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Mucous retention cyst of temporal bone: a mimic of cholesteatoma on DW-MRI
AM ER IC AN JOUR NA L OF OTOLARY NG OLOG Y –H EA D A N D N E CK ME D I CI N E AN D SUR G E RY 3 4 ( 2 0 13 ) 75 3–7 5 4
Available online at www.sciencedirect.com
ScienceDirect www.elsevier.com/locate/amjoto
Mucous retention cyst of temporal bone: a mimic of cholesteatoma on DW-MRI Amit Karandikar, FRCR a,⁎, Julian Goh, FRCR a , Siu Cheng Loke, FRCR a , Seng Beng Yeo, FRCS (Edin), FAMS (ORL) b , Tiong Yong Tan, FRCR c a b c
Diagnostic Radiology, Tan Tock Seng Hospital, Singapore Department of Otorhinolaryngology, Tan Tock Seng Hospital, Singapore Changi General Hospital, Singapore
ARTI CLE I NFO
A BS TRACT
Article history:
Non-EPI DW imaging is increasingly being used as a sensitive sequence in detecting
Received 20 June 2013
cholesteatomas especially if CT findings are not confirmatory. Cholesteatoma appears as a hyperintense focus on DWI. We present two cases of mucous retention cysts in the mastoid temporal bone/middle ear cavity, which present as hyperintense on non-EPI DWI and potentially may mimic cholesteatomas. Differentiating between the two conditions is important, as surgery can be avoided in mucous retention cysts. We have also discussed ways to differentiate between these two conditions on MRI. To our knowledge, this entity is not reported previously. © 2013 Elsevier Inc. All rights reserved.
Cholesteatoma is a diagnosis that needs to be excluded in all patients presenting with chronic discharging ears. Due to its high negative predictive value, CT is the primary investigation for evaluating cholesteatomas. The typical features of cholesteatomas on CT are soft tissue opacification with mass effect and erosions. Larger cholesteatomas can be diagnosed with certainty whilst smaller cholesteatomas may lack typical presentations. MRI plays an important role in characterizing soft tissues especially if CT scan results are inconclusive. NonEPI DW imaging has recently emerged as a sensitive sequence in detecting cholesteatomas. However false positive results have been reported with DWI particularly in post-operative cases [1]. We present two cases of mucous retention cysts in the mastoid temporal bone/middle ear cavity, which present as hyperintensity on non-EPI DWI and potentially may mimic cholesteatomas. To our knowledge, there are no prior reported cases of this entity. Both the patients were adults presenting with chronic suppurative otitis media with a clinical suspicion of choles-
teatoma. CT revealed non-specific opacification in middle ear and mastoid with no mass effect or bony erosion [Fig. 1]. MRI was subsequently performed on a 1.5 T GE machine. Apart from routine sequences (T1w pre/delayed post gadolinium, T2w), DW Propeller was done with b 1000 value.
1.
Case 1
Tiny hyperintense nodular focus on DW in mastoid temporal bone measuring 0.6 cm. T2w images reveal hyperintensity similar to CSF [Fig. 2].
2.
Case 2
Small hyperintense rounded focus on DW in middle ear cavity measuring 0.7 cm. The lesion is T2w hyperintense and shows peripheral enhancement due to granulation tissue [Fig. 3].
⁎ Corresponding author. Department of Radiology, 11 Jalan, Tan Tock Seng, Tan Tock Seng Hospital, Singapore, 308433. E-mail address: [email protected] (A. Karandikar). 0196-0709/$ – see front matter © 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.amjoto.2013.07.009
754
AM ER IC AN JOUR NA L OF OTOLARY NG OLOG Y –H EA D A N D N E CK ME D I CI NE AN D SUR G E RY 3 4 ( 2 0 13 ) 75 3–7 5 4
Fig. 3 – Nodular hyperintense focus (arrow) on DW in middle ear cavity (top centre) with T2w hyperintensity (bottom left) and rim enhancement (bottom right).
Fig. 1 – HRCT Temporal bone reveals non-specific opacification in mastoid air cells with no mass effect or bony erosion.
Fig. 2 – Nodular hyperintense focus on DW image (arrow) in the left mastoid temporal bone (image to the left). It is hyperintense on T2w (image to the right) with intensity similar to CSF.
Based on the DW images, a diagnosis of cholesteatoma was made. A canal wall up mastoidectomy was performed. No cholesteatoma was seen during surgery. At the site of DW abnormality, mucous retention cysts were seen. Retrospective review of MR images, revealed hyperintensity on T2w of both these lesions. The T2w hyperintensity was comparable with CSF. Mucous retention cysts are loculated fluid collections, which can be seen in the middle ear cavity or mastoid air cells. We feel pathologically, they are similar to mucocele of the paranasal sinuses and hence may sometimes be expansile. They present as hyperintense foci on DWI due to
restricted nature of fluid contents. They do not enhance centrally but may show rim enhancement due to peripheral granulation tissue. On retrospective analysis, we feel T2w images, can help differentiate these cysts from cholesteatomas. While cholesteatomas are known to be hyperintense to brain parenchyma on T2w, they are generally less hyperintense than the CSF [2,3]. On the other hand, we found retention cysts are more hyperintense on T2w, similar to CSF. The T2w signal may however be lower if the protein content is high with corresponding increase in T1w signal. Post contrast study is not very reliable in distinction, as both the conditions do not enhance centrally. They may show peripheral enhancement due to granulation tissue [Fig. 2]. Differentiating cholesteatoma from mucous retention cyst is important since the former needs surgery while the latter is a leave alone lesion. In conclusion, on DW Propeller alone, mucous retention cysts can present as a false positive finding for cholesteatomas. To our knowledge, this entity is not reported previously. Retention cysts are more hyperintense than cholesteatomas on T2w with hyperintensity similar to CSF. Hence T2w images can help the differentiation.
REFERENCES
[1] Dremmen M, Hofman P, Hof J, et al. The diagnostic accuracy of Non-Echo-Planar Diffusion-Weighted Imaging in detection of residual and/or recurrent cholesteatoma of the Temporal bone. AJNR Am J Neuroradiol 2012;33:439–44. [2] Barath K, Huber AM, Stampfli P, et al. Neuroradiology of cholesteatomas. AJNR Am J Neuroradiol 2011;32:221–9. [3] Maheshwari S, Mukherji S. Diffusion Weighted Imaging for differentiating recurrent cholesteatoma from granulation tissue after mastoidectomy: case report. AJNR Am J Neuroradiol 2002;23:847–9.
Available online at www.sciencedirect.com
ScienceDirect www.elsevier.com/locate/amjoto
Mucous retention cyst of temporal bone: a mimic of cholesteatoma on DW-MRI Amit Karandikar, FRCR a,⁎, Julian Goh, FRCR a , Siu Cheng Loke, FRCR a , Seng Beng Yeo, FRCS (Edin), FAMS (ORL) b , Tiong Yong Tan, FRCR c a b c
Diagnostic Radiology, Tan Tock Seng Hospital, Singapore Department of Otorhinolaryngology, Tan Tock Seng Hospital, Singapore Changi General Hospital, Singapore
ARTI CLE I NFO
A BS TRACT
Article history:
Non-EPI DW imaging is increasingly being used as a sensitive sequence in detecting
Received 20 June 2013
cholesteatomas especially if CT findings are not confirmatory. Cholesteatoma appears as a hyperintense focus on DWI. We present two cases of mucous retention cysts in the mastoid temporal bone/middle ear cavity, which present as hyperintense on non-EPI DWI and potentially may mimic cholesteatomas. Differentiating between the two conditions is important, as surgery can be avoided in mucous retention cysts. We have also discussed ways to differentiate between these two conditions on MRI. To our knowledge, this entity is not reported previously. © 2013 Elsevier Inc. All rights reserved.
Cholesteatoma is a diagnosis that needs to be excluded in all patients presenting with chronic discharging ears. Due to its high negative predictive value, CT is the primary investigation for evaluating cholesteatomas. The typical features of cholesteatomas on CT are soft tissue opacification with mass effect and erosions. Larger cholesteatomas can be diagnosed with certainty whilst smaller cholesteatomas may lack typical presentations. MRI plays an important role in characterizing soft tissues especially if CT scan results are inconclusive. NonEPI DW imaging has recently emerged as a sensitive sequence in detecting cholesteatomas. However false positive results have been reported with DWI particularly in post-operative cases [1]. We present two cases of mucous retention cysts in the mastoid temporal bone/middle ear cavity, which present as hyperintensity on non-EPI DWI and potentially may mimic cholesteatomas. To our knowledge, there are no prior reported cases of this entity. Both the patients were adults presenting with chronic suppurative otitis media with a clinical suspicion of choles-
teatoma. CT revealed non-specific opacification in middle ear and mastoid with no mass effect or bony erosion [Fig. 1]. MRI was subsequently performed on a 1.5 T GE machine. Apart from routine sequences (T1w pre/delayed post gadolinium, T2w), DW Propeller was done with b 1000 value.
1.
Case 1
Tiny hyperintense nodular focus on DW in mastoid temporal bone measuring 0.6 cm. T2w images reveal hyperintensity similar to CSF [Fig. 2].
2.
Case 2
Small hyperintense rounded focus on DW in middle ear cavity measuring 0.7 cm. The lesion is T2w hyperintense and shows peripheral enhancement due to granulation tissue [Fig. 3].
⁎ Corresponding author. Department of Radiology, 11 Jalan, Tan Tock Seng, Tan Tock Seng Hospital, Singapore, 308433. E-mail address: [email protected] (A. Karandikar). 0196-0709/$ – see front matter © 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.amjoto.2013.07.009
754
AM ER IC AN JOUR NA L OF OTOLARY NG OLOG Y –H EA D A N D N E CK ME D I CI NE AN D SUR G E RY 3 4 ( 2 0 13 ) 75 3–7 5 4
Fig. 3 – Nodular hyperintense focus (arrow) on DW in middle ear cavity (top centre) with T2w hyperintensity (bottom left) and rim enhancement (bottom right).
Fig. 1 – HRCT Temporal bone reveals non-specific opacification in mastoid air cells with no mass effect or bony erosion.
Fig. 2 – Nodular hyperintense focus on DW image (arrow) in the left mastoid temporal bone (image to the left). It is hyperintense on T2w (image to the right) with intensity similar to CSF.
Based on the DW images, a diagnosis of cholesteatoma was made. A canal wall up mastoidectomy was performed. No cholesteatoma was seen during surgery. At the site of DW abnormality, mucous retention cysts were seen. Retrospective review of MR images, revealed hyperintensity on T2w of both these lesions. The T2w hyperintensity was comparable with CSF. Mucous retention cysts are loculated fluid collections, which can be seen in the middle ear cavity or mastoid air cells. We feel pathologically, they are similar to mucocele of the paranasal sinuses and hence may sometimes be expansile. They present as hyperintense foci on DWI due to
restricted nature of fluid contents. They do not enhance centrally but may show rim enhancement due to peripheral granulation tissue. On retrospective analysis, we feel T2w images, can help differentiate these cysts from cholesteatomas. While cholesteatomas are known to be hyperintense to brain parenchyma on T2w, they are generally less hyperintense than the CSF [2,3]. On the other hand, we found retention cysts are more hyperintense on T2w, similar to CSF. The T2w signal may however be lower if the protein content is high with corresponding increase in T1w signal. Post contrast study is not very reliable in distinction, as both the conditions do not enhance centrally. They may show peripheral enhancement due to granulation tissue [Fig. 2]. Differentiating cholesteatoma from mucous retention cyst is important since the former needs surgery while the latter is a leave alone lesion. In conclusion, on DW Propeller alone, mucous retention cysts can present as a false positive finding for cholesteatomas. To our knowledge, this entity is not reported previously. Retention cysts are more hyperintense than cholesteatomas on T2w with hyperintensity similar to CSF. Hence T2w images can help the differentiation.
REFERENCES
[1] Dremmen M, Hofman P, Hof J, et al. The diagnostic accuracy of Non-Echo-Planar Diffusion-Weighted Imaging in detection of residual and/or recurrent cholesteatoma of the Temporal bone. AJNR Am J Neuroradiol 2012;33:439–44. [2] Barath K, Huber AM, Stampfli P, et al. Neuroradiology of cholesteatomas. AJNR Am J Neuroradiol 2011;32:221–9. [3] Maheshwari S, Mukherji S. Diffusion Weighted Imaging for differentiating recurrent cholesteatoma from granulation tissue after mastoidectomy: case report. AJNR Am J Neuroradiol 2002;23:847–9.