Babinski Sign

The Babinski sign, first described by Joseph François Félix Babinski in 1896, remains one of the most important findings in neurological examination. Originally called phénomène des orteils (“toe phenomenon”), it is defined as an involuntary dorsiflexion of the great toe upon plantar stimulation in patients with damage to the corticospinal tract¹.

Today, the Babinski reflex is recognized as a hallmark of upper motor neuron (UMN) dysfunction. It illustrates how corticospinal pathways normally inhibit primitive reflexes, which reappear once central control is lost.

Neurophysiological Basis

• Normal adults: plantar stimulation → flexion (downward movement) of toes or no response.

• UMN lesion: plantar stimulation → dorsiflexion of the hallux, sometimes with fanning of the other toes.

This abnormal response occurs because extensor hallucis longus overrides toe flexors due to loss of corticospinal inhibition².

Test Procedure

Patient position: supine, relaxed.Examiner technique:

• Stabilize the ankle with one hand.

• With the other, use a blunt object (e.g., reflex hammer handle) to stroke the lateral sole from heel to forefoot, then medially under the toes.

• Stroke should last ~5–6 seconds; firm but not painful.

Interpretation:

• Normal: toe flexion or no movement.

• Positive Babinski: reproducible dorsiflexion of the hallux ± toe fanning.

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Clinical Relevance

A positive Babinski sign strongly indicates UMN lesion affecting corticospinal tracts³. Common causes include:

• Stroke

• Multiple sclerosis

• Brain tumor or hemorrhage

• Spinal cord injury

• Metabolic states (hypoglycemia, hypoxia, anesthesia, postictal phase)

It is normal in infants <1 year due to immature corticospinal control.

False Positives

Extensor response may also appear without pyramidal tract pathology, e.g.:

• Deep sleep or general anesthesia

• Drug or alcohol intoxication

• Postictal state

• Severe exhaustion

• Coma or electroconvulsive therapy⁵

Related Reflexes

Additional confirmatory tests for UMN dysfunction include:

• Chaddock reflex: stroking around lateral malleolus

• Gordon reflex: squeezing the calf

• Oppenheim reflex: stroking the tibial crest

All elicit great toe extension if corticospinal damage is present.

Summary

The Babinski sign is a key neurological reflex, providing strong evidence of upper motor neuron lesions. A true positive response is characterized by active dorsiflexion of the hallux during plantar stimulation. Despite possible false positives, it remains one of the most reliable indicators of pyramidal tract dysfunction and should be part of every comprehensive neurological exam.

Sources:

1. Kumar SP, Ramasubramanian D. The Babinski sign – a reappraisal. Neurology India. 2000 Oct 1;48(4):314.

2. Walker HK. https://www.ncbi.nlm.nih.gov/books/NBK397/ In Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd edition. Butterworths; 1990.

3. Landau WM. Clinical definition of the extensor plantar reflex. The New England Journal of Medicine. 1971 Nov;285(20):1149.

4. Babinski J. Sur le reflexe cutane plantaire dans certaines affections du systeme nerveux central. Comptes rendus des Seances et Memoires de la Societe de Biologie. 1896:207–208.

5. Van Gijn J. Equivocal plantar responses: a clinical and electromyographic study. Journal of Neurology, Neurosurgery & Psychiatry. 1976 Mar 1;39(3):275–282.

6. Morrow JM, Reilly MM. The Babinski sign. British Journal of Hospital Medicine. 2011 Oct;72(Sup10):M157–M159.