Artikel
Clinical experience in intraoperative monitoring of cranial nerves III and VI
Intraoperatives Monitoring der Hirnnerven III und VI: klinische Erfahrungen
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Autoren
Veröffentlicht: | 4. Mai 2005 |
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Gliederung
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Objective
While monitoring of the facial nerve and others is widely implemented in neurosurgical units, there is still little experience with intra-operative EMG of the oculomotor nerves. The purpose of this clinical study was to assess the reliability and reproducibility of the technique in a variety of pathologies. Special attention was paid to the abducens nerve (CN VI).
Methods
CN VI was monitored in 43 patients with lesions in the posterior fossa and 6 patients with lesions involving the cavernous sinus. Bipolar needle electrodes were inserted close to the lateral rectus muscle along the lateral orbital wall. 18 patients received an electrode placed into proximity of the superior rectus muscle for recording of CN III. In all patients nerve function was monitored with continuous free-running EMG. Direct bipolar stimulation was performed in 14 patients for CN VI, in 4 patients for CN III, respectively. Stimulus parameters varied from 0.08-0.3mA and 3 to 30 Hz.
Results
Of 9 patients who presented with oculomotor or abducent palsy preoperatively, 5 worsened after surgery. 40 patients were asymptomatic in this regard. 26 of them remained unchanged while 14 patients developed new cranial nerve palsy postoperatively. In 2 patients CN VI could not be preserved. Increased EMG activity was observed in 9 (47%) of the 19 patients with a deterioration in nerve function, but also in 15 (50%) of the 30 patients without change in nerve function. In 13 (72%) of 18 cases direct electrical stimulation yielded clear stimulus-related changes in the EMG.
Conclusions
Intraoperative monitoring of the oculomotor nerves is useful for anatomical localization of the oculomotor and abducens nerve. In addition, direct electrical stimulation in the proximity of the nerves may be helpful to identify the nerves earlier. The prognostic value of the observed changes, however, is still controversial.