Artikel
Electrooculography with adhesive surface electrodes for localizing cranial nerves III, IV and VI during skull-base surgery
Elektrookulographie durch Oberflächenelektroden zur intraoperativen Auffindung der Hirnnerven III, IV und VI bei Schädelbasiseingriffen
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Veröffentlicht: | 30. Mai 2008 |
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Objective: Monitoring of cranial nerves III, IV and VI during skull-base surgery has until now been carried out with electromyography. Because of the invasive character of electrode placement and methodical uncertainties, this technique is not commonly used. We investigated the use of adhesive surface electrodes for electrooculography (EOG) in order to localize and monitor the cranial nerves III, IV and VI.
Methods: Patients undergoing skull-base surgery were monitored by EOG using three surface electrodes adjacent to each eye at fixed locations (below and above the pupil, upper left corner of the eye on the left eye, lower right corner of the eye on the right eye). During the operation, the oculomotor nerves were localized anatomically and stimulated using a bipolar electrode with a 200 µs square-pulse at an amperage of 0.1 to 1.0 mA. Reactions of the external eye muscles were detected by monitoring directional fluctuations of the orbital dipole, which were triggered by stimulation.
Results: 10 patients have been investigated so far (5x N III, 2x NIV, 3x NIV). Stimulation of cranial nerves III and VI elicited a change in EOG in all cases, indicating a clear response. Direction of EOG changes and latency between stimulation and answer corresponded to the expected values. During stimulation of N. IV clear changes in EOG could only be detected in one out of three patients. For control purposes, stimulations were also performed in adjacent structures (skull base/ dura mater) without eliciting any detectable reactions.
Conclusions: EOG using non-invasive surface electrodes is a safe and simple technique for localizing cranial nerves III and VI, with limited use for detecting NIV during skull base surgery. Further study will elucidate, whether prolongations in latency can predict imminent nerve damage or whether surgical manipulations of the oculomotor nerves elicit eye movements, as detected by EOG.