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Inter- and intra-patient variability of facial nerve response areas in the floor of the 4th ventricle


Bertalanffy, H; Tissira, N; Krayenbühl, N; Bosinov, O; Sarnthein, J (2011). Inter- and intra-patient variability of facial nerve response areas in the floor of the 4th ventricle. Neurosurgery, 68(1):23-31.

Abstract

BACKGROUND: Surgical exposure of intrinsic brainstem lesions through the floor of the 4 ventricle requires precise identification of facial nerve (CN VII) fibers to avoid damage.

OBJECTIVE: To assess the shape, size, and variability of the area where the facial nerve can be stimulated electrophysiologically on the surface of the rhomboid fossa.

METHODS: Over a period of 18 months, 20 patients were operated on for various brainstem and/or cerebellar lesions. Facial nerve fibers were stimulated to yield compound muscle action potentials (CMAP) in the target muscles. Using the sites of CMAP yield a detailed functional map of the rhomboid fossa was constructed for each patient.

RESULTS: Lesions resected included 14 gliomas, 5 cavernomas, and 1 epidermoid cyst. Of 40 response areas mapped, 19 reached the median sulcus. The distance from the obex to the caudal border of the response area ranged from 8-27 mm (median 17 mm). The rostrocaudal length of the response area ranged from 2-15 mm (median 5 mm).

CONCLUSION: Facial nerve response areas showed large variability in size and position, even in patients with significant distance between the facial colliculus and underlying pathological lesion. Lesions located close to the facial colliculus markedly distorted the response area. This is the first documentation of variability in CN VII response area in the rhomboid fossa. Knowledge of this remarkable variability may facilitate the assessment of safe entry zones to the brainstem and may contribute to improved outcome following neurosurgical interventions within this sensitive area of the brain.

Abstract

BACKGROUND: Surgical exposure of intrinsic brainstem lesions through the floor of the 4 ventricle requires precise identification of facial nerve (CN VII) fibers to avoid damage.

OBJECTIVE: To assess the shape, size, and variability of the area where the facial nerve can be stimulated electrophysiologically on the surface of the rhomboid fossa.

METHODS: Over a period of 18 months, 20 patients were operated on for various brainstem and/or cerebellar lesions. Facial nerve fibers were stimulated to yield compound muscle action potentials (CMAP) in the target muscles. Using the sites of CMAP yield a detailed functional map of the rhomboid fossa was constructed for each patient.

RESULTS: Lesions resected included 14 gliomas, 5 cavernomas, and 1 epidermoid cyst. Of 40 response areas mapped, 19 reached the median sulcus. The distance from the obex to the caudal border of the response area ranged from 8-27 mm (median 17 mm). The rostrocaudal length of the response area ranged from 2-15 mm (median 5 mm).

CONCLUSION: Facial nerve response areas showed large variability in size and position, even in patients with significant distance between the facial colliculus and underlying pathological lesion. Lesions located close to the facial colliculus markedly distorted the response area. This is the first documentation of variability in CN VII response area in the rhomboid fossa. Knowledge of this remarkable variability may facilitate the assessment of safe entry zones to the brainstem and may contribute to improved outcome following neurosurgical interventions within this sensitive area of the brain.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > University Hospital Zurich > Clinic for Neurosurgery
Dewey Decimal Classification:610 Medicine & health
Language:English
Date:2011
Deposited On:27 Feb 2011 10:27
Last Modified:26 Jan 2017 08:49
Publisher:Lippincott Wiliams & Wilkins
ISSN:0148-396X
Additional Information:This is a non-final version of an article published in final form in Bertalanffy, H; Tissira, N; Krayenbühl, N; Bosinov, O; Sarnthein, J (2010). Inter- and intra-patient variability of facial nerve response areas in the floor of the 4th ventricle. Neurosurgery:Epub ahead of print
Publisher DOI:https://doi.org/10.1227/NEU.0b013e31820781fb
PubMed ID:21206320

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