DIRECT BRAIN-STEM RECORDING OF AUDITORY-EVOKED POTENTIALS DURING VESTIBULAR SCHWANNOMA RESECTION - NUCLEAR BAEP RECORDING - TECHNICAL NOTE AND PRELIMINARY-RESULTS
C. Matthies et M. Samii, DIRECT BRAIN-STEM RECORDING OF AUDITORY-EVOKED POTENTIALS DURING VESTIBULAR SCHWANNOMA RESECTION - NUCLEAR BAEP RECORDING - TECHNICAL NOTE AND PRELIMINARY-RESULTS, Journal of neurosurgery, 86(6), 1997, pp. 1057-1062
The usefulness of intraoperative monitoring in cerebellopontine angle
surgery should be improved by obtaining faster and stronger brainstem
auditory evoked potential (BAEP) responses. A new technique of direct
recording at thee brainstem has been developed, which is applicable to
all tumor sizes. By placing a retractor with electrodes attached to i
ts tip at the cerebellomedullary junction, the authors have recorded B
AEP amplitudes that are 10 times greater than those recorded using the
conventional technique. Only small sampling numbers (64-256 recording
s) are required and are obtained in 5 to 15 seconds. The technique has
been applied successfully in 34 patients who underwent vestibular sch
wannoma resections. It has also been tested in patients with intrameat
al-extrameatal meningiomas and in those with vascular compressive diso
rders; there have been no false results. The advantages of this new te
chnique are: 1) identification of BAEP components is easier and faster
; 2) reliable BAEP responses are obtained in some cases in which conve
ntional BAEP responses are lost or severely deformed; and 3) BAEP resp
onse deterioration and improvement are recognized earlier than would o
ccur using the conventional technique. This last advantage provides th
e surgeon with a useful warning at a stage of surgery at which BAEP ch
anges are still temporary and can be reversed. This method is differen
t from other trials of intradural BAEP recordings in three respects: i
ts use is not limited to particular tumor sizes; there is no interfere
nce with the surgical process; and, most important, the obtained respo
nses correlate well with those of conventional BAEP responses, probabl
y because the recording site is in the vicinity of the anterior cochle
ar nucleus. In conclusion, the chances of useful monitoring feedback w
ith adequate adaptation of the microsurgical strategy are improved con
siderably.