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Primitive Reflexes

Topic updated on 07/12/17 8:04pm

Snapshot
  • A 72-year-old woman presents to the emergency department with right-sided upper and lower extremity weakness. The patient was in her usual state of health until earlier in the day when she fell while climbing the stairs. She subsequently hit her head on the hard wood surface on the floor. Medical history is significant for hypertension, hyperlipidemia, and type 2 diabetes mellitus. Physical examination is notable for 3/5 power in the right upper and lower extremity, and toes are upgoing on the right foot. A non-contrast head CT is significant for a subdural hematoma affecting the left hemisphere. (Subdural hematoma in a patient with a Babinski reflex)
Introduction
  • Primitive reflexes are normal in the infant; however, when present in an adult it becomes concerning for a frontal lobe lesion
    • this is also known as frontal release signs
      • examples of frontal release signs include
        • grasp reflex
        • snout reflex
        • root reflex
        • suck reflex
  • Other primitive reflexes
    • glabellar response
      • normal
        • when tapping between the eyes the patient may blink a few times
          • eventually the blinking extinguishes
      • abnormal
        • the blinking is continued with each tap (Myerson's sign)
        • clinical association
          • Parkinson's disease
 
Primitive Reflexes
Reflex Type
Description
Asymmetric tonic neck (ATNR)
  • Also known as a "fencing posture"
    • when the baby's head is turned the ipsilateral arm will straighten and the contralateral arm will bend
  • Appears
    • birth - 1 month
  • Disappears
    • 4-6 months
Babinski
  • In a newborn it is normal to see upgoing toes
    • this is secondary to non-complete myelination of descending cortispinal tracts
  • A normal finding in adults is plantar flexion
    • a present Babinski is suggestive of an upper motor neuron lesion
Grasp
  • When placing a finger or stroking the palm in the newborn the hand flexes
  • Appears
    • birth
  • Disappears
    • 4-6 months
Moro
  • May also be called a startle response
    • head extension leads to extension of the head and legs as well as jerking of the arms up and out
  • Appears
    • birth
  • Disappears
    • 4-6 months
Placing
  • Stimuation of the foot results in placing the foot on the flat surface to step on it
  • Appears
    • birth
  • Disappears
    • 4-6 months
Parachute
  • The arms extend when simulating a fall
  • Appears
    • 6-8 months
  • Disappears
    • never
Rooting
  • Cheek stimulation results in turning of the head toward the side of stimulation
    • this reflex assists in breastfeeding
  • Appears
    • birth
  • Disappears
    • 4-6 months
Trunk incurvation (Galant)
  • Stroking of one side of the back results in curving of the back towards the side of stimulation
  • Appears
    • birth
  • Disappears
    • 4-6 months
 
 


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