Impact of structural factors around the accessory nerve on the pathogenesis of essential neck and upper-back stiffness: a sonographic investigation

Shohei Shibasaki; Tomonori Kishino; Yoriko Sei; Keiichiro Harashima; Konomi Sakata; Hiroaki Ohnishi; Takashi Watanabe

doi:10.1111/cpf.12917

Impact of structural factors around the accessory nerve on the pathogenesis of essential neck and upper-back stiffness: a sonographic investigation

Clin Physiol Funct Imaging. 2024 Nov 19. doi: 10.1111/cpf.12917. Online ahead of print.

Authors

Shohei Shibasaki¹, Tomonori Kishino², Yoriko Sei¹, Keiichiro Harashima¹, Konomi Sakata², Hiroaki Ohnishi³, Takashi Watanabe⁴

Affiliations

¹ Department of Medical Technology, Kyorin University Faculty of Health Sciences, Tokyo, Japan.
² Department of Clinical Engineering, Kyorin University Faculty of Health Sciences, Tokyo, Japan.
³ Department of Laboratory Medicine, Kyorin University Faculty of Medicine, Tokyo, Japan.
⁴ President, Kyorin University, Tokyo, Japan.

PMID: 39562318
DOI: 10.1111/cpf.12917

Abstract

Introduction: Neck and upper-back stiffness involves discomfort/ache in the trapezius muscle (TM). The pathogenesis of 'essential neck and upper-back stiffness' without obvious causes remains uncertain. In symptomatic subjects, TM hardness correlates with decreased transverse cervical artery (TCA) blood flow to the TM. Neck and upper-back stiffness could be associated with both hemodynamic and neurological factors affecting the TM. We therefore sonographically evaluated structural factors around the accessory nerve innervating the TM impacting neck and upper-back stiffness.

Methods: Participants comprised 69 healthy young adults (33 men, 36 women; 21 ± 1 y) who completed questionnaires and underwent elastography to determine TM hardness as a strain ratio and pulsed Doppler sonography to determine TCA hemodynamics. Intermuscular length was measured as the distance between sternocleidomastoid and levator scapulae muscles around the accessory nerve. Relationships of intermuscular length with symptoms, TM hardness, and TCA hemodynamics were analyzed.

Results: Intermuscular length was greater in symptomatic subjects (median 2.3 mm, interquartile range 1.5-3.1 mm) than in asymptomatic subjects (median 1.8 mm, interquartile range 1.5-2.3 mm; p = 0.032). Intermuscular length correlated positively with symptom severity (r = 0.43, p = 0.014) and negatively with strain ratio for the TM (r = -0.39, p = 0.025) and peak systolic velocity in the TCA (r = -0.40, p = 0.022). Intermuscular length contributed independently to the presence of symptoms (p = 0.025, odds ratio 2.26, 95% confidence interval 1.11-4.62).

Conclusion: In symptomatic subjects, symptom severity, TM hardness and TCA hemodynamics all correlated with greater intermuscular length. Structures around the accessory nerve could be associated with the pathogenesis of essential neck and upper-back stiffness.

Keywords: accessory nerve; neck and upper‐back stiffness; sonography; transverse cervical artery; trapezius muscle.

Abstract

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