Anatomical variants of dorsal scapular nerve in relation to the middle scalene muscle in Japanese population

Abstract

Dorsal scapular nerve (DSN) block is often performed in Japanese pain clinics to treat neck pain and katakori (a unique symptom in Japanese population characterized by myofascial pain syndromes such as shoulder girdle pain). However, to the best of our knowledge, there are only a few studies regarding anatomical variations in DSN paths around the middle scalene muscle (MSM) in Japanese population. Thus, we conducted a cadaveric study to examine anatomical variations in DSN paths around the MSM in Japanese population. DSN anatomies of 70 adult Japanese cadavers used for research and gross anatomy practice at the Tokai University School of Medicine between 2015 and 2016 were examined. In all cadavers, DSNs originated from the brachial plexus (BP) and innervated the rhomboid major, rhomboid minor, and levator scapulae muscles via the MSM. Two types of DSN paths were observed: piercing-type (piercing the MSM) and anterior-type (running in front of the MSM). We surveyed all 140 sides in 70 Japanese cadavers; of these, 95 sides had piercing-type and 45 had anterior-type paths. Of the 70 cadavers, 42 had piercing-type and 17 had anterior-type paths on both the sides. In 9 cadavers, the left and right sides had piercing-type and anterior-type paths, respectively. In the other 2 cadavers, the right and left sides had piercing-type and anterior-type paths, respectively. We found 2 distinct anatomical variants for DSN paths around the MSM in this Japanese cohort. Our results suggest that the rate of anterior-type DSN path is higher in Japanese population. Therefore, it is necessary to maintain caution while injecting anesthetic agents during a DSN block and the type of DSN should be considered.

Surgeon-performed pericapsular nerve group (PENG) block for total hip arthroplasty using the direct anterior approach: a cadaveric study

“…We attribute this interstudy discrepancy to natural anatomical variability coupled with the small sample sizes (n=18 and n=13 specimens). However, we cannot rule out ethnic differences in neural topography13 since our population consisted exclusively of a South East Asian sample whereas Short et al ,5 who carried out their investigation in Toronto (Canada), presumably included more Caucasian subjects. However, irrespective of the relative contributions of high versus low articular branches, PENG blocks constitute a viable analgesic strategy for THA because they reliably anaesthetise all articular branches derived from the femoral nerve.…”

Topographic and morphometric anatomy of the proximal part of the dorsal scapular nerve

“…One of the methods frequently used for the relief of symptoms of DSN neuropathy is nerve blocks (Saporito, 2013). It has been reported that during middle scalene muscle block, the DSN may be damaged if it travels anterior to the muscle, because it remains more superficial (Tetsu et al, 2018). It has also been stated that there is a risk of DSN injury in interscalene nerve blocks (Kim et al, 2016).…”

“…According to classical anatomy knowledge, the DSN pierces the middle scalene muscle after its formation and runs in the posteroinferior direction (Moore et al, 2018;Moses et al, 2013;Schuenke et al, 2014;Standring, 2016;Tubbs et al, 2015). However, in the literature, variations have also been reported in terms of its relationship with scalene muscles (Lee et al, 1992;Nguyen et al, 2016Nguyen et al, , 2017Tetsu et al, 2018;Williams & Smith, 2020).…”