Cauda equina syndrome vs Conus medullaris syndrome
How to tell Cauda equina syndrome and Conus medullaris syndrome apart when a board question makes them look alike.
Cauda equina is painful asymmetric nerve roots; conus is early symmetric sphincter/perianal cord-level dysfunction.
Side by side
Cauda equina syndrome causes lumbosacral nerve-root compression with severe radicular back/leg pain, asymmetric LMN weakness, saddle anesthesia, areflexia, and bladder/bowel dysfunction.
Conus medullaris syndrome affects the terminal spinal cord with early symmetric saddle anesthesia, early bladder/bowel/sexual dysfunction, mixed UMN/LMN signs, and less prominent radicular pain.
Compression of multiple lumbosacral nerve roots below the conus creates polyradiculopathy.
Damage to the distal spinal cord/conus disrupts sacral cord segments and nearby roots.
Large central lumbar disc herniation, asymmetric radicular pain, LMN signs, and patchy saddle sensory loss support cauda equina syndrome.
Conus lesion near L1-L2 with early sphincter dysfunction, symmetric perianal sensory loss, and mixed signs supports conus medullaris syndrome.
The trap
Both are emergencies with saddle anesthesia and bladder symptoms, so pain asymmetry and timing of sphincter dysfunction help separate them.
Watch it explained
Test it nowThe repair move
For saddle anesthesia, decide whether the pattern is nerve-root cauda equina or terminal-cord conus.
Try a free question
CoreA patient has acute low back pain, asymmetric bilateral sciatica, saddle anesthesia, urinary retention, reduced ankle reflexes, and LMN leg weakness after a large lumbar disc herniation. Which diagnosis is most likely?
Show answer and explanation
Answer: A. Cauda equina syndrome. Radicular pain with asymmetric LMN deficits, saddle anesthesia, and bladder dysfunction supports cauda equina syndrome.
Why the other choices are tempting
- B. Conus medullaris has earlier symmetric sphincter/perianal dysfunction and less radicular pain.
- C. Brown-Sequard is hemicord tract loss.
- D. Anterior cord causes bilateral motor and pain-temperature loss below a cord lesion.
- E. Syringomyelia causes cape-like dissociated sensory loss.
Flashcards
Tap a card to flip it.
What pain pattern supports cauda equina syndrome?
Severe radicular back and leg pain, often asymmetric, supports cauda equina syndrome.
What timing supports conus medullaris syndrome?
Early bladder/bowel dysfunction with symmetric saddle anesthesia supports conus medullaris syndrome.
Quick answers
What is the fastest way to tell Cauda equina syndrome from Conus medullaris syndrome?
Cauda equina is painful asymmetric nerve roots; conus is early symmetric sphincter/perianal cord-level dysfunction.
What is the key clue for Cauda equina syndrome?
Cauda equina syndrome causes lumbosacral nerve-root compression with severe radicular back/leg pain, asymmetric LMN weakness, saddle anesthesia, areflexia, and bladder/bowel dysfunction.
What is the key clue for Conus medullaris syndrome?
Conus medullaris syndrome affects the terminal spinal cord with early symmetric saddle anesthesia, early bladder/bowel/sexual dysfunction, mixed UMN/LMN signs, and less prominent radicular pain.
What is the common trap with Cauda equina syndrome vs Conus medullaris syndrome?
Both are emergencies with saddle anesthesia and bladder symptoms, so pain asymmetry and timing of sphincter dysfunction help separate them.