Acoustic neuroma ingrowth in the cochlear nerve: does it influence the clinical presentation?

We examined the clinical presentation in patients with a histologically proven ingrowth of the cochlear nerve by acoustic neuroma to see whether this differs from what is known from large acoustic neuroma series. In total, 85 acoustic neuromas had an en bloc dissection to study histologically the relation between the cochlear nerve and the acoustic neuroma. In 21 of these 85 specimens, there was histologic proof of invasion of the cochlear nerve by the tumor. For 13 of these 21 tumors, sufficient clinical data could be retrieved to describe the clinical presentation in these patients. We collected clinical data such as age, sex, presenting symptoms, duration of symptoms, tone audiograms, tumor size measurements and volumetric calculations, and latency interval data I-V of brain stem evoked response audiometry and calculated whether there was any correlation among those data. We also compared these clinical data with the data from some large acoustic neuroma series. No clear difference could be shown between the clinical presentation of acoustic neuroma patients with cochlear nerve ingrowth and the clinical presentations in large acoustic neuroma series. This outcome favors the theory that the hearing impairment in acoustic neuroma patients is mainly the result of compression on the vessels of the cochlea and/or on the cochlear nerve.