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Epidural Steroid Injections and Selective Nerve Root Blocks
Epidural Steroid Injections and Selective Nerve Root Blocks Timothy S. Eckel, MD,* and Walter S. Bartynski, MD† Epidural steroid injections and lumbar nerve root block/steroid injection are commonly performed interventional treatments for spine-related pain. These procedures are the foundation of any image-guided spine pain management practice. While more generic and not target-specific, epidural steroid injections are highly effective in a large proportion of patients, including patients with axial pain (neck or low back pain), radiculopathy, or spinal stenosis with neurogenic claudication. When isolated lumbar nerve root irritation is more clearly suspected, transforaminal nerve root blocks can provide useful diagnostic information as well as deliver more specifically targeted steroid treatment. Sustained pain relief can be achieved in a substantial number of patients with both types of procedure. Here we review the clinical indications and technical approach to these fundamental image-guided procedures. Fluoroscopy can be the routine approach to all injections. Computed tomography or computed tomographic fluoroscopy can be used as the primary approach in lumbar epidural or nerve root injections or be used as an alternative technique in unique cases. While the basic technical approach to epidural steroid administration in the cervical, thoracic, and lumbar regions is similar, each region has unique issues that must be addressed. Tech Vasc Interventional Rad 12:11-21 © 2009 Elsevier Inc. All rights reserved. KEYWORDS epidural, steroid, selective nerve root block, neck pain, low back pain, radiculopathy, sciatica, spinal stenosis, image guided, anesthetic
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pidural steroid injections and selective lumbar nerve root blocks are commonly employed in the diagnosis and treatment of spinal pain and radiculopathy. Patients typically gain significant early or immediate relief from neck pain, low back pain, or radiculopathy, with many patients achieving long-term pain control. In general, these procedures are performed with C-arm fluoroscopic guidance. In the lumbar region, standard computed tomography (CT) or CT fluoroscopy may also be used. CT is cumbersome to employ for interlaminar epidural targeting in the cervical and thoracic regions due to patient access, gantry angle limitations, and needle tracking due to respi-
*Diagnostic and Interventional Neuroradiology, Annapolis Spine Institute/ Annapolis Radiology Associates, Annapolis, MD. †Department of Radiology, Division of Neuroradiology, Presbyterian University Hospital, University of Pittsburgh Medical Center, Pittsburgh, PA. Address reprint requests to Timothy S. Eckel, MD, Diagnostic and Interventional Neuroradiology, Annapolis Spine Institute/Annapolis Radiology Associates, 2002 Medical Parkway, Suite 235, Annapolis, MD 21401. E-mail: [email protected]. 1089-2516/09/$-see front matter © 2009 Elsevier Inc. All rights reserved. doi:10.1053/j.tvir.2009.06.004
ratory motion. Here we review the indications and procedural approach to these commonly performed treatments for spinal pain syndromes.
Clinical Evaluation of the Patient and Procedure Indications It is important to understand the basic clinical reason for referral and treatment in these patients. In general, patients referred for interlaminar steroid administration have neck pain or low back pain either alone or in combination with radiating arm or leg pain (radiculopathy). Selective lumbar nerve root blocks are employed when a specific nerve root is considered responsible for the patient’s radiculopathy and may be performed for diagnostic or therapeutic purposes. Selection of technique and injection volume is influenced by the intent of the procedure. Preprocedure imaging is important to evaluate for features related to the patient’s specific pain problem and to assess for unexpected findings or potential contraindications to injection, such as the presence of tumor, infection, fracture, or spinal cord abnormality. 11
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Contraindications for the Injection Procedures Active infection should not be present at the time of the procedure and is a relative contraindication. Patients with an allergy to contrast should be prepped 24 hours before the procedure (typically, prednisone 50 mg p.o. q6h ⫻ 4 doses). Coagulation abnormality is a specific contraindication to performing blocks. Aspirin should be withheld for 3 days, and other platelet inhibitors, such as Plavix, Pletal, and Aggrenox, should be withheld for 5 days before the procedure. Coumadin should be held for 5 days, in conjunction with their referring clinician, with prothrombin time (PT) and international normalized ratio (INR) checked and within a range of normal before the procedure. Intravenous heparin should be held for 4-6 hours and partial thromboplastin time (PTT) obtained and normal. Patients on low molecular weight heparin should have their medications held for at least 24 hours.
Patient Preparation Block procedures performed under imaging guidance are extremely safe, but informed consent discussion with patients should include the potential risks of bleeding, infection, allergy to injected materials, and nerve damage. The most common negative side effect is a transient numbness or weakness related to anesthetics applied near a nerve, which is generally self-limited. The patient is placed prone on the imaging table. The region of interest is thoroughly cleansed with 3-4 applications of either povidone-iodine 10% or chloraprep scrub (chlorhexidine gluconate and isopropyl alcohol), and the area is draped with sterile towels. Operator sterile technique is used, with appropriate hand cleansing and sterile gloves.
Epidural Steroid Injections Posterior interlaminar epidural steroid injections can be performed in the cervical, thoracic, or lumbar regions. In the cervical and thoracic areas, the indications are typically neck pain, cervical radiculopathy, thoracic region back pain, and occasionally thoracic radiculopathy. In the lumbar region, indications include low back pain, symptoms of spinal stenosis (neurogenic claudication), and lumbar radiculopathy. Injections can be focused to selected areas of these spine regions but standard location or nonspecific approaches are typically employed, as medications typically spreads across several spinal levels after injection.
Basic Equipment and Tray In general, an epidural needle (modified Tuohy or Crawford type tip) is used for interlaminar or interspinous access to the posterior epidural space. The tip design retains direction control but resists entering the dura and therefore helps prevent an unwanted intrathecal injection of steroid or anesthetic. In the cervical and thoracic regions, a smaller 22-g needle may be employed due to the presence of the spinal cord and potential risk of cord injury. In the mid to lower
T.S. Eckel and W.S. Bartynski lumbar region, larger Tuohy needles can be used (20-18 g) because the spinal cord is not present. Choice of steroid mixture varies depending on the region to be injected and availability. Typically employed injectable steroid suspensions include betamethasone (Celestone Soluspan), methylprednisolone acetate (Depo-Medrol), or triamcinalone acetonide (Kenalog). In the cervical and thoracic regions, 80 mg methylprednisolone acetate (Depo-Medrol) can be comixed with preservative-free saline (not an anesthetic) for distribution in the spinal canal due to the presence of the spinal cord. In the lumbar region, 80 mg methylprednisolone acetate can be comixed with 2-6 mL Bupivicain (0.25%-0.5%) for adequate distribution in the spinal canal. If the lumbar injection must be placed close to the conus or if severe spinal stenosis is present, reduced volume/concentration of anesthetic or preservative-free saline should be used to avoid conus anesthesia. In addition to the syringe for the steroid/anesthetic mixture, syringes for local anesthetic (8 mL lidocaine, 1%, which may be buffered with 3-mL bicarbonate) and contrast material (3 mL syringe filled with 1.5-2 mL nonionic contrast [iohexol 240 mgI/mL]) are necessary in addition to a short low-volume connection tubing system.
The Basic Approach to Targeting the Posterior Epidural Space Entering the posterior epidural space is a unique technique. One must pass through the ligamentum flavum or interspinous ligament without extending so far anterior as to pass through the dura and enter the thecal sac. An exacting approach is essential, aided by fluoroscopy and loss of pressure resistance, but requiring contrast injection to confirm epidural needle tip position. The “loss of resistance” technique has several components. A “loss of resistance” can be felt during needle advancement as the needle passes through the tough interspinous ligament or ligamentum flavum and into the epidural space. A “loss of resistance” can also be felt during low-pressure air or contrast injection through the epidural needle as the tip of the needle passes from the high resistance spaces of the interspinous ligament or ligamentum flavum, and into the low resistance epidural space. In all spine locations, the epidural needle is advanced (midline or oblique interlaminar approach) just posterior to the ligamentum flavum using the feel of tissue planes while advancing the needle coupled with lateral fluoroscopic confirmation of needle tip beyond the base of the spinous process. When performing injection from an interlaminar approach, the edge of the lamina can be targeted with needle advancement in the anteroposterior (AP) plane. When the lamina is encountered as a gauge of depth, the imaging plane can be changed to lateral as the epidural space is approached when the needle is advanced beyond the edge of the lamina. When the needle tip is close to the canal, loss of pressure resistance can be combined with AP and lateral fluoroscopy and contrast injection to confirm epidural space entry. One method of using the loss of resistance to injection involves using a 3-mL syringe with 1.5-2 mL nonionic con-
ESIs and selective NRBs’
13 Preprocedure imaging is important to assess. Magnetic resonance imaging typically demonstrates significant cervical disk degenerative changes, endplate spur formation with variable degrees of altered cervical lordosis from spasm, or areas of degenerative subluxation. The combination of uncinate and facet hypertrophy along with subluxation leads to foraminal narrowing with ultimate encroachment on exiting cervical nerve roots. It is important to assess the preprocedure imaging for an unexpected finding that could be associated with cervical pain, including: tumor, infection, trauma, syrinx, or a Chiari I malformation.
Figure 1 Loss of pressure resistance. A 3-mL syringe half filled with contrast (Iohexol 240) and connected to the 20 g Tuohy needle for lumbar epidural access. With slight pressurization within the syringe (arrow), the needle can, in small increments, be slowly and progressively advanced into the epidural space. When the posterior epidural space is engaged, the beads of contrast (arrowheads) rapidly enter the epidural space. Confirmation of needle tip position can be made with further contrast injection visualized with lateral fluoroscopy.
trast attached to the short connection tube. Contrast is brought to the tip of the tube and rapidly aspirated back into the syringe. This creates a string of contrast/room-air “beads” that can be watched in the tube for pressure change on epidural space entry (Fig. 1). With the syringe now filled with air and contrast, the connection tube is attached to the Tuohy needle hub with slight pressure applied to the syringe. The Tuohy needle is now observed with lateral fluoroscopy as it is gently advanced, maintaining slight intermittent pressure on the syringe (Fig. 2C). The epidural space is typically lower in pressure and, when reached, the beads of contrast in the connection tube rapidly enter the space and correct access is noted. The remainder of the contrast can be carefully injected, further confirming correct needle tip position in the posterior epidural space (Fig. 2). The fat just posterior to the ligamentum flavum or in muscular planes can behave somewhat like epidural fat and appear low in pressure on injection. If initial testing results in slight contrast posterior to the ligamentum flavum, simply reconnect the contrast/air-containing syringe with connector tube, continue to carefully advance the needle with closed system pressure and intermittent pulsation, and watch for correct entry into the epidural space.
Cervical Epidural Steroid Injections Cervical epidural steroid injections are generally used to treat neck pain and/or cervical radiculopathy due to cervical degenerative disk and facet disease. Patients typically complain of significant neck pain. Radiating pain may be nonspecific, due to muscle spasm or diskogenic pain, or explicitly radicular due to root compression in the neural foramen from uncinate and facet hypertrophy.
Cervical Epidural Steroid Injection Procedure In general, the C6-7 or C7-T1 level is targeted for posterior epidural steroid injection, where the cervical epidural space is most capacious (Fig. 3). The patient is placed in the prone position with the forehead comfortably supported on a thin soft towel or cushion. It is important to assess lateral or oblique fluoroscopy to ensure adequate visualization of the spinal canal and in particular the posterior epidural region to follow the needle while being placed. If visualization is poor due to patient body habitus and large shoulders, the patient can be placed in a swimmer’s position for improved visualization. This should be done before the start of the procedure because the needle will shift with this shoulder motion and change. After the neck region is cleansed and draped, midline AP view is established with fluoroscopy. The C-arm is then angulated caudal to cranial to establish clear vision and access in the region of the interspinous ligament between the C6 and C7 or C7 and T1 spinous processes in the AP projection. It is critical that the tips of the spinous processes be maintained centrally between the C7 and T1 pedicles because slight angulation will result in unwanted needle drift. After establishing proper midline trajectory, the entry point is marked and local anesthetic is applied. The 22-g epidural needle is introduced into the skin and progressively advanced through the interspinous ligament, directly in the midline, toward the epidural space. Confirmation of spinal canal entry and epidural space position is achieved through the combined use of lateral fluoroscopy and identification of loss of pressure resistance to injection through the epidural needle as described above. In lateral fluoroscopy, the base of the inferior surface of the C7 spinous process is slightly curved, indicating the position of the posterior epidural space. This helps with identification of needle tip position and approximate location of the epidural space. Once entry into the epidural space is confirmed with lateral and then AP fluoroscopy, the mixture of 80 mg methylprednisolone and 1-3 mL preservative-free saline is injected. The epidural contrast should be observed under AP fluoroscopy progressively diluting as the steroid/saline mixture is injected. When the dose has been delivered, the stylette is replaced, and the needle withdrawn.
Thoracic Epidural Steroid Injections Thoracic epidural steroid injections are usually performed for thoracic back pain. Accompanying preprocedure imaging
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ESIs and selective NRBs’ usually demonstrates thoracic degenerative changes in particular in the area of injection interest. Imaging should be inspected for other causes of thoracic spine pain, such as vertebral compression fracture, tumor, infection, or spinal cord lesion. The injections are typically more locally targeted to the location of the patients back pain or radiating pain. The size of the epidural space should be assessed on preprocedural images to identify the optimum level in the region of maximum pain for adequate and safe access to the epidural space. Thoracic Epidural Injection Procedure An oblique interlaminar approach to the thoracic posterior epidural space is necessary due to extreme angulation of the thoracic spinous processes. With the patient in the prone position, the back is cleansed and draped and the target location is identified. AP and lateral fluoroscopy should be inspected to identify the target injection area and ensure clear identification of the spinal canal and base of the spinous processes for adequate needle tip assessment. The operator should note the location and size of the posterior epidural space beneath the spinous process, for this is the target of needle tip placement. AP fluoroscopy is established overlying the area of injection. The C-arm is then obliqued and the interlaminar region is adjusted for targeting of the epidural space just anterior to the base of the spinous process. Local anesthetic is then applied and the 22-g epidural needle is inserted and advanced toward the posterior epidural space just anterior to the base of the spinous process. When the spinal canal is approached, lateral fluoroscopy is established. Using the standard technique of epidural space entry, the contrast syringe with connecting tube and beaded contrast is connected; slight pressure is applied and the Tuohy needle is advanced to the epidural space. When the space is entered, needle tip position is confirmed with the remaining contrast with lateral and then AP fluoroscopy. A combination of 80 mg methylprednisolone and 1- to 3-mL preservative-free saline is then injected. The epidural contrast should be observed under AP fluoroscopy progressively diluting as the steroid/saline mixture is injected. When the dose is delivered, the stylette is replaced, and the needle is withdrawn.
Lumbar Epidural Steroid Injections Lumbar epidural steroid injections are typically performed in patients suffering from low back pain, symptomatic spinal stenosis, or radiculopathy. Initial results are generally excel-
15 lent in most patients. Progressive symptom return or change in pain pattern often requires repeat injection. Preprocedure imaging should be assessed in conjunction with the patient’s clinical problem. Most patients demonstrate moderate to severe degenerative disk disease, disk protrusion, facet disease, central spinal stenosis, or lateral recess encroachment. A focused epidural injection can be performed but most injections are nonspecific. In general, the largest epidural space closest to the area of the suspected pain source is chosen for the site of injection. In patients with prior lumbar surgery, a target separate from the surgical site is typically chosen. It is usually not possible to successfully access the epidural space in the region of laminectomy and scar and dural puncture is likely. Imaging should be assessed for unexpected tumor, infection, or vertebral compression fracture as the source of pain. Lumbar Epidural Space Approach by Fluoroscopy The lumbar canal can be approached with a midline injection, as in the cervical region, or with an oblique approach as in the thoracic area. With an oblique approach, the targeted level of entry is identified with AP fluoroscopy and the C-arm is angled caudal to cranial to obtain an optimum angle to target the base of the spinous process (Fig. 2). After application of local anesthetic, a 20-g epidural needle is inserted into the skin and advanced toward the posterior epidural space. When needle direction is secure, lateral fluoroscopy is established and the posterior canal is approached. In the lumbar region, pedicles may be short and the facets significantly hypertrophic or sclerotic, obscuring bony landmarks of the posterior canal. Care and close coordination between lateral fluoroscopy and loss of pressure resistance is required to successfully enter the epidural space and not pierce the dura and enter the thecal sac. Lumbar Epidural Space Approach by CT The epidural space can also be approached under CT or CT fluoroscopy guidance (Fig. 4). After choosing the level of entry from preprocedure imaging, scout views followed by a stack of axial scans are obtained in the target area. Spinous process angulation tends to be greater than achievable gantry angulation and therefore a slightly oblique approach is required. A level is chosen from the axial stack that allows clear access to the posterior epidural space, avoiding the spinous process. The skin entry point is marked and the 20-g Tuohy needle is introduced in parallel to CT scanner laser alignment guide and progressively advanced with intermittent CT or CT
Figure 2 Lumbar interlaminar epidural approach. (A) With C-arm fluoroscopy, AP oblique approach is established with identification of the interlaminar space. Trajectory to the posterior lumbar canal is identified (arrow) and anesthetic is applied. The approach is designed so the tip of the Tuohy needle will ultimately lie just beneath the spinous process in the posterior epidural fat. (B) Tuohy needle (arrow) is directed to the posterior epidural space just beneath the base of the spinous process (arrowhead). (C) When loss of pressure resistance indicates that the needle has entered the epidural space (arrow), confirmation is made with further contrast injection observed in the lateral position (arrowheads). Note how posterior the needle is positioned and how it overlies poster spinal structures (arrow). By imaging alone there are no reliable markers for when you enter the posterior epidural space. (D) Epidural injection is confirmed in the AP projection (arrowheads). The needle tip lies just beneath the spinous process in the posterior epidural space. (E) As the steroid and anesthetic mixture is injected, the epidural contrast is seen to dilute (arrowheads).
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ESIs and selective NRBs’ fluoroscopy assessment to just outside the canal, superficial to the ligamentum flavum (Fig. 4A). As in all CT-guided procedures, the operator must remain aware of the location of the needle tip while advancing. Respiratory motion can challenge needle tip visualization and multiple-slice CT imaging or CT fluoroscopy in a consistent state of respiration (usually expiration) helps to maintain needle tip identification. A contrast/air-containing syringe with connector is attached with beads of contrast in the tube and gentle pressure is intermittently applied while the needle is progressively but cautiously advanced. When the epidural space is entered, contrast beads rapidly progress into the canal and epidural location can be confirmed with further injection of contrast and air. The thecal sac is typically well visualized and deflects slightly with the contrast/air injection. Injection of Steroid, and Anesthetic When the needle tip is close to the canal, the contrast- and air-filled syringe with connection tube is connected and slight pressure is applied. Again with the required coordination between fluoroscopy and loss of pressure resistance, the lumbar epidural space is entered and needle tip is confirmed with injection of the remaining contrast and observation on lateral and then AP fluoroscopy or CT. After needle tip confirmation, 80 mg methylprednisolone acetate comixed with 2-5 mL bupivicaine (0.25%-0.5%) is injected with AP fluoroscopic or CT observation to confirm appropriate dilution of the epidural contrast. When the dose is delivered, the needle is withdrawn and the procedure is complete. After the procedure, the patient commonly notices significant reduction in their pain symptoms due to the local anesthetic mixed with the steroid.
Technical and Procedure Challenges of Epidural Injections As mentioned above, performing an epidural injection in an area of prior laminectomy should be avoided because correct access to the epidural space is obliterated by scar and thecal sac puncture is likely. In patients with large body habitus, one should assess whether the posterior epidural space can be accessed with the available epidural needle or whether the operator can safely visualize the needle and injection in the lateral position at fluoroscopy. If epidural injection location cannot be confirmed, the procedure should not be attempted. Thecal sac access can occur, even when using careful technique with loss of resistance and image guidance. In most instances, reaccessing the epidural space at the level above or below is successful and sufficient. At times one can enter an
17 epidural vein and venous flow identified on contrast injection. In these instances, the needle tip should be repositioned and epidural spread of contrast established.
Lumbar Nerve Root Block and Transforaminal Steroid Administration Under most circumstances, lumbar root injections are performed for radiculopathy. The patient’s history and clinical examination are often helpful in targeting the root or roots contributing to the radiating leg pain. In general, L5 and S1 radiculopathy result in typical “sciatica” with pain in the buttocks, hip, and posterior thigh that projects below the knee with pain to the calf, ankle, and/or foot. L4 typically projects to the knee and/or anterior thigh with L2 and L3 projecting to the upper thigh and/or groin. Correlation with preprocedure imaging is helpful in confirming the area of root compression from disk protrusion or degenerative changes in the spinal canal, lateral recess, foramen, or far-lateral region and is helpful in assessing for single-level or multilevel compression. Lumbar nerve root block and steroid administration can be performed under fluoroscopic or CT guidance. The injections serve as short- and long-term treatment of radiculopathy and can be useful diagnostically in clarifying the exact level or root contributing to a patient’s radicular symptoms. In most instances, a transforaminal approach is chosen, although a parasagittal or postganglionic approach may be used if the injection is strictly diagnostic.
Basic Equipment and Tray A 22- or 25-g spinal needle can be used for distances less than 10 cm. If patient body habitus is larger with longer skin to target distance, a 20- or 22-g 5-7 inch needle is necessary for adequate directional control. A combination of 40-80 mg methylprednisolone comixed with 1.5-2 mL bupivicaine (0.25%) is used for the root injection with larger volume of anesthetic used if 2 or more locations are to be treated. Local anesthetic syringe is prepared with 8 mL lidocaine, and 2-mL bicarbonate may be added as buffer if desired. A 3 mL syringe is loaded with nonionic contrast (fluoroscopy: iohexol, 240 mg I/mL; CT: iohexol, 180 mg I/mL) and short low-volume connection tube attached.
Fluoroscopy Approach to the Lumbar Root With fluoroscopy, the C-arm is placed in the AP position with the lumbar pedicles and transverse processes of the level
Figure 3 Cervical interspinous epidural approach. (A) With C-arm fluoroscopy, midline AP approach at C7-T1 is established with a 22-g Tuohy needle using steep cranial-caudal angulation (arrow). (B) In the lateral projection with the patient in the swimmer’s position, the Tuohy needle can be seen just beneath the C7 spinous process (arrow). Slight curve in the lower margin of the spinous process helps identify the approximate location of the edge of the ligamentum flavum and the posterior epidural fat (arrowhead). (C) When loss of pressure resistance indicates that the epidural space has been entered, confirmation is made with further contrast injection observed in the lateral position (arrowheads). (D) Epidural injection is confirmed in the AP projection (arrowheads).
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T.S. Eckel and W.S. Bartynski to be treated clearly identified (Fig. 5). The C-arm is then obliqued to the side of treatment until clear access to the space under the pedicle of the root to be treated is identified. This often requires adequate obliquity to reflect to adjacent facet joint and articular process away from the trajectory. Facet hypertrophy may interfere with the approach, making a steep oblique approach necessary. The target location lies just beneath the pedicle adjacent to the nerve root to be treated within the epiradicular/ epidural space circumferential to the exiting root. After application of local anesthetic, the spinal needle is inserted and directed to just beneath the pedicle. Intermittent fluoroscopic observation is mandatory because the fascia and muscular planes often deflect the needle tip, in particular, when using the 25 g. Proper final position of the spinal needle is confirmed with AP and lateral fluoroscopy with the tip seen just beneath the pedicle on AP or AP oblique view; the needle tip is identified beneath the pedicle just anterior to the facet joint at lateral fluoroscopy. If the patient reports a paresthesia or radiating pain in the distribution of the local nerve root, needle advancement should be halted, and positioning should be checked under fluoroscopy to avoid damage to the root. Confirmation of needle tip position is made with a 0.5- to 1-mL injection of nonionic contrast to assure positioning is extravascular, and within the epiradicular space before injecting the particulate steroid suspension.
CT Approach to the Lumbar Root With the CT approach, scout views are obtained with the patient in the prone position, the level of the root to be treated/targeted, and a stack of axial images obtained. A grid or marker is necessary on the back skin surface to use as reference for measuring skin entry location. Imaging the area of abnormality responsible for the patient’s radiculopathy is helpful because it gives another look at the cause of root compression. At lower lumbar levels, inclusion of a portion of the sacrum helps confirm counting of the level targeted. When the appropriate level and root are identified, trajectory by CT is planned to gain direct access to the posterior surface of the root to be treated with skin entry location identified. The skin entry location is marked; the back is cleansed and draped and local anesthetic is applied. The 25- or 22-g spinal needle is introduced into the skin and progressively advanced adjacent to the posterior surface of the nerve root with CT or CT fluoroscopy guidance (Fig. 6). Again, the operator must remain aware of the
Figure 4 CT-guided lumbar interlaminar epidural approach. (A) After entry location is established and local anesthetic is applied (arrowhead), the 20-g Tuohy needle is directed to the posterior margin of the ligamentum flavum directed at the posterior epidural fat just behind the thecal sac. The ligamentum flavum can be entered and loss of pressure resistance is applied (arrow). (B) When the epidural space is entered, loss of pressure resistance is noted and contrast can be injected to confirm needle tip position (arrow).
ESIs and selective NRBs’
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Figure 5 Fluoroscopic-guided lumbar transforaminal nerve root block. Two roots are ultimately injected in this patient. (A) Approach for needle placement adjacent to the L5 nerve root. The nerve root exits just beneath the named pedicle. After initial AP positioning and with cranial-caudal angulation to align the disk, the C-arm is obliqued to establish the trajectory. After local anesthetic, a 25-g spinal needle is directed just beneath the L5 pedicle (arrow). Note how the iliac crest can overlap the trajectory compromising access to the foramen or disk space (arrowhead). (B) Lateral fluoroscopic image confirms needle position just anterior to the facet and beneath the pedicle (arrow), correctly located in the neural foramen. (C) Second needle was also placed adjacent to the L4 nerve root. Contrast injection observed with AP fluoroscopy confirms epiradicular location of the tips of the needles with contrast tracking along the nerves (arrows) as well as entering the epidural space locally.
location of the needle tip while advancing. Respiratory motion can cause challenge needle tip visualization and multiple-slice CT imaging or CT fluoroscopy in a consistent state of respiration (usually expiration) helps to maintain needle tip identification. Confirmation of needle tip position and nonvascular placement is made with a 0.3- to 0.5-mL nonionic contrast injection.
Nerve Root Injection After confirmation of needle tip position by CT or fluoroscopy, the steroid and anesthetic mixture is injected adjacent to the nerve root. The contrast used for location of the needle typically dissipates and spreads along the course of the treated nerve root, at times entering the spinal canal with slight epidural extension. It is typical for patients with radiculopathy to sense the injection and recognize their familiar
radicular pain, even to the level of the knee, foot, and ankle. This helps confirm appropriate level treatment. With the injection complete, the stylette is replaced, the needle is removed, and the procedure is finished. After the injection, the patient’s radicular pain is usually relieved due to the anesthetic in the injection. Postprocedure the patient must be cautioned regarding walking because the nerve root is partially anesthetized due to the local application of bupivicaine.
Technical and Procedural Challenges of Lumbar Root Injections Certain technical challenges may be present in accessing the lumbar nerve roots. With progressive degenerative disease, disk height loss and facet hypertrophy may obscure the tra-
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Figure 6 CT-guided lumbar nerve root block. (A) Approach to the L5 nerve root. The L5 root lies in the L5-S1 foramen (arrow). After establishing the skin entry point and trajectory from the scout CT images, a 25-g spinal needle is introduced and directed toward the right L5 root (arrowhead). (B) Needle tip is advanced just posterior to the nerve root and ganglion (arrow). (C) Contrast is injected to confirm needle tip position adjacent to the root (arrow). The steroid-anesthetic mixture is injected into the wheal of contrast established adjacent to the root.
jectory to the root, in particular, at L5S1. In addition, visualization of the S1 posterior foramen can be challenging. If access cannot be achieved at fluoroscopy, an approach is usually identified by CT and the injection can still be performed. With bone fusion overlying the facet and transverse process region, access can again be limited, again most commonly seen at L5S1. CT can again be helpful in these instances but if clear approach to the root is not recognized, the procedure may need to be abandoned. Vascular access may be recognized after needle placement and contrast injection. If contrast is not seen accumulating at the needle tip or if vessel opacification is identified, the needle must be repositioned so that clear recognition of contrast adjacent to the nerve is seen and no vascular contrast is en-
countered so the particulate steroid suspension can be safely injected.
Clinical Follow-Up and Expected Outcomes In some practices patients are followed after epidural or nerve root procedures, while in others, patients may be referred for repeat injections. Due to the relatively high steroid dose, the number of injections that can be performed is limited. Typically, three steroid injections may be performed in a given 6-month period. Patients typically respond well to epidural steroid and nerve root injections. When the injections are effective, patients typically receive 1-3 months of sustained and significant pain relief. Residual pain can be managed by repeat
ESIs and selective NRBs’ injection. The purpose of the injections is to reduce epidural or nerve root inflammation. It is important for patients to understand that activities that continue to aggravate their pain will limit their treatment response. If pain relief does not occur, an alternative pain generator should be considered or surgical treatment might be necessary.
Conclusions Epidural steroid administration and lumbar nerve root blocks are an effective treatment in patients with back pain or radiculopathy. The procedures are safe and pain relief can be sustained.
Suggested Reading Bartynski WS, Grahovac SZ, Rothfus WE: Incorrect needle position during lumbar epidural steroid administration: Inaccuracy of loss of air pressure resistance and requirement of fluoroscopy and epidurography during needle insertion. AJNR Am J Neuroradiol 26:502-505, 2005 Bowman SJ, Wedderburn L, Whaley A, et al: Outcome assessment after epidural corticosteroid injection for low back pain and sciatica. Spine 18:1345-1350, 1993 Bush K, Hillier S: A controlled study of caudal epidural injections of triamcinolone plus procaine for the management of intractable sciatica. Spine 16:572-575, 1991 Cyteval C, Fescquet N, Thomas E, et al: Predictive factors of efficacy of periradicular corticosteroid injections for lumbar radiculopathy. AJNR Am J Neuroradiol 27:978-982, 2006 Derby R, Kine G, Saal JA, et al: Response to steroid and duration of radicular pain as predictors of surgical outcome. Spine 17:S176-S183, 1992 Derby R, Lee SH, Date ES, et al: Size and aggregation of corticosteroids used for epidural injections. Pain Med 9:227-234, 2008 Dilke TF, Burry HC, Grahame R: Extradural corticosteroid injection in management of lumbar nerve root compression. BMJ 2:635-637, 1973
21 El-Khoury GY, Ehara S, Weinstein JN, et al: Epidural steroid injection: A procedure ideally performed with fluoroscopic control. Radiology 168: 554-557, 1988 Gajraj NM: Selective nerve root blocks for low back pain and radiculopathy. Reg Anesth Pain Med 29:243-256, 2004 Johnson BA, Schellhas KP, Pollei SR: Epidurography and therapeutic epidural injections: Technical considerations and experience with 5334 cases. AJNR Am J Neuroradiol 20:697-705, 1999 Kopacz DJ, Allen HW: Comparison of needle deviation during regional anesthetic techniques in a laboratory model. Anesth Analg 81:630-633, 1995 Lee IS, Kim SH, Lee JW, et al: Comparison of the temporary diagnostic relief of transforaminal epidural steroid injection approaches: Conventional versus posterolateral technique. AJNR Am J Neuroradiol 28:204-208, 2007 Renfrew DL, Moore TE, Kathol MH, et al: Correct placement of epidural steroid injections: Fluoroscopic guidance and contrast administration. AJNR Am J Neuroradiol 12:1003-1007, 1991 Riew KD, Park JB, Cho YS, et al: Nerve root blocks in the treatment of lumbar radicular pain. A minimum five-year follow-up. J Bone Joint Surg Am 88:1722-1725, 2006 Sasso RC, Macadaeg K, Nordmann D, et al: Selective nerve root injections can predict surgical outcome for lumbar and cervical radiculopathy: Comparison to magnetic resonance imaging. J Spinal Disord Tech 18: 471-478, 2005 Slipman CW, Issac Z: The role of diagnostic selective nerve root blocks in the management of spinal pain. Pain Physician 4:214-226, 2001 Spaccarelli KC: Lumbar and caudal epidural corticosteroid injections. Mayo Clin Proc 71:169-178, 1996 Stanley D, McLaren MI, Euinton HA, et al: A prospective study of nerve root infiltration in the diagnosis of sciatica. A comparison with radiculography, computed tomography, and operative findings. Spine 15:540-543, 1990 Watts RW, Silagy CA: A meta-analysis on the efficacy of epidural corticosteroids in the treatment of sciatica. Anaesthesiol Intens Care 23:564-569, 1995 White AH, Derby R, Wynne G: Epidural injections for the diagnosis and treatment of low-back pain. Spine 5:78-86, 1980
E
pidural steroid injections and selective lumbar nerve root blocks are commonly employed in the diagnosis and treatment of spinal pain and radiculopathy. Patients typically gain significant early or immediate relief from neck pain, low back pain, or radiculopathy, with many patients achieving long-term pain control. In general, these procedures are performed with C-arm fluoroscopic guidance. In the lumbar region, standard computed tomography (CT) or CT fluoroscopy may also be used. CT is cumbersome to employ for interlaminar epidural targeting in the cervical and thoracic regions due to patient access, gantry angle limitations, and needle tracking due to respi-
*Diagnostic and Interventional Neuroradiology, Annapolis Spine Institute/ Annapolis Radiology Associates, Annapolis, MD. †Department of Radiology, Division of Neuroradiology, Presbyterian University Hospital, University of Pittsburgh Medical Center, Pittsburgh, PA. Address reprint requests to Timothy S. Eckel, MD, Diagnostic and Interventional Neuroradiology, Annapolis Spine Institute/Annapolis Radiology Associates, 2002 Medical Parkway, Suite 235, Annapolis, MD 21401. E-mail: [email protected]. 1089-2516/09/$-see front matter © 2009 Elsevier Inc. All rights reserved. doi:10.1053/j.tvir.2009.06.004
ratory motion. Here we review the indications and procedural approach to these commonly performed treatments for spinal pain syndromes.
Clinical Evaluation of the Patient and Procedure Indications It is important to understand the basic clinical reason for referral and treatment in these patients. In general, patients referred for interlaminar steroid administration have neck pain or low back pain either alone or in combination with radiating arm or leg pain (radiculopathy). Selective lumbar nerve root blocks are employed when a specific nerve root is considered responsible for the patient’s radiculopathy and may be performed for diagnostic or therapeutic purposes. Selection of technique and injection volume is influenced by the intent of the procedure. Preprocedure imaging is important to evaluate for features related to the patient’s specific pain problem and to assess for unexpected findings or potential contraindications to injection, such as the presence of tumor, infection, fracture, or spinal cord abnormality. 11
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Contraindications for the Injection Procedures Active infection should not be present at the time of the procedure and is a relative contraindication. Patients with an allergy to contrast should be prepped 24 hours before the procedure (typically, prednisone 50 mg p.o. q6h ⫻ 4 doses). Coagulation abnormality is a specific contraindication to performing blocks. Aspirin should be withheld for 3 days, and other platelet inhibitors, such as Plavix, Pletal, and Aggrenox, should be withheld for 5 days before the procedure. Coumadin should be held for 5 days, in conjunction with their referring clinician, with prothrombin time (PT) and international normalized ratio (INR) checked and within a range of normal before the procedure. Intravenous heparin should be held for 4-6 hours and partial thromboplastin time (PTT) obtained and normal. Patients on low molecular weight heparin should have their medications held for at least 24 hours.
Patient Preparation Block procedures performed under imaging guidance are extremely safe, but informed consent discussion with patients should include the potential risks of bleeding, infection, allergy to injected materials, and nerve damage. The most common negative side effect is a transient numbness or weakness related to anesthetics applied near a nerve, which is generally self-limited. The patient is placed prone on the imaging table. The region of interest is thoroughly cleansed with 3-4 applications of either povidone-iodine 10% or chloraprep scrub (chlorhexidine gluconate and isopropyl alcohol), and the area is draped with sterile towels. Operator sterile technique is used, with appropriate hand cleansing and sterile gloves.
Epidural Steroid Injections Posterior interlaminar epidural steroid injections can be performed in the cervical, thoracic, or lumbar regions. In the cervical and thoracic areas, the indications are typically neck pain, cervical radiculopathy, thoracic region back pain, and occasionally thoracic radiculopathy. In the lumbar region, indications include low back pain, symptoms of spinal stenosis (neurogenic claudication), and lumbar radiculopathy. Injections can be focused to selected areas of these spine regions but standard location or nonspecific approaches are typically employed, as medications typically spreads across several spinal levels after injection.
Basic Equipment and Tray In general, an epidural needle (modified Tuohy or Crawford type tip) is used for interlaminar or interspinous access to the posterior epidural space. The tip design retains direction control but resists entering the dura and therefore helps prevent an unwanted intrathecal injection of steroid or anesthetic. In the cervical and thoracic regions, a smaller 22-g needle may be employed due to the presence of the spinal cord and potential risk of cord injury. In the mid to lower
T.S. Eckel and W.S. Bartynski lumbar region, larger Tuohy needles can be used (20-18 g) because the spinal cord is not present. Choice of steroid mixture varies depending on the region to be injected and availability. Typically employed injectable steroid suspensions include betamethasone (Celestone Soluspan), methylprednisolone acetate (Depo-Medrol), or triamcinalone acetonide (Kenalog). In the cervical and thoracic regions, 80 mg methylprednisolone acetate (Depo-Medrol) can be comixed with preservative-free saline (not an anesthetic) for distribution in the spinal canal due to the presence of the spinal cord. In the lumbar region, 80 mg methylprednisolone acetate can be comixed with 2-6 mL Bupivicain (0.25%-0.5%) for adequate distribution in the spinal canal. If the lumbar injection must be placed close to the conus or if severe spinal stenosis is present, reduced volume/concentration of anesthetic or preservative-free saline should be used to avoid conus anesthesia. In addition to the syringe for the steroid/anesthetic mixture, syringes for local anesthetic (8 mL lidocaine, 1%, which may be buffered with 3-mL bicarbonate) and contrast material (3 mL syringe filled with 1.5-2 mL nonionic contrast [iohexol 240 mgI/mL]) are necessary in addition to a short low-volume connection tubing system.
The Basic Approach to Targeting the Posterior Epidural Space Entering the posterior epidural space is a unique technique. One must pass through the ligamentum flavum or interspinous ligament without extending so far anterior as to pass through the dura and enter the thecal sac. An exacting approach is essential, aided by fluoroscopy and loss of pressure resistance, but requiring contrast injection to confirm epidural needle tip position. The “loss of resistance” technique has several components. A “loss of resistance” can be felt during needle advancement as the needle passes through the tough interspinous ligament or ligamentum flavum and into the epidural space. A “loss of resistance” can also be felt during low-pressure air or contrast injection through the epidural needle as the tip of the needle passes from the high resistance spaces of the interspinous ligament or ligamentum flavum, and into the low resistance epidural space. In all spine locations, the epidural needle is advanced (midline or oblique interlaminar approach) just posterior to the ligamentum flavum using the feel of tissue planes while advancing the needle coupled with lateral fluoroscopic confirmation of needle tip beyond the base of the spinous process. When performing injection from an interlaminar approach, the edge of the lamina can be targeted with needle advancement in the anteroposterior (AP) plane. When the lamina is encountered as a gauge of depth, the imaging plane can be changed to lateral as the epidural space is approached when the needle is advanced beyond the edge of the lamina. When the needle tip is close to the canal, loss of pressure resistance can be combined with AP and lateral fluoroscopy and contrast injection to confirm epidural space entry. One method of using the loss of resistance to injection involves using a 3-mL syringe with 1.5-2 mL nonionic con-
ESIs and selective NRBs’
13 Preprocedure imaging is important to assess. Magnetic resonance imaging typically demonstrates significant cervical disk degenerative changes, endplate spur formation with variable degrees of altered cervical lordosis from spasm, or areas of degenerative subluxation. The combination of uncinate and facet hypertrophy along with subluxation leads to foraminal narrowing with ultimate encroachment on exiting cervical nerve roots. It is important to assess the preprocedure imaging for an unexpected finding that could be associated with cervical pain, including: tumor, infection, trauma, syrinx, or a Chiari I malformation.
Figure 1 Loss of pressure resistance. A 3-mL syringe half filled with contrast (Iohexol 240) and connected to the 20 g Tuohy needle for lumbar epidural access. With slight pressurization within the syringe (arrow), the needle can, in small increments, be slowly and progressively advanced into the epidural space. When the posterior epidural space is engaged, the beads of contrast (arrowheads) rapidly enter the epidural space. Confirmation of needle tip position can be made with further contrast injection visualized with lateral fluoroscopy.
trast attached to the short connection tube. Contrast is brought to the tip of the tube and rapidly aspirated back into the syringe. This creates a string of contrast/room-air “beads” that can be watched in the tube for pressure change on epidural space entry (Fig. 1). With the syringe now filled with air and contrast, the connection tube is attached to the Tuohy needle hub with slight pressure applied to the syringe. The Tuohy needle is now observed with lateral fluoroscopy as it is gently advanced, maintaining slight intermittent pressure on the syringe (Fig. 2C). The epidural space is typically lower in pressure and, when reached, the beads of contrast in the connection tube rapidly enter the space and correct access is noted. The remainder of the contrast can be carefully injected, further confirming correct needle tip position in the posterior epidural space (Fig. 2). The fat just posterior to the ligamentum flavum or in muscular planes can behave somewhat like epidural fat and appear low in pressure on injection. If initial testing results in slight contrast posterior to the ligamentum flavum, simply reconnect the contrast/air-containing syringe with connector tube, continue to carefully advance the needle with closed system pressure and intermittent pulsation, and watch for correct entry into the epidural space.
Cervical Epidural Steroid Injections Cervical epidural steroid injections are generally used to treat neck pain and/or cervical radiculopathy due to cervical degenerative disk and facet disease. Patients typically complain of significant neck pain. Radiating pain may be nonspecific, due to muscle spasm or diskogenic pain, or explicitly radicular due to root compression in the neural foramen from uncinate and facet hypertrophy.
Cervical Epidural Steroid Injection Procedure In general, the C6-7 or C7-T1 level is targeted for posterior epidural steroid injection, where the cervical epidural space is most capacious (Fig. 3). The patient is placed in the prone position with the forehead comfortably supported on a thin soft towel or cushion. It is important to assess lateral or oblique fluoroscopy to ensure adequate visualization of the spinal canal and in particular the posterior epidural region to follow the needle while being placed. If visualization is poor due to patient body habitus and large shoulders, the patient can be placed in a swimmer’s position for improved visualization. This should be done before the start of the procedure because the needle will shift with this shoulder motion and change. After the neck region is cleansed and draped, midline AP view is established with fluoroscopy. The C-arm is then angulated caudal to cranial to establish clear vision and access in the region of the interspinous ligament between the C6 and C7 or C7 and T1 spinous processes in the AP projection. It is critical that the tips of the spinous processes be maintained centrally between the C7 and T1 pedicles because slight angulation will result in unwanted needle drift. After establishing proper midline trajectory, the entry point is marked and local anesthetic is applied. The 22-g epidural needle is introduced into the skin and progressively advanced through the interspinous ligament, directly in the midline, toward the epidural space. Confirmation of spinal canal entry and epidural space position is achieved through the combined use of lateral fluoroscopy and identification of loss of pressure resistance to injection through the epidural needle as described above. In lateral fluoroscopy, the base of the inferior surface of the C7 spinous process is slightly curved, indicating the position of the posterior epidural space. This helps with identification of needle tip position and approximate location of the epidural space. Once entry into the epidural space is confirmed with lateral and then AP fluoroscopy, the mixture of 80 mg methylprednisolone and 1-3 mL preservative-free saline is injected. The epidural contrast should be observed under AP fluoroscopy progressively diluting as the steroid/saline mixture is injected. When the dose has been delivered, the stylette is replaced, and the needle withdrawn.
Thoracic Epidural Steroid Injections Thoracic epidural steroid injections are usually performed for thoracic back pain. Accompanying preprocedure imaging
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ESIs and selective NRBs’ usually demonstrates thoracic degenerative changes in particular in the area of injection interest. Imaging should be inspected for other causes of thoracic spine pain, such as vertebral compression fracture, tumor, infection, or spinal cord lesion. The injections are typically more locally targeted to the location of the patients back pain or radiating pain. The size of the epidural space should be assessed on preprocedural images to identify the optimum level in the region of maximum pain for adequate and safe access to the epidural space. Thoracic Epidural Injection Procedure An oblique interlaminar approach to the thoracic posterior epidural space is necessary due to extreme angulation of the thoracic spinous processes. With the patient in the prone position, the back is cleansed and draped and the target location is identified. AP and lateral fluoroscopy should be inspected to identify the target injection area and ensure clear identification of the spinal canal and base of the spinous processes for adequate needle tip assessment. The operator should note the location and size of the posterior epidural space beneath the spinous process, for this is the target of needle tip placement. AP fluoroscopy is established overlying the area of injection. The C-arm is then obliqued and the interlaminar region is adjusted for targeting of the epidural space just anterior to the base of the spinous process. Local anesthetic is then applied and the 22-g epidural needle is inserted and advanced toward the posterior epidural space just anterior to the base of the spinous process. When the spinal canal is approached, lateral fluoroscopy is established. Using the standard technique of epidural space entry, the contrast syringe with connecting tube and beaded contrast is connected; slight pressure is applied and the Tuohy needle is advanced to the epidural space. When the space is entered, needle tip position is confirmed with the remaining contrast with lateral and then AP fluoroscopy. A combination of 80 mg methylprednisolone and 1- to 3-mL preservative-free saline is then injected. The epidural contrast should be observed under AP fluoroscopy progressively diluting as the steroid/saline mixture is injected. When the dose is delivered, the stylette is replaced, and the needle is withdrawn.
Lumbar Epidural Steroid Injections Lumbar epidural steroid injections are typically performed in patients suffering from low back pain, symptomatic spinal stenosis, or radiculopathy. Initial results are generally excel-
15 lent in most patients. Progressive symptom return or change in pain pattern often requires repeat injection. Preprocedure imaging should be assessed in conjunction with the patient’s clinical problem. Most patients demonstrate moderate to severe degenerative disk disease, disk protrusion, facet disease, central spinal stenosis, or lateral recess encroachment. A focused epidural injection can be performed but most injections are nonspecific. In general, the largest epidural space closest to the area of the suspected pain source is chosen for the site of injection. In patients with prior lumbar surgery, a target separate from the surgical site is typically chosen. It is usually not possible to successfully access the epidural space in the region of laminectomy and scar and dural puncture is likely. Imaging should be assessed for unexpected tumor, infection, or vertebral compression fracture as the source of pain. Lumbar Epidural Space Approach by Fluoroscopy The lumbar canal can be approached with a midline injection, as in the cervical region, or with an oblique approach as in the thoracic area. With an oblique approach, the targeted level of entry is identified with AP fluoroscopy and the C-arm is angled caudal to cranial to obtain an optimum angle to target the base of the spinous process (Fig. 2). After application of local anesthetic, a 20-g epidural needle is inserted into the skin and advanced toward the posterior epidural space. When needle direction is secure, lateral fluoroscopy is established and the posterior canal is approached. In the lumbar region, pedicles may be short and the facets significantly hypertrophic or sclerotic, obscuring bony landmarks of the posterior canal. Care and close coordination between lateral fluoroscopy and loss of pressure resistance is required to successfully enter the epidural space and not pierce the dura and enter the thecal sac. Lumbar Epidural Space Approach by CT The epidural space can also be approached under CT or CT fluoroscopy guidance (Fig. 4). After choosing the level of entry from preprocedure imaging, scout views followed by a stack of axial scans are obtained in the target area. Spinous process angulation tends to be greater than achievable gantry angulation and therefore a slightly oblique approach is required. A level is chosen from the axial stack that allows clear access to the posterior epidural space, avoiding the spinous process. The skin entry point is marked and the 20-g Tuohy needle is introduced in parallel to CT scanner laser alignment guide and progressively advanced with intermittent CT or CT
Figure 2 Lumbar interlaminar epidural approach. (A) With C-arm fluoroscopy, AP oblique approach is established with identification of the interlaminar space. Trajectory to the posterior lumbar canal is identified (arrow) and anesthetic is applied. The approach is designed so the tip of the Tuohy needle will ultimately lie just beneath the spinous process in the posterior epidural fat. (B) Tuohy needle (arrow) is directed to the posterior epidural space just beneath the base of the spinous process (arrowhead). (C) When loss of pressure resistance indicates that the needle has entered the epidural space (arrow), confirmation is made with further contrast injection observed in the lateral position (arrowheads). Note how posterior the needle is positioned and how it overlies poster spinal structures (arrow). By imaging alone there are no reliable markers for when you enter the posterior epidural space. (D) Epidural injection is confirmed in the AP projection (arrowheads). The needle tip lies just beneath the spinous process in the posterior epidural space. (E) As the steroid and anesthetic mixture is injected, the epidural contrast is seen to dilute (arrowheads).
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ESIs and selective NRBs’ fluoroscopy assessment to just outside the canal, superficial to the ligamentum flavum (Fig. 4A). As in all CT-guided procedures, the operator must remain aware of the location of the needle tip while advancing. Respiratory motion can challenge needle tip visualization and multiple-slice CT imaging or CT fluoroscopy in a consistent state of respiration (usually expiration) helps to maintain needle tip identification. A contrast/air-containing syringe with connector is attached with beads of contrast in the tube and gentle pressure is intermittently applied while the needle is progressively but cautiously advanced. When the epidural space is entered, contrast beads rapidly progress into the canal and epidural location can be confirmed with further injection of contrast and air. The thecal sac is typically well visualized and deflects slightly with the contrast/air injection. Injection of Steroid, and Anesthetic When the needle tip is close to the canal, the contrast- and air-filled syringe with connection tube is connected and slight pressure is applied. Again with the required coordination between fluoroscopy and loss of pressure resistance, the lumbar epidural space is entered and needle tip is confirmed with injection of the remaining contrast and observation on lateral and then AP fluoroscopy or CT. After needle tip confirmation, 80 mg methylprednisolone acetate comixed with 2-5 mL bupivicaine (0.25%-0.5%) is injected with AP fluoroscopic or CT observation to confirm appropriate dilution of the epidural contrast. When the dose is delivered, the needle is withdrawn and the procedure is complete. After the procedure, the patient commonly notices significant reduction in their pain symptoms due to the local anesthetic mixed with the steroid.
Technical and Procedure Challenges of Epidural Injections As mentioned above, performing an epidural injection in an area of prior laminectomy should be avoided because correct access to the epidural space is obliterated by scar and thecal sac puncture is likely. In patients with large body habitus, one should assess whether the posterior epidural space can be accessed with the available epidural needle or whether the operator can safely visualize the needle and injection in the lateral position at fluoroscopy. If epidural injection location cannot be confirmed, the procedure should not be attempted. Thecal sac access can occur, even when using careful technique with loss of resistance and image guidance. In most instances, reaccessing the epidural space at the level above or below is successful and sufficient. At times one can enter an
17 epidural vein and venous flow identified on contrast injection. In these instances, the needle tip should be repositioned and epidural spread of contrast established.
Lumbar Nerve Root Block and Transforaminal Steroid Administration Under most circumstances, lumbar root injections are performed for radiculopathy. The patient’s history and clinical examination are often helpful in targeting the root or roots contributing to the radiating leg pain. In general, L5 and S1 radiculopathy result in typical “sciatica” with pain in the buttocks, hip, and posterior thigh that projects below the knee with pain to the calf, ankle, and/or foot. L4 typically projects to the knee and/or anterior thigh with L2 and L3 projecting to the upper thigh and/or groin. Correlation with preprocedure imaging is helpful in confirming the area of root compression from disk protrusion or degenerative changes in the spinal canal, lateral recess, foramen, or far-lateral region and is helpful in assessing for single-level or multilevel compression. Lumbar nerve root block and steroid administration can be performed under fluoroscopic or CT guidance. The injections serve as short- and long-term treatment of radiculopathy and can be useful diagnostically in clarifying the exact level or root contributing to a patient’s radicular symptoms. In most instances, a transforaminal approach is chosen, although a parasagittal or postganglionic approach may be used if the injection is strictly diagnostic.
Basic Equipment and Tray A 22- or 25-g spinal needle can be used for distances less than 10 cm. If patient body habitus is larger with longer skin to target distance, a 20- or 22-g 5-7 inch needle is necessary for adequate directional control. A combination of 40-80 mg methylprednisolone comixed with 1.5-2 mL bupivicaine (0.25%) is used for the root injection with larger volume of anesthetic used if 2 or more locations are to be treated. Local anesthetic syringe is prepared with 8 mL lidocaine, and 2-mL bicarbonate may be added as buffer if desired. A 3 mL syringe is loaded with nonionic contrast (fluoroscopy: iohexol, 240 mg I/mL; CT: iohexol, 180 mg I/mL) and short low-volume connection tube attached.
Fluoroscopy Approach to the Lumbar Root With fluoroscopy, the C-arm is placed in the AP position with the lumbar pedicles and transverse processes of the level
Figure 3 Cervical interspinous epidural approach. (A) With C-arm fluoroscopy, midline AP approach at C7-T1 is established with a 22-g Tuohy needle using steep cranial-caudal angulation (arrow). (B) In the lateral projection with the patient in the swimmer’s position, the Tuohy needle can be seen just beneath the C7 spinous process (arrow). Slight curve in the lower margin of the spinous process helps identify the approximate location of the edge of the ligamentum flavum and the posterior epidural fat (arrowhead). (C) When loss of pressure resistance indicates that the epidural space has been entered, confirmation is made with further contrast injection observed in the lateral position (arrowheads). (D) Epidural injection is confirmed in the AP projection (arrowheads).
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T.S. Eckel and W.S. Bartynski to be treated clearly identified (Fig. 5). The C-arm is then obliqued to the side of treatment until clear access to the space under the pedicle of the root to be treated is identified. This often requires adequate obliquity to reflect to adjacent facet joint and articular process away from the trajectory. Facet hypertrophy may interfere with the approach, making a steep oblique approach necessary. The target location lies just beneath the pedicle adjacent to the nerve root to be treated within the epiradicular/ epidural space circumferential to the exiting root. After application of local anesthetic, the spinal needle is inserted and directed to just beneath the pedicle. Intermittent fluoroscopic observation is mandatory because the fascia and muscular planes often deflect the needle tip, in particular, when using the 25 g. Proper final position of the spinal needle is confirmed with AP and lateral fluoroscopy with the tip seen just beneath the pedicle on AP or AP oblique view; the needle tip is identified beneath the pedicle just anterior to the facet joint at lateral fluoroscopy. If the patient reports a paresthesia or radiating pain in the distribution of the local nerve root, needle advancement should be halted, and positioning should be checked under fluoroscopy to avoid damage to the root. Confirmation of needle tip position is made with a 0.5- to 1-mL injection of nonionic contrast to assure positioning is extravascular, and within the epiradicular space before injecting the particulate steroid suspension.
CT Approach to the Lumbar Root With the CT approach, scout views are obtained with the patient in the prone position, the level of the root to be treated/targeted, and a stack of axial images obtained. A grid or marker is necessary on the back skin surface to use as reference for measuring skin entry location. Imaging the area of abnormality responsible for the patient’s radiculopathy is helpful because it gives another look at the cause of root compression. At lower lumbar levels, inclusion of a portion of the sacrum helps confirm counting of the level targeted. When the appropriate level and root are identified, trajectory by CT is planned to gain direct access to the posterior surface of the root to be treated with skin entry location identified. The skin entry location is marked; the back is cleansed and draped and local anesthetic is applied. The 25- or 22-g spinal needle is introduced into the skin and progressively advanced adjacent to the posterior surface of the nerve root with CT or CT fluoroscopy guidance (Fig. 6). Again, the operator must remain aware of the
Figure 4 CT-guided lumbar interlaminar epidural approach. (A) After entry location is established and local anesthetic is applied (arrowhead), the 20-g Tuohy needle is directed to the posterior margin of the ligamentum flavum directed at the posterior epidural fat just behind the thecal sac. The ligamentum flavum can be entered and loss of pressure resistance is applied (arrow). (B) When the epidural space is entered, loss of pressure resistance is noted and contrast can be injected to confirm needle tip position (arrow).
ESIs and selective NRBs’
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Figure 5 Fluoroscopic-guided lumbar transforaminal nerve root block. Two roots are ultimately injected in this patient. (A) Approach for needle placement adjacent to the L5 nerve root. The nerve root exits just beneath the named pedicle. After initial AP positioning and with cranial-caudal angulation to align the disk, the C-arm is obliqued to establish the trajectory. After local anesthetic, a 25-g spinal needle is directed just beneath the L5 pedicle (arrow). Note how the iliac crest can overlap the trajectory compromising access to the foramen or disk space (arrowhead). (B) Lateral fluoroscopic image confirms needle position just anterior to the facet and beneath the pedicle (arrow), correctly located in the neural foramen. (C) Second needle was also placed adjacent to the L4 nerve root. Contrast injection observed with AP fluoroscopy confirms epiradicular location of the tips of the needles with contrast tracking along the nerves (arrows) as well as entering the epidural space locally.
location of the needle tip while advancing. Respiratory motion can cause challenge needle tip visualization and multiple-slice CT imaging or CT fluoroscopy in a consistent state of respiration (usually expiration) helps to maintain needle tip identification. Confirmation of needle tip position and nonvascular placement is made with a 0.3- to 0.5-mL nonionic contrast injection.
Nerve Root Injection After confirmation of needle tip position by CT or fluoroscopy, the steroid and anesthetic mixture is injected adjacent to the nerve root. The contrast used for location of the needle typically dissipates and spreads along the course of the treated nerve root, at times entering the spinal canal with slight epidural extension. It is typical for patients with radiculopathy to sense the injection and recognize their familiar
radicular pain, even to the level of the knee, foot, and ankle. This helps confirm appropriate level treatment. With the injection complete, the stylette is replaced, the needle is removed, and the procedure is finished. After the injection, the patient’s radicular pain is usually relieved due to the anesthetic in the injection. Postprocedure the patient must be cautioned regarding walking because the nerve root is partially anesthetized due to the local application of bupivicaine.
Technical and Procedural Challenges of Lumbar Root Injections Certain technical challenges may be present in accessing the lumbar nerve roots. With progressive degenerative disease, disk height loss and facet hypertrophy may obscure the tra-
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Figure 6 CT-guided lumbar nerve root block. (A) Approach to the L5 nerve root. The L5 root lies in the L5-S1 foramen (arrow). After establishing the skin entry point and trajectory from the scout CT images, a 25-g spinal needle is introduced and directed toward the right L5 root (arrowhead). (B) Needle tip is advanced just posterior to the nerve root and ganglion (arrow). (C) Contrast is injected to confirm needle tip position adjacent to the root (arrow). The steroid-anesthetic mixture is injected into the wheal of contrast established adjacent to the root.
jectory to the root, in particular, at L5S1. In addition, visualization of the S1 posterior foramen can be challenging. If access cannot be achieved at fluoroscopy, an approach is usually identified by CT and the injection can still be performed. With bone fusion overlying the facet and transverse process region, access can again be limited, again most commonly seen at L5S1. CT can again be helpful in these instances but if clear approach to the root is not recognized, the procedure may need to be abandoned. Vascular access may be recognized after needle placement and contrast injection. If contrast is not seen accumulating at the needle tip or if vessel opacification is identified, the needle must be repositioned so that clear recognition of contrast adjacent to the nerve is seen and no vascular contrast is en-
countered so the particulate steroid suspension can be safely injected.
Clinical Follow-Up and Expected Outcomes In some practices patients are followed after epidural or nerve root procedures, while in others, patients may be referred for repeat injections. Due to the relatively high steroid dose, the number of injections that can be performed is limited. Typically, three steroid injections may be performed in a given 6-month period. Patients typically respond well to epidural steroid and nerve root injections. When the injections are effective, patients typically receive 1-3 months of sustained and significant pain relief. Residual pain can be managed by repeat
ESIs and selective NRBs’ injection. The purpose of the injections is to reduce epidural or nerve root inflammation. It is important for patients to understand that activities that continue to aggravate their pain will limit their treatment response. If pain relief does not occur, an alternative pain generator should be considered or surgical treatment might be necessary.
Conclusions Epidural steroid administration and lumbar nerve root blocks are an effective treatment in patients with back pain or radiculopathy. The procedures are safe and pain relief can be sustained.
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