The bulbocavernosus reflex is a polysynaptic

Chemical synapse

Chemical synapses are specialized junctions through which neurons signal to each other and to non-neuronal cells such as those in muscles or glands. Chemical synapses allow neurons to form circuits within the central nervous system. They are crucial to the biological computations that underlie...

 reflex

Reflex

A reflex action, also known as a reflex, is an involuntary and nearly instantaneous movement in response to a stimulus. A true reflex is a behavior which is mediated via the reflex arc; this does not apply to casual uses of the term 'reflex'.-See also:...

 that is useful in testing for spinal shock

Spinal shock

Spinal shock was first defined by Whytt in 1750 as a loss of sensation accompanied by motor paralysis with initial loss but gradual recovery of reflexes, following a spinal cord injury – most often a complete transection. Reflexes in the spinal cord caudal to the SCI are depressed or absent ,...

 and gaining information about the state of spinal cord injuries (SCI). The test involves monitoring anal sphincter contraction in response to squeezing the glans penis

Glans penis

The glans penis is the sensitive bulbous structure at the distal end of the penis. The glans penis is anatomically homologous to the clitoral glans of the female...

 or tugging on an indwelling Foley catheter

Foley catheter

A Foley catheter is a flexible tube that is often passed through the urethra and into the bladder. The tube has two separated channels, or lumens, running down its length. One lumen is open at both ends, and allows urine to drain out into a collection bag...

. The reflex is spinal mediated and involves S2

Sacral spinal nerve 2

The sacral spinal nerve 2 is a spinal nerve of the sacral segment..It originates from the spinal column from below the 2nd body of the sacrum -Muscles:...

-S4

Sacral spinal nerve 4

The sacral spinal nerve 4 is a spinal nerve of the sacral segment..It originates from the spinal column from below the 4th body of the sacrum -Muscles:...

. The absence of the reflex without sacral spinal cord trauma indicates spinal shock. Typically this is one of the first reflexes to return after spinal shock. Lack of motor and sensory function after the reflex has returned indicates complete SCI. Absence of this reflex in instances where spinal shock is not suspected could indicate a lesion or injury of the conus medullaris

Conus medullaris

The conus medullaris is the terminal end of the spinal cord. It occurs near lumbar vertebral levels 1 and 2 . After the spinal cord tapers out, the spinal nerves continue as dangling nerve roots called cauda equina. This terminal nerve root tail is referred to as the filum terminale...

 or sacral nerve roots. Bulbocavernosus is an older term for bulbospongiosus, thus this reflex should be correctly called "Bulbospongiosus reflex".

This reflex can also be tested electrophysiologically, by stimulating the penis

Penis

The penis is a biological feature of male animals including both vertebrates and invertebrates...

 or vulva

Vulva

The vulva consists of the external genital organs of the female mammal. This article deals with the vulva of the human being, although the structures are similar for other mammals....

 and recording from the anal sphincter. This test modality is used in intraoperative neurophysiology monitoring to verify function of sensory and motor sacral roots as well as the conus medullaris

Conus medullaris

The conus medullaris is the terminal end of the spinal cord. It occurs near lumbar vertebral levels 1 and 2 . After the spinal cord tapers out, the spinal nerves continue as dangling nerve roots called cauda equina. This terminal nerve root tail is referred to as the filum terminale...

.