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Babinski response...

In medicine and neurology, the Babinski response to the plantar reflex is a reflex, named after Joseph Babinski (1857-1932), a French neurologist of Polish descent, that can identify disease of the spinal cord and brain and also exists as a primitive reflex in infants. When non-pathological, it is called the plantar reflex, while the term Babinski's sign (or Koch's sign) refers to its pathological form. Babinski's Sign, the lateral side of the sole of the foot is rubbed with a blunt instrument or device so as not to cause pain, discomfort or injury to the skin; the instrument is run from the heel along a curve to the toes (metatarsal pads).

There are three responses possible:

Flexor:
the toes curve inward and the foot everts; this is the response seen in healthy adults (aka a "negative" Babinski)

Indifferent:
There is no response.

Extensor:
the hallux dorsiflexes and the other toes fan out - the "positive Babinski's sign" indicating damage to the central nervous system. As the lesion responsible for the sign expands, so does the area from which the afferent Babinski response may be elicited. The Babinski response is also normal, while asleep and after a long period of walking.

Interpretation
Babinski's Sign in a healthy newborn The Babinski’s sign can indicate upper motor neuron damage to the spinal cord, in the thoracic or lumbar region or brain disease, constituting damage to the corticospinal tract. Occasionally, a pathological plantar reflex is the first (and only) indication of a serious disease process and a clearly abnormal plantar reflex often prompts detailed neurological investigations, including CT scanning of the brain or MRI of the spine, as well as lumbar puncture for the study of cerebrospinal fluid.

In infants
Infants will also show an extensor response. A baby's smaller toes will fan out and their big toe will dorsiflex slowly. This happens because the corticospinal pathways that run from the brain down the spinal cord are not fully myelinated at this age, so the reflex is not inhibited by the cerebral cortex. The extensor response disappears and gives way to the flexor response around 12-18 months of age.

Relationship to Hoffmann sign
The Hoffmann's sign is sometimes described as the upper limb equivalent of the Babinski's sign, because both indicate upper motor neuron dysfunction. Mechanistically, they differ significantly; the finger flexor reflex is a simple monosynaptic spinal reflex involving the flexor digitorum profundus that is normally fully inhibited by upper motor neurons. The pathway producing the plantar response is more complicated, and is not monosynaptic. This difference has led some neurologists to reject strongly any analogies between the finger flexor reflex and the plantar response.

Hoffmann's sign

In medicine, Hoffmann's sign, named after the German neurologist, Johann Hoffmann (born 1857, Rheinhesse; died 1919, Heidelberg), is a finding elicited by a reflex test which verifies the presence or absence of problems in the corticospinal tract. It is also known as the finger flexor reflex.
The test involves tapping the nail or flicking the terminal phalanx of the third or fourth finger. A positive response is seen with flexion of the terminal phalanx of the thumb.

Relation to Babinski sign
Hoffmann's sign is often considered the upper limb equivalent of the Babinski's sign because it, like the Babinski sign, indicates upper motor neuron dysfunction. Its mechanism differs considerably from the Babinski which is also known as the plantar reflex; Hoffmann's sign involves a monosynaptic reflex pathway in Rexed lamina IX of the spinal cord, normally fully inhibited by descending input. The pathways involved in the plantar reflex are more complicated, and different sorts of lesions may interrupt them. This fact has led some neurologists to reject strongly any analogies between the finger flexor reflex and the plantar response.


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editor: H.m.Hanse copyright in accordance with the GNU licence