Kremaster reflex

Under the Kremaster reflex the doctor understands the polysynaptic external reflex of the kremaster muscle, which moves the testicles upwards in response to stimuli. The reflex is exhaustive and can therefore be absent due to age-physiology. On the other hand, abnormal reflex behavior of the kremaster muscle can also indicate spinal cord lesions.

What is the cremaster reflex?

The Kremaster reflex is an innate external reflex of the Kremaster muscle. In contrast to self-reflexes, the affector and the receptor of the reflex movement in the kremaster muscle are not in the same organ. Since external reflexes run over several neurons connected in series, they are also called polysynaptic reflexes.

In the case of polysnaptic reflexes, in contrast to monosynaptic reflex movements, several subliminal stimuli can add up to form a subliminal stimulus. In this way, the cremaster reflex can be triggered faster than self-reflexes, but it is just as easy to tire. The reflex is therefore also assigned to exhaustive reflexes and can come to a standstill in old age due to physiological age.

The kremaster muscle consists of muscle fibers from the two lower abdominal muscles and accompanies the man's spermatic cord and testicles in a loop. The reflex of this muscle is controlled by the spinal cord and moves the testicles towards the trunk in response to certain stimuli. For this reason, the kremaster muscle is popularly known as the testicle lifter muscle.

Function & task

The afferent fibers of the kremaster muscle are located in the ramus femoralis, part of the genitofemoral nerve. Since the reflex is a foreign reflex and its afferents are thus separated from the efferents, the efferent fibers of the muscle are separated from the afferents in the genital branch to the genitofemoral nerve.

Most of the reflexes of the human skeletal muscles are so-called protective reflexes.Such as the eyelid closing reflex, for example, protect the organ of vision from injuries by automatically closing the eyelid in response to certain visual and sometimes also auditory stimuli.

The cremaster reflex is neither visually nor audibly triggered, but is controlled by temperature stimuli. The skin's thermoreceptors play a role in the Kremaster reflex. For example, if they register excessive cold in the area of ​​the inner thigh, they pass this information on to the spinal cord in the form of action potentials. The cremaster reflex is interconnected in the spinal cord segments L1 and L2. The response from the central nervous system reaches the kremaster muscle and causes it to contract. This contraction causes the testicles to move upwards.

They are moved to a more protected area, which is supposed to ensure the production of seeds in the event of counterproductive environmental stimuli. Thus, the cremaster reflex is assigned a kind of thermoregulatory function that ensures reproduction.

The interconnection via the spinal cord has the motor protective reflexes in common, since an interconnection via the brain would result in too long a reaction time. The reflex movements would occur too late to fulfill a protective function against certain stimulus perceptions.

The connection between the cremaster reflex and the thermoregulatory functions as the only cause is now disputed, as the testicles move upwards thanks to the reflex movements not only in response to temperature stimuli, but also in the event of extreme excitement.

The cremaster reflex is also physiological in animals and in certain breeds even pulls the testicles back into the abdomen.

Illnesses & ailments

The reflexes of the body are mainly examined by neurology. Pathological reflexes, such as those from the Babinski group, and a changed reflex behavior of the physiological reflexes can indicate central nervous damage there.

The cremaster reflex can also provide such clues. Although the exhaustive reflex can also be absent from a physiological point of view, it is used clinically to check the associated spinal cord segments. A lack of cremaster reflex at a young age can be an indication of spinal cord damage.

The cause of such damage to the central nervous spinal cord can, for example, be spinal cord trauma after an accident. Spinal infarcts also cause damage to the spinal cord. Degenerative diseases like ALS, for example, gradually break down the motor nervous system, the main switching points of which are located in the spinal cord. The inflammatory autoimmune disease multiple sclerosis can also cause lesions in the spinal cord, which are caused by immunological inflammation and which often permanently damage the central nervous system. More rarely, a tumor in segments L1 and L2 is the cause of a lack of cremaster reflex.

On the other hand, the cremaster reflex can also be absent regardless of spinal cord lesions. This is the case, for example, with testicular torsion. In this phenomenon, the testicle twists around the supplying stem of vessels and thus constricts its own blood circulation and innervation. Usually the phenomenon is caused by sports activities.

Testicular dystopias also have an impact on the cremaster reflex. The reflex does not tend to stay away because of it, but is particularly lively. The congenital anomalies are also known as testicular defects and are thus characterized by an abnormal position of the testicles. The so-called pendulum testicles in particular have an impact on the cremaster reflex. This is a retractile testicular defect. The testicles lie in the normal position in the scrotum on one or both sides, but because of a particularly lively cremaster reflex, they temporarily move into a high-crotal or inguinal position. If the patient does not suffer from the phenomenon and the testicles are in the scrotal position for most of the time, the pendulum testicle does not necessarily have to be treated.