Wk 8, Case 4 - Review

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.

Findings
MRI of the brain:

There is a 2.4 x 1.8 x 2.8 cm (transverse by AP by craniocaudal) multilobulated, multicystic mass in the medial left temporal bone, which appears to arise from the left endolymphatic sac and extends caudally with erosion of the medial temporal bone. The mass demonstrates heterogeneous T2 hyperintense signal and predominantly T1 hypointense signal with areas of intrinsic T1 hyperintense signal, which may represent proteinaceous content. The mass demonstrates heterogeneous postcontrast enhancement. There is partial extension of the mass into the left posterior fossa with mild mass effect on the left cerebellar hemisphere. There is also extension of the mass into the left cerebellopontine angle cistern with part of the mass abutting the cisternal segments of the left 7th and 8th cranial nerves. There is no diffusion restriction.

The remaining left internal ear structures are intact, including the left posterior semicircular canal which very closely approximates the mass. The right temporal bone structures are unremarkable. The mastoids are otherwise clear.

There is a 6 mm round enhancing lesion in the peripheral left cerebellar hemisphere, with mild associated adjacent vasogenic edema. There is also a 3 mm enhancing lesion in the inferior right cerebellar hemisphere, with no significant adjacent vasogenic edema.

The supratentorial brain appears normal in size and signal intensity. There is no diffusion restriction to suggest acute infarction. There is no midline shift. There is no extra-axial fluid collection. The intraorbital structures, sellar contents, cavernous sinus regions are normal. There is mild mucosal thickening in the left ethmoid sinus, and bilateral maxillary sinuses, left greater than right.

Impressions
1. Multilobulated, multicystic mass in the medial left temporal lobe bone arising from the left endolymphatic sac is most suspicious for an endolymphatic sac tumor in this patient with history of von Hippel-Lindau syndrome. There is erosion of the medial left temporal bone and mild intracranial extension into the left posterior fossa and the left cerebellopontine angle cistern with mild mass effect on the left cerebellar hemisphere, focal and the left sigmoid sinus with focal abutment of the cranial nerve VII/VIII complex. The left sigmoid sinus is patent. The remaining left internal ear structures are intact including the left posterior semicircular canal which is closely approximated by the mass.

2. A 6 mm enhancing lesion in the left cerebellar hemisphere, and a 3 mm enhancing lesion in the right cerebral hemisphere are suspicious for hemangioblastomas.

3. The right internal ear structures are unremarkable.