Babinski sign

Babinski sign: “dorsifelxion of the great toe and abduction(Fanning) of the other toes in response to stimulation of sole of the foot”.

When I followed the neurologic clinic as a medical student (internato is called in Itlay) I was amazed about how seriously the neurologists were looking for this upgoing movement of the great toe. I thought how this simple action could have such importance to make this distinction between normal health and disease.

I came across two great articles about the babinski sign, one is written by Professor Van Gijn(1) and the other “A letter to the editor ” by Professor J. Bogousslavsky. My real reference are their articles which are complete reviews in the subject but I like to write some of my personal notes on both the articles as to blog them and to keep this here for my own future interest.

Professor Julien Bogousslavsky, one of the known neurologists in the world published in a “Letter to the Editor”(2) a comment to an article on this sign. He tells that in his role as a lieutenant-colonel in the swiss army he examined each year thousands of young adults for their recruitment and he have had the opportunity to test the plantar reflex in 150-200 young healthy men each year.

What Professor J. Bogousslavsky says about his experience: “ In none of the 3850 subjects did I find a pathological babinski sign or even a suspect plantar reflex. Indeed, I examined so many people, because I wanted to find at least one case of babinski sign in a normal male. I did not succeed.”2

Certainly this statement of Prof. Bogousslavsky makes the routine search for the babinski sign in the clinic more important.

Who was Babinski? Dr. Joseph Francois Felix Babinski (1857-1932) was a polish ( French I would say)neurologist…wikipedia. There is an another biographical chapter which also shows original photos of the babinski sign.

Babinski discovered this sign in 1896, he discovered the important difference between the normal response and that in patients with diseases of the brain. His aim was to find an objective sign to distinguish hysterical from organic paralysis, prof. Van Gijn writes. Sometimes examining the plantar reflex adds little to the history and the rest of the examination; in other patients a babinski sign is an early and sometimes the only clue to an upper motor neuron(UMN) lesion.

The plantar reflex, tendon jerks and pupillary response are important tests commonly performed by non-neurologists.

It is not simple to determine whether the movements of the toes are normal or abnormal.

The plantar reflex involves more than just the toes. In a newborn scratching the sole will result in retraction of the entire leg. This is called “Flexion synergy” and consists in the flexion of the hip, knee, and dorsiflexion of the foot and toes. After growing older this response changes:

1. the synergy becomes less brisk as a whole

2. the toes no longer take part in the flexion synergy. This occurs because the corticospinal tract(CST) matures and has now more influence on the spinal cord and its motoneurones.

3. after stimulation of the sole the toes move down, not up. This response is a local skin reflex.

when the pyramidal tract( the CST) becomes damaged by disease, the plantar reflex can revert to the infantile type:

The dorsiflexion of the great toe(upgoing movement) returns to take part in the flexion synergy. THIS IS THE BABINSKI SIGN.

Clues in the examination of the plantar reflex(1):

1. The tendon of the extensor hallucis longus muscle must be active; it should protrudes under the skin overlying the great toe and the dorsum of the foot. Consider to stimulate the lateral border of the dorsum rather than at the sole.

-don’t consider the upward movement of the entire foot.

-don’t consider an immobile great toe while the other toes go down.

2. The upward movement of the great toe should coincide with contraction of other flexor muscles in the leg.

– the activity of the tensor fasciae latae is the most obvious (dimpling under the skin of the lateral thigh).

– palpate also the tendons of the hamstrings at the back of the knee.

– observe the contraction of the tibialis anterior just lateral to the shin.

Thanks to Professor Van Gijn for these clues and facts. Certainly there is a detailed description of the whole subject in his article and that of professor Bogousslavsky referenced below, but I wanted to make my personal notes and understandings to keep them here in my own diary and retrieve them easily.

Professor Gijn discusses also some of the erroneous beliefs about the plantar reflex and response, some of the important MYTHS:

1. that the stimulation should be painful and that it should starts under the lateral heel and ends up under the great toe.

2. that when in doubt one can use a babinski -variant: all have the same result.

3. that only the first movement counts; “even an initial downward movement may be seen , it has not necessarily disappeared all together”.

4. that a true babinski sign includes fanning of the smaller toes.

5. Professor Bogousslavsky adds an another myth to consider that the claim that up to 2% to 3% of normals may have a pathological plantar response. I mentioned his experience above; he refuses this claim and suggest to add it to the four myths considered by Prof. Gijn.

The specificity of the Babinski sign is 100%. It always indicate a pathological condition that involves the CST either structural or not such as intoxication or epilepsy. 10% of patients with a lesion of the CST will show a normal or at least a mute response, sensitivity of 90%. This may be caused by a weak flexion synergy of the leg, weak response in its whole.

Now, why the agreement between different observers is poor in most studies on Babinski sign?

As Prof. Van Gijn discusses, this response of the toes reflects a disorder inthe CST. Release of the refex activity causes the great toe to be recruited into the synergistic flexion reflex of the leg( toe “extensors” are flexors in physiological sense). To have a proper assessment of the plantar reflex one should consider not only the toe movements but also the simultaneous contraction of other flexor muscles in the leg.

Now as a final account I can say many things are new for me, I do not know about you who may probably read this post but as to me, although I have few experience in the clinic just a long period of “medstudent Internato”, there are new things here and I’m really delighted to learn them. I never looked for the entire flexion synergy, for the tibialis anterior contraction at the lateral side of the shin, or the tendons of the hamstrings, or even the tensor fasciae latae, I always concentrated my attention to the foot and especially the toes only, and also I think the residents and neurologists who were there too. I always considered the fanning as an important part of the babinski that could make the sign positive even alone without the partecipation of the great toe. Now this is only a myth and not a real fact. I always wanted to perform the stroking entirely from the lateral side of the heel until below the great toe thinking to make an enough pressure on the skin.

I immagine that in this modern era of high technology the accurate searching of signs at a neurologic examination may have diminished but the interest in the babinski sign should not as it remains an easy maneuver to do and sometimes the unic sign of a pathology.

An image of the babinski sign

(escuse me for English errors)

1. Jan van Gijn The Babinski SignPRACTICAL NEUROLOGY 2002 2: 42-44. doi:10.1046/j.1474-7766.2002.00305.x

2. Julien Bogousslavsky The Babinski Sign
PRACTICAL NEUROLOGY 2002 2: 126. doi:10.1046/j.1474-7766.2002.00411.x

3. Babinski J (1896) Sur le réfl exe cutané plantaire dans certaines

affections organiques du système nerveux central.

C R Societè de Biologie, 48, 207–8.

4. Babinski J (1898) Du phénomène des orteils et de sa valeurs

émiologique. Seminars Médicale, 18, 321–2. 5.

5. Babinski J (1903) De l’abduction des orteils (signe de

l’éventail). Revue Neurologique (Paris), 11, 1205–6.