Conus medullaris syndrome vs. Cauda equina syndrome

Both of these are orthopedic/neurosurgical emergencies! But in general, CM syndrome is more severe than CE syndrome.

Here's a comparison between the two...

Pro tip: Think of CM syndrome as a clean cut through the conus medullaris (although it's not).

	Conus medullaris syndrome	Cauda equina syndrome
	→    bilateral	→    unilateral or bilateral
Motor	→    symmetrical UMN weakness	→    asymmetrical LMN most often
Sensory	→    symmetrical numbness         'perianal anesthesia' common	→    asymmetrical most often (patchy sensory loss) →    ‘saddle anesthesia’ common
Reflexes	→    at the level:          HYPOreflexia →    below the level:   HYPERreflexia	→    HYPOreflexia
Impotence	→    common	→    rare
Sphincter dysfunction	→    EARLY →    Both, urinary and fecal incontinence	→    LATE →    urinary retention only
Radicular pain	→    absent	→    present
Back pain	→    more severe	→    less

*Cauda equina includes L2 to Coccygeal-1 pair of spinal nerves.

*The nucleus of Onuf (or Onufrowicz) is a small group of neurons in the ventral horn of the S2 (and S3 too according to some authors) segment of the spinal cord. These are motor neurons that supply the external urethral & anal sphincters; also the levator ani and perineal (bulbospongiosus & ischiocavernosus [erector clitoridis in females]) muscles.

PS: I have skipped the anatomical details from the diagram like the dorsal & ventral roots of the spinal nerves, etc. for the purpose of simplicity :)

[- Dr. Suneet Patel

Happy studying, peeps! :)]