Presentation
Right hearing loss with dizziness.
Patient Data
Permeative destructive lesion of right retrolabyrinthine location between the sigmoid sinus and the ICA centred on the vestibular aqueduct with calcification and spiculated tumoural matrix. Evidence of a tiny focal defect in the adjacent bony wall of the superior and posterior semicircular canals.
On the MRI sequences, there is an ill-defined expansile lobulated mass with irregular margin of the right temporal bone centred on the vestibular aqueduct. It elicits a high signal peripherally on T1, T2, FLAIR and T1 fat sat with no enhancement and a central area of isosignal to the brain tissue on T1, iso-to low signal on T2 with moderate heterogeneous enhancement on the postcontrast sequences and subtraction images. No restriction diffusion was seen on DWI/ADC.
A small colloid cyst is noted (incidental finding).
Case Discussion
The clinical presentation, the CT and MRI features are most consistent with an endolymphatic sac tumour. The other investigations did not show any feature in favour of vHL in this patient (probably a sporadic case).
The main imaging differential considerations include:
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most often located in the petrous apex, not vestibular aqueduc
smooth and expansile margins on CT
high signal of the entire lesion on T1 and T2
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centre of the lesion usually at the jugular bulb rather than the vestibular aqueduct
rarely foci of high signal on T1, flow voids on T2 very common
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jugular foramen meningioma
hyperostotic underlying bone
+/-scalloped margins
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expansion of aqueduct, with smooth margins
preserved normal shape of the aqueduct
others: petrous apicitis, bony metastasis
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