Abstract
Non-EPI DW imaging is increasingly being used as a sensitive sequence in detecting 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.
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. Non-EPI 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 .
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 cholesteatoma. 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.
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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 ].
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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 ].
