Korean J Pain.  2016 Jul;29(3):179-184. 10.3344/kjp.2016.29.3.179.

Risk of Encountering Dorsal Scapular and Long Thoracic Nerves during Ultrasound-guided Interscalene Brachial Plexus Block with Nerve Stimulator

• Kim YD
• Yu JY
• Shim J
• Heo HJ
• Kim H

• KMID: 2327639
• DOI: http://doi.org/10.3344/kjp.2016.29.3.179

Abstract

BACKGROUND
Recently, ultrasound has been commonly used. Ultrasound-guided interscalene brachial plexus block (IBPB) by posterior approach is more commonly used because anterior approach has been reported to have the risk of phrenic nerve injury. However, posterior approach also has the risk of causing nerve injury because there are risks of encountering dorsal scapular nerve (DSN) and long thoracic nerve (LTN). Therefore, the aim of this study was to evaluate the risk of encountering DSN and LTN during ultrasound-guided IBPB by posterior approach.
METHODS
A total of 70 patients who were scheduled for shoulder surgery were enrolled in this study. After deciding insertion site with ultrasound, awake ultrasound-guided IBPB with nerve stimulator by posterior approach was performed. Incidence of muscle twitches (rhomboids, levator scapulae, and serratus anterior muscles) and current intensity immediately before muscle twitches disappeared were recorded.
RESULTS
Of the total 70 cases, DSN was encountered in 44 cases (62.8%) and LTN was encountered in 15 cases (21.4%). Both nerves were encountered in 10 cases (14.3%). Neither was encountered in 21 cases (30.4%). The average current measured immediately before the disappearance of muscle twitches was 0.44 mA and 0.50 mA at DSN and LTN, respectively.
CONCLUSIONS
Physicians should be cautious on the risk of injury related to the anatomical structures of nerves, including DSN and LTN, during ultrasound-guided IBPB by posterior approach. Nerve stimulator could be another option for a safer intervention. Moreover, if there is a motor response, it is recommended to select another way to secure better safety.

Keyword

Brachial plexus block; Dorsal scapular nerve; Interscalene brachial plexus block; Long thoracic nerve; Nerve stimulation; Nerve injury; Regional anesthesia; Ultrasound

MeSH Terms

Anesthesia, Conduction
Brachial Plexus Block*
Brachial Plexus*
Humans
Incidence
Phrenic Nerve
Shoulder
Superficial Back Muscles
Thoracic Nerves*
Ultrasonography

Figure

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  Fig. 1 Ultrasound image of the site of interscalene brachial plexus block. CA: carotid artery, VA: vertebral artery, AS: anterior scalene muscle, MS: middle scalene muscle, C5: 5th cervical root, C6: 6th cervical root, C7: 7th cervical root.

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  Fig. 2 Risk of encountering dorsal scapular nerve and long thoracic nerve.

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  Fig. 3 Ultrasound image of dorsal scapular nerve. It derives from C5 nerve root. AS: anterior scalene muscle, MS: middle scalene muscle, Red circle: dorsal scapular nerve, C6: 6th cervical root.

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  Fig. 4 Ultrasound image of long thoracic nerve. It arises from the anterior branches of the 6th cervical nerve root. AS: anterior scalene muscle, MS: middle scalene muscle, Red circle: long thoracic nerve, C7: 7th cervical root.

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  Fig. 5 Ultrasound image of dual-guided interscalene brachial plexus block (A) and just cephalad image of A (B). Dorsal scapular nerve and long thoracic nerve are not seen (A). Dorsal scapular nerve is seen. It already passed and went to the cephalad direction of needle path (B). BP: brachial plexus, MS: middle scalene muscle, Red circle: dorsal scapular nerve, Arrow: needle.

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  Fig. 6 Ultrasound image of dorsal scapular nerve and long thoracic nerve at the site of interscalene brachial plexus block. Dorsal scapular nerve and long thoracic nerve are seen in the middle scalene muscle. AS: anterior scalene muscle, MS: middle scalene muscle, Red circle: dorsal scapular nerve, Green circle: long thoracic nerve, C5: 5th cervical root, C6: 6th cervical root, C7: 7th cervical root.

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