The cremasteric reflex is a superficial reflex observed in human males.
This reflex is elicited by lightly stroking the superior and medial (inner) part of the thigh.[1] The normal response is a contraction of the cremaster muscle that pulls up the scrotum and testis on the side stroked.
More specifically, the reflex utilizes sensory and motor fibers of the genitofemoral nerve, formed by fibers from both the L1 and L2 spinal nerves. When the inner thigh is stroked, sensory fibers of the femoral branch of the genitofemoral nerve and the ilioinguinal nerve are stimulated. These synapse in the spinal cord and activate the motor fibers of the genital branch of the genitofemoral nerve which causes the cremaster muscle to contract and elevate the testis.
In boys, this reflex may be exaggerated, and this can lead to the mistaken diagnosis of undescended testes.
Cremasteric reflex may be absent with: testicular torsion, upper and lower motor neuron disorders, as well as a spine injury of L1-L2. It can also occur if the ilioinguinal nerve is accidentally cut during a hernia repair.
The cremasteric reflex can be helpful in recognizing testicular emergencies. The presence of the cremasteric reflex does not eliminate testicular torsion from a differential diagnosis, but it does broaden the possibilities to include epididymitis, or other causes of scrotal and testicular pain. In any event, if testicular torsion cannot be definitively eliminated in an expeditious manner, a testicular doppler scan or exploratory surgical intervention should be implemented to prevent loss of the testicle.