gms | German Medical Science

Neurofibromatosis Type 2 (NF-2) is a rare inherited disease with bilateral vestibular schwannomas (VS). Hearing preservation is a major goal in the surgical treatment of these patients and might be superior to the general principle of surgical radicality in selected cases. It is highly dependent on reliable and fast electrophysiological monitoring (and the neurosurgeon´s willingness to react on the reported changes).

In case of bilateral good hearing, preoperative AEP are considered in the decision on the operation side. In case of the last hearing ear the option for subtotal removal is discussed with the patient, but is decided at surgery on microscopic and monitoring aspects. Monitoring set-up includes Median, Tibial Nerves SEP, cranial nerve EMG, multi-modality monitoring of auditory function by conventional and nearfield AEP.

Within a series of 148 NF-2 patients operated for 187 VS, 134 ears presented with preoperative hearing, 50 of which retained auditory function after tumor resection (37%), 31 after complete and 18 after subtotal surgery. In 26 VS operations AEP was preserved during opening of the auditory meatus and during resection of the tumor mass, but tumorous nerve change or strong adherence would have allowed complete resection only for the price of AEP loss. Therefore, resection was terminated after intrameatal decompression and at AEP preservation. However, 8 patients lost their auditory function within 1 to 10 days after surgery, while 18 maintained useful function for periods up to 13 years, so far. Temporary complete loss of single AEP components predicted the danger of secondary functional loss. The latency from onset of wave changes to wave losses was significantly shorter than in non-NF-2 conditions.

Intraoperative monitoring is a necessary part aiming for hearing preservation in VS-resection, if realistic preconditions are fulfilled by the NF-2 patient.