Definition
The bulbocavernosus reflex is a sacral polysynaptic reflex mediated predominantly through the S2-S4 segments.
How to test
The reflex can be elicited by squeezing the glans penis or clitoris, or by traction on an indwelling urinary catheter, while observing or palpating contraction of the anal sphincter.
Reflex arc
- Afferent limb: pudendal nerve
- Spinal cord integration: S2-S4
- Efferent limb: pudendal nerve
- Response: contraction of the bulbocavernosus / external anal sphincter complex
Significance in spinal cord injury
Immediately after an acute spinal cord injury, spinal shock may abolish reflex activity below the lesion.
The return of the bulbocavernosus reflex is traditionally used to indicate the end of spinal shock. After its return, persistent absence of motor or sensory function can be interpreted more reliably when determining neurological completeness.
Clinical use
The reflex also helps assess integrity of the sacral reflex arc in patients with suspected cauda equina, conus or sacral neurological dysfunction.