Unilateral Diagnostic Infiltration of Lumbar L3 Nerve Root Resulting in an Inadvertent Discogram: The Importance of Fluoroscopic Guidance in Interventional Pain Therapy

A 50-yr-old man came to the pain clinic with subacute lumbar pain and radiation in the right leg by the L3 dermatome, with only a minor sensory deficit (paresthesia) and no motor deficits. A computed tomography scan of the lumbar spine showed a right lateral disc herniation of the L3–L4 intervertebral disc, with compression on the L3 nerve root and probably also on the right L4 nerve root. A lateral magnetic resonance image (fig. 1) also showed the right-sided, upward intraforaminal disc herniation at the L3–L4 level, with compression on the L3 nerve root and dehydration of the L2–L3 and L3–L4 intervertebral discs.

After a neurologic examination, the neurosurgeon initiated conventional pharmacologic treatment with intramuscular nonsteroidal antiinflammatory drugs and a combination of paracetamol and a weak opioid (tramadol hydrochloride). Because of lack of efficacy, the patient was referred to the pain clinic for a transforaminal sleeve infiltration of the L3 nerve root with steroids as an initial, nonoperative treatment. After informed consent, this infiltration was performed using a conventional technique under strict sterile conditions with an image intensifier. The skin was anesthetized with 3 ml lidocaine, 2%. A 22-gauge needle (RCN-10 needle, 100 mm) was advanced obliquely toward the base of the corresponding pedicle of the L3 vertebra. The position of the needle was verified in a lateral view, where the ideal placement of the needle is with the tip in the cephaloventral corner of the neuroforamen.

Immediately after 0.5 ml dye (180 mg iodine per ml iohexol, Omnipaque®; Nycomed Ltd., Cork, Ireland) was injected, an intervertebral L3–L4 discogram was observed (fig. 2A), although the nerve root of L3 was our target. The injection was not painful and did not cause referring sensations. In the lateral view, dye was visible descending from the tip of the needle in the neuroforamen to the intervertebral disc (fig. 2B).

The needle was withdrawn 2 mm, and another 0.5 ml dye was injected, resulting in a normal spread of the contrast medium in the neuroforamen as a sleeve nerve root infiltration. One milliliter bupivacaine, 0.5%, and 40 mg methylprednisolone acetate were injected. Thirty minutes after this injection, the patient’s radicular pain was relieved, and he was sent home. Two weeks and 2 months later, the patient’s condition was reevaluated. The radicular pain symptoms were resolved, making surgery unnecessary.

Correct positioning of the needle for a targeted sleeve infiltration is only reliable after radiologic control in at least two planes and the use of dye on the targeted nerve root. The transforaminal technique for epidural infiltration was suggested because of the better spread of the injected fluid to the irritated nerve root and to the ventral epidural space. 4–7Complications of this technique and of the infiltration of local anesthetics and corticosteroids are rare but must not be overlooked. Complications may be attributed to poor or incorrect patient selection, drug-related reactions, and technique. There is also the risk of lasting paraplegia by injection of the artery of Adamkiewicz, so creating vascular ischemia of the spinal cord. 8 

Recently, in disc herniations, the involvement of an important inflammatory reaction coming from the intervertebral disc and nucleus pulposus has gained attention. 9More specifically, the importance of phospholipase A2 was shown in the generation of symptoms resembling low back pain and sciatica. 10Because most of the inflammatory reactions in the epidural space are found nearby the intervertebral disc and thus in the anterior plane of the epidural space, a more targeted infiltration of this corticosteroid is advocated. These sleeve infiltrations are becoming more commonly practiced for the treatment of (sub)acute lumbosciatica. For correct positioning of the needle, the use of x-ray facilities is indispensable. Here, we describe a case with an inadvertent easy injection of the intervertebral disc, resulting in a discogram that could be classified as irregular. 11The unexpected spread of the contrast dye could be due to several reasons. First, because the magnetic resonance protocol described a right-sided, upward intraforaminal disc herniation at the L3–L4 level with compression on the L3 nerve root, a direct injection in this disc herniation could be supposed. Second, the leakage of inflammatory mediators through an annulus fibrosus tear can cause severe epidural fibrosis. The placement of the needle in this fibrosis at a distance of the disc can, through fibrotic canals, give a connection with the leaking disc. Third, a true delineated anatomic connection between a nerve root and the disc are not described but could be present because both structures are of mesodermal origin.

If the above-mentioned connections are possible, even then, easy injection of contrast dye without reports of pain or other sensations from the patient is not explained. A vacuum phenomenon of the intervertebral disc is described in cadavers and in degenerated discs. 12A patient who is placed in a prone position with a pillow under his or her pelvis has an important passive lumbar spinal extension, and this can create a decrease in intervertebral disc pressure, therefore causing negative pressure in the intervertebral disc, which probably results in a suction force toward the disc. The infiltration of only 0.5 ml contrast dye allowed visualization of a whole disc. Discography is a reliable method of evaluating the integrity of the intervertebral disc. The normal annulus fibrosus offers fair resistance to distension, and the normal disc accepts only 1– 1.5 ml contrast medium. Injection in the degenerated disc is often done without difficulty. The easy injection of 2 ml or more contrast medium into a disc is a sign of some degree of degeneration within the annulus fibrosus and the nucleus pulposus. Extravasation of contrast medium occurs through fissures and tears of the annulus and may be seen with both degeneration and herniation.

We do not support the infiltration of corticosteroids into the disc because of the lack of evidence of good outcome of this technique and because of the risk of complications.

Moreover, the target for application of corticosteroids and local anesthetics here was the nerve root adjacent to the intervertebral disc. If we had injected our local anesthetics in this case without contrast dye control, a misinterpretation of this infiltration would have been possible. We believe that this observation is important for correct clinical practice.

Meticulous care should be taken when a transforaminal sleeve injection of steroids, local anesthetics, or both is performed. All previous publications describe the leakage of contrast medium out of the disc by execution of a lumbar discography. There were no publications describing this event, the leakage of dye into the disc while injecting it into the neuroforamen.

This observation emphasizes the importance of the use of contrast dye and radiographic evaluation while performing a transforaminal sleeve injection to avoid inadvertent infiltrations of structures other than the target structure.