title: Risk of Encountering Dorsal Scapular and Long Thoracic Nerves during Ultrasound-guided Interscalene Brachial Plexus Block with Nerve Stimulator.
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.
authors.affiliation: Department of Anesthesiology and Pain Medicine, Wonkwang University College of Medicine, Wonkwang Institute of Science, Iksan, Korea.
authors.forename: Yeon Dong
authors.initials: YD
authors.lastname: Kim
authors.affiliation: Department of Anesthesiology and Pain Medicine, Presbyterian Medical Center, University of Seonam College of Medicine, Jeonju, Korea.
authors.forename: Jae Yong
authors.initials: JY
authors.lastname: Yu
authors.affiliation: Department of Anesthesiology and Pain Medicine, Presbyterian Medical Center, University of Seonam College of Medicine, Jeonju, Korea.
authors.forename: Junho
authors.initials: J
authors.lastname: Shim
authors.affiliation: Department of Anesthesiology and Pain Medicine, Presbyterian Medical Center, University of Seonam College of Medicine, Jeonju, Korea.
authors.forename: Hyun Joo
authors.initials: HJ
authors.lastname: Heo
authors.affiliation: Department of Anesthesiology and Pain Medicine, Presbyterian Medical Center, University of Seonam College of Medicine, Jeonju, Korea.
authors.forename: Hyungtae
authors.initials: H
authors.lastname: Kim
keywords: Brachial plexus block; Dorsal scapular nerve; Interscalene brachial plexus block; Long thoracic nerve; Nerve injury; Nerve stimulation; Regional anesthesia; Ultrasound