CT fluoroscopy guides spinal interventions

Spinal disorders are an increasing cause of disability and a growing therapeutic challenge. CT fluoroscopy is a reliable technology that enables basic spine interventions to be performed with great precision and more difficult procedures to be carried out with safety and confidence. This technique decreases risk and maximizes patient comfort during such procedures.1,2

Multislice CT fluoroscopy allows the guidance and placement of needles to be monitored in 3D (Figure 1). Acquisition of three contiguous CT slices of varying thickness (1 to 16 mm) permits a volumetric approach with precise management of the patient's z-axis. A high frame rate (up to eight images per second) and short delay (0.33 sec) between needle movement and reproduction of the movement provides real-time imaging with image stability. Anatomy can be discerned with millimeter precision for needle placement.1

Procedures can be performed quickly, and x-ray exposure to patients is low. Additional benefits include precise needle positioning and a low rate of complications or technical failure. CT fluoroscopy can help patients avoid surgery for conditions such as thoracic and lumbar neurolysis, percutaneous laser disc decompression, and synovial cyst decompression.2-7 The need for general anesthesia and/or sedation is reduced as well.

Practitioners who are interested in this technique should undergo proper training. Hands-on workshops and web-based online training are necessary, practical approaches to complete academic teaching.

The scattered dose to the radiologist performing CT fluoroscopy-guided procedures is reduced significantly when all radiation protection devices and 80 kV protocols are combined. A lead apron and thyroid collar should be worn. Lead gloves can reduce the scattered dose to the fingers by 30% and to the wrist by 50%. Use of a facial screen enables a scattered dose reduction (SDR) of 94% for the upper chest and head. Placing a lead cover on the patient offers an SDR of 97% for the lower part of the body.

Interventions are of two types: basic and advanced. The former are relatively easy to perform; the latter need experience and proper training.

BEGINNING WITH BASICS

Several basic procedures should present little difficulty to the experienced interventional radiologist:

• Greater occipital nerve infiltration. The indication for this basic intervention is Arnold's neuralgia (greater occipital nerve from dorsal ramus of C2). The target is Arnold's nerve origin, between the posterior arches of C1 and C2, at the posterior aspect of the bony facet.

The procedure begins with an axial scan, with the patient lying prone, from C0 to C3 for targeting and vertebral artery delineation. Posterior puncture is made with a 25-gauge spinal needle. CT fluoroscopy guidance permits fast, correct needle tip placement at the level of the C2 bony facet (trigger zone) followed by steroid injection. If needle contact with the bony facet does not trigger neuralgia, pain may be due to atlas-axis spondylosis (pseudo-Arnold's neuralgia). The main danger with this procedure is vertebral artery puncture.3,4

• Cervical periradicular infiltration. This procedure is indicated by radiculopathy due to a disc herniation or degenerative foraminal stenosis. The target is the exit of the neuroforamen, just below the pedicle (foraminal roof). An axial scan of the patient in the supine position is used to locate the neuroforamen and anterior lying vertebral artery, which is approached laterally just behind or through the sternocleidomastoid muscle. CT fluoroscopy guides direct puncture from skin to roof of the neuroforamen with a 25-gauge needle. The needle is positioned at the anterior aspect of the bony facet for steroid injection (Figure 2A). Practitioners should again be aware of the risk of vertebral artery puncture. Nerve root injury at the foraminal exit is an additional risk.5-8

• Lumbar epidural infiltration. Patients with sciatic pain due to radicular impairment inside the spinal canal, symptomatic spinal stenosis, or acute low back pain of discogenic origin with failure of conservative treatment may benefit from this procedure. Intervention targets the epidural space between the ligamentum flavum, facet joint, dural sac, and symptomatic nerve root. An axial scan of the patient lying prone is used to locate the target slice and check concordance with clinical findings. Practitioners should take a paramedian posterior approach, using a 22-gauge needle, for CT fluoroscopy-guided direct puncture from the skin to the anterior aspect of the ligamentum flavum. Resistance will be lost when the ligamentum flavum is crossed. Injection of 0.2 mL purified air will confirm that the epidural needle tip is positioned correctly, and steroid injection can proceed.5,6,9

A perforated dura will cause injected air to wash out. The needle must be pulled back slightly in this case, and the presence of cerebrospinal fluid assessed using aspiration. If dural perforation induces headache, a blood patch can be considered. Punctures to the nerve root, epidural vein, and facet joint can occur on rare occasions.

• Lumbar periradicular infiltration. The indication for this intervention is foraminal or postforaminal symptomatic radicular conflict. The patient should be positioned prone. An axial scan is used to locate the target slice (spinal ganglion) and check concordance with clinical findings. A posterolateral approach should be adopted. CT fluoroscopy guides direct puncture (22-gauge needle) from the skin to the anterior aspect facet joint, at the neuroforaminal exit, in front of the spinal ganglion (Figure 2B). Steroid injection is the final step.5,6

• Lumbar synovial cyst treatment. This basic procedure can benefit patients with painful nerve compression due to a synovial cyst. The degenerative facet joint causing the synovial cyst is targeted most often, though sometimes the synovial cyst is punctured directly. An axial scan to locate the synovial cyst and the correspondent facet joint is performed with the patient lying prone. Taking a posterior approach, CT fluoroscopy is used to guide direct puncture with a 20-gauge needle from the skin to the facet joint.

Injection of contrast or sterile air will cause the facet joint and synovial cysts to opacify. The pressure should be increased with saline to rupture the cyst. The procedure should be stopped if the patient is suffering unbearable pain and direct cystic puncture performed instead. This involves the same technique as that used for lumbar epidural infiltration, with saline cystic rinsing followed by increased pressure to rupture the cyst wall. A steroid injection completes the procedure. 3,10

ADVANCED PROCEDURES

More difficult interventions also benefit from new technology and techniques:

• Upper thoracic sympathetic neurolysis. This procedure is indicated for patients with palmar hyperhidrosis (95%) and peripheral vascular diseases such as thromboangiitis obliterans and Raynaud's disease. The target is the thoracic sympathetic ganglion at the level of T3-T4. An axial scan is first performed from C7 to T5 with the patient lying prone. The target slice should be at the level of the T4 pedicle, to avoid the neuroforamen and intercostal nerve.

Local anesthesia from the skin to the pedicle can be used if the patient is anxious. CT fluoroscopy then guides direct puncture (22-gauge needle) from the skin to the pleurovertebral angle. The extrapleural space is widened with saline and the needle tip positioned at the anterior third of the paravertebral space. The tip's extravascular position can be confirmed using 2 to 4 mL contrast.3,4,11,12

Neurolysis of the thoracic ganglion is performed with rapid injection ( < 10 sec) of 8 mL of 8% phenol in glycerine (Figure 3A). The patient should then be moved quickly to a sitting position to avoid diffusion of phenol to the stellate ganglion. This sitting position should be maintained for two hours with the patient awake.

The main danger associated with this procedure is intravenous injection of the phenol in glycerine solution, which may be fatal. Diffusion of phenol to the stellate ganglion can cause Horner syndrome.

• Lumbar plexus neurolysis. Indications include significant peripheral artery disease and lower limb complex regional pain syndrome with a sympathetic component. Intervention is targeted at the anterolateral aspect of the L2 and L4 vertebral bodies, between the aorta (left) or inferior vena cava (right) and psoas muscle.

Contrast-enhanced abdominal CT is performed with the patient lying prone to delineate the ureters and determine the target slices. Single-sided puncture with CT fluoroscopy guidance is carried out at the L2 and L4 levels, from skin to target, with 22-gauge needles. Injection of 1 mL contrast will prove the extravascular positioning of the needle tip and evaluate diffusion. Lumbar plexus neurolysis is carried out by injecting 10 mL of an 8% phenol in glycerine solution at each level. Needles should be rinsed with 1 mL lignocaine before withdrawal (Figure 3B).

Ureteral puncture is a risk associated with this intervention. The procedure should be stopped if diffusion toward the posterior third of the vertebral body is observed. Potential complications include pain when injecting phenol and orthostatic hypotension.3,4,11,13

• Nucleoplasty (radiofrequency- or laser-induced disc decompression). Sciatic pain that is caused by a contained disc herniation and is resistant to six weeks of conservative treatment may respond to nucleoplasty. The target is the nucleus of the intervertebral disc. Patients lie prone for an axial CT scan, which is generally performed on the lower three lumbar levels. Local anesthesia is administered from the facet joint to the skin.

Direct disc puncture (18-gauge needle), via a posterolateral approach, is guided by CT fluoroscopy. The needle tip should be centered at the level of the nucleus in all planes. Disc decompression can then be induced using a laser fiber or RF probe, as required (Figure 4). Patients should then rest for four hours. Discitis (infectious or thermal) is the main risk associated with this procedure.11,14,15

• Vertebroplasty. This procedure is intended to manage pain in cases of a fractured endplate due to trauma, neoplasm, or osteoporosis; an aggressive angioma; or lytic metastasis. The target is the anterior third of the vertebral body. Patients are positioned prone with an intravenous drip and undergo an axial scan of painful vertebra and adjacent endplates.

The approach will depend on the vertebral level. A transpedicular approach is most commonly required, though sometimes a posterolateral approach may be taken at the lumbar level or an intercostovertebal approach at the thoracic level. Local anesthesia is administered from the periosteum to the skin. CT fluoroscopy-guided vertebral puncture is performed using an 11- or 13-gauge needle. A hammer may be necessary for crossing the cortex.

The needle tip is placed centrally at the anterior third of the vertebral body. Cement (3 to 5 mL) can then be prepared and injected slowly (Figure 5). CT fluoroscopy will help evaluate filling and diffusion. Patients should be confined to bed for four hours after the procedure.

The procedure should be halted if a leak occurs. Practitioners taking a posterolateral approach should avoid the nerve root. Epidural or venous leaks are other possible complications.4,6,11,16,17

LOOKING AHEAD

Triple-slice CT fluoroscopy, with its real-time volumetric approach, makes it possible to perform nonvascular interventions with the highest precision, safety, speed, and confidence. Spine interventions represent a significant number of patients in practice. Real-time CT fluoroscopy with multiplanar reconstruction, combined with navigation and/or robotics, will allow new minimally invasive treatments to be developed further.

Proper training will help strengthen professionalism in this emerging subspeciality.

DR. BRAT is head of radiology at the Centre Hospitalier Hornu-Frameries in Hornu, Belgium.

Additional procedures are described at www.ctfluoroscopy.org.

References

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• Silbergleit R, Mehta BA, Sanders WP, Talati SJ. Imaging-guided injection techniques with fluoroscopy and CT for spinal pain management. Radiographics 2001;21(4):927-939.

• Brat H, Bouziane T. Tomodensitometrie interventionnelle: Neurolyses et infiltrations perivertebrales. In: Louryan S, Lemort M, Baleriaux D, eds. Imagerie des nerfs peripheriques. Montpellier: Sauramps medical, 2004:117-149.

• Kastler B, Fergane B, Boulahdour Z, et al. Radiologie interventionnelle dans le traitement de la douleur. Paris: Masson, 2003:53-156.

• Brat H, Divano L. Tomodensitometrie interventionnelle: Infiltration peridurale ou periradiculaire? In: Louryan S, Lemort M, Baleriaux D, eds. Imagerie des nerfs peripheriques. Montpellier: Sauramps medical, 2004:109-116.

• Fenton DS, Czervionke LF. Image-guided spine intervention. Philadelphia: Saunders, 2003:73-126.

• Wagner AL. CT-fluoroscopic-guided cervical nerve root blocks. AJNR 2005;26(1):43-44.

• Wagner AL. Selective nerve root blocks with CT fluoroscopic guidance: technique, results, procedure time and radiation dose. AJNR 2004;25(9):1592-1594.

• Wagner AL. CT-fluoroscopic-guided epidural injections: technique and results. Am J Neuroradiol 2004;25(10):1821-1823. Erratum in: AJNR 2005;26(1):204.

• Lim AK, Higgins SJ, Saifuddin A, Lehovsky J. Symptomatic lumbar synovial cyst: management with direct CT-guided puncture and steroid injection. Clin Radiol 2001;56(12):990-993.

• Gangi A, Dietemann JL, Dondelinger RF. Tomodensitometrie interventionnelle. Paris: Vigot, 1994:200-212.

• Dondelinger RF, Kurdziel JC. Percutaneous block of the upper thoracic sympathetic chain with computed tomography guidance. A new technique. Acta Radiol 1987;28(5):511-515.

• Dondelinger RF, Kurdziel JC. Percutaneous phenol neurolysis of the lumbar sympathetic chain with computed tomography control. Ann Radiol (Paris) 1984;27(4):376-379.

• Gangi A, Dietemann JL, Ide C, et al. Percutaneous laser disk decompression under CT and fluoroscopic guidance: indications, technique, and clinical experience. Radiographics 1996;16(1):89-96.

• Gangi A, Dietemann JL, Guth S, et al. CT-guided interventional procedures for pain management in the lumbosacral spine. Radiographics 1998;18(3):621-633.

• Mathis JM, Barr JD, Belkoff SM, et al. Percutaneous vertebroplasty: a developing standard of care for vertebral compression fractures. AJNR 2001;22(2):373-381.

• Tohmeh AG, Mathis JM, Fenton DC, et al. Biomechanical efficacy of unipedicular versus bipedicular vertebroplasty for the management of osteoporotic compression fractures. Spine 1999;24(17):1772-1776.