A 54-year-old man presents to the emergency department complaining of severe lower back pain that began abruptly 48 hours ago after lifting a heavy piece of furniture. He reports that the pain radiates down the posterior aspect of both legs. Today, he noticed that he was unable to feel toilet paper when wiping and experienced an unexpected episode of urinary incontinence. Which of the following physical examination findings are highly consistent with the most likely diagnosis? (Select all that apply)
- Absent or severely diminished Achilles deep tendon reflexes bilaterallyAnswer
- Markedly decreased anal sphincter tone on digital rectal examinationAnswer
- CBilateral upgoing plantar reflexes upon plantar stimulation
- DSustained ankle clonus on rapid dorsiflexion of the foot
- EIncreased resting muscle tone with clasp-knife spasticity in the lower extremities
Answer
The highly consistent findings are absent or severely diminished Achilles deep tendon reflexes bilaterally and markedly decreased anal sphincter tone on digital rectal examination.
The patient's presentation of bilateral sciatica, saddle anesthesia, and bowel/bladder dysfunction following an acute lifting injury is classic for cauda equina syndrome. Cauda equina syndrome is a compressive neuropathy of the lumbosacral nerve roots below the termination of the spinal cord (typically below L1-L2). Because it affects peripheral nerve roots rather than the central spinal cord, it manifests exclusively with lower motor neuron signs. These include flaccid weakness, absent or diminished deep tendon reflexes (such as the Achilles and patellar reflexes), and decreased anal sphincter tone. Therefore, absent reflexes and decreased sphincter tone are the correct examination findings.
Step-by-Step Solution
Key Concept
Cauda equina syndrome is caused by compression of the peripheral nerve roots below the conus medullaris and therefore presents strictly with lower motor neuron signs (areflexia, flaccid weakness, decreased sphincter tone).