Resection of small acoustic neuroma using the transcanal transvestibular endoscopic approach

We evaluated the outcomes of resection of small acoustic neuromas using the transcanal transvestibular endoscopic approach. Two patients with a small acoustic neuroma were treated using this approach. The sizes of the tumors were 11 × 6 mm and 12 × 10 mm. Both tumors were removed completely without residual tumor tissue, and damage to the facial nerve and cochlear nerve was avoided. No patients developed postoperative vertigo, aggravation of postoperative facial paralysis, severe pain, or permanent postoperative complications. The patients were followed up for 6 months, and none developed recurrence. Resection of small acoustic neuromas by the transcanal transvestibular endoscopic approach is a simple and safe technique that achieves excellent functional results.

Neuro-axonal recruitment: A result of selective compression

Many acoustic neurinomas and CPA tumours present an audiometric picture of positive-recruitment hearing impairment although often the CMs are not significantly impaired (according to ECochG) and because, even in the case of a small acoustic neuroma, the interpeak latency between wave I and V (ERA) is increased in the majority of cases. Recruitment cannot be explained, in these cases, as an expression of an accompanying vascular inner ear lesion. Therefore, we attempt to interpret the differential audiometric picture to the various patterns of damage of the auditory nerve. The finding of tone decay is seen as an expression of myelin damage corresponding to the hearing loss in multiple sclerosis.The absence of any degree of tone decay excludes an isolated damage of the myelin sheaths; hearing loss then results from a disturbance also of the associated axons. At such a stage, where there is a functional loss to part of the neural fibres but with intact myelinated residual fibres, the result could be the phenomenon of recruitment for suprathreshold stimulation. This theory of selective compression is compared to an isolated efferent lesion theory as the cause for recruitment in AN and CPA tumours.