Article
Continuous monitoring of corticobulbar motor evoked potentials during skull base and brainstem surgery in a cohort of 35 patients
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Authors
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K. Seidel
- Universitätsklinik für Neurochirurgie, Inselspital Bern, Schweiz
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J. Beck
- Universitätsklinik für Neurochirurgie, Inselspital Bern, Schweiz
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L. Stieglitz
- Universitätsklinik für Neurochirurgie, Inselspital Bern, Schweiz
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P. Schucht
- Universitätsklinik für Neurochirurgie, Inselspital Bern, Schweiz
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A. Raabe
- Universitätsklinik für Neurochirurgie, Inselspital Bern, Schweiz
| Published: | June 4, 2012 |
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Outline
Text
Objective: To optimize cranial nerve (CN) monitoring recording of corticobulbar motor evoked potentials (MEP) of the facial and the vagal nerve have been described recently. As conventional mapping techniques can only been applied intermittently, methods for continuous monitoring of the functional integrity of the upper and lower motor neuron for all motor CN are needed.
Methods: A consecutive series of 35 patients who underwent skull base or brainstem surgery in our department from May 2009 to February 2011 was stratified in three different groups (G): G1= acoustic neuromas (n = 13), G2= meningioma of the skull base (n = 7) and G3=other tumors in or close to the brainstem (n = 15). The following motor CN were continuously monitored by transcranial electrical stimulation (TES): CN III (n = 4), CN V (n = 27), CN VI (n = 8), CN VII (n = 34), CN IX (n = 16), CN X (n = 13), CN XI (n = 8) and CN XII (n = 12). TES was performed with a train of five anodic stimuli, pulse duration of 0.5 ms within one pulse and an interstimulus interval of 4.0 ms. With an intertrain interval of 90 ms after this first train, a single pulse was delivered called double stimulation technique. A single pulse which already elicited a motor response was considered as a peripheral response which activated the CN directly and thus this response was not used for further monitoring.
Results: In 26 out of 35 patients (74%) corticobulbar tract (CBT) monitoring was obtained with a high reproducibility. In 6 patients (17%) monitoring of corticobulbar MEP had slight restrictions due to small MEP amplitude or high stimulation intensity. In 3 patients (9%) no continuous corticobulbar MEP could be obtained at baseline due to direct CN activation. Continuous reliable IOM was possible in the following percentage: CN III 75%, CN V 70%, CN VI 50%, CN VII 88%, CN IX 75%, CN X 85%, CN XI 75% and CN XII 83%. Postoperatively 6 out of 35 patients (17%) developed a new minor motor CN impairment. The affected nerves were CN V, CN VI (2 cases) and CN VII (3 cases). 4 of these 6 patients recovered to preoperative CN motor function in the 6 month follow-up visit.
Conclusions: Double stimulation technique provides continuous online assessment of the CBT, the motor CN nuclei and the peripheral CNs in many cases. This method may increase safety of brainstem and cranial base surgery.
References
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