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Interv Pain Med
Interv Pain Med
Interventional Pain Medicine
2772-5944
Elsevier

S2772-5944(23)00066-3
10.1016/j.inpm.2023.100240
100240
Case Report
Safety of dexamethasone in transforaminal epidural steroid injections: A case of temporary paraplegia caused by injection of lidocaine and dexamethasone into a lumbar radiculomedullary artery, with no neurologic sequelae
Levi David Levid@cox.net
a∗
Horn Scott a
Murphy Jestine a
Levin Josh b
a Jordan-Young Institute, Virginia Beach, VA, USA
b PM&R Section, Department of Orthopaedic Surgery and Neurosurgery, Stanford University, Redwood City, CA, USA
∗ Corresponding author. Levid@cox.net
08 3 2023
3 2023
08 3 2023
2 1 10024030 12 2022
5 2 2023
17 2 2023
© 2023 The Authors
2023
https://creativecommons.org/licenses/by-nc-nd/4.0/ This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
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pmc1 Introduction

Transforaminal epidural steroid injections (TFESIs) are often used in the treatment of radicular pain. Catastrophic complications have occurred, including paralysis from spinal cord infarction [[1], [2], [3]]. This complication is likely due to inadvertent injection of particulate steroid into a radiculomedullary artery [1].

Dexamethasone is now considered the steroid of choice for TFESIs, based on very small particulate size [4], and animal data demonstrating safe injection into the vertebral and carotid arteries [5,6]. There has been a single case report of a spinal cord infarction following a L4/5 TFESI with dexamethasone [7]. That case contrasts with the lab and animal research which has demonstrated the safety of dexamethasone [[4], [5], [6]]. In addition, in the past several years in which dexamethasone has been used extensively for TFESIs, there have not been any other case reports of spinal cord infarction with the injection of that steroid.

We present a case of presumed radiculomedullary artery injection, during an L1/2 TFESI, with temporary paraplegia caused by the anesthetic, but no apparent detrimental effect from the co-injected dexamethasone. The aberrant injection was determined to be in a radiculomedullary artery rather than subarachnoid based upon the epidural contrast flow pattern and the patient's ‘normal’ sensation with complete but temporary lower extremity paralysis.

2 Case report

Verbal and written permission was obtained from the patient for this case report. A 76-year-old man who had previously undergone L2-S1 fusion with L2-4 laminectomy was referred for an epidural steroid injection in October of 2022. He reported low back pain referring into the buttocks bilaterally with relatively diffuse intermittent lower limb pain, which had been present since the fusion three years prior. He was able to ambulate without an assistive device.

The MRI, November 2019, demonstrated adjacent segment disease with severe stenosis at L1/2. An updated MRI in August 2022 demonstrated continued severe stenosis at L1/2, but also a new, large T12/L1 disc extrusion with cephalad migration, some epidural hemorrhage/calcification with central stenosis and mild edema of the spinal cord. There was moderate left L1/2 foraminal stenosis from disc material (Fig. 1, Fig. 2, Fig. 3).Fig. 1 Sagittal T2 weighted MRI images of left paramedian, midline and right paramedian: L2-S1 posterior fusion with L2-4 laminectomy.

Fig. 1

Fig. 2 Sagittal and axial T2 weighted MRI slices at a level just cephalad to T12/L1 (top) and through the L1/2 level, demonstrating degree of central stenosis and probable cord edema.

Fig. 2

Fig. 3 Sagittal and axial T2 weighted MRI images at L1/2 just inferior to subpedicular level of needle placement. Please note, a true subpedicular L1 axial slice at the supraneural needle location was not performed on this MRI scan.

Fig. 3

The patient's symptoms had not changed significantly between the November 2019 and August 2022 MRIs. He continued to have low back, buttocks, and intermittent diffuse lower limb symptoms. He denied any significant weakness or any bowel or bladder issues. Neurosurgical consultation recommended continued nonsurgical treatment.

Physical exam revealed normal motor function, and muscle stretch reflexes were 0 out of 4 throughout the lower limbs. There was tenderness throughout the lumbar region and bilateral buttocks.

The patient underwent a bilateral L1/2 TFESI under fluoroscopy, using a supraneural approach. A 25-gauge 3.5 inch Quincke needle was directed just inferior to the pedicle, remaining lateral to the 6 o'clock position. The needle was advanced ventrally into the foramen approximately 50% of the foraminal depth in the lateral view. Both needles were placed prior to contrast injection (Fig. 4). The left side was injected first. Small bore extension tubing was primed with contrast and connected to the needle hub. In the AP view, Omnipaque 240 contrast medium was injected under digital subtraction imaging (DSI). There was contrast flow outlining the left L1 spinal nerve and some flow into the epidural space. The patient did have difficulty remaining motionless during the DSI. There was some opacity in a linear fashion just left of midline proximally, but this appeared to be the left side of the spinous process, secondary to the patient movement rather than vascular flow (Fig. 5 and Video 1). One ml of preservative-free lidocaine 1% was then injected as a test dose. After approximately 45 seconds passed, without clinical symptoms, 7.5 mg preservative-free dexamethasone was then injected. The same process was then performed on the right side: contrast with DSI then subsequent injection of lidocaine followed by dexamethasone injection. (Fig. 6 and Video 2).Fig. 4 Fluoroscopic AP and lateral images, pre-contrast, with both needles in place for bilateral L1/2 TFESI.

Fig. 4

Fig. 5 Fluoroscopic AP image during left L1/2 TFESI conventional (A) and digital subtraction imaging (B) (Contrast was instilled on the left side only on these images).

Fig. 5

Fig. 6 Fluoroscopic AP image during digital subtraction imaging for right L1/2 TFESI contrast injection (A) and AP ”wash” post contrast image following the bilateral injection (B).

Fig. 6

Supplementary video related to this article can be found at https://doi.org/10.1016/j.inpm.2023.100240

The following are the supplementary data related to this article.Left DSI

Left DSI

Right DSI

Right DSI

Approximately 3 ​min after the injection on the left side, which was 1 ​min following the injection on the right, the patient was asked to transfer off the procedure table. He reported that he could not move his legs. He remained in a prone position and motor exam revealed bilaterally 0/5 for hip flexion, hip extension, knee flexion, knee extension, ankle plantar flexion, and ankle dorsiflexion. He had no pain. On gross sensory exam, he reported ‘normal’ sensation, including light touch and heavy pressure throughout the lower limbs. A rectal exam was not performed, but he reported that he had normal feeling within the gluteal cleft to light touch in the region. Pain and temperature was not tested. There was no incontinence. There was slight rigidity in the lower limbs with passive range of motion, but this was subtle. There were no cardiopulmonary symptoms.

The patient was then placed in a supine position with his upper body slightly elevated with pillows in the unlikely scenario that this represented an intrathecal injection. This was felt to be improbable in light of his ‘normal’ sensory exam and epidural flow pattern.

At 5 ​min, the exam remained unchanged. At ten minutes, plantar flexion was 1 out of 5. At fifteen minutes, the motor exam improved throughout the lower limbs diffusely, 2 out of 5. At twenty minutes, the motor exam was 4 out of 5 throughout. By 30 minutes, motor exam was essentially normal. He was monitored for another 30 minutes and then discharged without any deficit.

In light of the mild cord edema seen on the August 2022 MRI and the transient weakness occurring following the TFESI, a non-urgent MRI of the lumbar spine was performed two weeks post-procedure. This demonstrated improvement of the previously seen mild cord edema and no other evidence of any abnormality of the visualized portion of the spinal cord (Fig. 7). At three weeks, the patient was clinically unchanged compared to pre-injection.Fig. 7 Sagittal and axial T2 weighted MRI images from two weeks post-procedure, November 2022, with axial slice just cephalad to T12/L1 level. The sagittal image demonstrates slight improvement in cord edema compared to image 1 and 2, pre-procedural MRI.

Fig. 7

3 Discussion

This case almost certainly represents an injection of lidocaine and dexamethasone entered into a radiculomedullary artery. The patient's symptoms of complete, temporary lower limb paralysis with preservation of sensation were likely due to intra-arterial local anesthetic injection into a vessel that fed the spinal cord. The lack of neurologic sequelae from subsequent injection of dexamethasone is extremely fortunate and invaluable to our understanding of the safety of non-particulate steroid for TFESIs. If a particulate steroid had been used, the patient's paralysis likely would have been permanent [1].

Radiculomedullary arteries typically anastomose with the anterior spinal artery which supplies the anterior two thirds of the spinal cord. Anesthetizing this portion of the spinal cord, which includes the lateral corticospinal tract, would be expected to cause loss of motor function. Preservation of light touch and proprioception is also expected, as these functions travel through the dorsal columns. This was observed in the only other case report of anesthetic injection into a radiculomedullary artery, occurring during a cervical TFESI [8]. Temporary, complete motor loss with preservation of light touch and proprioception appeared to be present in the prior [8] and current report, although formal proprioception testing was not performed in this case. In both cases, about 1 mL of lidocaine was injected (2% in the prior [8], 1% in the current). The resolution of symptoms occurred at 20 ​min in the prior case [8], which is very similar to the current report.

The use of an anesthetic test dose is somewhat controversial. In the abovementioned report by Karasek, clinical symptoms began about 1 ​min following the test dose, which likely prevented a catastrophic complication from an injection of particulate steroid [8]. The authors of the current case report routinely perform a test dose during all TFESIs. It also provides the secondary benefit of local anesthesia for the radicular symptoms which the authors find useful. However, in the authors’ practice, there is generally not a full minute interval between the anesthetic and steroid injections. In this case, only about a 45 second waiting period was performed, which might have been inadequate for the development of any clinical symptoms.

DSI was employed in this case report. There is substantial evidence that detection of vascular uptake is greater with DSI compared to conventional live fluoroscopy [9,10]. The authors routinely use DSI for transforaminal injections above L4. The likelihood of encountering a radiculomedullary artery in the upper lumbar region is much greater than other locations in the lumbar spine [11]. The procedure in this report was performed at the L1/2 level. Potentially due to patient movement, the arterial flow was not recognized. Clearly, DSI can be helpful despite certain limitations in the detection of all aberrant flow. Even with the use of DSI, an unfortunate case of spinal infarct was reported during an L5/S1 TFESI [12].

Although unlikely, there are other possible explanations for the temporary paraplegia observed in this case. It is conceivable that the symptoms were secondary to a subarachnoid injection. However, the preservation of sensation, including light touch, in the absence of any motor function, strongly argues against this explanation. In addition, the contrast flow pattern appeared to be epidural. The presence of an epidural flow pattern does not preclude simultaneous vascular flow. In fact, the incidence of vascular flow patterns during lumbar TFESI is twice as high with simultaneous epidural flow, 8.9%, as compared to vascular flow patterns without epidural flow, 4.2% [13]. Practitioners must resist the temptation to focus on the epidural pattern, as it may limit recognition of critical aberrant flow. In order to best detect flow in a radiculomedullary artery, physicians must focus on the midline region proximal to the injection level during conventional live fluoroscopy or DSI.

Another explanation for the temporary paraplegia, although also improbable, is temporary central canal compression of the injectate between the two levels of stenosis, T12/L1 and L1/2. Compressive lesions from interlaminar epidural steroid injections have been reported to cause motor and sensory loss in the lower limbs and perineal region with bowel and bladder symptoms [14]. Although the levels above and below the injection were clearly very stenotic (Image 2), the injection in this report was performed via the transforaminal route, and contrast flow was seen along the exiting nerve. Therefore, a compressive mass effect of the injectate would be unlikely. The clinical scenario of painless, complete, and temporary lower limb motor loss without perineal or other significant sensory loss is much more consistent with anesthetization of the anterior spinal cord.

Although it is not possible to determine with certainty, it is presumed in this case, that it was the left sided, rather than the right, L1/2 TFESI which was responsible for the radicular artery injection. This assumption is based upon two factors. First, the largest radiculomedullary artery, the artery of Adamkiewicz, has a much higher prevalence on the left side [11]. Second, the flow pattern visualized on left DSI (Video 1) was much less clear than the right side. As the patient did have difficulty remaining motionless, the linear paramedian opacity was interpreted as the left side of the spinous processes proximal to the injected level. In retrospect, this interpretation certainly may have been erroneous.

This case report describes a very fortunate outcome in which an injection of dexamethasone with lidocaine entered a radiculomedullary artery and caused only temporary paralysis with no permanent neurologic sequelae. The most significant observation is the lack of spinal cord infarction with an intra-arterial injection of a particulate free corticosteroid, dexamethasone. This report provides further evidence for the safety of dexamethasone in transforaminal epidural steroid injections.

Funding

None of the authors have any financial disclosures related to the content of this study. There was no external funding for this study.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

The authors would like to thank Ry Levi for his assistance in proofreading this report.
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