Plantar reflex Babinski response/Babinski sign (pathological) | |
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![]() The reflex occurs upon stroking of the sole of the foot with a blunt object such as a pen. If the reflex occurs in adults as illustrated at bottom it may be due to nerve damage or disease. | |
ICD-9-CM | 796.1 |
MedlinePlus | 003294 |
The plantar reflex is a reflex elicited when the sole of the foot is stimulated with a blunt instrument. The reflex can take one of two forms. In healthy adults, the plantar reflex causes a downward response of the hallux (flexion).
An upward response (extension) of the hallux is known as the Babinski response or Babinski sign, named after the neurologist Joseph Babinski. The presence of the Babinski sign can identify disease of the spinal cord and brain in adults, and also exists as a primitive reflex in infants. [1]
While first described in the medical literature by Babinski in 1896, [2] the reflex has been identified in art at least as early as Botticelli's Virgin and Child with an Angel , painted in the mid-15th century. [3]
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 [4] (metatarsal pads). Many reflex hammers taper at the end of the handle to a point which was used for testing the plantar response in the past; due to the tightening of infection control regulation this is no longer recommended. Either a single use device or the thumb nail should be used.[ citation needed ]
There are three responses possible:
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.
The Babinski sign can indicate upper motor neuron lesion 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.
The phrase "negative Babinski sign" is sometimes used for the normal flexor plantar response. [6]
Infants will usually show an extensor response. In one study of 256 healthy infants, the response to testing was extensor in 73.8%, flexor in 8.9%, and equivocal in 17.3% [7] This extensor response occurs 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 usually disappears – giving way to the flexor response – by 12 months of age. [8] Its persistence beyond age 2–3 indicates a problem in the brain or spinal cord. [9] [10]
The Hoffmann's reflex is sometimes described as the upper limb equivalent of the Babinski sign [12] 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.
The plantar reflex can be elicited in a number of ways, which were described in the late 19th and early 20th century. These have their own eponyms. [13] [14] [15]
The foot is an anatomical structure found in many vertebrates. It is the terminal portion of a limb which bears weight and allows locomotion. In many animals with feet, the foot is a separate organ at the terminal part of the leg made up of one or more segments or bones, generally including claws and/or nails.
The leg is the entire lower limb of the human body, including the foot, thigh or sometimes even the hip or buttock region. The major bones of the leg are the femur, tibia, and adjacent fibula. The thigh is between the hip and knee, while the calf (rear) and shin (front) are between the knee and foot.
Toes are the digits of the foot of a tetrapod. Animal species such as cats that walk on their toes are described as being digitigrade. Humans, and other animals that walk on the soles of their feet, are described as being plantigrade; unguligrade animals are those that walk on hooves at the tips of their toes.
The extensor hallucis longus muscle is a thin skeletal muscle, situated between the tibialis anterior and the extensor digitorum longus. It extends the big toe and dorsiflects the foot. It also assists with foot eversion and inversion.
The ankle jerk reflex, also known as the Achilles reflex, occurs when the Achilles tendon is tapped while the foot is dorsiflexed. It is a type of stretch reflex that tests the function of the gastrocnemius muscle and the nerve that supplies it. A positive result would be the jerking of the foot towards its plantar surface. Being a deep tendon reflex, it is monosynaptic. It is also a stretch reflex. These are monosynaptic spinal segmental reflexes. When they are intact, integrity of the following is confirmed: cutaneous innervation, motor supply, and cortical input to the corresponding spinal segment.
An upper motor neuron lesion Is an injury or abnormality that occurs in the neural pathway above the anterior horn cell of the spinal cord or motor nuclei of the cranial nerves. Conversely, a lower motor neuron lesion affects nerve fibers traveling from the anterior horn of the spinal cord or the cranial motor nuclei to the relevant muscle(s).
The tibial nerve is a branch of the sciatic nerve. The tibial nerve passes through the popliteal fossa to pass below the arch of soleus.
The extensor hallucis brevis is a muscle on the top of the foot that helps to extend the big toe.
The deep fibular nerve begins at the bifurcation of the common fibular nerve between the fibula and upper part of the fibularis longus, passes infero-medially, deep to the extensor digitorum longus, to the anterior surface of the interosseous membrane, and comes into relation with the anterior tibial artery above the middle of the leg; it then descends with the artery to the front of the ankle-joint, where it divides into a lateral and a medial terminal branch.
In humans, the sole of the foot is anatomically referred to as the plantar aspect.
The flexor retinaculum of foot is a strong fibrous band in the foot.
The interphalangeal joints of the foot are the joints between the phalanx bones of the toes in the feet.
Primitive reflexes are reflex actions originating in the central nervous system that are exhibited by normal infants, but not neurologically intact adults, in response to particular stimuli. These reflexes are suppressed by the development of the frontal lobes as a child transitions normally into child development. These primitive reflexes are also called infantile, infant or newborn reflexes.
Hoffmann's reflex is a neurological examination finding elicited by a reflex test which can help verify the presence or absence of issues arising from the corticospinal tract. It is named after neurologist Johann Hoffmann. Usually considered a pathological reflex in a clinical setting, the Hoffmann's reflex has also been used as a measure of spinal reflex processing (adaptation) in response to exercise training.
The Chaddock reflex is a diagnostic reflex similar to the Babinski reflex. Chaddock's sign is present when stroking of the lateral malleolus causes extension of the great toe, indicating damage to the corticospinal tract.
The extensor digitorum reflex is tested as part of the neurological examination to assess the sensory and motor pathways within the C6 and C7 spinal nerves. It is also known as Braunecker-Effenberg reflex, or BER.
Cornell's sign is a clinical sign in which scratching along the inner side of the extensor hallucis longus tendon elicits an extensor plantar reflex. It is found in patients with pyramidal tract lesions, and is one of a number of Babinski-like responses.
Babinski–Nageotte syndrome is an alternating brainstem syndrome. It occurs when there is damage to the dorsolateral or posterior lateral medulla oblongata, likely syphilitic in origin. Hence it is also called the alternating medulla oblongata syndrome.
Cutaneous, superficial, or skin reflexes, are activated by skin receptors and play a valuable role in locomotion, providing quick responses to unexpected environmental challenges. They have been shown to be important in responses to obstacles or stumbling, in preparing for visually challenging terrain, and for assistance in making adjustments when instability is introduced. In addition to the role in normal locomotion, cutaneous reflexes are being studied for their potential in enhancing rehabilitation therapy (physiotherapy) for people with gait abnormalities.
If there is no movement, then this is considered a neutral response and has no clinical significance." "Sometimes there is no response to stimulation. This is called a neutral response. This response does not rule out pathology.
Table 73.1 Variants of the Babinski Sign