Patient History
24-year-old male with right-sided ear fullness and chronic left-sided hearing loss.
Findings
Non-contrast CT of the head:
A mildly expansile, erosive mass is noted within the left temporal bone posterior to the otic capsule and left internal auditory canal, extending superiorly along the posterior petrous ridge to the level of the superior semicircular canal, and inferiorly into the left occipital bone with loss of cortex along the inferior margin. The mass abuts the posterior semicircular canal, and there is likely some dehiscence. A rounded cystic area extends into the posterior fossa adjacent to the sigmoid sinus with minimal mass effect on the anterior left cerebellar hemisphere, measuring approximately 7 x 12 mm in axial dimension.The left mastoid air cells and petrous apex are well aerated. There is no fluid or soft tissue within the middle ear cavity. The right temporal bone and inferior structures are unremarkable.
No evidence of intracranial hemorrhage, or infarct. No extra axial fluid collection. Ventricles are normal in size. Basal cisterns are patent. Lobular mucosal thickening in the left greater than right maxillary sinuses. Remaining paranasal sinuses are clear. The orbits and visualized extracranial soft tissues are unremarkable.
Impressions
Expansile, erosive mass centered within the left temporal bone posterior to the otic capsule. Mild extension into the posterior fossa with minimal mass effect on the left cerebellum. There is dehiscence of the left posterior semicircular canal. This appearance is most suggestive of endolymphatic sac tumor. Recommend contrast-enhanced MRI of the temporal bone for further characterization.
