Ultrasound-Guided Cervical Spine Injections

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Chapter 21 Ultrasound-Guided Cervical Spine Injections

Samer Narouze

Chapter Overview

Chapter Synopsis: In the past few years, there has been a tremendous growth in interest in US-guided cervical injections as ultrasound allows direct, real-time visualization of soft tissue structures (e.g., vessels, nerves). Thus, it is an attractive alternative in cervical spine and neck injections, where there are a multitude of vital soft tissue structures compacted in a small area. This chapter will review various applications of ultrasound in cervical spine injections. Techniques for third occipital nerve block, cervical medial branch nerve block, and cervical facet intraarticular injections are discussed in detail. Advantages as well as limitations of ultrasound relative to fluoroscopy are highlighted. US-guided stellate ganglion block and US-guided atlanto-axial joint injections are discussed in other chapters.

Ultrasonography provides good visualization of bony surfaces, which may make it useful in various superficial spine injections (e.g., medial branch block, facet intraarticular injections, and nerve root blocks).¹ However, it is not as useful in neuraxial blocks because of the bony artifacts and the limited acoustic window.

Important Points:

Ultrasonography is especially useful in cervical spine injections because there are many soft tissue structures compacted in a small area. The best example is cervical sympathetic (stellate ganglion) block.

Ultrasonography plays an important role as an adjunct to fluoroscopy in cervical nerve root blocks because it can identify vessels in the vicinity of the nerve root, hence avoiding vascular injury and injection, but fluoroscopy can only detect intravascular injections after the fact.

Ultrasonography can be useful in identifying the third occipital nerve as well as the cervical medial branches.

Ultrasonography can facilitate atraumatic cervical facet intraarticular injections.

By identifying the vertebral artery (both typical and atypical anatomy), ultrasonography can make atlanto-axial injections safer.

Clinical Pearls:

Most US-guided cervical spine injections centered on differentiating C6 and C7 vertebral level. This can be accomplished by following the course of the vertebral artery as well by the identifying the characteristic C6 transverse process.

One should always use Doppler US while performing US-guided cervical spine injection to help identify normal and abnormal vessels.

For novices, it is always recommended to initially use US in conjunction with fluoroscopy, until one acquires the necessary skills and experience.

Clinical Pitfalls:

US-guided cervical spine injections are advanced US applications that require extra training and experience. Novices should start practicing US musculoskeletal applications first before advancing to spinal applications.

In cervical nerve root block and atlanto-axial joint injections, it may be wise to use both ultrasound and fluoroscopy, as one modality (ultrasound) helps avoid vascular injury and the other modality (fluoroscopy) helps detect intravascular injection.

Introduction

Ultrasonography in pain medicine (USPM) is a rapidly growing medical field in interventional pain management. Traditionally, spine interventional procedures for pain management are performed with imaging guidance such as fluoroscopy and computed tomography (CT). In the past few years, there has been a tremendous growth in interest in USPM.

Ultrasonography allows direct real-time visualization of soft tissue structures (e.g., vessels, nerves). Thus, it is an attractive alternative in cervical spine and neck injections, where there is a multitude of vital soft tissue structures compacted in a small area. However, it faces unique challenges in lumbar spine injections because the major shortcoming of ultrasonography is the limited resolution at deep levels.

Ultrasonography provides good visualization of bony surfaces, which may make it useful in various superficial spine injections (e.g., medial branch block, facet intraarticular injections, nerve root blocks).¹ However, it is not as useful in neuraxial blocks because of the bony artifacts and the limited acoustic window.²

Ultrasound-Guided Cervical Sympathetic Chain (Stellate Ganglion) Block

Please refer to Chapter 8.

Ultrasound-Guided Cervical Nerve Root Block

Anatomy

The cervical spinal nerve occupies the lower part of the foramen with the epiradicular veins in the upper part. The radicular arteries arising from the vertebral, ascending cervical, and deep cervical arteries lie in close approximation to the spinal nerve.³

Huntoon ⁴ was able to show that the ascending and deep cervical arteries may contribute to the anterior spinal artery (not only the vertebral artery). More than 20% of the foramina dissected had either the ascending or deep cervical artery or a large branch within 2 mm of the needle path for a cervical transforaminal procedure. One third of these vessels were spinal branches that entered the foramen posteriorly, potentially forming a radicular or a segmental feeder vessel to the spinal cord, making it vulnerable to inadvertent injury even during correct needle placement. Variable anastomoses between the vertebral and cervical arteries were found; therefore it is possible to introduce steroid particles into the vertebral circulation via the cervical arteries.⁴

Limitations of the Current Technique

Currently, the guidelines for cervical transforaminal injection technique involve introducing the needle under fluoroscopic guidance into the posterior aspect of the intervertebral foramen just anterior to the superior articular process in the oblique view to minimize the risk of injury to the vertebral artery or the nerve root.³ Despite strict adherence to these guidelines, adverse outcomes have been reported.^5,⁶ A potential shortcoming of these current guidelines is the presence of a critical feeder vessel to the anterior spinal artery in the posterior aspect of the intervertebral foramen that could be injured in the pathway of the needle.⁴ Ultrasonography may be more adventitious because it allows for visualization of soft tissues, nerves, and vessels, and facilitates real-time visualization of the injectate around the nerve.

Literature Review of Ultrasound-Guided Cervical Nerve Root Block

Galiano et al ⁷ described the use of ultrasonography in cervical periradicular injections in cadavers. They used CT images for confirmation. However, they were not able to comment on the relevant blood vessels in the vicinity of the vertebral foramen, and this raised some concerns about the safety of performing the procedure with ultrasonography at that time.⁸ Now with the introduction of high-resolution ultrasound transducers and gaining more experience, we were able to visualize small critical arteries with ultrasonography.

Narouze et al ⁹ reported a pilot study of 10 patients who received cervical nerve root injections using ultrasonography as the primary imaging tool with fluoroscopy as the control. In four patients, these authors were able to identify vessels at the anterior aspect of the foramen; two patients had critical vessels at the posterior aspect of the foramen, and in one patient, this artery continued medially into the foramen, forming a segmental feeder artery. In these two cases, such vessels could have been injured easily in the pathway of a correctly placed needle under fluoroscopy.