An acoustic neuroma is a tumor that grows from the nerves responsible for balance and hearing. More accurately called vestibular schwannoma, these tumors grow from the sheath covering the vestibulocochlear nerve. Acoustic neuromas are benign (not cancerous) and usually grow slowly. Over time the tumor can cause gradual hearing loss, ringing in the ear, and dizziness. Because of their slow growth, not all acoustic neuromas need to be treated. Treatment options include observation, surgery, and radiation.