engleski

Intramedullar stimulation of the facial and hypoglossal nerves: recording technique and estimation of the stimulated site

The facial and hypoglossal nerves were electrically stimulated at the facial colliculus and the hypoglossal triangle in 22 patients with intrinsic pontine or medullary tumors after fourth ventricle exposure. Needle EMG responses were recorded in the orbicularis oculi and orbicularis oris muscles, and the genioglossal muscles. Patients with medullary tumors (n=13) had no preoperative deficit of the facial nerve and in aptients with pontine tumors (n=9) the hypoglossal nerve was not affected. For normal facial nerve EMG mean latencies were for the orbicularis oculi 5.2+0.62 ms and for orbicularis oris 5.2+0.52 ms. For normal hypoglossal nerve EMG mean latency for the genioglossal muscle was 4.1+0.58 ms. By stimulating 18 possibly affected facial nerves EMG mean latencies were for orbicularis oculi 5.3+0.35 ms, and for orbicularis oris 5.4+0.16 ms, significantly not longer than normal facial nerve EMG latencies. By stimulating 26 possibly affected hypoglossal nerves EMG mean latency for the genioglossal muscle was 5.3+0.35 ms. We found a significant difference (P<0.05) in latency for genioglossal EMG responses between the two groups of patients. This may be due to the fact that medullary tumors have more tendency to grow exophytically and compress the lower cranial motor nuclei.

facial nerve; hypoglossal nerve

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