Should Imaging Studies Be Routinely Performed Prior to Epidural Steroid Injections?

To the Editor:—

Epidural lipomatosis (EL) is a rare disorder that results from overgrowth of normal epidural fat. It is often associated with exogenous intake of steroids and is most commonly isolated to the thoracic spine. We present a unique case of steroid-induced thoracic, lumbar, and sacral EL. It is important to recognize that EL, among other disorders, can present in a similar clinical fashion as herniated disc disease but requires a different approach for its management. We also raise the question of when an imaging study should be obtained before an invasive intervention.

A 43-yr-old, 84-kg man with a long-standing history of steroid-dependent asthma presented with new onset lower back pain of 3 months’ duration. Symptoms were first noticed after a hospital stay for an asthma attack, during which he received corticosteroids therapy. He described aching pain in the lower back, with lancinating pain radiating down the legs in a radicular pattern. Symptoms were exacerbated by back flexion and were relieved by warm baths and lying flat. During physical examination, he had tenderness upon palpation of the lumbar paraspinal muscles, as well as pain with back flexion and extension. Bilateral straight leg raise was negative at 70°. Motor power of the lower extremities was within normal limits. Magnetic resonance imaging of the spine revealed extensive EL from the lower thoracic spine through S1, causing moderate to severe deformity and constriction of the thecal sac from L3 to S1 (fig. 1).

Before magnetic resonance imaging, the patient received a lumbar epidural steroid injection by another institution for suspected disc herniation, which gave him no relief. Based on the imaging findings, we referred the patient to physiotherapy and recommended tapering his steroid intake, if clinically feasible.

Epidural lipomatosis is a rare manifestation of Cushing syndrome. The abnormal fat deposition is reportedly induced by endogenous or exogenous steroids. 1In two publications, EL has been attributed to epidural steroid injection. 2,3The clinical presentation of EL includes back pain that can be associated with radicular symptoms. The causal effect between EL and radiculopathy is generally well-accepted. 4 

This patient’s magnetic resonance imaging showed a unique picture of extensive EL affecting the thoracic, lumbar, and sacral spine. This diagnosis was missed by a physician who performed an epidural steroid injection based on clinical presentation, an intervention that could have exacerbated his disease. 2,3We believe the diagnosis of EL can often be missed if the appropriate imaging studies are not performed because of its rare incidence and because of a clinical presentation similar to that of herniated disc disease. There is a wealth of information that could be obtained from imaging the spine, such as detecting anatomic abnormalities or gross deformities like spinal stenosis, as well as other spinal cord disorders. The information obtained may influence the invasive management plan, at times eliminating it, at other times modifying it. Does that imply that we should order magnetic resonance imaging for every patient referred with back pain and radiculopathy, knowing the financial burden of such an expensive test? One can argue that the cost of a single neurologic injury can offset the cost of many imaging studies. However, to justify the routine use of such an expensive test, one needs to compute the prevalence of many disorders of the spine, such as EL, spine tumors, certain spinal cord diseases, and others—a task that is yet to be performed. For example, the incidence of EL among patients receiving chronic steroid therapy has been found to be high (90%) in one review of 21 cases (19 of 21). 1Although it is yet to be determined whether routine imaging must precede invasive management of lower back pain, this case suggests that magnetic resonance imaging should be considered before treatment in patients whose history or physical examination results are consistent with excessive corticosteroid concentrations.