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Cervical Plexus Block Review Article pISSN 2005-6419 • eISSN 2005-7563 KJA Cervical plexus block Korean Journal of Anesthesiology Jin-Soo Kim1, Justin Sangwook Ko2, Seunguk Bang3, Hyungtae Kim4, and Sook Young Lee1 Department of Anesthesiology and Pain Medicine, 1Ajou University College of Medicine, Suwon, 2Samsung Medical Center, Sungkyunkwan University College of Medicine, 3Daejeon St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, 4Presbyterian Medical Center, Jeonju, Korea Cervical plexus blocks (CPBs) have been used in various head and neck surgeries to provide adequate anesthesia and/ or analgesia; however, the block is performed in a narrow space in the region of the neck that contains many sensitive structures, multiple fascial layers, and complicated innervation. Since the intermediate CPB was introduced in addition to superficial and deep CPBs in 2004, there has been some confusion regarding the nomenclature and definition of CPBs, particularly the intermediate CPB. Additionally, as the role of ultrasound in the head and neck region has expanded, CPBs can be performed more safely and accurately under ultrasound guidance. In this review, the authors will describe the methods, including ultrasound-guided techniques, and clinical applications of conventional deep and superficial CPBs; in addition, the authors will discuss the controversial issues regarding intermediate CPBs, including nomenclature and associated potential adverse effects that may often be neglected, focusing on the anatomy of the cervical fascial layers and cervical plexus. Finally, the authors will attempt to refine the classification of CPB methods based on the target com- partments, which can be easily identified under ultrasound guidance, with consideration of the effects of each method of CPB. Keywords: Airway obstruction; Cervical fascia; Cervical plexus; Cervical plexus block; Phrenic nerve palsy; Ultrasonog- raphy. Introduction (CEA) [8–12]. Traditionally, CPBs were classified as deep or su- perficial [13], but in 2004, Telford and Stoneham [14] suggested The cervical plexus block (CPB) provides effective anesthe- the intermediate CPB involving a sub-investing fascial injection sia and analgesia for the head and neck region [1–7]; the most in addition to the superficial and deep CPBs on the basis of the common clinical use for CPBs has been carotid endarterectomy cadaveric study by Pandit et al. [15]. In 2010, Choquet et al. [16] attempted to refine the concept of intermediate CPBs using ul- trasound technique. Nevertheless, “superficial,” “intermediate,” Corresponding author: Jin-Soo Kim, M.D., Ph.D. and “deep” are poorly defined anatomical terms that simply Department of Anesthesiology and Pain Medicine, Ajou University indicate the topographic relationship of the tissue with respect College of Medicine, 206, Worldcup-ro, Yeongtong-gu, Suwon 16499, to the skin; therefore, there has been some confusion in the no- Korea menclature and definition of CPBs, particularly the intermediate Tel: 82-31-219-5748, Fax: 82-31-219-5579 Email: [email protected] CPB. ORCID: https://orcid.org/0000-0003-4121-2475 Since the role of ultrasound in the head and neck region has expanded, CPBs can be performed more safely and accurately Received: 29 May 2018. Revised: 19 June 2018. under ultrasound guidance, which is used to easily identify var- Accepted: 24 June 2018. ious important landmarks including muscles, cervical vertebrae, large vessels, nerves, and the cervical fascia [17]. Particularly, Korean J Anesthesiol 2018 August 71(4): 274-288 understanding the detailed configuration of the cervical fasciae https://doi.org/10.4097/kja.d.18.00143 CC This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/ licenses/by-nc/4.0/), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Copyright ⓒ The Korean Society of Anesthesiologists, 2018 Online access in http://ekja.org KOREAN J ANESTHESIOL Kim et al. is essential to a successful CPB because certain cervical fasciae has been suggested to reduce confusion with the superficial lay- are known to have a substantial role in the diffusion of local an- er of the deep cervical fascia [36]. The deep cervical fascia can esthetic solution [15,18–20]. Nonetheless, the structural char- be divided into three layers [35]: (a) the superficial layer, which acteristics of the cervical fasciae have not been fully investigated was also called the investing fascia but is now referred to as the from the perspective of regional anesthesia. Furthermore, there masticator fascia, submandibular fascia, or sternocleidomastoid has been a disagreement with regard to accurate identification of (SCM)-trapezius fascia, although it has been argued that the the deep cervical fascia, especially in the lateral cervical region SCM-trapezius fascia is incomplete between the SCM and trape- [21–24], and anatomical variations also exist [20,25]. zius muscles [21,22]; (b) the middle layer, which is suggested as Accordingly, this review first describes the anatomy of the to be named as strap muscle fascia or visceral fascia; and (c) the cervical fascial layers and cervical plexus, then the methods for deep layer, which is suggested to be named as the perivertebral performing CPBs including ultrasound techniques, and then the fascia instead of the prevertebral fascia because the term “pre- effects of conventional deep and superficial CPBs and the rela- vertebral fascia” should be used for the anterior part only. The tively new but controversial intermediate CPB. Moreover, this carotid space, containing major vessels, the deep cervical lymph review will discuss potential adverse effects related to CPBs that nodes, and nerves, is a very important structure that can be af- may often be neglected, and finally, attempt to refine the clas- fected during a CPB, and this space is usually referred to as the sification of CPB methods based on the target compartments “carotid sheath and its contents” [36]. According to the literature that can be easily identified under ultrasound guidance, with [37,38], the carotid sheath is a definite histological structure that consideration for the effects and potential adverse effects of each is distinct from other fascial layers, and the common carotid method of CPB. sheath shows inter-individual and/or site-dependent variations in thickness. However, there is disagreement about whether the Anatomy carotid sheath is formed by all three layers of deep cervical fas- cia, only the deep or superficial layer of the deep cervical fascia, Cervical fascia or has no demonstrable layer of fascia [36]. Palliyalil et al. [39] described that the carotid sheath is a strong fibroelastic tissue The study of cervical fascial layers is clinically important in barrier that shields its contents from saliva and local infection predicting the spread of disease [26–28], optimizing surgical after neck surgery, but local anesthetics seem to infiltrate the management [29], and performing regional anesthesia in the carotid sheath [40]. Fig. 1 shows a schematic drawing of the cer- neck area [15,18–20], and cervical fascial alteration may play a vical fasciae as Guidera et al. [35] suggested. significant role in the pathogenesis of chronic neck pain [30,31]. However, descriptions of fascial arrangements and definitions Cervical plexus of fascial spaces in the neck area are inconsistent and unclear, and the terminology is variable. According to the 41th edition of The cervical plexus is situated in a groove between the longus Gray’s Anatomy [32], the fascia is described as “sheaths, sheets capitis and the middle scalene muscles, underneath the preverte- or other masses of connective tissue large enough to be visible bral fascia but not in the interscalene groove, as the anterior sca- to the unaided eye,” and the Fascia Nomenclature Committee lene muscle is almost absent cranially proximal to the C4 or C3 of Fascia Research Congress describes it as “a sheath, a sheet, levels [42]. Two nerve loops, which are formed by the union of or any other dissectible aggregations of connective tissue that the adjacent anterior spinal nerves from C2 to C4, give off four forms beneath the skin to attach, enclose, and separate muscles superficial sensory branches, listed in cranio-caudal order as and other internal organs” [33]. Nonetheless, the structural clas- follows: lesser occipital (C2, C3), great auricular (C2, C3), trans- sification of cervical fasciae has been the subject of controversy verse cervical (C2, C3), and supraclavicular nerves (C3, C4); despite the use of more recent techniques and materials for pre- these initially run posteriorly and soon pierce the prevertebral serving and studying fascial structure. As Grodinsky and Holy- fascia. Afterwards, they pass through the interfascial space be- oke [34] described in their pioneering study based on cadaver tween the SCM and the prevertebral muscles before reaching the dissection in 1938, the inherent difficulties in dissecting cervical skin and superficial structures of the neck via the nerve point of fascial spaces and the obvious artificiality of grouping them may the SCM muscle [43,44]. Thus, superficial branches of the cervi- produce confusion in the description of cervical fasciae and dis- cal plexus travel a relatively long distance from the paravertebral crepancies among different authors. According to recent work space
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