Superficial reflexes are motor responses that occur when the skin is stroked. The cremasteric reflex is a superficial reflex found in human males that is elicited when the inner part of the thigh is stroked. Stroking of the skin causes the cremaster muscle to contract and pull up the ipsilateral testicle toward the inguinal canal. Like other superficial reflexes, it is simply graded as present or absent. A female counterpart of the cremasteric reflex is the Geigel reflex. In the female, it involves the contraction of muscle fibers along the upper part of the Poupart or inguinal ligament and is sometimes called the inguinal reflex. Similar to the other superficial reflexes such as the abdominal and the normal planter reflexes the cremasteric reflex is not usually tested in contrast to the deep tendon, the brainstem, and primitive reflexes. The cremasteric reflex is most commonly performed in the evaluation of acute scrotal pain and the assessment for testicular torsion that is commonly associated with an apparent loss of the reflex.
The cremaster muscle is a paired structure made of thin layers of striated and smooth muscle. The muscle name is derived from a Greek word meaning “suspender.” In reality, the muscle has 2 parts, a lateral and medial cremaster muscle. The lateral muscle originates from the internal oblique muscle and inguinal ligament, and the medical cremaster muscle usually originates from the pubic tubercle but sometimes from the lateral pubic crest. The muscles that are covered by a fascia loop over the spermatic cord and testicles and insert into the testicle tunica vaginalis. In the female, the cremaster muscle is found on the round ligament.
The cremasteric artery, a branch of the inferior epigastric artery, along with anastomotic flow from the other arteries supplying the scrotum provides blood flow to the muscles.
The innervation for the cremasteric reflex is provided by the sensory and motor fibers of the genitofemoral nerve that originates from the L1 and L2 spinal nerve nuclei. Stroking of the inner thigh stimulates the sensory fibers of the genitofemoral and ilioinguinal nerves. After these sensory nerves synapse in the spinal cord, the motor fibers of the genitofemoral nerve are activated, and cremaster muscle is caused to contract with resultant elevation of the ipsilateral testicle. Because it is a superficial reflex, it is different from muscle stretch reflexes. For the cremasteric reflex, the sensory signal has to ascend the cord to the brain before descending again to reach the motor neurons.
The cremasteric reflex can be performed in assessing scrotal pain. While some studies report a high correlation of loss of cremasteric reflex and testicular torsion, there are a surprising number of studies reporting persistence of the reflex during verified cases of torsion. Additionally, other studies confirm that it is also absent from significant numbers of males and more so at younger ages. The frequency of the intact reflex has been reported in 61.7% to 100% of boys between 24 months and 12 years of age.
The cremasteric reflex is a protective and physiologic superficial reflex of the testicles. The cremasteric reflex appears to play a role in preserving thermoregulation of the testicles as part of spermatogenesis. The reflex raises and lowers the testicles to control its temperature. In a cold environment, the cremaster muscle causes the testicles to move closer to the body. During fight or flight and sexual arousal, it is responsible for putting the testicles into a more protected location closer to the body.
Contraction of the cremaster muscle can play a role in the twisting of the testicle during a torsion event. In the setting of a bell clapper deformity of the testicular anatomical suspension, the muscular contraction can result in excessive twisting and ultimately torsion and death of a testicle. At puberty, as the testicles become heavier and more pendulous, the risk of testicular torsion increases significantly. The heavier testicular bell clapper may be vulnerable to greater motion and subsequent twisting as the cremasteric muscles contract. Some studies suggest that testicular torsion is more common during the winter months when the cremasteric reflex may occur more frequently due to the colder temperatures.
Additionally, the muscle will sometimes undergo severe spasm causing pain and limitation of activity. Treatment with botulinum toxin has been reported as a successful treatment option.
If the reflex is exaggerated, it can lead to a misdiagnosis of cryptorchidism in some children. The reflex can be absent in a significant percentage of normal male children as well as patients with upper and lower motor neuron disorders, spinal injury at the L1 and L2 level or if the ilioinguinal nerve has been cut inadvertently during hernia repair.
Testing of the reflex may be helpful in providing objective evidence of successful spinal anesthesia. The cremasteric reflex appears to disappear consistently following successful spinal anesthesia. In one study of 150 patients, the presence or disappearance of the cremasteric reflex consistently indicated the presence or absence of sensation correctly to pinprick at L1 after injection of a local anesthetic intrathecally.
The cremasteric reflex is performed as part of an evaluation of acute scrotal pain to assess for evidence of testicular torsion. The absence of the reflex is considered to be diagnostic for testicular torsion. The cremasteric reflex has been reported to be absent in 100% of cases of testicular torsion, making it a potentially useful sign in this diagnosis. However, a significant number of case reports and small case series exist demonstrating that the test is not 100% specific, and the reflex can be present in cases of testicular torsion. Doppler ultrasound should be applied liberally to the workup of acute scrotal pain because of the significant overlap of signs and symptoms and lack of specificity of the cremasteric reflex. Over-reliance on signs and symptoms instead of a liberal imaging policy to differentiate between testicular torsion, testicular appendage torsion or epididymo-orchitis will consistently result in a small but significant number of twisted testes that will be missed.
The absence of a cremasteric reflex in significant proportions of males at different ages would greatly impact on the specificity of this reflex in the diagnosis of testicular torsion.
The cremasteric reflex is variable in performance. The definition of a positive cremasteric is unclear and is not well defined. Is a twitch of the muscle a positive response or should the specific distance of testicle movement with the reflex to be considered positive?
Another important practical point related to cremasteric reflex in spinal anesthesia is that while cremasteric reflex absence after spinal anesthesia may be an indicator of efficient anesthesia in adults, yet, it is an unreliable sign of assessing efficient spinal anesthesia in children.