Non-Traumatic Elevation Techniques of the Hypoglossal Nerve during Carotid Endarterectomy: A Cadaveric Study

Abstract

Objective: Ligation and dissection techniques of sternocleidomastoid artery, vein, ansa cervicalis and posterior belly of digastric muscle were developed in a cadaveric study for achieving minimally invasive elevation of the hypoglossal nerve during carotid endarterectomy and were subsequently used in patient treatment. Methods: Carotid bifurcations, the extracranial part of the hypoglossal nerve, the sternocleidomastoid artery and vein and neighboring neurovascular structures were studied on 10 formalin-fixed adult cadaver heads (20 sides) under the surgical microscope. Landmarks and measurements for identification of the sternocleidomastoid artery and vein are described. Results: The distance between the hypoglossal loop and the carotid bifurcation was measured as 14.5 - 25.2 mm (mean: 19.24 mm). 30 % of 20 sides were determined to have a Zone II-type carotid bifurcation. In 33 % of the Zone-II-type bifurcations, a low-lying hypoglossal loop was demonstrated. The sternocleidomastoid artery begins 2.2 - 3.5 mm (mean: 2.94 mm) supero-posterior from the occipital artery after the crossing point between the occipital artery and the hypoglossal nerve. The sternocleidomastoid artery and vein complex was 17.1 - 21.5 mm (mean 18.47 mm) away from the carotid bifurcation and forms a right angle with the descending hypoglossal nerve. The contribution of the sternocleidomastoid branch of the occipital artery always reaches the middle parts of the sternocleidomastoid muscle. Conclusion: Carotid endarterectomy through having knowledge of the normal and variable trajectories of the structures can almost always be accomplished as a safe procedure when appropriate maneuvers are applied. Dissection and ligation of the sternocleidomastoid artery, vein, ansa cervicalis and posterior belly of digastric muscle are very simple but effective techniques to obtain adequate exposure either for safe arterial reconstruction or to diminish the necessity for more complicated technical procedures.

Key words

Hypoglossal nerve - sternocleidomastoid artery - sternocleidomastoid vein - microsurgical anatomy - carotid endarterectomy - high bifurcation

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