With the original MRI in hand, we consulted a neurosurgeon and neuro-radiologist here in the US, with the help of a mutual contact, and their reading of it was it was not a cavernoma, but a
Ependymoma, in the wall of the ventricle, located near the Pons in the brain and Cereballa aqueduct, thus causing the blockage. It was suggested that along with a shunt procedure, a followup surgery to remove the tumor should be done. They also suggested MRI of the spine to rule out tumors there.