6 MONTH OLD: NORMAL EXAM
Behavior
The baby is sitting comfortably in his mother’s lap. He is socially aware, inquisitive and readily responds to visual objects and sounds. He smiles, laughs, and jabbers. At this age a baby will start to make repetitive speech sounds that are nonspecific such as da, ma, or ba.
Cranial Nerves
The baby is able to visually track an object throughout the horizontal and vertical planes. An interesting or colorful object is most helpful. To test visual fields, have the baby focus on an object in front of him and then bring a second object from behind him until he sees the object in his peripheral vision. He should turn toward the new object. Saccadic eye movements are tested by using interesting toys and sounds and watching the eyes jump from object to object. To test hearing, produce a sound out of the baby’s sight and then watch the baby turn and localize the sound. Facial movements are noted as the baby smiles or cries.
Motor - Sitting
Independent sitting is accomplished by 6 to 8 months. This baby has good sitting posture (head erect and spine straight) and has enough stability to reach for objects with both hands. He even stretches to obtain an object without loosing his balance.
Motor - Hand
The baby is able to reach out and pick up an object and bring it to the midline, usually to his mouth. He reaches equally well with either hand. Hand preference before one year of age is always abnormal and indicates a motor deficit in the non-preferred hand.
At this age, the baby is able to transfer an object from hand to hand. By 5 to 6 months, a baby grasps objects that are the size of a cube. An ulnar or palmer grasp is a raking motion with the fingers trapping the object against the palm.
The next stage of hand development is to use the thumb in concert with the fingers to grasp an object. This is called a whole hand grasp. The baby is starting to use the thumb so has developed a whole hand grasp. A thumb-finger pincer grasp develops at 7 to 9 months.
Motor - Tone
Tone is assessed for the upper and lower extremities by passive range of motion when the baby is cooperative. Distraction is a great way to get that cooperation. Babies at this age have found their feet and can suck on their toes. On passive range of motion, the lower extremity should be flexible enough to bring the foot to the baby’s mouth. There shouldn’t be any ankle clonus.
Motor - Traction
On traction, which is pulling to a sitting position, the baby has good head and trunk control. The head and shoulders are flexed forward and the arms are flexed. The baby actively helps himself to get to the sitting position by pulling with the arms. Also notice that the legs are flexed at the hips and are off the mat as the baby pulls himself to sitting. On being laid back down to the supine position, the baby doesn’t flop back, but is able to control the lowering of his head and trunk to the mat.
Position - Prone
In the prone position, the baby brings his chest all the way off the mat and supports his weight on his hands, not his forearms. He works for toys out of his reach. He is close to crawling. He can roll over from front to back and back to front.
Reflexes - Deep Tendon Reflexes
It is hard to get the baby relaxed and cooperative enough to get the limb in the optimal position for obtaining deep tendon reflexes. At this age, all the deep tendon reflexes tested in an adult exam should be obtainable.
Reflexes - Plantar Reflex
There is still a lot of plantar grasp at this age as well as withdrawal, which makes testing for the plantar response difficult at this age. The toes are still up going until one year of age. The most useful finding at this age is if there is asymmetry in the toe findings.
Primitive Reflexes
At six months of age this baby has lost the Moro reflex and the asymmetric tonic neck reflex. Persistence of either one of these primitive reflexes would be abnormal.
Postural Reflexes - Positive Support Reflex
Some consider the positive support reflex as a primitive reflex, but others consider it a postural reflex. I think it is a postural reflex because it is necessary for erect posture and blends into volitional standing. Infants with prenatal or perinatal corticospinal tract disease will often refuse to support their weight on their feet.
The positive support reflex is the first postural reflex to develop and is present by 3 to 4 months of age. When the baby is placed in vertical suspension with the feet touching the mat, the baby will extend the legs and attempts to support his weight while being balanced by the examiner. By 5 to 6 months of age the baby fully supports his weight while standing and by 7 months enjoys bouncing.
Postural Reflexes - Landau
The Landau is an important postural reflex and should develop by 4 to 5 months of age. When the infant is suspended by the examiner’s hand in the prone position, the head will extend above the plane of the trunk. The trunk is straight and the legs are extended so the baby is opposing gravity. When the examiner pushes the head into flexion, the legs drop into flexion. When the head is released, the head and legs will return to the extended position. The development of postural reflexes is essential for independent sitting and walking.
Postural Reflexes - Lateral Propping
Lateral propping or protective extension is essential for the baby to be able to sit independently. This postural reflex 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. Asymmetric lateral propping can be an early sign of hemiparesis. The baby will prop on one side but on the paretic side he will not extend the arm to catch himself.
Postural Reflexes - Parachute
The parachute reflex is the last of the postural reflexes to develop. It usually appears at 8 to 9 months of age. When the baby is turned face down towards the mat, the arms will extend as if the baby is trying to catch himself. Prior to developing this reflex, the baby will actually bring the arms back to the plane of the body and away from the mat.
Head Examination
The head circumference should be measured and plotted. This is usually done at the end of the exam because babies usually resent the restriction of head movement necessary to obtain an accurate measurement. Head shape should be noted and the sutures palpated.
Craniosynostosis (premature closure of the suture) can cause a misshaped head. Bone growth occurs perpendicular to the suture. If one suture is closed, compensatory growth will occur in the remaining open sutures. Synostosis of the sagittal suture (the most common type of synostosis) results in scaphocephaly (a thin elongated head). Synostosis of the coronal sutures results in brachycephaly (a wide flat head). Synostosis of the metopic suture results in trigonocephaly (a triangular shaped head).
The most common cause of a misshapen head is flattening of the occipit on one side and is not from lambdoid synostosis but is positional in nature (caused from the baby lying supine with the head turned to one side as a preferred position).
It is important not only to palpate the sutures but also the fontanelles. The posterior fontanelle cannot be palpated after six weeks. The anterior fontanelle is often small by six months. Closure of the anterior fontanelle occurs between 10 and 20 months. The anterior fontanelle should be palpated while the child is sitting and quiet and it should be flat or slightly concave. A full, slightly bulging fontanelle can be seen with a child that is supine or crying.