Radiopaque Line in Front of the Lumbar Spine During a S1 Transforaminal Epidural Injection: Where Is the Contrast?

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A 48-year-old man presented with low-back and bilateral leg pain that had started a month ago. Numeric rating score for pain was 8 of 10. Pain was aggravated by walking and standing. On physical examination, straight leg raise test was positive bilaterally at 60 degrees. Magnetic resonance imaging showed a L5-S1 central disc protrusion with bilateral S1 root compression. After considering his physical examination and magnetic resonance imaging findings, bilateral S1 transforaminal epidural steroid injection (TFESI) was performed. While performing the left S1 TFESI, initially, an odd intravascular dissemination was seen. One hour after the intervention, his pain was relieved (numeric rating score, 1/10).
The position of the needle before contrast injection and the lateral and anteroposterior views after contrast administration are seen in Figures 1–3, respectively. After its administration, the contrast cannot be seen around the needle tip; instead, it is readily identified lining the posterior part of a venous structure, probably inferior vena cava.
To the best of our knowledge, this is a very rare intravascular dissemination of this kind in the literature.
With its ability to provide analgesia in a very short time frame, epidural injection, especially TFESI, is an effective and frequently used treatment option in spinal pain. Relatively minor complications including vasovagal events, dural puncture, intradiscal injection, infection, and bleeding may be encountered.1 Major complications like stroke, spinal cord injury, and death occur rarely, usually due to direct needle trauma or intravascular placement of the medications, causing distal radicular arteries embolism.2
Studies on the intravascular injections demonstrated that intravascular placement occurs more frequently during TFESI compared to interlaminar approach. It is commonly seen in the sacral region, followed by the lumbar and cervical spine. Intravascular injection can be prevented by changing the needle type and improving imaging. El Abd et al3 has shown presence of vascularity in 5.26% of the patients with digital subtraction angiography who had negative aspiration test or negative intravascular puncture on fluoroscopy. However, digital subtraction angiography is not easily accessed and its radiation dose is higher; thus, fluoroscopy is commonly used and the detection of intravascular injection through this modality is paramount. This is done by visualization of the contrast dissemination into the vascular tree alongside the epidural spread. Another hint is the inability to visualize the contrast material on the needle tip as in this case.
We conclude by recommending the inspection of the anterior spine for visualization of contrast in inferior vena cava and determining if intravascular dissemination was present.

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