if you all of a sudden lose the hearing in one of your ears make an appointment to see a doctor at once. this is a sign of acoustic Neuroma a tumor that grows on the nerve on the ear. If the aousti neuroma is caught early enough they can zap it with gamma knife radiatio. My dad told his eye dotor he had lostthe hearing in his left ear and the dotor sent dad in for an MRI., which revealed a small tumor this was in January Dad had a smal tumor. He received gamma knife radiation Tuesday. the radiation kills the tumor in 92% of the caes.