Oct 6, 2020, 16:44 PM by Brendan Thelen M.D., Pain Medicine Fellow; Wyndam Strodtbeck M.D., Faculty Anesthesiologist; Virginia Mason Medical Center, Seattle, WA

Note: This article originally appeared in the ASRA News, Volume 16, Issue 2, pp. 21-27 (May 2016).

Section Editor: Kevin Vorenkamp, MD

 

Authors

Brendan Thelen M.D. 
Pain Medicine Fellow

Wyndam Strodtbeck M.D.
Faculty Anesthesiologist

Virginia Mason Medical Center
Seattle, WA

 

Abstract 

Cervical radicular pain (CCRP) is often due to a combination of factors including intervertebral disc prolapse or herniation, narrowing of the intervertebral foramen, osteoarthritis of facet joints, and spondylolisthesis. Cervical selective nerve root blocks (CSNRB) with local anesthetic are used for evaluation of radicular pain in patients with pathology that exists at multiple vertebral levels. The diagnostic information the block provides can prove to be helpful in planning surgical intervention. Most of these blocks are performed at the C5-C7 level and typically performed with an anterior lateral approach under fluoroscopic guidance. When a therapeutic benefit is desired, corticosteroids are included with a similar approach and they are regarded as cervical transforaminal epidural steroid injections (CTFESI). Serious complications have been recorded using the anterior lateral technique with use of particulate steroid, including cerebral and spinal cord infarction and perforations of the vertebral artery. A posterior approach is infrequently used due to the challenges faced while advancing the needle under fluoroscopy; however an anterior-lateral approach may be difficult for the lower cervical levels in patients with thick or short necks where the shoulders may interfere with fluoroscopic visualization. In this imaging article, we describe performing a prone C8 SNRB in an obese individual to provide diagnostic information for surgical planning.

 

Introduction

CSNRB and CTFESI can be used as diagnostic and treatment tools for cervical radicular pain.^[1-3] Cervical radiculopathy can be caused by degenerative processes, such as cervical intervertebral disc prolapse, but can also be caused by a combination of factors including narrowing of the intervertebral foramen, disc herniation, osteoarthritis of facet joints, and spondylolisthesis of the cervical spine.^[1] In patients with cervical radiculopathy with multilevel degeneration, it can be difficult from magnetic resonance imaging (MRI) findings to distinguish which nerves are causing clinical symptoms. Anderberg et al.^[2] found a 60% correlation between performed level of SNRB and MRI level of the most significant degeneration. The correlation between SNRB results and levels decided by dermatomal radicular pain distribution was only 28%. However, the authors concluded that SNRB is useful for selecting pain mediating nerve roots in the symptomatic multilevel degenerated cervical spine patient with radicular pain.

The anterolateral approach to CSNRB and CTFESI is most commonly used; however this may not always be the safest approach. Furthermore, CTFESI have been associated with catastrophic complications when particulate steroids are used, including cerebral and spinal cord infarctions.^[1],[4],[5] Ma et al.^[4] found a higher rate of complications associated with the anterolateral approach to placement compared to a more posterior approach of the needle. Xiao et al.^[1] proposed a safer alternative using a posterior approach for cervical nerve root blocks with pulsed radiofrequency ablation, but only had a very small subset for C8 selective nerve root blockade and they did not clearly define their technique.

 

Case Report

The patient is a 61-year-old male who presents with a three-year history of worsening right upper extremity pain after sustaining a work injury. He has a large circumferential neck size, and he measures at 6’3” tall and 245 lbs. His body mass index (BMI) is 30 kg/m². The pain is described as an electric shooting pain from his neck down through his shoulder and medial arm to his right third, fourth, and fifth fingers. He describes his pain as being dull and constant, rating 4/10 on the numerical rating scale, worsening to 8/10 intensity when he is moving his arms. Extension and turning his head to the affected side increases pain down his affected arm. Pain has made it difficult for him to work. The patient notes subjective weakness and atrophy of deltoid muscles. The patient had an average of two months of pain relief with each previous interlaminar cervical epidural steroid injections. He has tried physical therapy without benefit. His medications include gabapentin 300 mg twice daily and duloxetine 60 mg daily.

No electromyography (EMG) abnormalities are seen. MRI of the cervical spine shows severe multilevel right-sided neuroforaminal narrowing at C3-C4, C4-C5, C5-C6, and C7-T1.  The patient was referred to the pain clinic for performance of a right-sided diagnostic C8 selective nerve root block to aid in surgical planning.

The procedure, as described below, was performed without complications. At five minutes following injection, the patient had very clear dermatomal anesthesia involving the right C8 nerve root. He noted improvement in his medial forearm pain but had difficulty quantifying the percentage of improvement in his overall pain.

 

Description of the Technique  The patient was positioned prone on the fluoroscopy table with the head positioned in a face cradle in a partially flexed position. Sedation was not necessary and was not used during this diagnostic procedure. We used fluoroscopy with digital subtraction angiography capability to identify the relevant anatomy. True anterior-posterior imaging of the cervical spine was obtained with the C7 vertebral body at the center of the image. The target entry site was identified just inferior to the right C7 pedicle and lateral to the right T1 superior articulator process with a slight ipsilateral oblique view.  Next, a small skin wheal was made with 1% lidocaine. Then, a 3.5-inch 22 gauge Quincke spinal needle was advanced in coaxial fashion under intermittent fluoroscopic guidance and until the needle is viewed in the superior part of the C8 neuroforamen. Lateral view was then obtained and confirmed needle placement in the posterior 1/3 of the neuroforamen. After negative aspiration, 0.5 mL of Isovue-M 300 contrast was injected under digital subtraction angiography and contrast was noted to be spreading along the spinal nerve with minimal spread around the pedicle into the epidural space (Figure 1). Then 0.75 mL of 0.5% bupivacaine was injected, and the needle removed.  Final fluoroscopic image after injection demonstrated excellent spread along the right C8 nerve root with minimal epidural uptake, but no spread noted up to the C7 nerve root or down to the T1 nerve root (Figure 2). If a therapeutic TFESI had been intended, then more central spread would have been desired and accomplished with additional anterior-medial advancement.

Figure 1. Digital subtraction angiography used to show no vascular uptake and lateral spread along the right C8 nerve root with minimal central epidural spread.  Figure 2. Fluoroscopy single spine view-needle placement at the C8 nerve root with contrast showing spread along the nerve root with minimal central epidural spread

 

Figure 3: Axial view of C8 selective nerve root block by lateral and prone approaches. The final needle position is within the posterior aspect of the foramen. Multiple areas of vascular supply are illustrated including vertebral artery and spinal segmental arteries which are in close proximity of needle placement. Modified from Rathmell JP: Atlas of Image Guided Intervention in Regional Anesthesia and Pain Medicine, 2nd edition. Philadelphia, Lippincott Williams & Wilkins, 2012.[6] To see a short video of this in action, click here.

 

Discussion

We described performance of a C8 SNRB using a posterior approach. Prior authors described use of a posterior positioning of the needle in CTFESI reducing the rate of complications compared to the anterolateral approach (Figure 3).^[4] The obese patient with a short and large circumferential neck represents an increased technical challenge including acquiring appropriate fluoroscopy imaging for guidance. The location of the C8 neuroforamen in a patient with large shoulders or a short, thick neck presents an additional technical challenge when advancing under fluoroscopy in the anterolateral position. The posterior approach for a C8 SNRB or TFESI offers an alternative to the anterior lateral approach without an increased risk of complications and, in certain patient populations, offers a chance of improved accurate final needle placement.

 

References