Which cranial nerve is affected the earliest in acoustic neuroma?

The pear shapped tumour from the cranial nerve VIII continue to enlarge and compress the trigeminal nerve. Cranial nerve 5 is the earliest nerve to be involved in Acoustic neuroma. The tumor is almost always arises from the Schwann cells of the vestibular, but rarely from the cochlear division of VIIIth nerve within the internal auditory canal. As it expands, it causes widening and erosion of the canal and then appears in the cerebellopontine angle. Here, it may grow anterosuperiorly to involve the IXth, Xth, and XIth cranial nerves.