In neurology, the Babinski reflex is a pathological foot limb reflex from the pyramidal tract group. This reflex group refers to damage to the motor neurons through which motor function is controlled in humans. Such damage can occur in the context of diseases such as multiple sclerosis (MS) and amyotrophic lateral sclerosis (ALS).
What is the Babinski reflex?
The Bambinski reflex is a pathologic foot limb reflex that can occur when the lateral edge of the foot is brushed. The Bambinski reflex is a pathologic foot limb reflex that can occur when brushing the lateral edge of the foot. The reflex movement is also called Babinski sign and is a pyramidal tract sign from the Babinski reflex group. In adults, it is therefore a pathological reflex indicating neuronal disease. Other names for the phenomenon are the big toe reflex or toe reflex. Pyramidal tract signs are usually interpreted as indicating lesions of the motor neurons. These efferent neurons conduct bioelectrical impulses as action potentials out of the central nervous system and conduct them into the muscle fibers. Thus, the motoneurons are the switching point for body movements. Both voluntary movements and reflex movements are connected via the neurons. The first motoneuron is located in the motor cortex of the brain. The lower motoneuron, on the other hand, is located in the anterior horn of the spinal cord. As a symptom, the Babinski reflex can occur with any type of damage to either motoneuron. This means that inflammation as well as degenerative phenomena can be the primary cause of the pathological reflex. The Babinski reflex was named after Joseph François Félix Babinski. The French neurologist first linked the big toe reflex to neuronal diseases in the 19th century.
Function and task
Human reflexes are motor reflexes that have an evolutionary background. Most of them are protective reflexes, such as the eyelid closure reflex, which is designed to protect the eyeball and thus the visual system. When something approaches the eye, the eyelid closes involuntarily and automatically. The cough reflex also has a protective function. It is triggered when the mucous membrane of the respiratory tract is strongly irritated. This is to expel fluids and food residues from the respiratory tract in case the person swallows. In this way, the cough reflex protects the organism from suffocation. Humans can only influence their reflexes to a certain extent and are only consciously aware of them to a certain extent. Reflexes change with age. For example, an adult has far fewer reflexes than an infant. Babies, for example, have a sucking reflex. The sucking movement is triggered as soon as the infant’s mouth is touched. It is irrelevant whether the breast, a finger or even an object such as a pacifier actually touches the infant’s mouth. The sucking reflex is lost after a certain age. The length of time until reflex loss can vary gradually from person to person. On average, sucking can no longer be triggered after about one year of age. In addition to the sucking reflex, babies have numerous reflexes more. One of them is also the Babinski reflex. When the lateral edge of babies’ feet is brushed, their big toe stretches upward and the other phalanges perform a grasping movement at the same time. At this stage of development, the muscle groups of the foot limbs are still activated together. Like the sucking reflex, however, the Babinski reflex is lost from an average age of one year. From this age on, motor function is subject to a higher-level control that allows the separate activation of the individual muscle groups. This control is exerted via the superior and inferior motor neurons. Thus, when the Babinski reflex can be observed in the adult, there is a loss of higher-order control and the muscle groups that were formerly activated together can therefore be activated simultaneously again.
Diseases and disorders
The Babinski reflex is considered a symptom by neurologists. In the past, the pathologic reflex was given a much higher priority than it is today. Meanwhile, the mere presence of the Babinski sign on one or even both feet is not considered diagnostic.Therefore, the reflex is interpreted today as a solid indication of motor neuron damage only in combination with other reflexes of the Babinski group and against the background of other findings. Another reflex of the Babinski group is, for example, the Gordon reflex. Conspicuous findings may include paralysis, muscle weakness, gait unsteadiness, or spasticity. If brushing does not trigger the Babinski reflex but only the upward movement of the big toe, this alone is not sufficient for a suspected diagnosis of lesions on the motoneurons. Lesions of the first motoneuron are accompanied by spastic manifestations. If, on the other hand, a suspected diagnosis of damage to the second motoneuron is made, muscle weakness or paralysis can be observed. Both neurons can be damaged by central nervous system diseases such as ALS or MS. In the autoimmune disease multiple sclerosis, immunological inflammations are responsible for the lesions. In contrast, the degenerative disease of amyotrophic lateral sclerosis progressively degenerates the motor system and thus attacks both the brain and the spinal cord. Reflex examination is a standard neurological diagnostic procedure. However, if pathological reflexes can be detected, this has not only diagnostic but often also prognostic value. In multiple sclerosis, pyramidal tract signs such as the Babinski reflex are evaluated as factors for an unfavorable prognosis if they occur early in the disease.
