Artikel
Transcranial glossopharyngeal and hypoglossal nerve motor-evoked potential (TES-MEPs) in CPA surgery: a prospective study to determine the normative data
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Autoren
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Giulia Del Moro
- Department of Neurosurgery, Eberhard Karls University, Tübingen, Germany; Department of Neurosurgery, Università degli Studi di Padova, Padova, Italy
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Marina Liebsch
- Department of Neurosurgery, Eberhard Karls University, Tübingen, Germany
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Anja Kurio
- Department of Neurosurgery, Eberhard Karls University, Tübingen, Germany
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Karlheinz G. Decker
- Department of Neurosurgery, Eberhard Karls University, Tübingen, Germany
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Marcos S. Tatagiba
- Department of Neurosurgery, Eberhard Karls University, Tübingen, Germany
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Florian H. Ebner
- Department of Neurosurgery, Eberhard Karls University, Tübingen, Germany
| Veröffentlicht: | 2. Juni 2015 |
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Gliederung
Text
Objective: Intraoperative lower cranial nerves motor evoked potentials (LCN-MEPs), obtained by transcranial electrical stimulation (TES) surpass most of the disadvantages of standard IOM techniques. Despite their use has already been reported, normal wave latency and amplitude data are lacking.
This study was conducted to investigate the reliability and normative latency and amplitude range of pharyngeal and tongue motor evoked potentials for IX and XII nerve function monitoring during cerebellopontine angle (CPA) surgeries.
Method: LCN-MEPs were prospectively recorded in 26 patients undergoing CPA surgeries for pathologies not involving the IX and XII cranial nerves.
TES was performed using corkscrew electrodes positioned at hemispheric montage (C3/C4 and CZ). Stimulation was always applied contralaterally to the mointored side using 1 or 5 rectangular pulses ranging from 120 to 300 V with 50 micros of pulse duration and an interstimulus interval of 2 ms. IX and XII nerves potentials were recorded from needles placed in the stylopharyngeus and intrinsic tongue muscles respectively.
Results: Glossopharyngeal nerve mean latency was of 17.3 ms (+ 2.88) with 50.5 microV (+ 43.7) of mean amplitude 50.5, while hypoglossal nerve mean latency was 14.4 ms (+ 1.80) and mean amplitude was 275 microV (+ 253).
Latencies revealed to be stabile and not voltage depending, with a variation <11% for XII e <14% for IX. Conversely amplitudes showed a high interindividual and voltage variability.
Between the end and begin of surgery in 3 cases we observed a reduction of the XII nerve amplitude >30% with an equivalent reduction in hand MEPs (31%, 45%, 49%) without any post-operative motor deficit.
IX-MEPs reduction >30% (37%, 38%, 50%) was observed in 3 other cases accompanied by a smaller hand-MEP amplitude reduction (12%, 0%, 26% respectively). None of these patients experienced any post-operative deficit
Conclusions: Glossopharyngeal and hypoglossal MEPs obtained with TES are reliable with constant latencies that remain stable during surgery. Inter-individual amplitude variability is high and voltage depending, as expected. During a surgical procedure not involving the LCN, a healthy IX or XII nerve can reduce ist amplitude up to 50% without any post-operative deficit. The ratio with hand-MEPs might be a useful tool in order to discriminate physiological from pathological reductions. Further refinements of this technique are necessary to minimize artifacts and to improve IX nerve monitoring stability.
