DOI:10.2214/AJR.07.2331
AJR 2007; 189:563-565
© American Roentgen Ray Society
A Cervical Nerve Block Approach to Improve Safety
Louis A. Gilula1 and
Daniel Ma2
1 Mallinckrodt Institute of Radiology, Washington University School of Medicine,
510 S. Kingshighway Blvd., St. Louis, MO 63110.
2 Department of Medicine, Tufts/New England Medical Center, Boston, MA.
Received September 14, 2006;
accepted after revision April 19, 2007.
Address correspondence to L. A. Gilula
(gilulal{at}mir.wustl.edu).
FOR YOUR INFORMATION
A data supplement for this article can be viewed in the online version of
the article at:
www.ajronline.org.
Abstract
OBJECTIVE. The objective of this report is to describe a previously
unreported technique of selective cervical nerve block, performed from January
1, 2004, to May 19, 2006, in 560 injections, that was designed to allow
continual monitoring of injectate passage and verification of needle tip
position. We also illustrate faulty needle placement in a cadaveric neck.
CONCLUSION. Using a short connecting tube, contrast material mixed
with the final injectate, and fluoroscopy when performing a selective cervical
nerve block allows continual monitoring of injectate including where washout
of the original testing contrast material actually flows. A true lateral view
shows a more dangerous anterior needle tip placement. In addition, performing
a test with anesthetic and contrast material, waiting 1.5 minutes before
administering the final injectate, and using a water-soluble steroid may
provide further safety with selective cervical nerve block.
Keywords: anesthesia • anesthetic • cervical nerve block • CNS • injection technique • spinal injection
Introduction
Fluoroscopically guided extraforaminal selective cervical nerve
blocks require precise needle tip positioning. Improper placement diminishes
the procedure's therapeutic and diagnostic potential while increasing
probability for complications
[1]. Death, spinal cord
infarction, injection into an anterior radicular artery, epidural sac
puncture, and vertebral artery injury have been reported during selective
cervical nerve blocks [1].
These complications are thought to be related to medication passage
[2]. Currently, standard
imaging protocols involve frontal and oblique views for accurate visualization
of the needle tip [3]. However,
adding a lateral view shows needle tip displacement anterior to the articular
pillars, which is associated with an increased incidence of complications
[1]. This study is designed to
describe the inadequacy of using only frontal and oblique views; to stress the
need for the lateral view to verify the adequacy of needle tip placement; and
to present an injection technique, which we could not find previously
reported, that provides potential marked improvement in safety with medication
injection.
Materials and Methods
To illustrate the inadequacy of only frontal and oblique fluoroscopic views
in determining needle tip position, we used a cadaveric neck as performed with
live patients, omitting only sterility and anesthetic procedures, to show the
importance of a true lateral view. In our standard procedural protocol,
patients are in a lateral decubitus position with the side of interest
elevated and the head and neck bent slightly toward the table (Appendix S1,
available online at
www.ajronline.org).
In this cadaveric neck, the needle tip is more than 3 needle-tip widths
anterior to the articular pillar on the lateral view
(Fig. 1A), whereas it projects
over the posterior aspect of the foramen on the oblique
(Fig. 1B) and along the
midportion of the pillar on the frontal
(Fig. 1C) views.
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Fig. 1B —Radiographs show needle positions in cadaver. Oblique view shows
that same anteriorly displaced needle appears adequately positioned as needle
tip projects over anterior surface of articular pillar.
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Injection Technique
To ascertain that the needle tip is not intravascular, dense myelographic
contrast material (iohexol [Omnipaque 300, Amersham Health]) is injected
before injecting the final injectate (Appendix S2 and Figs. S1A-S1D).
A slight needle tip movement can move a needle intravascularly, thereby
misleading the operator about the location of medication delivery. In January
2004, we began using a short lymphangiographic tube (MX453, Medex) (Palmer W,
personal communication) attached to a 10-mL syringe with dense contrast
material (Omnipaque 300) (Appendix S3 and Figs. S2 and S3). The tube is
tightly attached, "press fit," to the 25-gauge needle hub with one
of the operator's hands holding the connecting tube hub at its attachment to
the syringe containing contrast material. That same operator's hand rests on
the patient's head to keep the tube and needle from moving (Fig. S3B). A small
amount of contrast material (Omnipaque 300) is injected with frontal
fluoroscopy to verify that the contrast material does not pass
intravascularly. If it does, the operator repositions the needle tip slightly
with minimal turning or advancement while checking contrast flow. When
contrast material is not intravascular, a frontal fluoroscopic spot view is
taken while observing injection (Fig.
2A). The fluoroscopic tube is rotated to precisely overlap
bilateral articular pillars in the lateral view (Fig. S1D) for a second spot
view and then to an oblique view maximally profiling the foramen
(Fig. 2B). The tube is rotated
back to the frontal position, and the syringe with contrast material is
exchanged with a 3-mL syringe containing 0.5 mL of methylprednisolone acetate
(80 mg/mL; Depo-Medrol, Pharmacia Upjohn), 0.5 mL of preservative-free
lidocaine 2%, and 0.5 mL of Omnipaque 300. Intermittent fluoroscopy during
placement ensures absence of intravascular filling. The 3-mL syringe is
removed, and the tubing, which holds 0.2 mL of injectate, is cleared with the
contrast syringe to deliver the entire injectate. A final frontal spot view
shows the extent of injectate flow (Fig.
2C).
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Fig. 2A —Nerve block and focal foraminal epidural at left C5-C6 level in
33-year-old man undergoing selective cervical nerve block for right CT
radiculopathy. Frontal view shows injectate with contrast flow, dispersion of
contrast material, and no vascular filling.
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Fig. 2B —Nerve block and focal foraminal epidural at left C5-C6 level in
33-year-old man undergoing selective cervical nerve block for right CT
radiculopathy. Oblique view shows contrast material outlining anterior margin
of pillar and posterior surface of exiting nerve.
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Fig. 2C —Nerve block and focal foraminal epidural at left C5-C6 level in
33-year-old man undergoing selective cervical nerve block for right CT
radiculopathy. Final frontal view shows 1.5 mL of injectate at end of
injection. No contrast-filled vascular structures showed during or at end of
injection. Injectate passed from C4 to C7 in epidural space.
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This latter technique with connecting tube and injectate-containing
contrast material mixed with steroid and anesthetic has been used in 560
injections from January 1, 2004, to May 19, 2006. No deaths or severe
neurologic complications have been encountered with this newer technique. We
have seen no problems mixing contrast material with injectate in several
thousand nerve blocks of various types performed over several years. For
additional safety, this technique has been recently further modified since
February 28, 2007, by using a test dose of anesthetic (4% lidocaine) and
contrast material with digital subtraction, waiting 90 seconds and replacement
of deposteroid with water-soluble steroid suitable for intravascular injection
(dexamethasone [Decadron, Merck & Co.]); see Appendix S3 for details.
Discussion
Selective cervical nerve blocks and transforaminal cervical spine epidurals
have been associated with death and severe neurologic complications
[1]. Because of potential
complications, some physicians have anecdotally stopped performing such
blocks. However, large retrospective studies have documented that
complications associated with selective cervical nerve blocks or foraminal
epidural blocks can be infrequent and minor given careful technique
[1,
4].
During fluoroscopically guided selective cervical nerve blocks, true
lateral views can display anterior needle tip displacement, which sometimes
may be considered as otherwise adequate using only oblique and frontal views
as illustrated by the cadaveric example. Prevention of anterior needle tip
displacement is notable for two reasons. First, vertebral artery closeness to
the articular pillars has been reported as a potential problem by
Vallée et al. [5].
Therefore, an anteriorly displaced needle tip threatens vertebral artery
integrity. Second, anterior needle tip displacement can still significantly
increase the probability of minor complications
[1]. During analysis of 1,036
fluoroscopically guided selective cervical nerve blocks, Ma et al.
[1] found that a needle tip
displaced more than 2 needle-tip widths anterior to the articular pillar
significantly increased the probability of dizziness, numbness, transient
weakness, and radicular pain. This is important because the published
literature does not generally stress the importance of obtaining a lateral
view to establish safe needle tip positioning. Indeed, in the selective
cervical nerve block guidelines established by the International Spine
Intervention Society, only frontal and oblique views are recommended to
determine whether the position of the needle tip is adequate
[3]. Many publications
concerning selective cervical nerve blocks repeat these guidelines
[5,
6].
Although lateral views may show anterior needle tip displacement, this view
alone may be insufficient to monitor potential severe complications. Cadaveric
studies show that anatomic variation may occasionally place aberrant deep
cervical artery and thyrocervical trunk branches along the ideal needle path
placement during selective cervical nerve blocks, especially from the C5 to C7
nerves [1]. Many serious
complications of selective cervical nerve blocks are thought to be related to
placing injectate into vital arteries
[1]. A major problem with
current injection techniques is inadequate flow monitoring during injection.
Once contrast material is injected to verify that needle tip position is
satisfactory, injectate washout is all that has been checked. However,
contrast material can washout into soft tissues around nerves or blood
vessels, into the epidural space, or even into blood vessels.
The addition of a high-density contrast agent to the injectate allows
monitoring of injectate flow to see even tiny blood vessels filling during
injectate placement. Although various procedures use intravascular contrast
material, we could find no articles in the literature about adding contrast
material to the final selective cervical nerve block injectate to monitor all
injectate flow. Because the needle tip may move easily during needle
positioning, syringe attachment, or minimal patient motion, adding dense
contrast material to the injectate and using a short lymphangiographic
connecting tube (Palmer W, personal communication) allow early recognition of
vascular filling while minimizing needle movement. The use of digital
subtraction during fluoroscopy can help show tiny blood vessels (Appendix
S3).
Several authors recommend CT guidance for selective cervical nerve blocks,
stating that CT "is the safest and most effective method of localizing
the neural foramen, thereby ensuring steroid deposition at this exact
location" [7]. CT can be
valuable to place a needle in a desired position. However, neither CT nor CT
fluoroscopy can be used to monitor vascular filling during injection,
especially fast-moving arterial flow that may not be confined within a CT
section plane. Also because it is necessary to observe the vertebral body
above and below the injected level to detect vascular filling, the CT beam may
inadequately display such a spine length. CT also presents more procedural
cost than fluoroscopy. Therefore, because of potential serious risks
associated with selective cervical nerve blocks, we strongly encourage
radiologists to stop using CT or CT fluoroscopy for selective cervical nerve
block in recognition of the fact that rapid filling of critical vascular
structures can be missed with CT (Appendix S4).
In conclusion, we strongly believe that using a true lateral view to
confirm needle tip placement within 3 needle-tip widths anterior to the
articular pillar surface, using a short lymphangiographic connecting tube,
adding dense contrast material to the injectate, testing with anesthetic mixed
with contrast material before steroid injection, using digital subtraction,
using a water-soluble steroid, and monitoring the entire injectate placement
with intermittent fluoroscopy in the frontal position can provide a method to
markedly improve the safety of selective cervical nerve blocks.
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Abstract
Introduction
