Dorsal scapular nerve injury: a complication of ultrasound-guided interscalene block

Abstract

Editor'In-plane ultrasound guidance is often used for interscalene block. This approach shifts the traditional needle insertion point of the Winnie's approach, that is, in the groove between the anterior and the middle scalene muscles,1Winnie AP Interscalene brachial plexus block.Anesth Analg. 1970; 49: 455-466doi:10.1213/00000539-197005000-00029Crossref PubMed Scopus (414) Google Scholar to a more distal (either medial or lateral and caudal) puncture site.2Mariano ER Loland VJ Ilfeld BM Interscalene perineural catheter placement using an ultrasound-guided posterior approach.Reg Anesth Pain Med. 2009; 34: 60-63doi:10.1097/AAP.0b013e3181933af7Crossref PubMed Scopus (51) Google Scholar The increased risk of both vascular and phrenic nerve lesions, carried by the medial to lateral approach,3Kessler J Schafhalter-Zoppoth I Gray AT An ultrasound study of the phrenic nerve in the posterior cervical triangle: implications for the interscalene brachial plexus block.Reg Anesth Pain Med. 2008; 33: 545-550PubMed Google Scholar often makes anaesthetists to choose a lateral to medial needle direction to reach the brachial plexus in the interscalene groove through the middle scalene muscle. However, this approach increases the theoretical risk of damage to other branches of brachial plexus, namely the long thoracic and the dorsal scapular nerves (DSN), which run inside or in close proximity to the middle scalene muscle.4Hanson NA Auyong DB Systematic ultrasound identification of the dorsal scapular and long thoracic nerves during interscalene block.Reg Anesth Pain Med. 2013; 38: 54-57doi:10.1097/AAP.0b013e31826f0a63Crossref PubMed Scopus (40) Google Scholar DSN originates from the fifth cervical nerve root, with a possible contribution of C6 and after its origin runs in close proximity of the upper trunk of the brachial plexus, before piercing the middle scalene muscle and passing posteriorly, beneath the levator scapula muscle. It is responsible for the motor innervation of the levator scapula muscle itself, which elevates the scapula, and of both the rhomboid major and minor muscles, which pull the scapula medially.5Tubbs RS Tyler-Kabara EC Aikens AC et al.Surgical anatomy of the dorsal scapular nerve.J Nerurosurg. 2005; 102: 910-911doi:10.3171/jns.2005.102.5.0910Crossref PubMed Scopus (39) Google Scholar DSN injuries can be the origin of a well-defined chronic pain syndrome, often referred to as DSN syndrome. DSN syndrome is often characterized by a dull ache along the medial border of the scapula, eventually radiating to the lateral surface of the arm and forearm. Patients usually complain of a not well-defined shoulder pain and dysfunction, with different degrees of functional impairment. Weakness and hypotrophy of the rhomboid, the levator scapulae muscles, or both can be present as well. The long thoracic nerve (LTN) runs within or next to the middle scalene muscle, often in close proximity of the DSN and thus can be injured by the same mechanisms during performance of an in-plane ultrasound-guided interscalene block. A lesion of the LTN often results in a chronic pain syndrome of the shoulder, with associated different degree of serratus anterior muscle palsy, determining impairment of shoulder elevation and a characteristic scapular winging with medial translation and rotation of the inferior angle towards the midline.6Wiater JM Flatow EL Long thoracic nerve injury.Clin Orthop Relat Res. 1999; 368: 17-27Crossref PubMed Google Scholar Both DSN syndrome and LTN syndrome symptoms are not specific and the often poorly defined pain characteristics and extension are the cause of frequent misdiagnoses, being confused with other shoulder chronic pain syndromes. DSN lesions have been described in the context of trauma to the brachial plexus or entrapment syndromes, in which they are a relatively common cause of shoulder dysfunction.7Sultan HE Younis El-Tantawi GA Role of dorsal scapular nerve entrapment in unilateral interscapular pain.Arch Phys Med Rehabil. 2013; 94: 1118-1125Abstract Full Text Full Text PDF PubMed Scopus (29) Google Scholar 8Jerosch J Castro WH Geske B Damage of the long thoracic and dorsal scapular nerve after traumatic shoulder dislocation: case report and review of the literature.Acta Orthop Belg. 1990; 56: 625-627PubMed Google Scholar However, may be because of difficulty in diagnosing if not specifically searched for, DSN injuries have never been described as a direct complication of an ultrasound-guided interscalene block. In this context, a lesion, likely due either to direct needle trauma or to intraneural injection, seems to be not only possible, but also likely relatively frequent (even if not reported), if DSN and LTN are not preliminary systematically identified, in order to choose the safest needle trajectory. Hanson and Auyong4Hanson NA Auyong DB Systematic ultrasound identification of the dorsal scapular and long thoracic nerves during interscalene block.Reg Anesth Pain Med. 2013; 38: 54-57doi:10.1097/AAP.0b013e31826f0a63Crossref PubMed Scopus (40) Google Scholar demonstrated that DSN and LTN can be identified by ultrasound in the majority of patients (Fig. 1). We encourage this practice in all patients undergoing an ultrasound-guided interscalene block. None declared. Download .zip (.0 MB) Help with zip files