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00007632-200301010-0000700007632_2003_28_21_furman_transforaminal_1miscellaneous-article< 89_0_8_6 >Spine© 2003 Lippincott Williams & Wilkins, Inc.Volume 28(1)1 January 2003pp 21-25Incidence of Intravascular Penetration in Transforaminal Cervical Epidural Steroid Injections[Cervical Spine]Furman, Michael B. MD, MS*; Giovanniello, Michael T. MD†; O’Brien, Erin M. MD‡From the *The Center for Pain Management and Rehabilitation, KDV Orthopaedics and Rehabilitation, York, Pennsylvania, the†Center for Physical Medicine and Pain Management, Salt Lake City, Utah, and the‡Rothman Institute, Thomas Jefferson University Hospital, Philadelphia, Pennsylvania.Acknowledgment date: November 19, 2001.First revision date: April 17, 2002. Second revision date: May 14, 2002.Acceptance date: May 20, 2002.Device status/drug statement: The devices and drugs are approved by the FDA or by corresponding national agency for this indication.Conflict of interest: No funds were received in support of this work. No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this article.Address reprint requests to Michael B. Furman, MD, MS, The Center for Pain Management and Rehabilitation, KDV Orthopaedics and Rehabilitation, 908 South George Street, York, PA 17403. E-mail: Design. A prospective, observational, human, in vivo study was conducted.Objectives. To evaluate the incidence of vascular penetration during fluoroscopically guided, contrast-enhanced transforaminal cervical epidural steroid injections, and to determine whether the observation of blood in the needle hub can be used to predict a vascular injection.Summary of Background Data. Incorrectly placed intravascular cervical spinal injections result in medication flow systemically and not to the desired target. A recently published study demonstrates a high incidence of intravascular injections in transforaminal lumbosacral epidural injections. No studies so far have evaluated the incidence of vascular injections in transforaminal cervical epidural steroid injections, nor have they calculated the ability of observed blood in the needle hub to predict a vascular injection in the cervical spine.Methods. The incidence of fluoroscopically confirmed intravascular uptake of contrast was prospectively observed in 337 patients treated with cervical transforaminal epidural steroid injections. The ability of observed blood in the needle hub to predict intravascular injection was also investigated. For each subject, the injection level was chosen on the basis of the clinical scenario including history, physical examination, and review of imaging studies. Some patients had multilevel injections. Using fluoroscopic guidance, the authors placed a 25-gauge needle into the epidural space using a transforaminal approach according to accepted standard technique. Needle tip location was confirmed with biplanar imaging. The presence or absence of blood in the needle hub spontaneously (“flash”) and after attempted aspiration by pulling back on the syringe’s plunger was documented. Contrast then was injected under real-time fluoroscopy to determine whether the location of the needle tip was intravascular. The results were recorded in a prospective manner indicating the presence or absence of blood in the needle hub and whether a vascular pattern was noted with contrast injection, and these were correlated. Relevant epidemiologic data also were recorded.Results. The study included 504 transforaminal epidural steroid injections. The overall rate of fluoroscopically confirmed intravascular contrast injections was 19.4%. Use of observed blood in the needle hub to predict intravascular injections was 97% specific, but only 45.9% sensitive. There was no significant difference in intravascular rates related to age or gender.Conclusions. As compared with a previous study of lumbosacral epidural steroid injections, there is an overall higher incidence of intravascular injections with cervical transforaminal epidural steroid injections. Use of observed blood in the needle hub to predict an intravascular injection is not sensitive, and therefore the absence of blood in the needle hub despite aspiration is not reliable. The reported sensitivity and specificity rates are similar to lumbar data. Fluoroscopically guided procedures without contrast confirmation instill medications intravascularly, and therefore not in the desired epidural location. This study confirms that there is a need not only for fluoroscopic guidance, but also for contrast instillation in cervical transforaminal epidural steroid injections.Cervical epidural steroid injections (CESIs) are an accepted treatment for the symptoms of neck pain with a radicular component secondary to cervical disc pathology or spinal stenosis. 2,16,19 To the mechanism of therapeutic benefit is attributed relief of the inflammation secondary to mechanical or chemical nerve root irritation. 12 However, clinical studies evaluating ESI efficacy describe variable results, 4,13 and there are no controlled, blinded studies of CESIs with a placebo group. Most of these studies evaluate CESIs performed without fluoroscopic guidance using a paramedian (interlaminar) approach. 14,15,20The epidural space also may be approached transforaminally. 21 The needle tip can be steered more ventrally where the posterior anulus interfaces with the ventral aspect of the nerve root and thecal sac (Figures 1 and 2). Because a smaller volume usually is injected, this technique theoretically may allow a higher concentration of medication to be administered closer to the site of pathology.Figure 1. Anteroposterior (A) and oblique (B) radiographs of a right C6 transforaminal epidural steroid injection (precontrast needle placement) demonstrates proper needle position at the “6 o’clock” (midpedicular) position inferior to the pedicle (anteroposterior) and dorsal in the foramen (oblique).Figure 2. Anteroposterior radiograph of a normal left C7 transforaminal epidural steroid injection demonstrates proper needle position in the lateral aspect of the foramen. Contrast (1 mL) flows along the left C7 nerve and nerve root sheath medially to the pedicle and into the epidural space.Many physicians performing cervical ESIs do not use fluoroscopy or contrast to confirm correct, extravascular needle placement into the epidural space. Without fluoroscopic guidance, the injection may be outside the epidural space 17 or intravascular, resulting in medication delivery missing the desired location. Intravascular injections can be either venous or arterial.The internal posterior vertebral venous plexus within the epidural space is located predominantly dorsolaterally, 3,8 and must be avoided during injections. An inadvertent venous injection results in anesthetic and corticosteroid instillation systemically instead of locally, and the desired therapeutic benefit may not be obtained. Although systemic local anesthetics can cause significant toxicity in various animal models, 5,6,10 the cited studies describe anesthetic concentrations of significantly higher magnitudes than those typically used for cervical transforaminal ESIs.However, administration of local anesthetic or steroids intraarterially can result in adverse central nervous system and cardiovascular effects. 1,11 This is of particular concern, and there is increased risk when injections are performed in the cervical region. Brouwers et al 1 described a cervical anterior spinal artery syndrome after diagnostic blockade of the right C6 nerve. These authors presumed that the mechanism of infarction was from impaired perfusion of the major feeding anterior radicular artery of the spinal cord. Because the exact etiology is unknown, other possibilities may include steroid particulate or vasospasm causing an infarction. In addition, Kozody et al 11 presented two case reports illustrating that low doses of anesthetic can induce grand mal seizures during nonfluoroscopically guided stellate ganglion blocks presumed to result from arterial injection. Paraplegia thought to be secondary to undetected intraarterial penetration has been reported after fluoroscopically guided, contrast-enhanced lumbar transforaminal epidural steroid injections. 9 The authors are additionally aware of at least six other cases of spinal cord injury resulting in substantial neurologic disability, each attributed to cervical transforaminal injections. These cases, however, are still under legal investigation, and have not been reported in the literature. Although the mechanism of pathology is unknown, it is presumed to be secondary to arterial injections of steroid, lidocaine, or both.Many injectionists depend on observation of blood in the needle hub spontaneously or after aspiration to indicate that their needle tip is in a blood vessel. However, a recently published study demonstrates a high incidence (11.2%) of vascular injections and a low sensitivity (44.7%) of spontaneous observation of blood in the needle hub (“flash”) or blood aspirate for predicting an intravascular injection in lumbar transforaminal ESIs. 7 No studies so far have evaluated the incidence of vascular injections in cervical transforaminal ESIs or whether blood in the needle hub can be used to predict an intravascular injection.The purpose of this study was to use fluoroscopic guidance and contrast enhancement for prospective evaluation of the incidence of intravascular injections in cervical transforaminal ESIs, and to correlate this with the ability of blood in the needle hub to predict them.Materials and MethodsApproval for the study was obtained through the Institutional Review Committee at York Hospital located in York, Pennsylvania. All the patients referred to the authors’ practice who were considered appropriate candidates for a transforaminal cervical ESI were included prospectively in the study during a 38-month period (April 1998 to May, 2001) for treatment of the symptoms associated with cervical disc pathology. Patients receiving interlaminar ESIs were excluded, as well as patients who were pregnant and those who had known allergies to contrast dye, iodine, fish, or shellfish. If the injectionist considered the needle placement “difficult,” requiring multiple attempts or demonstrating a questionable contrast flow pattern, it was excluded from the study.All the procedures were performed in the authors’ procedure suite under fluoroscopic guidance with contrast enhancement by the three authors. The patients were prepared and draped in a sterile fashion in the supine position. The authors’ registered nurse obtained intravenous access, provided optional sedation, and monitored appropriate vital signs and pulse oximetry.For cervical transforaminal ESIs, the fluoroscope was positioned so that an anterior oblique view of the appropriate neural foramen was visualized. The overlying soft tissue then was anesthetized using 1% lidocaine without epinephrine. An appropriate-length styletted 25-gauge needle was guided down the posteroinferior aspect of the foramen. The anterior foramen was avoided because of its proximity to the vertebral artery. Under biplanar visualization, the needle was advanced to the “6 o’clock” position of the lateral masses in the posteroinferior aspect of the foramen, thus avoiding nerve, dorsal root ganglion, dural sleeve puncture (Figure 1A and 1B), and the vertebral artery. For all levels, after confirming ideal needle position using biplanar fluoroscopy, the authors injected 0.5 to 2 mL of nonionic contrast with real-time fluoroscopic visualization of the contrast flow. They confirmed that the flow was along the spinal nerve and nerve root sheath into the epidural space medial to the pedicle (Figure 2). On the rare occasion when suboptimal fascial flow was visualized despite needle repositioning, the patient was excluded from the study.An injection was classified as a “flash” when there was spontaneous blood flow back into the needle hub or catheter. A “positive aspiration” was recorded when blood appeared in the hub or catheter after the syringe’s plunger was pulled back (with negative pressure). If either of these events occurred, the injection was described as positive for “observed blood in the needle hub.” The injection was classified as “intravascular” (the gold standard) when uptake into a blood vessel was visualized during real-time fluoroscopically observed contrast installation (Figure 3). The incidence of intravascular injections was calculated from this information.Figure 3. As shown in this anteroposterior image, a right C6 transforaminal epidural steroid injection resulted in intravascular uptake. Although this static image clearly demonstrates contrast in small blood vessels, this flow pattern typically is present for a very short time because the contrast is quickly drawn away via the vascular system.Subsequently, the alleged predictors of intravascular flow (observation of blood flow into the needle hub spontaneously or after aspiration) were correlated with real-time fluoroscopically observed intravascular uptake. Data were collected prospectively and also included the patients’ age, gender, and diagnosis. Statistical evaluation was performed on the aforementioned data including χ2 test, sensitivity, specificity, and power analysis to determine the significance of the findings.ResultsThis study included 504 cervical transforaminal ESIs performed on 337 patients. Of these patients, 62 underwent two-level procedures. The mean age of the patients was 49 years (range, 24–88 years). The epidemiology is presented in Table 1. Injections were performed at the C3 to C8. Table 2 presents the incidence of injection by level, showing that 220 injections were left-sided (43.7%) and 284 were right-sided (56.3%).Table 1. EpidemiologyTable 2. Incidence of Transforaminal Epidural Steroid Injections by LevelUsing fluoroscopic guidance with contrast confirmation, 98 vascular injections resulted in an overall intravascular injection rate of 19.4%. Table 2 presents the breakdown of cervical levels. The population was too small within each of the C3 to C8 levels for statistically significant conclusions to be drawn about incidence of vascular injection at each level individually.There also was no significant difference in incidence of intravascular injections based on gender (17.7% male and 20.8% female) (χ2 = 0.735, P = 0.391) or age. Correlation with age, evaluated by grouping patients by decade, was found to have no significant relation (χ2 = 4.11, P = 0.661).Although there were 98 documented vascular injections, only 45 of these were predicted by observation of blood in the needle hub (sensitivity, 45.9%) (Table 3). The 406 nonvascular injections were predicted by absence of blood in the needle hub in 394 cases (specificity, 97%).Table 3. Ability of Flash or Positive Blood Aspiration to Predict Vascular InjectionTP = true positive; FP = false positive; FN = false negative; TN = true negative.Sensitivity = 45.9%.Specificity = 97.0%.DiscussionIn this prospective study of 504 injections, the incidence of intravascular injections during cervical transforaminal ESIs was observed to be 19.4% overall. These data show a higher incidence of cervical intravascular injections than the previously published overall intravascular rates for lumbosacral transforaminal ESIs (10.8–11.2%), and a lower incidence than the rate for S1 transforaminal ESIs (21.3%). 7,18 There have been no previous studies documenting the incidence of intravascular cervical ESIs.Use of observed blood in the needle hub to predict intravascular injections was only 45.9% sensitive. This cervical technique (using 25-gauge needles with the patient in a supine position) resulted in sensitivity similar to that observed in the lumbosacral spine (using 22-gauge needles with the patient in the prone position). 7 Therefore, using observed blood in the needle hub was predictive of intravascular injection in less than half of the documented vascular injections. The sensitivity is most likely not related to patient position (supine vs prone) or needle gauge (22 vs 25), as shown by the similar findings of these two studies. The explanation for the low sensitivity may be that there is not enough pressure in the venous system to result in spontaneous flow of blood through the needle into the needle hub. Attempted aspiration may result in enough negative pressure to collapse the vessel, thus preventing uptake of blood through the needle into the hub, regardless whether there is a 22- or 25-gauge needle. During the injection of contrast or medications, however, there is enough positive pressure to keep these smaller vessels distended, resulting in an intravascular injection. Therefore, use of blood observed in the hub either spontaneously or after aspiration should clearly not be considered a reliable predictor of an intravascular injection.Although these studies investigated only transforaminal cervical and lumbar ESIs, the implications of this finding extend throughout injection therapy. Considering that more than half of intravascular injections may be missed without contrast and fluoroscopic confirmation, the technique for many “blind” injections should be reconsidered. In the cervical region, this is of particular importance secondary to the potential risk of serious adverse central nervous system and/or cardiovascular effects with arterial injections from anesthetic or particulate present in steroid. 1,11In the current study, the authors found that observation of blood in the needle hub was 97% specific. This is similar to the findings in the lumbar spine at 97.9%. 7 Although absence of blood in the needle hub is unreliable, the presence of blood in the needle hub reliably predicts a vascular injection, and the needle tip should be repositioned. Interestingly, it was observed that for 12 (3%) of the 406 contrast-confirmed, nonvascular injections, blood was observed in the needle hub. This finding is most likely attributable to tissue trauma and/or blood uptake that occurred as the needle was advanced because the final needle tip position was not likely within the blood vessel.The low sensitivity of observing blood in the needle hub suggests that previous studies using this to predict intravascular injections may have underestimated the incidence of vascular injections in ESIs. This could result in a lower reported efficacy in a “blind” (non–fluoro-scopically guided, contrast-enhanced) ESI because the medication is not necessarily going to the desired target. Using biplanar imaging to confirm needle position before contrast installation typically results in expected flow patterns along the spinal nerve and the nerve root sheath, and into the epidural space medial to the pedicle. Despite biplanar imaging before contrast injection, the authors occasionally still observe a fascial pattern that is corrected with needle tip position adjustment. Although the data on the incidence of fascial injections was not collected, these could further decrease the efficacy of ESIs if the needle tip position is not repositioned to optimize flow. Therefore, future studies investigating the efficacy of ESIs need to document clearly a correctly placed, nonvascular injection along the spinal nerve and nerve root sheath, and into the epidural space using fluoroscopy and contrast enhancement.None of these patients experienced symptoms or any adverse effects from intravascular injection of contrast. In almost all cases, once an intravascular injection was encountered, the needle tip could be repositioned with subsequent nonvascular flow appreciated using contrast and fluoroscopic confirmation. No other medications were injected until the needle was repositioned and a nonvascular injection confirmed. Occasionally, an intravascular injection could not be avoided despite needle repositioning, and the injection at that level was terminated without administration of the medication. However, the incidence of this termination rate was not documented in the current study.The authors expect that an incorrectly placed venous intravascular cervical spinal injection would result in systemic medication flow that does not reach the desired target, thus decreasing the efficacy of a CESI. Cadaver anatomic studies demonstrate that the internal vertebral venous plexus (IVVP) is a network of interconnecting vessels that may help to regulate and bypass the major veins. 8 Therefore, except for decreased efficacy, it is unlikely that a venous injection would result in significant morbidity. However, incorrectly placed arterial intravascular injections can possibly also result in significant neurologic, cardiorespiratory compromise, or both. 1,9,11 Unfortunately, the current study did not differentiate between intraarterial and intravenous vascular injections.Because this study was observational, the efficacy of cervical transforaminal ESIs was not monitored. Also, no adverse reactions were noted in any of the study participants before they were discharged. Therefore, the outcome or adverse reaction rates cannot be compared between the patients who originally had intravascular injections and those who did not.Key Points * There is a high incidence of intravascular cervical transforaminal epidural steroid injections (ESIs). * Use of observed blood in the needle hub to predict intravascular location of the needle tip is not sensitive. * There is a need for fluoroscopic guidance and contrast injection before cervical transforaminal epidural steroid injections (ESIs) to avoid intravascular injections.AcknowledgmentsThe authors thank Nicole Meads, RTR, and Jenna Bridell for their help in data collection, and Kristi Peters, MS, Research Associate, and Ted Bell, BS, Research Assistant (Emig Research Center, York Hospital) for their help in data analysis.References1. Brouwers PJAM, Kottink EJBL, Simmon MAM, et al. A cervical anterior spinal artery syndrome after diagnostic blockade of the right C6 nerve root. Pain 2001; 19: 397–9. 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