Spinal Accessory Nerve: Ultrasound Findings and Correlations with Neck Lymph Node Levels

Abstract

Purpose: To evaluate the ultrasound characteristics of the spinal accessory nerve (SAN) and correlate nerve location with neck lymph node level.

Materials and Methods: 50 participants with 100 SANs were enrolled in this study. The SAN was traced from the trapezius muscle to the upper neck and was identified by a hypoechoic linear structure without color Doppler flow. The ultrasound characteristics of the SAN, such as visibility, diameter, relationship with adjacent structures, and its correlation with lymph node levels, were evaluated.

Results: The SAN was identified in 96 %-100 % of segments. The mean diameter of the SAN was 0.54 ± 0.09 mm. The SANs was located between the trapezius and levator scapulae muscles and 90.8 % were traced into the trapezius muscle. In the upper neck, the SAN passed deep into the sternocleidomastoid (SCM) muscle in 38 % of cases and between the two heads of the SCM muscle in 62 % of cases. The SAN was found at neck lymph node levels II, III, IV, and V, but not I or VI.

Conclusion: Continuous ultrasound monitoring of the SAN and its correlation with lymph node levels is possible in most patients. Our current findings may assist in the future prevention of SAN injury during ultrasound-guided procedures.

Zusammenfassung

Ziel: Bewertung der sonografischen Charakteristika des Nervus accessorius (SAN) und die Korrelation zwischen der Lage des Nervs und der Ebene der Halslymphknoten.

Material und Methoden: In diese Studie wurden fünfzig Teilnehmer mit 100 SANs aufgenommen. Der SAN wurde vom Musculus trapezius bis zum oberen Hals ausfindig gemacht und als echoarme lineare Struktur ohne Farbdopplerfluss identifiziert. Die Ultraschalleigenschaften des SAN wie Sichtbarkeit, Durchmesser, Beziehung zu den umgebenden Strukturen und dessen Beziehung mit der Ebene der Lymphknoten wurde bewertet.

Ergebnisse: Der SAN wurde in 96 – 100 % der Segmente nachgewiesen. Der mittlere Durchmesser des SAN betrug 0,54 ± 0,09 mm. Die SAN befanden sich zwischen dem M. trapezius und dem M. levator scapulae und 90,8 % wurden im M. trapezius ausfindig gemacht. Im oberen Hals verlief in 38 % der Fälle der SAN tief in den M. sternocleidomastoideus (SCM) hinein und bei 62 % zwischen den beiden Köpfen des SCM. Der SAN wurde bei den Halslymphknoten II, III, IV und V, jedoch nicht bei I oder VI entdeckt.

Schlussfolgerung: Eine fortlaufende sonografische Überwachung des SAN und dessen Beziehung zur Ebene der Halslymphknoten ist bei den meisten Patienten möglich. Unsere aktuellen Befunde könnten dazu beitragen, Verletzungen des SAN bei ultraschallgestützten Prozessen in Zukunft zu verhindern.

Key words

ultrasound - anatomy - thyroid

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