Vestibular Schwannoma(Acoustic Neuroma) is a small nerve sheath tumour of the Vestibular Nerve. Unfortunately, this nerve is almost entirely hidden inside the temporal bone, so it is not easily visible on CT scans till it has grown significantly large! MRIs do not visualise bones so even a small Vestibular Schwannoma can easily be picked up and thereby help the Surgeon operate upon it early before permanent nerVe damage sets in.