History of Babinski's sign

The discovery of the symptom is attributed to Joseph Babinski. The Paris-born scientist described his achievement in 1896.
Although the assessment of reflexes is essentially one of the components of a neurological examination, doctors of other specialities, such as internists, orthopaedists or psychiatrists, also check for the presence of Babinski's sign in their patients - as they treat conditions one of the manifestations of which is precisely an abnormal motor response of the foot.

How is the presence of this symptom checked?

Babinski's sign is tested by teasing the foot. This is done with a variety of instruments, some of the more common ones being ordinary spanners, medical spatulas or the tip of a neurological hammer. The test consists of a continuous movement along the lateral edge of the foot, starting from the heel up to the level of the little toe. This movement should be firm, but at the same time should not cause pain to the patient under examination. Under normal conditions, a sole reflex should occur, i.e. a downward flexion of all five toes.

The reaction, which can be described as the presence of a positive Babinski sign, consists of dorsiflexion (i.e. upwards) of the toe and, not always occurring, fan-like spreading of the remaining toes. Movements of the foot may be accompanied by reactions from other parts of the lower limbs, such as the knee or hip (mainly flexion activity).

A similar movement pattern (in the presence of pathology) can be induced by performing other manoeuvres, such as:

• compression of the anterior surface of the lower leg (Oppenheim's sign),
• irritation of the skin of the lateral ankle (Chaddock sign),
• compression of the gastrocnemius muscle, located at the rear of the shin (Gordon's sign).

In some patients, the assessment of the symptom is difficult or even impossible. This is the case for those patients in whom skin irritation causes a reflex retraction of the foot before any flexion reaction occurs.

When does the pathological Babinski sign appear?

The phenomena described may be physiological: this is the case in children, in whom the aforementioned foot movements may appear until they are about 2 years old (some authors state that the symptom should disappear by the end of the first year of life, while others consider it physiological even until the child is 3 years old). This situation is due to the immaturity of the elements of the nervous system that conduct motor stimuli. As the body matures and the myelination of nerve sheaths is completed, Babinski's physiological sign disappears.

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If Babinski's sign appears after the previously described period of life, it is considered pathological. The cause of its presence is damage to the so-called pyramidal tract (one may also hear terms such as central/upper motor neuron damage or corticospinal tract defect). These structures control the motor activity of the muscles by transmitting impulses generated in the brain to the motor organs.

Abnormalities in these parts of the brain can lead to:

• multiple sclerosis
• brain injuries,
• amyotrophic lateral sclerosis,
• tumours of the central nervous system,
• meningitis,
• strokes,
• spinal cord injuries.

Babinski's sign may appear either unilaterally or bilaterally. Its finding in only one limb may facilitate the presumption of where the pathology within the nervous system is located.

The pathological motor reaction triggered by skin irritation may be permanent or transient: the latter situation occurs, for example, during epileptic seizures. It is interesting to note that a positive symptom may occur in some people during deep sleep: the reason for this phenomenon and its significance, however, remain unclear.

There are conditions that can mask the presence of a pathological reflex despite the existence of damage within the central nervous system. It may not be possible to induce Babinski's sign in patients with arthritic lesions in the foot, in patients with peripheral nerve damage and in cases of so-called spinal shock (a syndrome associated with sudden spinal cord injury).

Treatment of Babinski's sign

The abnormal motor response of the foot represents only a pathological reflex - its mere presence is not a necessity to undertake treatment, as Babinski's symptom in itself does not cause any disorders, such as difficulties with movement.

It is much more important to find the cause of the symptom, as this is what should be treated - for this reason, its occurrence in a patient requires the implementation of a broader diagnostic approach. This includes imaging the structures of the central nervous system using computed tomography or magnetic resonance imaging, as well as certain laboratory tests, such as (in justified cases) assessment of cerebrospinal fluid (CSF) collected by lumbar puncture.