Primitive Reflexes of the Hand: survival-diagnostics!
Primitive Reflexes of the Hand:
the power of survival & hand diagnostics!
Primitive reflexes are automatic reflex actions of the body originating in the central nervous system.
They are called "primitive" because they are among the reflexes found in newborns and infants, but may re-appear later in life due to illnesses, particularly those affecting the frontal lobes.
If primitive reflexes retain past the first year of life (at the very latest) they can interfere with social, academic, and motor learning
- sometimes resulting in: learning disorders, ADHD, Autism Spectrum, and various other neurodevelopmental disorders.
Some primitive reflexes are needed for survival and development in the womb and in the early months of life; but after a few months these are supposed to disappear.
Then the reflexes become replaced by controlled motoric skills!
Four primitive hand reflexes (including the 'grasp reflex' and ) are discussed below - including their potential diagnostic value in adults!
For the hand there are two primitive reflexes which are part of the normal development in newborns: the (1) 'palmar (grasp) reflex' and the so-called (2) 'Babkin relfex' (which manifests due to application of pressure to both palms - this may result in varying responses such as: head flexion, head rotation, opening of the mouth). These two primitive hand reflexes usually disappear between the 3rd to 6th month of postnatal life; in neurologically healthy adults these reflexes are always absent.
NOTICE: In the illustration above- and below only the 'grasp reflex' relates to the hand.
Interestingly, there are two other (primitive) reflexes which have become associated with neurodevelopmental disorders in adults - though sometimes they can also can be observed in healthy adults.
The so-called (3) 'palmomental reflex' has become associated with disorders related to the frontal lobe; and the so-called (4) 'Hoffmann's reflex' became associated with disorders related to the cortico spinal tract.
These four primitive reflexes related to the hand are described below, plus for each the associated diagnostic issues are discussed.
The palmar grasp reflex appears at birth and persists until five or six months of age. This reflex helps the baby to get it's earliest control to touch objects. When an object is placed in the infant's hand and strokes their palm, the fingers will close and they will grasp it with a palmar grasp (see video above). The grip is strong but unpredictable; though it may be able to support the child's weight, they may also release their grip suddenly and without warning. The reverse motion can be induced by stroking the back or side of the hand.
In adults the palmar reflex is a sign indicative for tumor- or vascular lesions in the frontal lobes (which may be the result of a vascular lesion in the cerebral hemisphere). Such reappearance of these reflexes in adults is attributed to the release of the spinal reflex center from the disturbed higher brain mechanism, suggesting that these reflexes are only inhibited, and not lost, after the infantile period. Interestingly, this reflex has also been observed to have some (low) significance in schizophrenia.
The Babkin reflex occurs in newborn babies, and describes varying responses to the application of pressure to both palms. This reflex helps the baby to stimulate the breast causing breast milk to flow while breastfeeding. Infants may display head flexion, head rotation, opening of the mouth, or a combination of these responses (see video above). Smaller, premature infants are more susceptible to the reflex, with an observed occurrence in a child of 26 weeks gestation. It is named for Russian neurologist Boris Babkin in 1956 - who stated that the reflex disappears within the first three or four months of life in most of normal infants.
In some of the infants with cerebral palsy, the reflex activity persisted through the first year of life, while it declined rapidly after five months of life in infants with mental retardation. In case that the Babkin reflex can be elicited after five months of age in an infant, a careful observation for the appearance of neurological symptoms is required.
NOTICE: It is unclear whether there have been any reports of the Babkin reflex in adults due to brain damage.
The palmomental reflex concerns a potentially abnormal neurologic sign, elicited by scratching the palm of the hand at the base of the thumb (see 1st video above), characterized by contraction of the muscles of the chin and corner of the mouth on the same side of the body as the stimulus (see 2nd video above).
However, it is important to be aware that it is not very ususual to see it in healthy individuals (percentages varying from 0.5% up to 20% have been reported); an exaggerated reflex may occur in patients with pyramidal tract disease, latent tetany, increased intracranial pressure, central facial paresis, vascular dementia. The palmomental reflex is also more common in patients with neurological diseases such as: stroke, multiple sclerosis, motor neurone disease, and cerebral tumours; and it is also commoner in: those who suffered from severe head injuries, Alzheimer's disease, Down syndrome, fragile-X syndrome, and schizophrenia.
NOTICE: It is unclear whether there have been any reports of the Babkin reflex in adults due to brain damage.
In medicine, Hoffmann's reflex, named after German neurologist Johann Hoffmann, is a finding elicited by a reflex test which verifies the presence or absence of problems in the corticospinal tract. The test involves tapping the nail or flicking the terminal phalanx of the middle or ring finger. A positive response is seen with flexion of the terminal phalanx of the thumb (see video above).
A positive Hoffmann's sign can be present in an entirely normal patient. A positive Hoffmann's sign in the normal patients is more commonly found in those who are naturally hyper-reflexive (e.g. 3+ reflexes). An asymmetrical positive Hoffmann's sign (especially with acute onset) may be recognized as additional clues for finding a disease process.
The grasp reflex, a normal primitive reflex in newborns.
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