Ultrasound-Guided Deep or Intermediate Cervical Plexus Block

Abstract

To the Editor On the basis of 28 cadaver dissections and injections in 2 volunteers, Usui et al.1 described an ultrasound-guided technique for blocking the deep cervical plexus and cervical sympathetic chain. Although we agree with the authors that these 2 neural structures, which are under the prevertebral fascia, may be theoretically both blocked with a single injection, we offer the following comments. First, the local anesthetic solution was deliberately injected into the longus capitis muscle of both volunteers. Intramuscular (IM) injections of local anesthetics may result in reversible myonecrosis and clinically relevant myopathy after nerve blocks of the neck and eye.2 Because the cervical sympathetic trunk is located posterior and lateral to the prevertebral fascia on the upper part of the longus colli muscle,3 a direct IM injection should be avoided, and a subfascial injection is recommended. Second, anatomical description and ultrasound image interpretations in their Figures 1 and 2 are quite confusing. In the schematic drawings, only the prevertebral layer (fascia) is drawn by the authors. On ultrasound images, the colored parts markedly overlap muscles and cover the connective tissue of the superficial cervical fascia, which is not drawn. In the posterolateral portion of the neck, this connective tissue is defined as the posterior cervical space.4 This space, deep to the sternocleidomastoid and trapezius muscles, and superficial to the prevertebral fascia, can be seen in their Figure 5. The posterior cervical space corresponds to the superficial cervical space described by Pandit et al.5 The superficial divisions of the cervical plexus cross this space, then cutaneous branches emerge from the posterior border of the sternocleidomastoid muscle. We suggest the technique promoting the lowest incidence of adverse events. The deep cervical plexus block can be difficult and risky because the needle is advanced to the spinal canal and vertebral artery. Pandit et al.5 reported the accuracy and safety of the superficial/intermediate cervical plexus block when compared with any technique using a deep injection.6 The main conclusion of this review is that the deep block is more than twice as likely to yield a serious life-threatening complication as a result of block placement than is the superficial block. An original technique of ultrasound-guided intermediate cervical plexus block is currently being studied in our institution. In brief, the needle is advanced in plane at the C4 level between the anterior border of elevator scapulae muscle and posterior border of the sternocleidomastoid muscle to reach the posterior cervical space in which the local anesthetic solution is injected (Fig. 1). For carotid surgery, the local anesthetic solution spreads towards the carotid sheath. Figure 1: A, Transverse sonogram of the lateral cervical area at the C4 level: the posterior cervical space is located between the sternocleidomastoid (SCM), elevator scapulae (ES), longus colli (LC), and scalene (SM) muscles. B, Technique of ultrasound-guided intermediate cervical plexus block: the needle is located in the posterior cervical space; the local anesthetic (LA) solution spreads towards the carotid sheath (green dashed line).Olivier Choquet, MD Christophe Dadure MD, PhD Xavier Capdevila, MD, PhD Department of Anesthesiology and Critical Care Medicine Lapeyronie University Hospital and Montpellier 1 University Montpellier, France [email protected]