Cervical Spine Block

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    Cervical Spine Ultrasonography

    Dr. Geoff A Bellingham MD FRCPC

    Department of Anesthesia & Perioperative Medicine

    Schulich School of Medicine & Dentistry, Western University

    London, Ontario, Canada

    Table of Contents

    1. Type of Probe Used

    2. Counting Levels

    3. Cervical Facet Joint Injections

    4. Cervical Medial Branch Blocks

    5. Cervical Nerve Root Blocks

    6. Vascular Anatomy of the Cervical Spine

    1. Type of Probe Used

    Cervical spinal structures are typically superficial to skin but can vary in depth depending on the

    body habitus of the patient. As such, ultrasound probes with higher frequencies (14-5 MHz) can

    usually be used to provide clinicians with good spatial resolution. Increased spatial resolutionwill mean better definition of the tissue structures but does sacrifice the depth of penetration of

    the beam.

    2. Counting Levels

    The ability to identify vertebral levels of the cervical spine using ultrasound relies on visualizing

    characteristic anatomical boney landmarks and vessels unique to each vertebrae. There are three

    reported methods for counting levels.

    The first method which has been described relies on a midline sagittal scan of the cervical spine

    to count the levels starting cranial to caudad. This technique relies on identifying characteristic

    shapes of the spinous processes. The spinous processes of C2 to C6 have varying frequencies of

    bifidity/nonbifidity. In contrast, the atlas (C1) has no true spine and consists of two lateral

    masses connected posteriorly by a long, curved arch. One may rely on the relative absence of a

    spinous process in a sagittal plane to identify C1 and to then count caudally to the desired level

    (Figures 1 A and B).

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    Figure 1.A. Midline longitudinal scan over the cervical spinous processes. C1 has only a rudimentary spinousprocess. B. Short axis view demonstrating bifid spinous process of C2 (arrows).

    Narouze SM. Ultrasound guided cervical spine injections: Ultrasound prevents whereas contrast fluoroscopyDetects intravascular injections. Regional Anesthesia and Pain Medicine 37 (2): 127-30.

    It has been suggested to use the bifid morphology of the C2 spinous process to act as an

    additional boney landmark to help verify the vertebral level. This is best appreciated using a

    transverse scan. However, the spinous processes from C2-C6 have varying degrees of bifidity

    and consistency in this feature is lacking. In a recent anatomical study performed in South

    Africa, only 58.9% of caucasian spines had the presence of bifid spinous processes and only

    31.6% were found in the black specimens studied. When this did occur, C2 was the most

    common level to have this feature (89%), followed by C5 (83%), C4 (79%), C3 (59.4%), and C6

    (41.7%) (Asvat R 2012). Given the variation in morphology, bifidity should not be a sonographic

    landmark used to assist in identifying vertebral levels. This has been also corroborated in surgical

    literature (Moro T et al. 2007).

    The most significant and consistent anatomical feature that can be appreciated on scanning the

    cervical spine are the characteristic morphologies of the transverse processes. Only C3-C6 have

    an anterior and posterior tubercle with a groove for the spinal nerve between them. Under

    ultrasound, these tubercles are hyperechoic and provide a characteristic 2-humped camel sign

    (Narouze et al. 2009). The C6 level distinguishes itself by having the most prominent anterior

    tubercle compared to other levels, referred to classically as Chassaignacs tubercle. The C7

    vertebra distinguishes itself by having only a rudimentary anterior tubercle and a prominent

    posterior tubercle (Martinoli C et al. 2002).

    The level of the C6 vertebra can be roughly identified through use of the cricoid cartilage as a

    surface landmark. Placing the ultrasound probe laterally and in a transverse plane on the neck,

    one may appreciate the double hump of the anterior and posterior tubercle of its transverse

    process (Figure 2). This level can be confirmed by moving the probe caudally to the C7 level. If

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    correct, one should only appreciate the single posterior tubercle of C7 with the nerve root and

    vertebral artery lying anteriorly (Figure 3).

    Figure 2.Axial transverse ultrasound image showing the prominent anterior tubercle (at) of the C6 transverseprocess (C6 TP). N represents nerve root; CA, carotid artery; pt, posterior tubercle.

    Figure 3.Axial transverse ultrasound image showing the characteristic morphology of the C7 transverse process(TP). C7 represents nerve root; VA, vertebral artery. The vertebral artery lies anterior to the C7 nerve root.

    Narouze SN, Vydyanathan A, Kapural L, Sessler DI, and Mekhail N. Ultrasound-guided cervical selective nerve rootblock. Reg Anesth Pain Med 2009; 34: 343-348.

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    The final method utilizes the relative position of the vertebral artery to the transverse processes,

    as reported by Narouze et al. (2009). At the C7 level, the artery runs anterior to the transverse

    process prior to entering the foramen of the C6 transverse process in 90% of cases. (Narouze SN

    2011a)

    3. Cervical Facet Joint Injections

    There have been two proposed techniques to perform ultrasound guided cervical facet joint

    injections.

    An antero-lateral approach has been reported by Galiano et al. (2006). The report assessed the

    feasibility of identifying the zygapophyseal joints under ultrasound followed by ultrasound

    guided needle placement accuracy. Needles were guided to the zygapophyseal joints from C2-3

    to C6-7 on both sides of one cadaver, and intra-articular placement was confirmed via computed

    tomography.

    Of 40 ultrasound examinations between C2-3 to C6-7, the joint space was not depicted on 4

    attempts. All 10 needle tips were located in the joint space during the simulated injections, which

    were verified by CT.

    All cadavers were positioned in a lateral position. The technique used to identify the proper level

    relied on identification of the transverse processes of the sixth and seventh vertebrae. Once the

    appropriate level was identified, the transducer was positioned in an axial plane, with the joint

    space in the middle of the image. This view allowed for the guidance of a needle from an antero-

    lateral approach. The facet joints appeared as hyperechoic signals, with the joint space appearing

    as an anechoic gap between the articular processes (Figure 4).

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    A posterior approach to cervical facet intra-articular injection has been proposed by Narouze

    (Narouze S.N. 2011b). A proposed advantage is that the patient does not have to change positions

    if the injections are to be performed bilaterally.

    A sagittal scan is first obtained at midline to identify the correct cervical level. By moving the

    probe laterally, the next sonographic image produced is that of the lamina of the cervical

    vertebrae. Moving further laterally, the facet column will next appear with a characteristic saw

    sign. (Figure 5) If doubt exists if the saw sign represents the lamina or facet pillar, scanning

    further laterally should only reveal soft tissue representative of the paraspinal muscles, and no

    bone. This can help to confirm that the boney saw sign image produced was representative of

    the facets, the most lateral structures in the posterior spine.

    Injections of the facet joints can then be performed by advancing the needle from the caudal

    aspect of the ultrasound probe.

    Figure 4.A, Axial transverse ultrasound image of a cervical facet jointinfiltration at level C6-7 demonstrating the needle placement in thetarget area, using a linear transducer (L12-5 MHz). B, Correspondingaxial transverse CT image of a cervical facet joint infiltration at levelC6-7. The box outlines the location of the ultrasound image. C,Schematic drawing of the facet joint injection. The needles are inserted

    at an angle (a) of 60 to 75 degrees in respect to the parasagittal plane.iap, inferior articular process; js, joint space; l, lamina; n, needle; ntneedle tip; sap, superior articular process; sp, spinous process; vb,vertebral body.

    Galiano K, Obwegeser AA, Bodner G, Freund MC, Gruber H, MaurerH, Schatzer R, Fiegele T, and Ploner F. Ultrasound-guided facet jointinjections in the middle to lower cervical spine. Clin J Pain 2006; 22:538-543.

    Figure 5.Sagittal longitudinalsonogram showing the articular

    processes of the facet joints asthe saw sign. The white arrow

    points to the C45 facet jointspace and indicates the path aneedle could be guided to

    perform an intraarticularinjection.

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    4. Cervical Medial Branch Blocks

    There have been two studies which have assessed the feasibility of third occipital nerve and

    cervical medial branch blocks under ultrasound guidance.

    The first investigation to report neural blockade of cervical zygapophysial joints focused on

    targeting the third occipital nerve. In this study, authors described the technique used and

    confirmed that the nerve could be visualized bilaterally in all 14 volunteers studied. Needles

    were then directed under ultrasound guidance to the nerve and were correctly placed 23 out of 28

    attempts, confirmed via fluoroscopy (Eichenberger U et al. 2006).

    Investigators performed the injection by placing the ultrasound probe perpendicular to the lateral

    aspect of the neck nearly in a transverse plane, starting just caudal to the mastoid process.

    Volunteers were placed in a lateral position. As the probe was moved caudally, the transverse

    process of C1 could be visualized. Moving further caudal by approximately 2 cm, the transverseprocess of C2 could next be identified. (Refer to Figure 6A)

    Once this image was obtained, the transducer was moved 5-8 mm posteriorly to visualize the

    arch of the atlas (C1) and the articular pillar of C2 (cranial part of the C2-3 facet joint). With this

    view, the probe could be slid caudally to obtain a view of the facet joints of C2-3 and C3-4. The

    third occipital nerve crossed the articulation of C2-3 and could be searched for over the

    articulation, approximately 1 mm from the bone, with a median diameter of 2.0 mm. (Figures 6

    A-C)

    Performance of the injection was described as an out of plane approach by the authors. The

    needle was introduced immediately anterior to the ultrasound probe and advanced perpendicular

    to the beam until it reaches the desired target point.

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    Figure 6B.Ultrasound image transverse view of the C2C3 zygapophysial joint. The gray circle indicates the targetpoint for the needle tip during the ultrasound-guided needle placement for third occipital nerve block. 1 C2C3 jointline; 2 superior articular process of C3; 3 inferior articular process of C2; 4 intervertebral foramen of C2C3; C3white reflex of the surface of the vertebral body of C3; LS levator scapulae muscle; SCM sternocleidomastoidmuscle; SM scalenus medius muscle; TM trapezius muscle; TR ultrasound shadow of the transverse process of C2.

    Eichenberger U, Greher M, Kapral S, Marhofer P, Wiest R, Remonda L, Bogduk N, and Guratolo M. Sonographicvisualization and ultrasound-guided block of the third occipital nerve. Anesthesiology 2006; 104: 303-8.

    Figure 6A.Cervical spine (C2C5): Transducer alignment in relation tothe cervical spine for ultrasound-guided third occipital nerve block (asreported by Eichenberger U et al. 2006) in the transverse view (TV) andthe longitudinal view (LV). The circle indicates the target point.

    Eichenberger U, Greher M, Kapral S, Marhofer P, Wiest R, Remonda L,Bogduk N, and Guratolo M. Sonographic visualization and ultrasound-guided block of the third occipital nerve. Anesthesiology 2006; 104:303-8.

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    Figure 6C.Ultrasound image longitudinal view (LV) along the articular pillars from C2 to C5. LC longissimuscapitis muscle; LS levator scapulae muscle; SC splenius capitis muscle; SCM sternocleidomastoid muscle; SMCsemispinalis capitis muscle.

    Eichenberger U, Greher M, Kapral S, Marhofer P, Wiest R, Remonda L, Bogduk N, and Guratolo M. Sonographicvisualization and ultrasound-guided block of the third occipital nerve. Anesthesiology 2006; 104: 303-8.

    The second investigation sought to block the medial branches between C3 and C6 under

    ultrasound guidance. Of 46 cervical medial branch blocks, all needle tips were positioned on the

    articular pillars. The second phase of the study used contrast to evaluate the spread of 0.3 mL of

    contrast/local anesthetic. Contrast was found to cover the appropriate level in 94.5% of cases

    without complications. The incidence of aberrant spread to adjacent levels was 13.5%, similar to

    reports using fluoroscopy. (Finlayson RJ et al. 2012)

    Investigators identified the appropriate level for C3 and C4 medial branch blocks by firstscanning in the coronal plane and identifying a drop-off representing the C2-C3 junction.

    Scanning caudally from this junction, the articular pillar of C3 and subsequently C4 could be

    identified. Identification of the C6 and C7 levels was performed by identifying the characteristic

    structures of the transverse processes (as described in Section 2).

    For all levels scanned and injected, the probe was oriented in the transverse plane. The scan

    started posteriorly to identify the spinous process and lamina. The probe then moved anteriorly to

    identify the contour of the articular process. Once satisfied that an echogenic linear image of the

    bone of the pillar was achieved, the probe was tilted slighted posteriorly to maximize the length

    of the image, following the long axis of the pillar. (Figure 7) Color Doppler was performed to

    identify any blood vessels near the proximity of the target. The needle was then inserted in plane

    from a postero-lateral approach.

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    Figure 7.A, Transverse scan at the level of C4 showing needle in position after injection. B, Explanatory linedrawing needle (N), local anesthetic (LA), lamina (Lam), articular pillar (AP), posterior tubercle (PT) of TP.

    Finlayson RJ, Gupta G, Alhujairi M, Dugani S, Tran DQH. Cervical medial branch block: A novel technique using

    ultrasound guidance. Reg Anesth Pain Med 2012; 37: 219-223.

    5. Cervical Nerve Root Blocks

    The feasibility of selected cervical nerve root blocks has been evaluated in three studies

    (Narouze et al. 2009, Yamauchi et al. 2011, and Galiano et al. 2005), two of which involved

    injecting patients with fluoroscopic confirmation of correct needle position. All studies reported

    that identification of the correct cervical level can be obtained. Guidance of a needle to the nerve

    root can also be accomplished safely, with the added benefit of detection of critical vessels

    supplying the nerve roots and spinal cord. However, the studies suggested that spread of solution

    remains limited to the extraforaminal portions of the nerve root targeted.

    The technique employed by Narouze et al. (2009) seems to provide the most ergonomic approach

    for performing this injection. Patients are placed in a lateral decubitus position so that an

    ultrasound probe can be applied to the lateral aspect of the neck. This allows the examiner the

    ability to identify the transverse processes easily in order to determine cervical level (as

    described in Section 2). A linear high-frequency array is used.

    Once an optimum transverse view of the transverse processes is obtained, slight tilting of the

    transducer is used to visualize the spinal nerve as a round hypoechoic signal. Between levels C3-

    C6, the nerve can be found situated between the anterior and posterior tubercles of the transverseprocesses. (Figure 8) At C7, the spinal nerve is seen to lie anterior to the prominent posterior

    tubercle only. Again, the rudimentary anterior tubercle is not seen in this view, and the vertebral

    artery is observed to be lying anterior the nerve itself.

    After the proper sonoanatomy is delineated, color doppler can be used to help identify any

    critical vessels in the vicinity of the nerve route in addition to the proposed path of the needle to

    be used to block the nerve.

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    A 22-guage, blunt-tip needle can be introduced lateral to the lateral end of the transducer. The

    needle is advanced in the plane of the ultrasound beam from posterior to anterior to the desired

    nerve root at the foraminal opening.

    As described by Narouze et al (2009), diagnostic blocks were performed by injecting 2 mL of1% lidocaine. Therapeutic blocks used a mixture of dexamethasone (8 mg) and 1% lidocaine.

    Figure 8.A, Axial transverse ultrasound image showing the sharp anterior tubercle (at) of the C6 transverse process

    (C6 TP). N indicates nerve root; CA, carotid artery; pt, posterior tubercle. Solid arrows point to the needle in placeat the posterior aspect of the intervertebral foramen. B, Illustration showing the relevant anatomy at C6 level and theorientation of the ultrasound transducer.

    Narouze SN, Vydyanathan A, Kapural L, Sessler DI, and Mekhail N. Ultrasound-guided cervical selective nerve rootblock. Reg Anesth Pain Med 2009; 34: 343-348.

    6. Vascular Anatomy of the Cervical Spine

    One of the advantages of using ultrasound for cervical spine interventions is the ability to

    visualize vascular structures. In contrast to fluoroscopic guided interventions, physicians can

    identify and avoid injury to vessels rather than identifying vascular cannulation after it has

    occurred through the injection of contrast dye.

    Published reports of catastrophic injuries from vascular insult in this region include paralysis,

    brain injury, and even death (Baker R et al 2003, Brouwers PJ et al 2001, Rozin L et al 2003,

    Tiso RL et al 2004). An understanding of the vascular anatomy of the cervical spine is therefore

    an important component of ultrasound based techniques for cervical spine interventions.

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    The blood supply to the spinal cord is derived from a single anterior artery and paired posterior

    spinal arteries which run in a cephalad to caudad direction (Hoeft MA et al. 2006). The supply is

    segmental in nature and relies on the blood supplied by radicular arteries which enter via the

    intervertebral foramina. Consequently, any injury or compression of the radicular arteries (and

    their blood supply) can lead to ischemic damage to the spinal cord.

    The radicular arteries most often run anterior to the spinal nerve, and are least likely to be found

    posterior to it (Turnbull IM et al. 1966, Huntoon M. 2005). Arteries tend to enter the foramina

    inferior to the spinal nerve and follow a tortuous course along the inferior and anterior aspect of

    the nerve. The approximate location of the radicular arteries within the foramina tends to be

    determined by the vessels from which they originate. Those which originate from the vertebral

    artery lie over the most anteromedial aspect of the foramen (Hoeft M et al. 2006). Figure 9

    Figure 9.Axial view of cervical transforaminal injection at the level of C6. Arterial branches arise variably from thevertebral artery to supply the nerve root itself or to join the anterior or posterior spinal artery. Spinal segmentalarteries that arise from the depth of the ascending cervical artery enter the foramen at variable locations and oftencourse through the foramen, penetrate the dura, and join the anterior or posterior spinal arteries that supply the spinalcord. The needle placement is representative of a fluoroscopically guided transforaminal injection.

    Hoeft MA, Rathmell JP, Monsey RD, and Fonda BJ. Cervical transforaminal injection and the radicular artery:Variation in anatomical location within the cervical intervertebral foramina. Regional Anesthesia and Pain Medicine31 (3) 2006: 270-274.

    The variations in blood supply to the radicular arteries has been investigated in several

    anatomical studies. The anastamoses of these vessels are numerous and varied but are typically

    reported to come from the vertebral, ascending cervical, superior intercostals, and deep cervical

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    arteries. The dominant blood supply for the radicular arteries originate from the vertebral

    arteries. In an anatomical study of 35 fetal and adult cadavers, 80% of radicular arteries in the

    cervical region originated from these vertebral vessels (Dommisse et al. 1974). In the same

    study, the remainder of radicular anastamoses originated from the deep cervical and superior

    intercostal arteries, and occasionally from the ascending cervical artery.

    Those radicular arteries that arise from the deep cervical, superior intercostals or ascending

    cervical arteries can traverse the entire extent of the foramen. (Figure 10) It is this group of

    vessels that may be at particular risk of injury from interventions given the variation in anatomy.

    In an anatomical study of 95 intervertebral cervical foramina, 21 had an arterial vessel proximal

    to the posterior aspect of the foraminal opening. Seven of these were spinal branches that entered

    the foramen posteriorly, potentially forming radicular or segmental medullary vessels to the

    spinal cord (Huntoon M 2005).

    In the study by Huntoon M (2005), the ascending cervical artery typically ascended on the

    anterior tubercles of the transverse processes, with an average outer diameter of 1.0 mm. If itcame to supply a spinal branch, it typically occurred at the C3-4 or C4-5 foramen, entering the

    posterior and inferior aspect of the foraminal opening (Huntoon M 2005).

    The deep cervical arteries commonly provided branches to the roots of the brachial plexus.

    However, in five instances, the vessels formed large spinal branches and entered the posterior

    aspect of the foramen, directly posterior to the exiting ventral ramus. These critical vessels were

    observed to always enter at either C5-6, C6-7, or C7-T1 (Huntoon M 2005).

    Thus far in studies concerning ultrasound based interventions of the cervical spine, posterior and

    lateral approaches with a needle are most commonly used. This assists in avoiding injury to thevertebral artery. However, radicular arteries which enter the foramina originating from the deep

    cervical, ascending cervical and superior intercostals are those which if injured, could cause

    deleterious consequences. These are the additional vessels which should be sought using doppler

    techniques prior to needle insertion.

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    Figure 10.Illustrations demonstrating ascending cervical and deep cervical arteries anastomosing with the vertebralartery posterior to the spinal nerves. The needle placement is representative of a fluoroscopically guidedtransforaminal injection. The intention of the authors paper is to illustrate the potential for vessel injury using thefluoroscopically guided technique.

    Huntoon MA. Anatomy of the cervical intervertebral foramina: vulnerable arteries and ischemic neurologic injuriesafter transforaminal epidural injections. Pain 117 (2005): 104-11.

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