastoid air cells. Page 4 of 18

5 If the acute coalescent mastoiditis is not controlled by antibiotics there is progressive bone resorption not only of the walls of the mastoid air cells but also of the mastoid cortex. This allows direct extension or infection to adjacent structures and hence potential complications. THE COMPLICATIONS WHICH SHOULD BE ASSESSED FOR ARE:- Brain - cerebritis, cerebral abscess and extradural abscess. Venous Sinuses - Venous sinus thrombosis in the sigmoid sinuses and jugular bulb. Soft tissues overlying the mastoid - Subperiosteal abscess postauricular region. Neck - Bezold's abscess (abscess tracking in the soft tissues of the neck). Petrous apex - Abscess within a pneumatised petrous apex. Page 5 of 18

6 Imaging findings OR Procedure details HOW TO SCAN? The rationale for CT scanning in acute coalescent mastoiditis is to identify the sites of bone resorption in the petrous temporal bone and cover the potential sites of complications in the brain and neck. Our recommended CT protocol involves 2 scans. CT Petrous Temporal Bones (Fine detail axial and coronal reconstructions). AND CT Brain and Neck 100mls IV contrast with a 40second delay. Scan from the vertex to the sternal notch. COMPLICATIONS BEZOLD'S ABSCESS Page 6 of 18

7 Fig.: A1. A case of acute coalescent mastoiditis. Note a pocket of air within the post auricular soft tissues. Page 7 of 18

8 Fig.: A2. The same patient with contrast enhanced axial section through the upper neck shows the abscess has extended down the neck. This neck abscess is known as a Bezold's abscess. It has resulted from osteolysis at the mastoid tip. Page 8 of 18

9 Fig.: A3. A further contrast enhanced axial image in the same patient more inferiorly demonstrates the Bezold's abscess extending down the neck. VENOUS SINUS THROMBOSIS Page 9 of 18

10 Fig.: B1. Axial thin slice petrous temporal bone CT demonstrates acute coalescent mastoiditis. Note the intracranial air adjacent to the sigmoid sinus plate, implying destruction of the mastoid cortex. Page 10 of 18

11 Fig.: B2. Contrast enhanced axial images demostrate left sigmoid and jugular venous sinus thrombosis on the left. Note the normal contrast opacification on the right. This patient also has a simultaneous Bezold's abscess. Page 11 of 18

12 Fig.: C1. A case of left acute coalescent mastoiditis. Note the bony destruction of the sigmoid sinus plate. Page 12 of 18

13 Fig.: C2. The contrast enhanced CT was inconclusive. MRV confirmed loss of flow in the left sigmoid sinus due to venous sinus thrombosis. MRI can be a useful adjunct in the imaging of acute coalescent mastoiditis, particularly for assessing intracranial pathology. SUBPERIOSTEAL ABSCESS Page 13 of 18

14 Fig.: D1. Contrast enhanced soft tissue CT demonstrates an intracranial (extradural) abscess and a subperiosteal extracranial abscess. The right transverse sinus is elevated by the extradural abscess and at risk of thrombosis, though it remains patent on this scan. The subperiosteal abscess causes significant post auricular swelling. CEREBRAL ABSCESS Page 14 of 18

15 Fig.: E1. A further case of right acute coalescent mastoiditis. Note the intracranial air and the right extracranial soft tissue swelling. Page 15 of 18

16 Fig.: E2. Contrast enhanced CT in the same patient demonstrates a right subperiosteal abscess but note also the right intracerebral abscess within the posterior fossa. Page 16 of 18

17 Conclusion The complications of acute coalescent mastoiditis are potentially life threatening. CT imaging of these patients should therefore be performed urgently. We recommend CT Petrous Temporal Bones AND CT Brain and Neck (100mls IV contrast scanned at 40 seconds). Review axial thin slice bone imaging: to confirm features of acute coalescent mastoiditis. to assess for bony defects in the mastoid cortex. to assess for air either within the extracranial soft tissues or intracranially. Contrast enhanced CT imaging should be reviewed for: venous sinus thrombosis cerebral or extradural abscess subperiosteal abscess Bezold's abscess Petrous apex abscess (in a pneumatised pertrous apex) MRI is a useful adjunct in the assessment of complications in acute caoalescent mastoiditis. Page 17 of 18

18 Personal Information Dr Alistair Thomson BM MRCSEd FRCR Radiology Registrar, Dept of Radiology, Queen Alexandra Hospital, Southwick Hill Road, Cosham, Portsmouth, Hants, PO6 3LY References 1. Vazquez E et al. Imaging of complications of acute mastoiditis. Radiographics Vol (2003) 2. Antonelli P et al. Computed Tomography and the diagnosis of acute coalescent mastoiditis. Otolaryngology - Head and Neck surgery Vol 120: (1999) 3. Tarantino V. et al. Acute mastoiditis: A 10 year retrospective study. International Journal of Pediatric otorhinolaryngology. Vol 66, Issue (2002) Page 18 of 18