The neurologist refers to the Chaddock reflex as a pathological foot limb reflex of the Babinski group. Reflexes of this group are known as pyramidal tract signs and refer to damage to central motor neurons. The sensitivity of the Chaddock reflex is now controversial.
What is the Chaddock reflex?
The neurologist refers to the Chaddock reflex as a pathological foot limb reflex of the Babinski group. The Chaddock reflex is a pathologic reflex of the foot limbs. It falls into the so-called Babinski group and thus belongs to the pyramidal tract signs. All pyramidal tract signs are extraneous reflexes. Other reflexes from the Babinski group are the Gordon and the Babinski reflex. As a symptom, these abnormal reflex movements are usually associated with a lesion of the central motor neurons. The motoneurons are part of the motor system and thus control the movements of skeletal muscles. Both voluntary movements and reflex movements are wired through the motoneurons. These neurons are a part of the pyramidal tracts and thus of the central nervous system. The lower motoneuron is located in the anterior horn of the spinal cord. From here, nerve impulses are transmitted efferently as bioelectrical excitations from the central nervous system to the muscles of the skeletal musculature. The Chaddock reflex was named after Charles G. Chaddock, who documented the reflex movement in the 20th century. Japanese K. Yoshimura is considered the first describer of the Chaddock reflex, although it was Chaddock’s extensive documentation that made the movement known as the Babinski group reflex.
Function and task
Reflexes are automated and involuntary bodily movements that are interconnected in the central nervous system via the pyramidal pathways rather than directly in the brain. This circuitry makes the movements more immediate and less time-consuming. Thus, only a few milliseconds pass between the trigger and the reflex to that trigger. Reflex triggers are specific perceptions of the sensory systems. Most reflexes in humans are protective reflexes. Examples are the cough reflex and the eyelid closure reflex. For example, the eyelid closes involuntarily as soon as the visual system sees something approaching the eye. This protects the eyeball from injury and loss of function. The cough reflex, on the other hand, protects against suffocation. It is triggered when the receptors in the mucous membranes of the respiratory tract detect an irritation. Such irritations are triggered, for example, by food components or liquids that accidentally pass through the trachea instead of the esophagus. Because of their protective function, human reflexes have an evolutionary value. The human reflex system changes with age. Infants, for example, have significantly more reflexes than an adult. In infants, the sucking reflex is the best-known reflex. For example, when a finger is put to a baby’s mouth, this touch automatically triggers a sucking movement. Thus, the baby’s mouth does not distinguish between the mother’s breast and a hand limb or even an object, such as a pacifier. The sucking reflex usually regresses by the infant’s first year of life, since the child no longer relies on it from that age. The entire reflex system changes during the first years of life. These changes are primarily due to the development of higher-level control of movement. The motor neurons are responsible for the higher-level control of voluntary and reflex motor activity. Infants under one year of age have all the reflexes of the Babinski group in addition to the teat reflex. Thus, the Chaddock reflex is also physiological for babies. Only in adults is there talk of a pathological phenomenon. At an age of less than one year, the superior control of motor function is not yet fully developed. Therefore, muscle groups that are close together, such as those of the toe limbs, always move as a group. For example, in the Chaddock reflex, brushing the outer dorsum of the foot triggers an upward movement of the big toe. The other toe limbs perform a spreading movement at the same time. When this phenomenon is observed in an adult human, there is, so to speak, a regression to a stage during which the individual muscle groups were not yet individually activatable. Since the central motor neurons are the superior control authority for movements, a damage of these structures can be assumed.
Diseases and ailments
The Chaddock reflex, like all other reflexes in the Babinski group, is symptomatic. Usually, reflex movement is symptomatically associated with lesions of central motor neurons. However, the sensitivity of the Chaddock reflex is controversial. Although reflex examination has been a standard investigation in neurological diagnosis, the presence of a pathological reflex alone is far from sufficient for the diagnosis of neurological disease. For example, only multiple pyramidal tract signs are an actual indication of motor neuron damage. In addition, the remaining findings must also be characterized by abnormalities in the area of motor function. In the case of damage to the first motoneuron, the primary findings are usually spastic phenomena. Damage to the second motoneuron, on the other hand, manifests itself in muscle weakness, insecure movements or paralysis. Both motoneurons can be damaged by various diseases of the central nervous system. Among the best known of such diseases are multiple sclerosis (MS) and amyotrophic lateral sclerosis (ALS). ALS is a degenerative disease of the motor nervous system. Multiple sclerosis, on the other hand, is an autoimmune disease in which the affected person’s immune system attacks the body’s own nerve tissue and causes inflammation in it. Pyramidal tract signs such as the Chaddock reflex are invoked, particularly at the onset of the disease, as criteria for an unfavorable prognosis.
