Observe coordination of swallowing, sucking, and tongue thrusting. Pinch nostrils, observe reflex opening of mouth with tip of tongue to midline.
Use the same techniques to elicit deep tendon reflexes as you would for an adult. You can substitute your index or middle finger for the neurologic hammer, as shown below.
The triceps, brachioradialis, and abdominal reflexes are difficult to elicit be- An absent anal reflex suggests fore 6 months of age. The anal reflex is present at birth and important to loss of innervation of the external elicit if a spinal cord lesion is suspected. sphincter muscle caused by a
Although a normal flexion plantar response is obtained in 90% of infants, a positive Babinski response to plantar stimulation (dorsiflexion of big toe and fanning of other toes) can be elicited in some normal infants until 2 years of age.
spinal cord abnormality such as a congenital anomaly (e.g., spina bifida), tumor, or injury.
You can try to elicit the ankle reflex as for adults by tapping on the Achilles tendon but often will not get a response. Another method shown below is to grasp the infant's malleolus with one hand and abruptly dorsiflex the ankle. Don't be surprised if you note rapid, rhythmic plantar flexion of the newborn's foot (ankle clonus) in response to this maneuver. Up to 10 beats are normal in newborns and young infants; this is unsustained ankle clonus.
When the contractions are continuous (sustained ankle clonus), central nervous system disease should be suspected.
The newborn and infant's developing central nervous system can be evaluated by assessing infantile automatisms, called primitive reflexes. These develop during gestation, are generally demonstrable at birth, and disappear at defined ages. Abnormalities in these primitive reflexes suggest neurologic disease and merit more intensive investigation. The most important primitive reflexes are illustrated on the next page.
There are additional primitive reflexes shown on p. 731 not usually used in the general examination but helpful in a more extensive evaluation of an infant with abnormal neurologic findings. A summary of some general indicators of central nervous system disease in newborns and infants, including mild disease, is provided here.
A neurologic or developmental abnormality is suspected if primitive reflexes are
■ Absent at appropriate age
■ Present longer than normal
■ Associated with posturing or twitching
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