Soft Tissue Extramedullary Plasmacytoma Leading to Cauda Equina Syndrome: Case Presentation and Clinical Considerations

Cauda equina syndrome (CES) is a rare neurological emergency that requires prompt diagnosis and immediate surgical intervention for the best potential patient outcome. CES results from the compression of spinal roots along the lower spine usually at the level of L2 or below. It typically presents with severe low back pain, pain radiating to lower extremities, motor weakness, sensory loss, saddle anesthesia, bladder and bowel dysfunction. It is most commonly caused by a large central intervertebral disc herniation or central canal spinal stenosis but can also occur on occasion from abscesses, neoplasms, and inflammatory conditions. If the patient's symptoms are overlooked and surgical intervention is delayed there is a risk for long-term damage to neurological function. Here, we will present a case of a 46-year-old female with a long-standing history of back pain that presented to her primary care office with worsening back pain symptoms as well as a new presentation of urinary incontinence. A prompt MRI confirmed CES and the patient was advised to report to the nearest ED. At the hospital, neurosurgeons performed a laminectomy and found a mass along L3 that was compressing the cauda equina and associated nerve roots. The pathology of the mass revealed an extramedullary plasmacytoma (EMP) that was later determined to originate from the right psoas muscle. The case provides insight into the patient's presentation of CES and the key differentiating factors that led the medical care team to order the appropriate work up and prevent the long-term complications associated with an untreated CES.