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Cremasteric Reflex
Introduction
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 females, it involves the contraction of muscle fibers along the upper part of the Poupart ligament and is sometimes called the inguinal reflex. Similar to the other superficial reflexes, such as the abdominal and the normal plantar reflexes, the cremasteric reflex is not usually tested, in contrast to the deep tendon, the brainstem, and the primitive reflexes. The cremasteric reflex is most commonly used in the evaluation of acute scrotal pain and in the assessment of testicular torsion, which is commonly associated with an apparent loss of the reflex.[1][2][3]
The cremaster muscle is a paired structure made of thin layers of striated and smooth muscle. The muscle's name is derived from a Greek word meaning “suspender.” In reality, the muscle has 2 parts, the lateral and medial cremaster muscle. The lateral muscle originates from the internal oblique muscle and the inguinal ligament, and the medial 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 females, 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 the cremaster muscle is caused to contract with the 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 used to assess scrotal pain. While some studies report a high correlation between loss of the cremasteric reflex and testicular torsion, a surprising number also report the persistence of the reflex in verified cases of torsion. Additionally, other studies confirm that it is absent from significant numbers of males, particularly at younger ages. The frequency of intact reflexes has been reported to range from 61.7% to 100% in boys between 24 months and 12 years of age.
Function
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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 their temperature. In a cold environment, the cremaster muscle draws the testicles 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][5][6][7]
Issues of Concern
Contraction of the cremaster muscle can contribute to testicular torsion. In the setting of a bell clapper deformity of the testicular anatomical suspension, 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 sometimes experiences severe spasms, causing pain and limited activity. Treatment with botulinum toxin has been reported as a successful treatment option.
Clinical Significance
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 in patients with upper and lower motor neuron disorders, spinal injury at the L1 and L2 levels, or when the ilioinguinal nerve has been cut inadvertently during hernia repair. Testing the reflex may help provide objective evidence of successful spinal anesthesia. The cremasteric reflex appears to disappear consistently following successful spinal anesthesia. In a study of 150 patients, the presence or absence of the cremasteric reflex consistently indicated the presence or absence of sensation to pinprick at L1 after intrathecal injection of a local anesthetic.
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 of 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 demonstrate that the test is not 100% specific and that 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 the 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 consistently results in a small but significant number of twisted testes that are missed.
Other Issues
The diagnostic value of the cremasteric reflex in testicular torsion is limited by its variability. A substantial proportion of males across age groups may lack this reflex, which reduces its specificity. In addition, the definition of a “positive” cremasteric reflex is poorly standardized, and uncertainty remains as to whether a minimal muscle twitch is sufficient or whether a measurable elevation of the testicle is required. In clinical practice, this variability is also relevant in the setting of spinal anesthesia. Although the absence of the cremasteric reflex may indicate adequate anesthesia in adults, it is not a reliable marker of anesthetic depth in children.[8]
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References
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. Urology annals. 2018 Jan-Mar:10(1):20-23. doi: 10.4103/UA.UA_35_17. Epub [PubMed PMID: 29416270]
Frohlich LC, Paydar-Darian N, Cilento BG Jr, Lee LK. Prospective Validation of Clinical Score for Males Presenting With an Acute Scrotum. Academic emergency medicine : official journal of the Society for Academic Emergency Medicine. 2017 Dec:24(12):1474-1482. doi: 10.1111/acem.13295. Epub 2017 Oct 16 [PubMed PMID: 28833896]
Level 1 (high-level) evidenceEstremadoyro V, Meyrat BJ, Birraux J, Vidal I, Sanchez O. [Diagnosis and management of testicular torsion in children]. Revue medicale suisse. 2017 Feb 15:13(550):406-410 [PubMed PMID: 28714632]
Schwarz GM, Hirtler L. The cremasteric reflex and its muscle - a paragon of ongoing scientific discussion: A systematic review. Clinical anatomy (New York, N.Y.). 2017 May:30(4):498-507. doi: 10.1002/ca.22875. Epub 2017 Apr 3 [PubMed PMID: 28295651]
Level 1 (high-level) evidenceLemini R, Guanà R, Tommasoni N, Mussa A, Di Rosa G, Schleef J. Predictivity of Clinical Findings and Doppler Ultrasound in Pediatric Acute Scrotum. Urology journal. 2016 Aug 25:13(4):2779-83 [PubMed PMID: 27576885]
Sharp VJ, Kieran K, Arlen AM. Testicular torsion: diagnosis, evaluation, and management. American family physician. 2013 Dec 15:88(12):835-40 [PubMed PMID: 24364548]
Crawford P, Crop JA. Evaluation of scrotal masses. American family physician. 2014 May 1:89(9):723-7 [PubMed PMID: 24784335]
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 [PubMed PMID: 11167458]
Level 3 (low-level) evidence