Brief Research Report Ultrasound-Guided Cervical Nerve Root Block: Spread of Solution and Clinical Effectpme_

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1 Pain Medicine 2011; 12: Wiley Periodicals, Inc. Brief Research Report Ultrasound-Guided Cervical Nerve Root Block: Spread of Solution and Clinical Effectpme_ Masanori Yamauchi, MD, PhD,* Daisuke Suzuki, PhD, Tomohisa Niiya, MD, PhD,* Hironori Honma, MD,* Nobuko Tachibana, MD,* Akihiko Watanabe, MD, PhD,* Mineko Fujimiya, MD, PhD, and Michiaki Yamakage, MD, PhD* Departments of *Anesthesiology and Anatomy, Sapporo Medical University School of Medicine, Sapporo, Japan Reprint requests to: Masanori Yamauchi, MD, PhD, Department of Anesthesiology, Sapporo Medical University School of Medicine, S1 W16, chuo-ku, Sapporo, Hokkaido , Japan. Tel: ; Fax: ; Disclosure Financial support was provided solely from institutional and departmental sources (Sapporo Medical University School of Medicine) for this study. None of the authors has any conflict of interest. We have not presented this study in any meetings. Abstract Objectives. We investigated the clinical effects and accuracy of ultrasound-guided cervical nerve root block. Additionally, spinal level and spread of injected solution were confirmed by anatomic dissection of fresh cadavers. Design Setting, Patients, and Interventions. Twelve patients diagnosed with mono-radiculopathy between C5 7 underwent ultrasound-guided nerve root block. An insulated needle was advanced with an in-plane approach using nerve stimulation and 2 ml of 0.375% ropivacaine with 4 mg of dexamethasone was injected using nerve stimulation. Ultrasound-guided C5 7 nerve root block was also performed in ten fresh cadavers. Blue dye (2 ml) was injected onto each nerve root and anatomic dissection was performed to confirm the exact spinal level and spread pattern of the dye. Results. Pain score before the procedure (65 [46 80], median [interquartile range]) was decreased to 25 [3 31] at 24 hours (P = 0.003) and 40 [28 66] at 30 days (P = 0.02) after the root block. Obvious side effects were not seen. All target nerve roots in patients and cadavers were correctly identified by ultrasound imaging. The needle tip did not reach the pedicle of the vertebral arch in the anteroposterior view of fluoroscopy, and spread pattern of contrast medium was extraforaminal and extraneural. Conclusions. This study suggests that injected solution by ultrasound-guided cervical nerve root block mainly spreads to the extraforaminal direction compared with conventional fluoroscopic technique. Therefore, present clinical study involves possibility of safer selective nerve root block with sufficient analgesic effects by ultrasound guidance, despite the absence of intraforaminal epidural spread of solution. Key Words. Cervical; Interventional; Nerve Block; Radiculopathy; Ultrasound Introduction Selective cervical nerve root block is widely performed to diagnose the spinal level of cervical radiculopathy and relieve radicular pain, headache, shoulder stiffness, or extremity pain [1 3]. Various complications associated with cervical nerve root block have been reported [4,5]. Intravascular injection may produce serious complications including central nervous system infarction and bleeding [6,7]. Fluoroscopic guidance is usually utilized for selective cervical nerve root block, and computed tomography (CT) [8] or magnetic resonance imaging guidance [9] is also employed in difficult cases. Although cervical nerve roots and vessels are identified more clearly by CT guidance than by fluoroscopy, cerebellar infarction and brainstem infarction have been reported even under CT guidance [10]. Recently, it has been reported that ultrasound-guided selective cervical nerve root block facilitated confirmation of nerves, vessels, needles, and injected solutions, and it is expected that a more appropriate procedure can be performed than that by fluoroscopic guidance alone [11 13]. However, there have not been many reports on the effects and features of ultrasound-guided selective cervical nerve root block, and the relation between needle tip position and spread pattern of local anesthetic is not known. In the present study, the authors clinically investigated the efficacy and accuracy of ultrasound-guided cervical nerve root block using nerve stimulation and fluoroscopy. The accuracy of determination of spinal level and spread of the injected solution was confirmed by dissection of fresh cadavers in an anatomic study. We 1190

2 Ultrasound-Guided Cervical Root Block investigated how local anesthetics spread by ultrasoundguided cervical nerve root block comparing with the conventional fluoroscopic technique, and that clinical effects and facility of the ultrasound-guided technique was also evaluated. Methods Clinical Study The protocol of this study was approved by the ethics committee of our hospital and written informed consent was obtained from all patients after receiving complete information prior to therapy. Twelve patients who were diagnosed with mono-cervical radiculopathy by history, distribution of paresthesia, physical examination, irregular alignment in cervical X-ray imaging and nerve root compression in magnetic resonance imaging were scheduled to undergo ultrasound-guided cervical nerve root block. Patients eligible for this prospective study were suffering from radicular pain or numbness between C5 7 areas and their symptoms had persisted for at least 2 months despite appropriate medication and conservative treatment. Patients were excluded if they met any of the following criteria: contraindications to regional block technique, cervical radiculopathy at multiple levels, age <18 or >80 years, pregnancy, and inability to comprehend pain scales. During the procedure, intravenous midazolam (2 mg) was administered as a requirement for patients sedation. The interventional procedure was performed by MaY under ultrasound guidance using a modified Narouze et al. technique [12]. Briefly, patients were placed supine on the radiographic table with the chin deviated approximately 0 30 away from the side, and a soft mat was inserted between the ipsilateral upper body and the table. The angle of the C-arm was adjusted to obtain the proper anteroposterior view of the cervical spine. First, C5 7 nerve roots were identified in ultrasound imaging (Micro- Maxx, SonoSite, Inc., Bothwell, WA, USA) by the shape of the transverse process; the C5th and C6th transverse processes both have obvious anterior and posterior tubercles, as opposed to the C7th transverse process, which has a rudimentary anterior tubercle and a prominent posterior tubercle [11,12]. Thus, we could define the C7 and C6 nerve roots at first, and then the C5 nerve root can be easily identified by moving the transducer cranially. The skin was prepared under strictly aseptic conditions with iodinated alcohol, and the ultrasound probe (HFL38, 13 6 MHz, 38-mm linear array, SonoSite, Inc.) was aseptically covered. Then a short axial view of the target nerve root surrounded by the anterior and posterior tubercles of the transverse process was visualized in ultrasound imaging in confirming location of vessels around the nerve root by color Doppler mode, and a 50-mm 22-G insulated needle (Hakko, Co., Tokyo, Japan) was gently introduced by an in-plane approach toward the posterior edge of the nerve root located at the inside of the posterior tubercle (Figure 1). The needle was connected to a constant voltage nerve stimulator (Stimuplex DIG, B-Braun/ Figure 1 Axial ultrasound imaging of C7 nerve root block (A), the fluoroscopic imaging during the block (B), and spread of contrast medium (C). C7 nerve root (C7) was partially surrounded by posterior tubercles (PT) of the transverse process, and a needle tip was introduced between C7 and PT. Contrast medium was spread to the peripheral direction and did not reach the epidural space (C). McGaw Medical, Bethlehem, PA, USA) that was set at 2 Hz with pulse width of 100 ms and a current of 0.8 ma. The needle position was considered acceptable if an evoked pickling paresthesia and motor response as twitch muscle contraction in the affected region was elicited between ma. After careful aspiration to exclude blood or cerebrospinal fluid, 0.5 ml of physiological saline was injected and the spread was confirmed by ultrasound imaging. Needle position was verified and the spread of 2 ml of contrast medium was examined with an anteroposterior fluoroscopic view and, if necessary, the needle position was adjusted (Figure 1). After careful aspiration, a total of 2 ml of a mixture of 0.375% ropivacaine and dexamethasone (4 mg) was slowly injected. All injections were performed under real-time ultrasound guidance. Finally, the needle was removed and light pressure was applied on the injection site for 2 minutes. Sensory and motor function scores at the dermatome where cervical nerve roots were blocked were assessed at 2, 6, and 1191

3 Yamauchi et al. 24 hours after the nerve block (0 = complete block, 1 = severe intense block, 2 = mild block, 3 = normal function). The next morning, all patients were discharged after confirming no complications or negative side effects and were instructed to continue their medication. Side effects and worsening of the symptoms of radiculopathy were recorded. Intensity of radicular pain was scored by the patient on a visual scale from 0 (no pain) to 100 mm (maximum intensity). In order to normalize the data, the percentages of pain relief given in the response to treatment were calculated using the following formula: ( pretreatment score posttreatment score) 100 pretreatment score The pain score was evaluated by the referring physician at 2, 6, and 24 hours while being in the hospital and 7 and 30 days in the ambulatory unit. Data were analyzed by Wilcoxon signed-rank test for paired values. A value of P < 0.05 was considered significant. The results are expressed as means standard deviation or median values [interquartile range]. Cadaver Study The protocol of this study was approved by the university s ethics committee, and fresh cadavers obtained with written informed consent prior to death were used. Ultrasound-guided cervical selective nerve block was performed in 10 randomly selected cadaveric specimens. We did not use nerve stimulation and fluoroscopic confirmation in the cadaver study. Specimens were kept in a freezer at -20 C and then thawed at room temperature 24 hours prior to the experiment. The experiment was performed at room temperature (22 C). C5 and C7 root block was performed at the same side and C6 root block was performed at the opposite side. Right C5 and C7 block and left C6 block were performed in the first cadaver. The right and left sides were changed in the next cadaver, and the blocks were alternately performed for all cadavers. After a 50-mm 22-G insulated needle had been advanced to the proper position under ultrasound guidance, 2 ml of blue dye was injected adjacent to each nerve root. Anatomic dissection around C5 7 and the cervical plexus was performed to confirm the exact spinal level and spread pattern of the dye. Results Clinical Study Twelve patients (seven men and five women) were enrolled in this study (Table 1), and no patients required sedation during procedure. The spinal levels of all nerve roots were correctly identified by ultrasound imaging, and there was no need to alter the needle position after fluoroscopic confirmation in any of the cases. Needle tip position was located at the inside of the transverse process of the target spinal level, not too medially into the foramen, in all patients. The needle tip did not reach the pedicle of the Table 1 vertebral arch in the anteroposterior view of fluoroscopy. Contrast medium clearly spread along the nerve roots as an extraneural pattern in 10 patients, spread along the scalene muscle like a myogram in two patients, and did not spread into the epidural space in all patients. An adequate response was evoked by nerve stimulation before injection of solution in all patients. Sensory and motor function scores were 0 or 1 for a few hours, and the motor functions had completely recovered to the preblocked level on the next day in all cases (Table 2). Pain score was significantly decreased almost half of the control state (65 mm) for 7 days (P < 0.01) and maintained about 40 mm for 30 days after the block (P < 0.05). Percentages of pain relief were also improved only 13% at 30 days (P < 0.05, Table 3). Side effects, such as intravascular injection revealed by fluoroscopy, inappropriate region block, respiratory or cardiovascular depression, local anesthetic toxicity, bruising and bleeding or hematoma at the injection site, worsening of symptoms, and other abnormalities were not seen. Cadaver Study Age of cadavers ranged years. All nerve roots were clearly visible in ultrasound imaging (Figure 2). Anatomic dissection proved that ultrasound identification of the spinal level was correct and the injected blue dye spread surrounding the nerve roots was located outside of the intervertebral foramen. There was no failed injection case. Discussion Demographic data N (m/f) 12 (7/5) Age (years) Body height (cm) Body weight (kg) Site of radiculopathy C5 4 cases C6 4 cases C7 4 cases Mean values standard deviation. The present clinical and anatomic studies showed that real-time ultrasound guidance can perform accurate and Table 2 Sensory and motor function scores after the nerve block 2 Hours 6 Hours 24 Hours Sensory score 0 (0 1.0) 2 ( ) 3 ( ) Motor function score 0 (0 1.0) 2 ( ) 3 ( ) Median values (interquartile range). 1192

4 Ultrasound-Guided Cervical Root Block Table 3 Results Pain score Pre 65 (46 80) 2 hours 0 (0 8) hours 0 (0 10) hours 25 (3 31) days 31 (12 38) days 40 (28 66) 0.02 Pain relief score (%) Pre 0 (0) 2 hours 100 (92 100) hours 100 (84 100) hours 59 (43 96) days 53 (10 80) days 13 (0 52) 0.02 Median values (interquartile range). Pre = precervical root block. P values were compared with Pre. safe cervical nerve root block, and that this technique provides lasting analgesic effect for 1 month. Therefore, ultrasound-guided cervical nerve root block could avoid intravascular or intraneuronal injection. However, the ultrasound-guided technique was different from conventional fluoroscopic technique; ultrasound guidance caused peripheral side nerve root injection. These findings indicate that ultrasound-guided cervical nerve root block is a feasible procedure compared with the fluoroscopic technique. Although fluoroscopically guided cervical nerve root block is widely known as a standard procedure, unintentional intravascular injection can cause fatal complications such as vertebral artery dissection or brain and spinal cord infarction [6,7]. The rate of complications from cervical nerve root block has been reported to be % [14,15], and most of the severe complications were caused by intravascular injection of a steroid or local anesthetic [16,17]. Intravascular puncture and intraneural injection may cause severe and irreversible nerve injury. Nakagawa et al. [11] and Narouze et al. [12] reported that ultrasound guidance enabled accurate and safe needle placement by identification of the C3 7 transverse process in the same manner as that in the present study. Both reports emphasized that ultrasound imaging could visualize the transverse process with nerve roots and vessels and would enable safer cervical nerve root block. The ultrasound technique can avoid radiation exposure and allergic reaction by the contrast medium. Elicited continuous twitch response can identify the needle position, and it is widely known that the needle tip-nerve distance can be roughly estimated by a stimulating current; over 0.8 ma indicates too far, ma indicates appropriate distance, and 0.5 ma or less indicates too near or position [18]. Thus, in addition to ultrasound confirmation of the needle tip, use of fluoroscopy and/or nerve stimulation would increase the safety margin of cervical nerve P root block in a difficult case. Although a needle tip position and spread of solution were more peripheral than usual conventional technique, hydrostatic pressure and osmotic effects lead to absorb the solution into the nerve fiber and intracellular fluid flow may spread local anesthetic and steroid toward the central lesion where compression or inflammation of the nerve root would occur. The limitations of this study should be considered. First, clinical effects of this procedure are still uncertain. The needle tip position advanced by ultrasound guidance would be relatively peripheral compared with that using the fluoroscopic technique. This extraforaminal injection is expected to reduce fatal side effects, and most patients in this study were satisfied with the effects and procedure. However, this ultrasound-guided technique does not enable steroid injection or pulsed radiofrequency treatment around the dorsal root ganglion, which may have advantages in long-term improvement of radicular pain [19]. Transforaminal epidural block is expected to improve radicular pain more effectively and for longer time than selective nerve root block [20]. Further prospective blind studies should be performed to assess the long-term effects of ultrasound-guided selective nerve root block compared with the long-term effects of other techniques. Another limitation of this study is that it is still uncertain whether intravascular injection can be avoided without fluoroscopy. Ultrasound-guided cervical nerve block enables confirmation of the vertebral and thyroid artery and avoidance of needle tip insertion into the arteries. Narouze et al. [12] showed that critical vessels could be visualized with high-resolution ultrasound system. To decrease risk of intravascular administration, test injection of the physiological saline, use of high-resolution linear ultrasound machine, or confirmation by Doppler mode is needed. The present Figure 2 Ultrasound imaging of C7 nerve root block in cadaver study. C7 nerve root (C7) was appeared from posterior tubercles (PT) of the transverse process. A needle (arrow head) was manipulated till touching the C

5 Yamauchi et al. cadaver study also has limitations. Although some studies have proved similar connective tissue, muscle and nerve characters of a fresh cadaver as in the in vivo body [21,22], spread of the injected solution may differ from that in clinical treatment. Detection of vessels by color Doppler and observation of physiological response are also impossible in a cadaver study. In this study, we kept specimens at room temperature after thawing for longer than 6 hours, and the influence of nerve, muscle and connective tissue characters was considered to be small [23]. Further study is needed to prove the relation between injected volume and spread around the nerve root. The present clinical study suggests that ultrasoundguided cervical nerve root block may enable safe selective nerve root block by identifying the correct spinal level and vessels. Therefore, despite the absence of intraforaminal epidural spread, this technique resulted in sufficient analgesic effect for radicular pain. The fresh cadaver study also showed that injected solution mainly spreads to the extraforaminal direction and that ultrasound-guided cervical nerve root block could avoid intraforaminal epidural block. Our results indicate that selective cervical nerve root block has the possibility to shift from fluoroscopic guidance to ultrasound guidance for its feasibility and portability. This study suggests that injected solution by ultrasoundguided cervical nerve root block mainly spreads to the extraforaminal direction compared with conventional fluoroscopic technique. Therefore, present clinical study involves the possibility that this ultrasound-guided technique would perform safer selective nerve root block with sufficient analgesic effects, despite the absence of intraforaminal epidural spread of solution. Further study with large number samples may shift technique of selective cervical nerve root block from fluoroscopic guidance to ultrasound guidance for its feasibility and portability. Acknowledgments We acknowledge Dr Mitsuhiro Aoki, Associate Professor in Department of Physical Therapy, School of Health Sciences, Sapporo Medical University, who provided invaluable assistance in performing this trial. References 1 Razzaq AA, O Brien D, Mathew B, Bartlett R, Taylor D. Efficacy and durability of fluoroscopically guided cervical nerve root block. Br J Neurosurg 2007;21: Martin DC, Willis ML, Mullinax LA, et al. Pulsed radiofrequency application in the treatment of chronic pain. Pain Pract 2007;7: Anderberg L, Annertz M, Rydholm U, Brandt L, Säveland H. Selective diagnostic nerve root block for the evaluation of radicular pain in the multilevel degenerated cervical spine. Eur Spine J 2006;15: Pobiel RS, Schellhas KP, Eklund JA, et al. Selective cervical nerve root blockade: Prospective study of immediate and longer term complications. Am J Neuroradiol 2009;30: Schellhas KP, Pollei SR, Johnson BA, et al. Selective cervical nerve root blockade: Experience with a safe and reliable technique using an anterolateral approach for needle placement. Am J Neuroradiol 2007;28: Wallace MA, Fukui MB, Williams RL, Ku A, Baghai P. Complications of cervical selective nerve root blocks performed with fluoroscopic guidance. Am J Roentgenol 2007;188: Brouwers PJ, Kottink EJ, Simon MA, Prevo RL. A cervical anterior spinal artery syndrome after diagnostic blockade of the right C6-nerve root. Pain 2001;91: Wagner AL. CT fluoroscopic-guided cervical nerve root blocks. Am J Neuroradiol 2005;26: Strobel K, Pfirrmann CW, Schmid M, et al. Cervical nerve root blocks: Indications and role of MR imaging. Radiology 2004;233: Suresh S, Berman J, Connell DA. Cerebellar and brainstem infarction as a complication of CT-guided transforaminal cervical nerve root block. Skeletal Radiol 2007;36: Nakagawa M, Shinbori H, Ohseto K. Ultrasoundguided and fluoroscopy-assisted selective cervical nerve root block. Masui 2009;58: Narouze SN, Vydyanathan A, Kapural L, Sessler DI, Mekhail N. Ultrasound-guided cervical selective nerve root block: A fluoroscopy-controlled feasibility study. Reg Anesth Pain Med 2009;34: Martinoli C, Bianchi S, Santacroce E, et al. Brachial plexus sonography: A technique for assessing the root level. AJR Am J Roentgenol 2002;179: Ma DJ, Gilula LA, Riew KD. Complications of fluoroscopically guided extraforaminal cervical nerve blocks. An analysis of 1036 injections. J Bone Joint Surg Am 2005;87: Furman MB, Giovanniello MT, O Brien EM. Incidence of intravascular penetration in transforaminal cervical epidural steroid injections. Spine 2003;28: Huntoon MA. Anatomy of the cervical intervertebral foramina: Vulnerable arteries and ischemic neurologic 1194

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