Cerebral Palsy and the Pediatric Evaluation

Part 2: The Developmental Process: Primitive and Postural Reactions
The second installment in this series on Understanding the Pediatric Evaluation revolves around two fundamental elements of the developmental process that are critical in the greater understanding of the long-term rehabilitation plan. Primitive and postural reactions are characteristic of critical early development that effectively signal progression and movement towards improved development. They are the easiest, earliest, and more frequently used tools in assessing neurological and motor development in newborns and infants.

Primitve Reactions

Primitive reactions are mediated in the brainstem and are fully present at birth. They are characterized by automatic movement patterns that become more difficult to elicit after the first 4-6 months of life. Some examples below:

Moro Reaction: The Moro reaction is obtained by holding the baby’s head and shoulders off of the mat with the arms held in flexion on the chest. The examiner suddenly lets the head and shoulders drop back a few inches while releasing the arms. The arms should fully abduct and extend, then return towards the midline with the hand open and the thumb and the index finger forming a “C” shape. An absent or incomplete Moro is seen in upper motor neuron lesions.

Prone: In the prone position, the baby should be able to extend the neck to the point where the head can be turned side to side. When the arms are extended by the side of the trunk, the baby should be able to bring them forward into a flexed position. The buttock should be somewhat elevated because the hips are flexed and adducted. A baby that is flat on the mat and can’t turn the head back and forth has low tone and weakness.

Head Lag: Starting in the supine position, the baby is pulled by the arms to the sitting position. The head and the arms are observed during the maneuver. The arms should remain partially flexed at the elbow and the head may lag behind the trunk, but should not be fully flexed backwards. When the baby is in the sitting position, the head should be able to come to the upright position for at least a few seconds before dropping forward or backward.

Postural Reactions

Postural Reactions develop following / during the disappearance of the primitive reactions. They can be considered voluntary actions that are produced by multiple sensory and structural inputs. They are complex motor responses to afferents like tendons, joints, skin, internal organs, and even the eyes and ears. They are characterized by predictable postural adjustments to specific applied sudden changes in position. As the child develops, the postural reactions (or postural performance) improve and manifest in more comprehensive ways as he /she ages. Some examples below:

Head and Trunk Control: When pulled to a sitting position, a baby this age should be able to have only slight head lag and, when sitting, the head should be upright but there may still be some wobbling of the head. The back is still rounded, so the baby slumps forward.

Prone: In the prone position, the baby is now able to bring his head up and look forward with the head being 45 to 90 degrees off the mat. Weight is borne on the forearms. When the head and chest are well off the mat, the baby is ready to start to roll from the prone to the supine position. Rolling front to back usually occurs at 3 to 5 months of age. Rolling over too early can be due to excessive extensor tone.

Lateral Propping: Lateral propping or protective extension is essential for the baby to be able to sit independently. This postural reaction develops at 5 to 7 months of age. Anterior propping actually develops first, then lateral propping. For anterior propping the baby will extend the arms forward to catch himself and prevent falling forward. Lateral propping occurs when the baby is falling to one side or the other and he extends the arm laterally to catch himself.


The understanding of these reactions is fundamental in the effective and accurate assessment of the success of the rehabilitation protocol. To be more precise, Infants with cerebral palsy have been known to manifest persistence or delay in the disappearance of primitive reflexes and pathologic or absent postural reactions. Therefore, the emergence of postural reactions (and the reduction of primitive reactions) is the primary treatment goal and thus any protocol that promotes this will ultimately contribute to improved function.

Part 1 of this series identified the need to place primary focus on the developmental age rather than the chronological age. Although not age appropriate, the persistent appearance of primitive reactions in older children is simply an indication of their current status and placement along the developmental path. It should also be remembered that the actual "manifestation" of these primitive reactions may look significantly different in an older child than a 6 month old. The structural proportions (length, weight, mechanics, torque, etc) are very different, therefore the same "reaction" may subjectively appear to be more severe or, at times, appear to be something completely different.

What does this all mean and how does it apply to my understanding of Cerebral Palsy? The answer is quite simple and straight-forward: the developmental process is something that cannot be circumvented or skipped. If the child with Cerebral Palsy continues to manifest primitive reactions in conjunction with the absence of postural reactions,any expectations of higher order function (crawling, independant sitting, gross / fine motor skills) is unrealistic. Rather than a message of "gloomy reality", the fundamentals of the development of the human organism will allow you to understand the "right path" and therefore effectively reduce any unecessary anxiety and worry associated with the unknown. More importantly, it clearly identifies those interventions that are essentially "shortcuts" along the path...which initially produce increased levels of hope and expectation, but in the end reduce maximum potential.

I apologize for the relatively longer post...it has been quite the challenge to even keep it this short! The third installement: Cerebral Palsy and the Pediatric Evaluation: A Case Study Report will blend the theoretical elements of part 1 and 2 and demonstrate their application in a practical examination of the progress of an actual CP child. I hope that it achieves my goal of creating a link and close the loop of understanding.