In Cushing's1book "Intracranial Tumours," published in 1932, the term "acoustic tumour" was used to describe the growth which originates in that portion of the acoustic nerve which lies within the internal auditory canal. Dr. Cushing stated that histologically such a tumor resembles those seen in other parts of the body in Recklinghausen's disease, that it is probably congenital and that clinically a loss of vestibular response to caloric tests is an early objective sign which precedes complete loss of hearing. As an acoustic tumor increases in size, the nerves in the internal auditory canal (cochlear, vestibular, facial and intermediate nerve of Wrisberg), together with the internal auditory artery, which is the main source of blood supply for the inner ear, are compressed against the bony wall of the canal, and an increasing impairment of function results. Indeed, the pressure of the growing tumor often enlarges the auditory canal;