Acoustic Schwannoma: The most common tumor of the cerebellopontine angle is the acoustic Schwannoma. This tumor arises from Schwann cells of the sheath of the 8th cranial nerve, in most cases presumably the vestibular portion of the 8th nerve. In this slide the tumor is the large, bulbous structure on the left side of the slide. From its location you can predict that neurologic derangement will include cerebellar, brain stem (especially pontine), and cranial nerve dysfunction. Symptoms of 8th nerve involvement are among the earliest presenting complaints.