cremasteric reflex

Cremasteric reflex

Cremasteric reflex is a superficial reflex found in human males that is elicited when the inner part of the thigh is stroked in a downward direction. Stroking of the skin causes the cremaster muscle to contract and pull up the ipsilateral testicle toward the inguinal canal 1. Like other superficial reflexes, cremasteric reflex is simply graded as present or absent. 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 cremasteric reflex 2.

However, 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 3.

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.

Cremasteric reflex nerve

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.

Cremasteric reflex muscle

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.

Cremasteric reflex function

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 4.

Cremasteric reflex test

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 cremasteric reflex during verified cases of torsion 1. Additionally, other studies confirm that it is also absent from significant numbers of males and more so at younger ages 1. The frequency of the intact cremasteric reflex has been reported in 61.7% to 100% of boys between 24 months and 12 years of age. The absence of a cremasteric reflex in significant proportions of males at different ages would greatly impact on the specificity of cremasteric reflex in the diagnosis of testicular torsion.

Clinical significance

If the cremasteric reflex is exaggerated, it can lead to a misdiagnosis of cryptorchidism in some children. The cremasteric 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 cremasteric 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.

References
  1. Mellick LB, Al-Dhahir MA. Cremasteric Reflex. [Updated 2019 Jul 10]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK513348
  2. Manohar CS, Gupta A, Keshavamurthy R, Shivalingaiah M, Sharanbasappa BR, Singh VK. Evaluation of Testicular Workup for Ischemia and Suspected Torsion score in patients presenting with acute scrotum. Urol Ann. 2018 Jan-Mar;10(1):20-23.
  3. Okuda Y, Mishio M, Kitajima T, Asai T. Cremasteric reflex is not a useful indicator of spinal anaesthesia in anaesthetised children. Anaesthesia. 2001 Jan;56(1):91.
  4. Schwarz GM, Hirtler L. The cremasteric reflex and its muscle – a paragon of ongoing scientific discussion: A systematic review. Clin Anat. 2017 May;30(4):498-507.
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