The anal wink
, anal reflex
, perineal reflex
, or anocutaneous reflex
is the reflexive
contraction of the external anal sphincter
upon stroking of the skin around the anus.
A noxious or tactile stimulus will cause a wink contraction of the anal sphincter muscles and also flexion. The stimulus is detected by the nociceptors in the perineal skin to the pudendal nerve, where a response is integrated by the spinal cord sacral segments S1-S3.
The absence of this reflex indicates that there is an interruption of the reflex arc, which may be in the sensory afferent limb or the motor efferent limb. The synapse between the afferent and efferent limbs occurs in the lowest sacral segments of the spinal cord.
Child abuse controversy
Dr. Bruce Woodling
developed the anal wink test
which he alleged was an indisputable diagnostic indicator that a child had been sodomised
. In a clinical setting, he would spread a child’s buttocks and touch the anus with a cotton swab. If the anus "winked", Woodling testified, this was "proof of sodomy". His testimony was prominent in the McMartin preschool
child abuse case.
It has since been established that Woodling never made any effort to validate his test, and it has been utterly discredited.
Woodling's pseudoscientific testimony during the trial of Ray Buckey contributed to Buckey spending five years in prison without bail. Buckey was later released without conviction.