Curriculum · Musculoskeletal / Orthopedic / Rheumatology
Cauda equina syndrome
What it is
The cauda equina is the group of nerve roots that arise from the culmination of the spinal cord (the conus medullaris) and extend inferiorly in the intradural space towards the coccyx. Cauda equina syndrome is damage to or compression of the cauda equina, the nerve fibers L3-S5 located below L2.
Causes and risk
The common causes are a large posteromedial disc herniation, trauma and tumors. A herniated lumbar disc, a spinal epidural hematoma and infection are also causes.
How it presents
The alarming signs are urinary retention, which is diagnostic, saddle anesthesia, weakness, decrease anal tone and paresthesia. In full: lower back pain with severe radicular pain; asymmetric, areflexic, flaccid paresis of the legs with muscle atrophy; hyporeflexia with absent knee jerk reflex and ankle jerk reflex; saddle anesthesia, which is a lack of sensitivity in the dermatomes S3-S5 affecting the areas around the anus, genitalia, and inner thighs and which may be asymmetric; and asymmetric unilateral numbness or paresthesia in lower limb dermatomes. Urinary retention is late in onset, the bowel habits change from loss of anal sphincter control, rectal tone or the bulbocavernosus reflex is decreased, and there is erectile dysfunction. The onset is given as gradual and typically unilateral, and the clinical features as unilateral and asymmetrical; the severe radicular pain is also given as usually bilateral, so this point is not clear.