Percutaneous Image-Guided C-Spine Procedures

SPINE

VASCULAR/INTERVENTIONAL

CME

ABBREVIATIONS KEY AP ⫽ anteroposterior CC ⫽ craniocaudal LL ⫽ lateral-lateral RF ⫽ radio-frequency

Percutaneous Image-Guided C-Spine Procedures F. Massari, Z. Rumboldt, W. Vandergrift, G. Bonaldi, and A. Cianfoni

CME Credit The American Society of Neuroradiology (ASNR) is accredited by the Accreditation Council for Continuing Medical Education (ACCME) to provide continuing medical education for physicians. The ASNR designates this enduring material for a maximum of one AMA PRA Category one creditTM. Physicians should claim only the credit commensurate with the extent of their participation in the activity. To obtain credit for this activity, an online quiz must be successfully completed and submitted. ASNR members may access this quiz at no charge by logging on to eCME at http://members.asnr.org. Nonmembers may pay a small fee to access the quiz and obtain credit via http://members.asnr.org/ecme.

ABSTRACT Spinal neurointerventional radiology, through image-guidance with fluoroscopy or CT, offers a wide variety of percutaneous procedures in the cervical spine for tissue diagnosis, pain management, disk procedures, and osteoporotic and neoplastic vertebral fracture treatment. Different approaches to the cervical spine, including the anterolateral, lateral, posterior, transmaxillary, and transoral, can be used, depending on the target structure and type of procedure. Due to the presence of vital and delicate structures, the knowledge of locoregional anatomy and image-guidance principles, along with a rigorous technique, is the key to safe and successful interventions. This article reviews indications, relevant anatomy, and procedural techniques of percutaneous image-guided accesses to the cervical spine. Learning Objective: Spinal neurointerventional radiology offers a wide variety of percutaneous procedures for diagnosis and treatment of different pathologies affecting the cervical spine. Readers will be able to list indications, identify relevant locoregional anatomy, and understand image-guidance principles and procedural techniques of percutaneous image-guided accesses to the cervical spine to perform safe and successful interventions.

INTRODUCTION

Image-guidance, with fluoroscopy and/or CT, permits precise and safe performance of a wide variety of percutaneous cervical spine procedures, which include injections for diagnosis and treatment of neck and radicular pain, radio-frequency facet denervation, spinal biopsies, discography and disk decompression, cement augmentation of vertebral fractures, and treatment of vertebral tumors.1-6 Anterolateral, lateral, posterior, transmaxillary, and transoral accesses can be variably performed depending on the targeted structure and on the type of procedure to be performed. Fluoroscopy, CT, or a combination of the 2 62

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can be used for guidance, depending on operator preference, local anatomy, and individual procedure. Each access poses specific anatomic, image-guidance, and procedural considerations. Cervical procedures carry the risk of injuries to the regional delicate vital structures. Thorough knowledge of the normal, fluoroscopic, and cross-sectional anatomy; adherence to a rigorous image-guidance and procedural technique; and considerable operator experience are strongly recommended to reduce the potential for serious complications. This article will review indications, relevant anatomy, imaging-guidance principles, and procedural techniques for each percutaneous cervical spine access.

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Received September 4, 2012; accepted after revision January 31, 2013. From the Departments of Radiology (F.M., Z.R.) and Neurological Surgery-Neuroscience (W.V.), Medical University of South Carolina, Charleston, South Carolina; Department of Neuroradiology (G.B.), Ospedali Riuniti, Bergamo, Italy; and Department of Neuroradiology (A.C.), Neurocenter of Italian Switzerland, Lugano, Switzerland. The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this article. Please address correspondence to Francesco Massari, MD, Department of Radiology, Medical University of South Carolina, 96 Jonathan Lucas, Charleston, South Carolina, 29425; e-mail: massarimd@ gmail.com http://dx.doi.org/10.3174/ng.2140079

Fig 1. Cross-sectional supra- and infrahyoid anatomy. The anterior neck can be divided, for practical purposes, with regard to percutaneous accesses into infrahyoid (row A) and suprahyoid (row B) compartments. T indicates trachea; E, esophagus; T1, T1 vertebral body and ribs; C1, C1 lateral mass; C2, C2 vertebral body; CCA, common carotid artery (red arrow); IVJ, internal jugular vein (blue arrow); VA, vertebral artery (green arrow); ICA, internal carotid artery (purple arrow); ECA, external carotid artery branches (brown arrow). Note the relationships between major cervical arterial and venous structures, esophagus, cervical airway, and spine. The carotid arteries move from medial to lateral, ascending in the neck; the common carotid bifurcates approximately at the hyoid level. The vertebral arteries lie anterior to the head of the first rib at the level of T1; they most commonly enter the vertebral foramen at C6, course just ventral to the nerve roots in the foramina, and loop dorsally at C0 –C1. The relationship between the mandible/maxilla and spine elements in the suprahyoid neck is variable and depends on flexion/extension of the cranio-vertebral junction (CVJ), open/closed mouth, and CT gantry tilt.

Fig 2. 3D volume-rendering CT images and corresponding fluoroscopic views of the C-spine. (A and B, anterior view; C and D, posterior view; E and F, lateral view; and G and H, oblique view). Anterior and posterior vertebral elements have opposed CC angulation (red arrows); fluoroscopic views for anterior (B) and posterior (D) access are hence different. The posterior fluoroscopic view is also called the “pillar view” because it profiles the articular pillars. Due to the curvatures of the spine, the fluoroscopic view for a percutaneous access is individual for each level. The oblique foraminal view is obtained with an ipsilateral obliquity of approximately 45° and a slight caudal angulation (G and H).

General Anatomy Principles

Cross-sectional CT anatomy at different levels of the cervical spine is shown in Fig 1. Elements of regional anatomy relevant to the performance of cervical spine procedures are the following:

The anterior neck can be divided, for practical purposes, into infra- and suprahyoid regions. All the delicate and vital structures, besides the spinal cord, lie anterior and anterolateral to the cervical spine, except for the region C0-C2, where the vertebral artery Neurographics 4:62–77 June 2014 www.neurographics.com

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loops posteriorly, just above the lateral mass and posterior arch of C1. A purely anterior access to the cervical spine is obstructed by the presence, from caudad to cephalad, of the proximal supra-aortic vessels, airway and thyroid cartilage, hyoid bone, submandibular glands, mandible and maxilla. The common carotid artery usually bifurcates at the level of the hyoid bone. The relationship between the mandible/maxilla and spine elements in the suprahyoid neck is variable and depends on flexion/extension of the head and on an open/ closed mouth. The cervical spine is characterized by lordotic curvature and by opposite craniocaudal (CC) angulation of the anterior and posterior vertebral elements (Fig 2E and F).

Fig 3. Cross-sectional images depicting relevant anatomy for the anterolateral approach to the C-spine. T indicates trachea; E, esophagus; CCA, common carotid artery (red arrow); IVJ, internal jugular vein (blue arrow); VA, vertebral artery (green arrow); Th, thyroid gland (yellow arrow); Th cart, thyroid cartilage (white arrow); Brach plex, brachial plexus (purple arrow).

There is a substantial individual variability in the neck appearance (short versus long), visibility with image-guidance, and percutaneous accessibility. General Image-Guidance Principles

Fluoroscopic guidance is versatile, offers good visualization of osseous structures, and panoramic and real-time procedure control. Precise orthogonal AP and LL views are needed for precise needle guidance and visualization. To obtain an AP view, one angles the tube in the opposite CC direction to profile, respectively, the anterior and posterior elements, due to their above-mentioned opposite CC angulation. Furthermore, the lordotic curvature of the cervical spine implies that the CC angulation is individual to each vertebral level. A precise level-specific AP view is identified by a midline positioned spinous process and a well-profiled target structure (ie, vertebral body, disk space, articular pillars, or interlaminar space) (Fig 2A–D). In a correct LL view, the disk endplates and the disk space are well-profiled, and the articular pillars are superimposed at the level of interest (Fig 2E and F). In some patients, the shoulders obstruct the fluoroscopic visibility of the lower cervical spine. Oblique views (Fig 2G and H), arm and shoulder traction, and high-level fluoroscopy can partially help in such cases. CT guidance offers superior visualization of soft-tissue and osseous structures and, with intravenous contrast administration, can clearly depict vascular structures, but it lacks panoramic and real-time procedural control. CT can also be a solution when the shoulders obstruct fluoroscopic visibility of the lower cervical spine. The CT guidance image plane should ideally be parallel to the desired needle path. Therefore, the CT gantry, similar to the fluoroscope, can be tilted in the CC direction, depending on the desired needle access, within certain limits (usually 20°-30° in both directions).

Fig 4. Anterolateral-approach technique with CT guidance. A 22-G ⫻ 17-cm spinal needle is aligned with the gantry laser light, inserted between the carotid artery and trachea to the target, and serves as a guidewire (A). An introducer needle is then coaxially advanced over this guidewire to the target (B and C). The strict alignment of the needle with the gantry laser light allows the entire needle to be imaged on a single section, for better control and precision. 64

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Fig 5. Anterolateral-approach technique with fluoroguidance. The left hand palpates the common carotid artery, retracts it laterally, and reaches deep for the anterior aspect of the spine (A and B), protecting the foramen transversarium and splaying the trachea and esophagus medially (arrowheads, B), while the right hand inserts the needle under realtime fluoroscopy and docks it into the target (C and D). Image A reproduced with permission from the American Society of Neuroradiology.7

Percutaneous Anterolateral C-Spine Accesses

Indications. This access is used almost exclusively in the infrahyoid neck, to access the prevertebral space from C4 to T1 (for biopsy or stellate ganglion block), the disk spaces from C3-C4 to C7-T1 (for biopsy aspiration, discography, percutaneous disk decompression), and the vertebral bodies from C4 to C7 (for biopsy, percutaneous tumor ablation, vertebroplasty). Relevant Anatomy. Most of the delicate and vital structures in the infrahyoid neck are located anterior and anterolateral to the cervical spine (Fig 3). The airway is located midline, is easily seen on CT and fluoroscopy, and can be manually mobilized sideways. The thyroid gland wraps the anterolateral aspect of the trachea and the lateral portions of the thyroid cartilage. The recurrent laryngeal nerve courses posterior and medial to the thyroid lobes. The hypopharynx-esophagus, located midline behind the trachea and in front of the prevertebral space, can be mobilized by deep palpation, more easily toward the left side; the most lateral portions of the hypopharynx, the pyriform sinuses, lie behind the thyroid cartilage. The common carotid artery and internal jugular vein in their course from the superior mediastinum to the neck move from anterolateral to posterolateral to the trachea, and course laterally and behind the thyroid gland, with the internal jugular vein lateral to the

Fig 6. Preprocedure awareness of local vascular anatomy for an anterolateral approach. Vascular loops, kinks, and retopharyngeal course of the carotids (“kissing carotids”) (arrows in A) may be poorly controllable with palpation and retraction and may be interposed along the anterolateral approach (circles and dashed arrow on C and D).

carotid artery (Figs 1 and 3). The carotid artery and the jugular vein are contained within the carotid space, along with cranial nerve X in the infra-hyoid neck, and can be palpated and mobilized laterally. The vertebral artery courses in the fat space anterolateral to the C7 and T1 vertebral bodies, posterior to the carotid sheath, before entering the transverse foramen, most commonly at C6. Once inside the transverse foramen, the vertebral artery courses lateral to the uncinate processes of the vertebral bodies, shielded by the transverse processes at each vertebral level, but uncovered and vulnerable in the anterior portions of the neuroforamina (Figs 1 and 3). The proximal nervous structures of the brachial plexus are located in the fat space called the “scalene triangle,” posterior to the carotid sheath, posterior and lateral to the anterior scalene muscle, and anterior to the middle scalene muscle. The sympathetic chain is located in the retropharyngeal fat plane anterior to the prevertebral space, along the anterolateral aspect of the longus capitis colli muscles; more specifically, the stellate ganglion is ventral to the head of the first rib. Technique. The patient is positioned supine, with slight head hyperextension; general anesthesia is strongly recommended. The access is anterolateral oblique, anterior to the sternocleidomastoid muscle, between the common carotid artery Neurographics 4:62–77 June 2014 www.neurographics.com

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Fig 7. Disk decompression. A C5–C6 right-sided contained disk herniation (A) causing severe radicular pain, resistant to conservative treatment, is treated percutaneously with fluoroguided insertion of a trocar needle in the disk space, slightly toward the right side. A nucleoplasty is performed coaxially with a coblation wand (B and C).

Fig 8. Disk biopsy and epidural abscess drainage. C3–C4 and C5–C6 diskitis with prevertebral and epidural abscess depicted in sagittal T2 (A) and sagittal T1 enhanced images (B). Anterolateral transdiskal access to the epidural collection, opacification with 0.5 mL of contrast (C), and coaxial insertion of an 18-G catheter for partial drainage (D).

laterally and the trachea and esophagus medially. The thyroid gland is often traversed at the C7 level. This access is limited below C7 by the anterior and medial course of the carotid and above C4 by the carotid bifurcation and the mandible. A straighter paratracheal anterior approach is performed for stellate ganglion blocks, with small-caliber needles (usually 25 G). CT Guidance. The CT gantry is tilted along the desired access plane (disk space/vertebral body). A localization scan is performed, preferably with IV contrast to depict the course of the carotid artery and vertebral artery. A 22-G ⫻ 17-cm spinal needle is aligned with the gantry laser light to stay in plane and is then inserted, under intermittent CT guidance, between the carotid artery and the trachea-esophagus to the target, avoiding major vessels and the esophagus. The hub is cut off, and the shaft of the needle serves as a guidewire. An introducer trocar of desired caliber (usually 14 –17 G) is then inserted coaxially over this guidewire to the target (Fig 4). Through the introducer, in a coaxial fashion, different devices can be introduced to perform a variety of procedures. 66

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Fluoroguidance. Biplane fluoroscopy is desirable. True lateral and AP views to profile the vertebral body and the disk space at the level of interest are obtained. The access is preferentially from the right side (to avoid the esophagus, and easier for right-handed operators). The left hand palpates the pulsatile carotid artery, retracts it laterally, and reaches deep with the finger tips for the anterior aspect of the spine, protecting the foramen transversarium laterally and splaying the trachea and esophagus medially. The right hand inserts the needle under real-time biplane fluoroscopy and docks it into the target (there is brief radiation exposure to the hands) (Fig 5). Alternatively, the use of a “prong deflector” has been described to avoid left-hand radiation exposure.8 A coaxial technique with a 22-G K-wire can be used (see “CT Guidance”). The disk space is accessible with this approach medial to the uncinate process; also the vertebral body access should be medial to the uncovertebral joint, which is safer for the vertebral artery.9-11 C7 and T1 access is not recommended with large-caliber needles due to poor control of carotid (anteriorly located, not easily pal-

Fig 9. Vertebral biopsy and vertebroplasty. C4 and C5 lytic lung cancer metastases with C4 collapse (A and B) and severe pain. There is increased risk of cement leakage in the epidural space due to erosion of the posterior vertebral wall. In such extreme cases, which pose a relative contraindication to the cement augmentation, we recommend the use of ultraviscous cement, extremely slow and careful injection, under good-quality real-time continuous fluoroscopic visualization. Fluoroscopic-guided anterolateral approach (15-G needle), and cement augmentation (C and D). Postoperative reformatted coronal and sagittal CT images (E and F).

Fig 10. Vertebral biopsy and tumor ablation. T1 osteoid osteoma (A–C). Axial postcontrast T1-weighted MR image shows how the soft-tissue thickening splays the trachea and the carotid and vertebral arteries (B). Combined CT and fluoroscopic-guided anterolateral access and radio-frequency ablation of the tumor with an umbrella-type RF coaxial needle (D–F).

pable, and poorly mobilized) and vertebral arteries (course of the vertebral artery outside the foramen transversarium) at this level. Special Considerations

Vascular anatomy in the neck can be quite variable; vascular loops, kinks, and the retropharyngeal course of carotid

arteries (“kissing carotids”) (Fig 6) may be poorly controllable with palpation and retraction. Preprocedural awareness of the individual local vascular anatomy is, therefore, strongly recommended, especially when using fluoroscopic guidance. Neurographics 4:62–77 June 2014 www.neurographics.com

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The thyroid gland, the superior and middle thyroid vessels, the superior and inferior laryngeal nerves, the loop of the hypoglossal nerve, and the cervical ganglia of the sympathetic system can be traversed with this access; however, the small-caliber needles used for these procedures are unlikely to cause serious damage to these blood vessels and nerves.12 Illustrative case are found in Figures 7, 8, 9, and 10. Percutaneous Lateral C-Spine Accesses

Indications. Lateral access is used for the central canal at the C1-C2 level (for CSF collection or myelography), the C3-C8 neuroforamina (for diagnostic, prognostic, and therapeutic selective nerve root blocks in radicular pain), the zygapophyseal (facet) joints, and the median branch nerves (for diagnostic, prognostic, and therapeutic blocks in facet-related pain).

Fig 11. Axial CT image depicting relevant anatomy in a lateral approach to the C-spine. CCA indicates common carotid artery (purple arrow); IVJ, internal jugular vein (orange arrow); VA, vertebral arteries in the anterior portion of the foramen (yellow arrows); Z-joint space (blue arrow). Foraminal access, posterior to the scalene triangle and to the vertebral artery (red arrow).

Relevant Anatomy. There are no vital or particularly delicate structures along a purely lateral access path to the cervical spine. The sternocleidomastoid muscle and the retrojugular fat plane are usually traversed to perform a lateral approach to the articular masses (Fig 11). The zygapophyseal joint space is best accessed from a lateral approach when CT is used for guidance (with thin sections, or when volume-averaging effects might hinder visualization of the joint space). The median branch nerves course circling

Fig 12. Fluoroscopic and CT relevant anatomy for lateral access. Lateral oblique foraminal view (A) and corresponding CT angiography volumerendering image (B) show the course of the vertebral artery in the anterior portion of the foramina and the narrow window to access the posterior portion of the foramen (C and D). The lateral approach to the median branch nerves targets the lateral mass at the crossing of 2 imaginary bisecting diagonal lines under fluoroscopy (E). The diagonal lines correspond to the groove or the so-called waist of the articular pillars, well-seen on reformatted coronal CT images (F, green arrows). 68

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Fig 13. Anatomy for C1–C2 puncture of the subarachnoid space. The prone decubitus position puts the cord in a dependent position and widens the dorsal subarachnoid space (arrow and dot in A and B). Standard C1–C2 puncture to perform myelography or CSF collection. The target is ventral to the spinolaminar line at C1–C2 (C). The needle should be placed in the lower C1–C2 interspace to avoid low-lying posterior inferior cerebellar artery branches. Contrast is injected only if spontaneous CSF flow is noted. Note the filling defect of the spinal cord following contrast injection (D).

around the articular masses, from anterior to posterior, in a groove along the “waist” of the articular pillar, where they can be targeted easily from a lateral approach for anesthetic injections (Fig 12). The access to the neuroforamina is retrojugular and has a more anterior obliquity (Figs 11 and 12). This more anterolateral access has to take into consideration the positions of the jugular vein and vertebral artery. The vertebral artery crosses, caudad to cephalad, the anterior portion of the neuroforamina, while the nerve root occupies the posterior portion of the foramen (Fig 12). Sometimes a posteriorly located or dilated internal jugular vein is in the way of the desired approach to the foramen. The brachial plexus lies ventral to the foraminal access. The anatomy of the dural sac at the C1-C2 level is relevant for the CSF collection and myelographic procedures: At C1C2, the dural sac has a posterior extroversion, which widens the dorsal subarachnoid space along the spinolaminar line, just posterior to the spinal cord, and is the target of lateral approaches to the intradural compartment (Fig 13). Technique. The patient can be positioned supine, prone, or in the lateral decubitus position, depending on individual

procedures, as well as patients’ and operators’ preferences. The purely lateral access to the lower cervical spine, in some cases, may require access through the base of the neck/ supraclavicular fossa. In the lateral decubitus position, it is important to place a support under the head to obtain a straight neutral alignment of the cervical spine; the recumbent shoulder in this position is usually elevated and might hinder proper lateral fluoroscopic visibility of the lower cervical spine. This approach can be performed with local anesthesia or intravenous conscious sedation. As for any other cervical access, we recommend the importance of precise image-guidance: If CT is used, the gantry should be tilted along the desired access plane and the needle should be aligned with the gantry to avoid off-plane misplacement; if fluoroscopy is used, it is important to obtain precise AP and LL views at the level of interest and, at the operator’s discretion, additional oblique en face views for “bull’s-eye” needle guidance. Contrast injection is usually necessary to predict the spread of injectate and rule out vascular runoff. Neurographics 4:62–77 June 2014 www.neurographics.com

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C1-C2 Dural Puncture. Head imaging is performed to rule out intracranial hypertension and tonsillar herniation. The patient is in a prone position, which allows dependent ventral spinal cord location and widening of the dorsal subarachnoid space; the head is straight with a support for the forehead. Under a precise LL fluoroscopic view, the target is the gap between the posterior elements of C1 and C2, just ventral to the spinolaminar line. The needle should be placed in the lower C1-C2 interspace to avoid low-lying posterior inferior cerebellar artery branches. The needle is slowly inserted with a bull’s-eye technique until it reaches midline on the AP view or spontaneous flow of CSF is obtained. No contrast is injected unless spontaneous CSF flow is noted (the spinal cord can be accidentally punctured with a small-caliber needle [22–25 G]), usually with no complications except for transient shocking pain, but intramedullary injection of contrast agent carries the risk of permanent cord damage.13 Median Branch Nerve Block. A median branch nerve block is quick and practical under fluoroguidance; in the lateral decubitus position, with a precise LL view at the level of interest, the target is the point of intersection of the 2 diagonal lines bisecting the rhomboid shape of the articular masses (Fig 12). Selective Nerve Root Block. Under fluoro-guidance, the patient is positioned supine, with a slight contralateral head rotation. An anterolateral view to profile the foramen at the level of interest allows bull’s-eye insertion of a small-caliber needle to contact the superior articular process along the posterior portion of the foramen; the needle is then gently walked off the bone ventrally to penetrate the foramen. The AP view is used to assess the depth of insertion in the foramen. Contrast injection with real-time fluoroscopic control is recommended to rule out vascular runoff (some advocate the use of digital subtraction).14 Under CT guidance, purely lateral and posterior approaches have been described, with needle placement just outside the foramen, next to the emergence of the spinal nerve from the neuroforamen.15 Zygapophyseal (Facet) Joint Puncture: The lateral access is preferred if CT guidance is used; the posterior access is instead preferred if fluoroguidance is used. Special Considerations

At C1-C2, the dura is not firmly attached to the walls of the central canal and can be resilient to perforation; in fact, during attempts of C1-C2 dural puncture, the dura can tent. Therefore, often needle advancement has to reach and even pass midline to obtain access to the subarachnoid space (Fig 14). Intraforaminal cervical injection carries the risk of vertebral artery (anteriorly located in the foramen) and spinal artery 70

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Fig 14. Lateral approach. C1–C2 puncture (A and B). The needle is inserted to reach and even pass the midline (otherwise the dura can “tent” and prevent needle access to the subarachnoid space). No contrast is injected unless spontaneous CSF flow is noted. Zygapophyseal joint puncture (C and D). Under CT-guidance, a lateral access is preferred. Intra-articular spread of contrast (0.2 mL) confirms the correct needle position. Median branch nerve block (E and F): under lateral fluoroscopic view. The center of the articular mass is the target. Bone contact is made with the needle (E), and contrast injection (F) rules out vascular runoff. Neuroforaminal selective nerve root block (G and H). Under a precise oblique foraminal view, the target is the superior articular process of the articular mass. Bone contact is made with the needle (G), and the needle is walked off ventrally into the foramen. An AP view controls the depth of insertion into the foramen (H); contrast injection under real-time fluoroscopic control rules out vascular runoff (H).

injury and embolization.16 Strong clinical indications, strict technique, preprocedural knowledge of vascular anatomy in the foramen (Fig 15A), a performant image-guidance system, and the use of nonparticulate steroids are strongly recommended. Due to reported devastating complications and the unproven superiority of intraforaminal-versus-interlaminar

Fig 15. Preprocedural awareness of local vascular anatomy before a lateral access to the neuroforamen. The patient was referred for a C4 –C5 right selective nerve root block for C5 radicular pain due to foraminal disk herniation. When we reviewed the MR imaging, the “foraminal disk herniation” had a suspicious appearance: A localizing contrast-enhanced CT scan revealed a vertebral artery loop in the foramen (arrow in A) obstructing the needle access to the foramen. The common carotid artery and internal jugular vein may also stand in the way of an anterolateral foraminal access (A). Ectatic left internal jugular vein along the desired needle access to the left neuroforamen (dashed yellow arrow in B).

Fig 16. Bony landmarks used in fluoroscopy for a posterior access. In the posteroanterior pillar view, the lateral margins of the lateral masses are profiled and the waist of the articular pillars corresponds to the median branch nerve grooves (arrowheads on A and B). Lateral and medial borders of the articular masses (green dashed lines on A and B) delineate the safety area. A needle superimposed on this area can be safely advanced until bone contact is made. Medial to this area is the central canal. In the lateral view, the spinolaminar line (red) marks the posterior border of the central canal and the interarticular line (yellow) marks the posterior aspect of the articular pillar. The nerve roots, brachial plexus, and vertebral arteries lie ventral to the posterior longitudinal line (white).

steroid injections, we perform selective nerve root block only for diagnostic purposes, with a small amount of local anesthetic agent. In some instances, the anterolateral approach to the foramen implies traversing the jugular vein (Fig 15B), but this is usually uneventful with small-caliber needles. Illustrative Cases are seen in Figure 14. Percutaneous Posterior C-Spine Accesses

Indications. The posterior access is used for the interlaminar space (for epidural blocks), posterior bony elements (for

bone biopsies and cementoplasty), the C1-C2 neuroforamen (for C2 nerve blocks), C1-C2 and lower facet joints (for joint blocks), and median branch nerves (for facet radio-frequency [RF] denervation). Relevant Anatomy. No vital structures are along the path of a posterior access to the spine, but there is a risk of straying into the central canal and spinal cord injury, or straying lateral and ventral to the articular pillars, where spinal nerves, the brachial plexus, the vertebral artery, and the neurovascular bundle can be encountered. When Neurographics 4:62–77 June 2014 www.neurographics.com

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Fig 17. Vascular anatomy for posterior access to the upper C-spine (C0 –C2). The vertebral arteries course just lateral to the C1–C2 joint (A) and cranial to the C1 ring (B and C), before entering the dura at C0 –C1 (red arrows).

Fig 18. Fluoroscopic-guided posterior access to the lateral masses. On the AP view, the needle tip has to be constantly superimposed on the lateral aspect of articular pillar (A); this maneuver prevents it from entering the central canal and straying into the anterior neck. On the lateral view, the obliquity of the access is determined and the needle can be safely advanced until the spinolaminar line is reached (B); at this point, another AP view has to be obtained to ensure proper needle direction (superimposition of the needle tip on the articular masses as above). The needle can then be advanced to make bone contact with the articular masses at the interarticular line (C). If no bone contact is obtained, the needle might be straying too lateral and ventral in the anterior neck.

Fig 19. Posterior approach to the C1 lateral mass under CT guidance. Painful lytic metastasis of the C1 lateral mass (A and B). The arrowhead in A points to the vertebral artery, with an eroded transverse foramen. The asterisks in A and C mark the needle entry point. CT-guided needle insertion below the vertebral artery loop (D and E). Cement filling of the lytic lesion by using CT fluoroscopy (F and G). Images reproduced with permission from Elsevier Inc, previously published in The Spine Journal.17

using fluoroguidance, one should be familiar with the bony landmarks of the cervical spine relevant to the posterior access (Fig 16). Posterior access to the upper Cspine (C1-C2) requires thorough knowledge of the verte72

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bral artery anatomy, coursing lateral to the C1-C2 joint and cranial to the C1 ring (Fig 17). In the C1-C2 foramen, the C2 nerve root is surrounded by a large venous plexus.

Fig 20. RF denervation of the cervical zygapophyseal (facet) joints under fluoroscopic guidance. AP (A) and lateral (B) views of the cervical spine show the needle tips located in bone contact along the lateral cervical masses in the median branch nerve grooves just dorsal to the posterior longitudinal line with a posterior access for RF median branch rhizotomy in this patient with unilateral neck pain, with a prior positive diagnostic median branch nerve block at the same levels.

Fig 21. Paramaxillary access. Subzygomatic skin entry and course through the masticator space between the vertical ramus of the mandible and the maxilla. Right-to-left range (A) and CC range of angulation (obtained through flexion-extension of the CVJ and/or CT gantry tilt) (B) make this approach very versatile. Contrast-enhanced localization CT scan displays crucial vascular anatomy (mainly the ICA) (dashed circle in A).

Technique. The patient is positioned prone. This approach can be performed with local anesthesia, intravenous conscious sedation, or general anesthesia, depending on individual procedure requirements. CT Guidance. The CT gantry is tilted along the desired access plane (interlaminar/articular pillar, C1-C2 foramen, and so forth). The needle is aligned with the gantry and advanced to the target. Fluoroscopy Guidance. A biplane is desirable, but not absolutely necessary. If single-plane fluoroscopy is used, intermittent anteroposterior (AP) and lateral-lateral (LL) checks are mandatory to avoid violating the central canal or straying ventral and lateral to articular pillar. As a rule, the LL view is used to control the CC obliquity of the access and to assess depth, and the AP view is used to control the rightleft-access direction. Especially if median branch nerves are

the target (for RF denervation), along the lateral masses, the needle tip is maintained superimposed on the articular pillar on the AP view (Fig 18A). In the lateral view, the needle can be advanced safely until the spinolaminar line is reached (Fig 18B), and at this point, an AP view is necessary to verify that the needle is on target. The needle can then be advanced safely until bone contact is made at the interarticular line (Fig 18C); in the lateral view, if needle does not make bone contact at the interarticular line, it might be straying lateral and ventral to the spine into the neck. Special Considerations

When performing RF median branch denervation, the thermal ablation occurs along the length of the active needle tip (5–10 mm); therefore, the active needle shaft has to be placed parallel and adjacent to the course of the nerve to be ablated, usually in contact with the bone of the articular pillar waist. Neurographics 4:62–77 June 2014 www.neurographics.com

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Fig 22. Paramaxillary access under CT guidance for sclerotherapy of a lymphatic malformation extending to the foramen ovale (A and B) in a 7-month-old patient. A 22-G spinal needle is inserted in the malformation at the level of the skull base (C). Contrast injection reveals opacification of the cystic lesion in axial (D) and reformatted sagittal (E) and coronal (F) images. Doxycycline is then injected for sclerotherapy. Courtesy of Dr Imran Chaudry, MUSC, Charleston, South Carolina.

Fig 23. Transoral approach. Reformatted CT sagittal midline image of a patient with an open mouth to show the range of CC access to the anterior elements of the upper cervical spine. The tongue can be depressed or moved sideways, and the soft palate can be moved cranially to access the bony elements through the retropharyngeal and prevertebral spaces. The access is strictly midline because paramedial access poses a risk of injury to the internal carotid and vertebral arteries.

Illustrative cases are seen in Figures 19 and 20.

tions of C1, C2, C3 (for biopsy, vertebral augmentation, percutaneous tumor ablation).

Percutaneous Paramaxillary C-Spine Accesses

Indications. Paramaxillary access is used to access the retropharyngeal and prevertebral space at the C0-C3 level (for biopsies); skull base; foramen ovale; clivus (for biopsy, injections, radio-frequency ablation); and the ventral por74

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Relevant Anatomy. The access is subzygomatic through the masticator space between the vertical ramus of the mandible and the maxilla (alveolar process or maxillary sinus). It traverses the temporalis and pterygoid muscles, lateral to the pterygoid plates and the parapharyngeal space and me-

Fig 24. Preprocedural awareness of local vascular anatomy. CT angiography source images (A and B) depicting the expected lateral course of the internal carotid arteries ventral to the lateral masses of C1 and C2. 3D volume-rendering and axial source CT angiography images (C and D) of a patient with a midline retropharyngeal course of the right internal carotid artery. In such a situation, a fluoroscopic-guided transoral approach to C2 (red arrow on D) would pose a high risk of injury to the internal carotid artery (yellow circle on D).

dial to the upper cervical portion of the internal carotid artery and jugular vein (Fig 21A). The anatomic space is large and allows a wide right-to-left and CC access range. Along the path is the pterygoid venous plexus, the internal maxillary artery, and the maxillary branch of the trigeminal nerve, but complications have been reported very rarely.18 Technique. The patient is positioned supine. General anesthesia is strongly recommended. We exclusively perform this access exclusively under CT guidance due to the superior visualization of vascular structures. Contrastenhanced localization CT displays crucial locoregional vascular anatomy (mainly the ICA) and allows safe planning of the right-to-left-access obliquity. The CC obliquity of the access varies, depending on the target structure. While the skin-entry point has to be immediately subzygomatic (a more caudal entry may involve the buccal space), the head of the patient can be positioned in different degrees of flexion/extension and/or the CT gantry can be tilted to align the paramaxillary access to the

desired deep target (skull base– clivus-C1-C2-C3). As an example, compared with a neutral head position, extension of the head allows a more cranial target to be reached through the same skin access (Fig 21B). Once the desired angle of the image plane is obtained, we strongly recommend alignment of the needle to the laser light of the CT gantry so that the whole needle path, from its skin-entry point to the final target, is displayed on a single CT section and can be safely advanced in-plane to the target, avoiding straying off-section. We routinely first insert a 22-G ⫻ 17-cm spinal needle to serve as a guidewire for coaxial placement of a blunt tip 14- to 16-G trocar cannula in the target. Biopsy/aspiration/injection needles are then inserted coaxially through the cannula. Special Considerations

Attention should be paid not to traverse the buccal space and the pharyngeal mucosa, to diminish the potential risk of infection of the deep targeted structures. Neurographics 4:62–77 June 2014 www.neurographics.com

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Fig 25. Transoral fluoroscopic-guided C2 and C3 vertebral augmentation. Painful lytic metastasis to the C2 and C3 vertebral bodies on a reformatted coronal CT image (A). Lateral views of the transoral approach and vertebroplasty of C3 (B) and C2 (C) vertebral bodies, with satisfactory cement filling of the lytic lesions on a postprocedural lateral radiograph (D) and reformatted CT images (E and F).

Illustrative cases are seen in Figure 22. Percutaneous Transoral C-Spine Accesses

Indications. Transoral access is used for the C1-C3 anterior bony elements (for biopsy, vertebral augmentation, percutaneous tumor ablation). Relevant Anatomy. With the mouth open, the tongue depressed or moved sideways, and the soft palate moved cranially, there is good visibility of the posterior oropharyngeal mucosa. Through the large mouth opening, the midline ventral aspect of the C1-C3 bony elements can be palpated and accessed, traversing the mucosa, the thin retropharyngeal, and prevertebral spaces. With different degrees of mouth opening, flexion-extension of the craniocervical junction, and angle of needle access, the anterior elements from C1 to C4 can be targeted (Fig 23). Midline access is safe, while off-midline, the internal carotid arteries run just lateral to the parapharyngeal space and ventral to the lateral masses of C1, and the vertebral arteries run in the C2 and C1 foramen transversarium (Fig 24A and B). Technique. The patient is positioned supine, under general anesthesia, with the orotracheal tube positioned on 76

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one side of the mouth. A surgical mouth opener can be used, preferably radio-transparent. Biplane fluoroguidance is preferred to CT because it is less cumbersome and offers real-time control in a very delicate area. Complete asepsis in the oral cavity is not possible, but we use a diluted solution of povidone-iodine (Betadine, Purdue Products L.P., Stamford, CT) to clean the mucosal surfaces. Then we create a sterile passage, inserting a tubular sonography probe cover into the mouth. The probe cover is then pierced at the closed end, where all the instruments and devices we might use during the procedure will pass without direct contact with the mucosal surfaces. The access is strictly midline. The needle is inserted in the mouth, a tongue depressor can be used to move the tongue and the soft palate out of the way. The needle is gently rested on the posterior wall of the pharynx; its position is checked on 2 precise orthogonal views to ensure that the CC direction is correct. The access is strictly midline before advancing the needle to the target.

Special Considerations

A retropharyngeal course of the internal carotid artery has to be ruled out before planning a transoral approach (Fig 24C and D).

There is a theoretic risk of infection from the oral flora (antibiotic prophylaxis with amoxicillin and clavulanic acid is recommended). Illustrative cases are seen in Figure 25.

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CONCLUSIONS

9.

Due to the complex, delicate, and vital anatomic environment, percutaneous image-guided procedures in the cervical spine require thorough knowledge of locoregional anatomy, precise and reliable imaging guidance, accurate planning, and rigorous technique, to avoid serious complications. Fluoroscopic or CT guidance can be chosen on the basis of personal preference, anatomic features, type of approach, and specific procedure to be performed. REFERENCES 1. Kranz PG, Raduazo P, Gray L, et al. CT fluoroscopy-guided cervical interlaminar steroid injections: safety, technique, and radiation dose parameters. AJNR Am J Neuroradiol 2012;33: 1221–24 2. Eckel TS, Bartynski WS. Epidural steroid injections and selective nerve root blocks. Tech Vasc Interv Radiol 2009;12:11–21 3. Falco FJ, Erhart S, Wargo BW, et al. Systematic review of diagnostic utility and therapeutic effectiveness of cervical facet joint interventions. Pain Physician 2009;12:323– 44 4. Van Zundert J, Vanelderen P, Kessels A, et al. Radiofrequency treatment of facet-related pain: evidence and controversies. Curr Pain Headache Rep 2012;16:19 –25 5. Gangi A, Tsoumakidou G, Buy X, et al. Percutaneous techniques for cervical pain of discal origin. Semin Musculoskelet Radiol 2011;15:172– 80 6. Anselmetti GC, Bonaldi G, Carpeggiani P, et al. Vertebral augmentation: 7 years experience. Acta Neurochir Suppl 2011;108:147– 61 7. Bonaldi G, Baruzzi F, Facchinetti A, Fachinetti P, Lunghi S. Plasma radio-frequency-based diskectomy for treatment of cervical herniated nucleus pulposus: feasibility, safety, and

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preliminary clinical results. AJNR Am J Neuroradiol 2006; 27:2104 –11 Bartynski WS, Grahovac SZ, Rothfus WE. Cervical diskography performed with a “prong deflector” for improved access to the cervical disk spaces. AJNR Am J Neuroradiol 2005;26: 1004 – 07 Tampieri D, Weill A, Melanson D, et al. Percutaneous aspiration biopsy in cervical spine lytic lesions: indications and technique. Neuroradiology 1991;33:43– 47 Kattapuram SV, Rosenthal DI. Percutaneous biopsy of the cervical spine using CT guidance. AJR Am J Roentgenol 1987;149:539 – 41 Ottolenghi CE, Schajowicz F, Deschant FA. Aspiration biopsy of the cervical spine: technique and results in thirty-four cases. J Bone Joint Surg Am 1964;46:715–33 Gupta S, Henningsen JA, Wallace MJ, et al. Percutaneous biopsy of head and neck lesions with CT guidance: various approaches and relevant anatomic and technical considerations. Radiographics 2007;27:371–90 Simon SL, Abrahams JM, Sean Grady M, et al. Intramedullary injection of contrast into the cervical spinal cord during cervical myelography: a case report. Spine 2002;27: 274 –77 Furman MB, Giovanniello MT, O’Brien EM. Incidence of intravascular penetration in transforaminal cervical epidural steroid injections. Spine 2003;28:21–25 Wolter T, Knoeller S, Berlis A, et al. CT-guided cervical selective nerve root block with a dorsal approach. AJNR Am J Neuroradiol 2010;31:1831–36 Inamasu J, Guiot BH. Iatrogenic vertebral artery injury. Acta Neurol Scand 2005;112:349 –57 Cianfoni A, Distefano D, Chin SH, Varma AK, Rumboldt Z, Bonaldi G. Percutaneous cement augmentation of lytic lesion of C1 via posterolateral approach under CT guidance. Spine J 2012;12:500 – 6 Esposito MB, Arrington JA, Murtagh FR, et al. Anterior approach for CT-guided biopsy of skull base and parapharyngeal space lesions. J Comput Assist Tomogr 1996;20: 739 – 41

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