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Methods
The lateral side of the sole of the foot is rubbed with a blunt implement so as not to cause pain, discomfort or injury to the skin; the instrument is run from the heel along a curve to the metatarsal pads. There are three responses possible:
- Flexor: the toes curve inward and the foot everts; this is the response seen in healthy adults.
- Indifferent: there is no response.
- Extensor: the hallux dorsiflexes, and the other toes fan out - the 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
The Babinski’s sign can indicate upper motorneuron 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[1] 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 somewho? neurologists to reject strongly any analogies between the finger flexor reflex and the plantar response.citation needed
References
- ^ Harrop JS, Hanna A, Silva MT, Sharan A (2007). "Neurological manifestations of cervical spondylosis: an overview of signs, symptoms, and pathophysiology". Neurosurgery 60 (1 Supp1 1): S14–20. doi:. PMID 17204875.
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