A 52-year-old man is brought to the emergency department with a 6-hour history of severe lower back pain and progressive leg weakness. He reports that the pain began after he attempted to lift a heavy crate. He also mentions that he leaked urine on his way to the hospital and feels as though he cannot fully empty his bladder. Past medical history is negative, and he does not take any medications. Physical examination reveals 3/5 strength in bilateral plantar flexion and knee extension. There is an absence of the Achilles tendon reflex bilaterally. Sensory testing reveals diminished sensation over the perineum and inner thighs. A digital rectal exam demonstrates significantly decreased anal sphincter tone.
Which of the following is the most appropriate next step in management?
The correct answer is:
A) Emergent MRI of the lumbosacral spine
This patient is presenting with classic signs of cauda equina syndrome (CES), a surgical emergency caused by the compression of multiple lumbar and sacral nerve roots. The hallmarks of CES include severe back pain, bilateral lower extremity weakness, saddle anesthesia (sensory loss over the perineum and inner thighs), and bladder or bowel. Because CES is an emergency that requires surgical decompression, typically within 24–48 hours, to prevent permanent neurological deficits, the immediate next step is imaging with an emergent MRI to confirm the location and cause of the compression.
Answer choice B: Intravenous dexamethasone, is incorrect. While steroids are often used in cases of acute spinal cord compression, which occurs at the level of the spinal cord, ending at L1−L2), their role in cauda equina syndrome, which involves peripheral nerve roots, is not well-established and does not take precedence over obtaining definitive imaging.
Answer choice C: Lumbar puncture and cerebrospinal fluid (CSF) analysis, is incorrect. This would be appropriate for suspected inflammatory or infectious processes like Guillain-Barré syndrome. However, the acute onset following heavy lifting and the presence of saddle anesthesia and urinary retention strongly point to a mechanical compression, such as massive disc herniation.
Answer choice D: Oral muscle relaxants and bed rest, is incorrect. This is appropriate for simple mechanical low back pain or muscle strain. In the presence of red flag symptoms like urinary incontinence and saddle anesthesia, this approach likely would lead to permanent paralysis or bladder dysfunction.
Answer choice E: Physical therapy evaluation, is incorrect. Physical therapy is a staple of chronic back pain management but is contraindicated in the acute phase of a surgical emergency like CES.
Key Learning Point
Cauda equina syndrome is a clinical diagnosis characterized by saddle anesthesia, bladder/bowel dysfunction, and bilateral neurological deficits. It is most commonly caused by a massive midline disc herniation. The most appropriate next step is emergent MRI, followed by immediate surgical decompression to avoid permanent disability.
