Observation

A proper examination begins with observation. The infant’s clothing should be removed slowly and gently, and the diaper should be opened only for the period in which the covered area is evaluated. The examiner should make no quick moves. It is a common error to begin handling the infant before an adequate and systematic observation period.

The examiner should delineate the presence of congenital abnormalities, including midline defects of the cranium, face, palate, and spine. Midline defects are often associated with abnormalities of the neural tube. Abnormalities of the trunk, limbs, and skin are readily observed. Skin pigmentation changes are important because of the shared ectodermal beginnings of the integument and the nervous system. In particular, the presence of abnormalities associated with neurocutaneous syndromes should be ascertained, even though manifestations may not be present in the newborn. Freckling in the axillary areas is highly suggestive of neurofibromatosis.

Assessment of most cranial nerves can be accomplished in part through observation. The cranial nerves enabling eye movements and facial movements can be readily monitored.

Gross motor abilities of the newborn infant can be partially evaluated by observation. The head is preferentially turned to the right for longer periods than to the left. Term infants have predominant flexor tone, with resultant flexion of the arms at the elbows and of the legs at the knees. Bilateral fisting of the hands, including adduction and infolding of the thumbs (i.e., cortical thumbs), is expected. Limb position and posturing should be roughly symmetric. While supine, the infant manifests spontaneous limb movements that are often asymmetric and have a rapidly jerking quality. Jitteriness or tremulousness of the hands or jaw is sometimes spontaneous. These movements may indicate hyperexcitability of the central nervous system (CNS). Causes of hyperexcitability are discussed later in this chapter.

The examiner should mentally quantitate frequency and amplitude of limb movements. Diminished frequency or amplitude of arm movements may indicate brachial plexus injury; involvement of an arm and ipsilateral leg may indicate hemiparesis. While prone, the infant normally maintains a flexed posture of the arms and legs, with resultant elevation of the pelvis and flexion of the hips and knees.

The infant’s respiratory rhythm and chest movement should be observed to indicate adequate contraction of intercostal muscles. Although diaphragmatic breathing is normally accentuated in the newborn, the absence of intercostal muscle participation and a “sucking in” of the sternum may indicate anterior horn cell disease, neuromuscular junction disease, or spinal cord injury. The presence of a pectus excavatum deformity in the newborn should not be regarded as an isolated congenital deformity until neuromuscular conditions in which the diaphragm overpowers the intercostal muscles have been excluded.

The level of alertness increases with CNS maturation. At 37 weeks’ gestation, crying is common during wakefulness. At term, the infant remains alert for reasonable periods and responds to visual, auditory, and tactile stimulation. Crying is often forceful. Sleep and wake periods are clearly delineated.

Cranial Vault Evaluation

Among the most important facets of the examination is the measurement of the occipitofrontal (head) circumference. For the most part, this measurement is a reflection of brain growth. However, undue enlargement may be associated with cephalohematoma, subdural fluid collection, hydrocephalus, hydranencephaly, macrocephaly, or megalencephaly (Chapters 21–28). Serial measurements provide an index of brain growth in sick neonates. Microcephaly may be associated with many conditions, including intrauterine infection, hereditary abnormalities, maternal substance abuse, and poor nutrition.

The measurement of the occipitofrontal circumference should be performed carefully. An assistant may be necessary to stabilize the head during measurement. The measuring tape should be moved up and down the head until the largest circumference is obtained. The shape of the head influences the measure of the circumference. The nearer the head shape approximates a perfect circle, the smaller is the head circumference compared with the circumference of a noncircular head, despite the fact that the area of a plane through the maximal circumference and the brain volumes are the same. A similar relationship exists between a perfect sphere and the volume contained within it. The occipitofrontal circumference should be plotted on a graph standardized for gender, race, and gestational age to determine if the measurement falls within the normal range (i.e., two standard deviations above or below the mean) (Figure 4-1) [Braun et al., 2004]. On average, occipitofrontal circumference increases 2 cm during the first month of life, 6 cm during the first 4 months, 7 cm during the first 6 months, and 12 cm during the first 12 months of life [Fujimura and Seryu, 1977].

Fig. 4-1 Head circumference charts.

(From Nellhaus G. Composite international and interracial graphs. Pediatrics 1968;41:106.)

Infants delivered vaginally may have some deformity of the head because of scalp and subcutaneous edema with resulting caput succedaneum formation; vacuum extraction delivery often results in caput formation. Infants delivered by cesarean section usually have relatively round heads. The caput deformity, usually transient, produces an increased diameter and may confound accurate occipitofrontal circumference measurements. Cephalohematomas, which are delimited by the periosteum of the individual cranial bones, produce asymmetry of the head and increase the occipitofrontal circumference. Most occur over the parietal bones. A caput succedaneum, unlike a cephalohematoma, extends over two or more cranial bones and is not restricted to the subperiosteal (subgaleal) space. Subgaleal hematomas result from bleeding under the scalp aponeurosis and are often preceded by forceps or vacuum-assisted delivery space [Kilani and Wetmore, 2006]. The scalp may be edematous and boggy because of underlying blood. Although most subgaleal hematomas are benign, hypovolemic shock may ensue if a large amount of blood is sequestered in the subgaleal space.

The anterior fontanel, readily palpable at birth, is concave or flat in relation to the surrounding cranium. The fontanel should be assessed with the child held in the sitting position if there is any question of increased pressure. The fontanel may bulge during crying or in the presence of pathologic increased intracranial pressure. Unfortunately, the presence of normal conformation of the fontanel does not guarantee normal pressure; conversely, a bulging anterior fontanel strongly suggests increased intracranial pressure. The anterior fontanel varies in size but usually ranges from 1 to 3 cm in its longest dimension [Popich and Smith, 1972]. The fontanel pulsates synchronously with the infant’s pulse. The posterior fontanel in the neonate usually is open but admits only a fingertip. The presence of an enlarged posterior fontanel suggests the possibility of intrauterine increased intracranial pressure. From time to time, particularly in the presence of wormian bones, auxiliary fontanels may be palpable. A detailed discussion of the infant skull can be found in Chapter 28.

The cranial sutures (e.g., sagittal, metopic, lambdoidal, squamosal) are readily palpable in the newborn. Infants delivered vaginally may manifest overriding of the sutures that, with normal head growth, resolves during the first week of life. The sagittal and lambdoidal sutures are most frequently involved. The sutures are readily separated from one another with palpation. The abrupt steplike contour of the overriding bone at the suture interface distinguishes this condition from that of premature closure of the sutures. When a suture closes prematurely, growth continues along the line of apposition of the bones across the suture. For example, sagittal synostosis causes an increase in the anteroposterior diameter (i.e., scaphocephaly). Increased bitemporal diameter occurs in the presence of coronal synostosis (i.e., brachycephaly). Asymmetric suture closure may lead to grossly asymmetric head shape (i.e., plagiocephaly).

Auscultation over the infant skull, particularly the anterior fontanel and neck vessels, usually reveals a venous hum in a number of locations. Rarely, systolic-diastolic bruits, particularly those that are focal and asymmetric, indicate the presence of an arteriovenous malformation [Dodge, 1956]; however, these bruits may be heard in normal infants.

Cranial ultrasound, computed tomography (CT), and MRI are informative concerning subdural hematomas, cystic lesions, hemorrhages, and enlarged ventricles.

Developmental Reflexes

Developmental reflexes are primitive reflexes with complex responses, and largely reflect the integrity of the brainstem and spinal cord; the role of higher centers, although of importance, is not fully known. Many of these reflexes are present at birth and undergo modification during the first 6 months of life. Detailed discussion of these reflexes is presented in Chapter 3. Their persistence beyond the expected date of dissipation suggests maturational lag or impaired CNS function. This group includes the Moro, rooting, grasping, tonic neck, stepping, and placing reflexes. Generalized diminution of the manifestation of these reflexes suggests diffuse depression of brain function. Asymmetry indicates central or peripheral nervous system dysfunction that must be further localized. It is likely that infants born after breech presentation may have significant suppression of active movements when examined at the second and fourth days of life [Sekulic et al., 2009]. A stereotypic “elbowing” movement in newborns has been described. A curved wooden model of an ultrasonographic probe is gently used to exert pressure on the right and left subcostal regions. The newborn reacts with a particular defensive arm movement in which there is a three-phase response [Saraga et al., 2007].

Motor Function

Gentle manipulation of the infant’s limbs allows for assessment of muscle tone and strength. Tone is defined as resistance to passive movement (see Chapter 5). Tone at each large joint should be evaluated while the infant is at rest. Spontaneous movements and resistance of the infant to limb and trunk movement provide a measure of muscle strength. The examiner should recall any clues from the observation period suggesting muscle weakness and corroborating changes in tone and strength at this time. The infant should be supine with the head in the midposition while tone is evaluated so that the tonic neck reflex does not augment tone unilaterally.

The newborn infant should be held in the horizontal position while attitude and posture of the limbs and trunk are observed. The infant should then be held in vertical suspension again to determine whether the expected flexor tone of the limbs is present and symmetric. When held in the vertical position, the hypotonic and weak infant tends to slide through the examiner’s hands. The infant’s arms are held loosely at the sides, and the expected configuration of the shoulder girdle is poorly maintained. In the horizontal position, the infant appears to be looped over the examiner’s arms. Infants with increased tone manifest an opisthotonic position in conjunction with obligate extension in both vertical and horizontal positions. Although it usually manifests in older infants, scissoring (i.e., crossing of the legs because of excessive, involuntary adductor magnus contraction) may be evident. The most common cause of generalized decreased tone is depression of CNS function, which may result from hypoxic-ischemic encephalopathy, neonatal sepsis, intraventricular hemorrhage, subdural hemorrhage, or metabolic abnormalities (e.g., hypoglycemia). Congenital malformations, including neuronal migration disorders, may be associated with hypotonia. Tone and strength may be decreased in a number of neuromuscular conditions, including spinal muscular atrophy, neonatal myasthenia gravis, congenital myopathies, and neonatal myotonic dystrophy. Muscle tone may be increased in a variety of conditions that cause a neonatal encephalopathy, including many metabolic disorders, hypoxic-ischemic encephalopathy, neonatal stroke, intrauterine infection, congenital malformations, and trauma.

While the infant is being handled, stimulation may engender jittery or tremulous movements of the jaw or limbs. Such movements are arrhythmic and do not have a definite phasic composition. The movements usually terminate when stimulation ends, although noises or abrupt changes in light may trigger them. Sometimes, there may be spontaneous tremulousness. Crying enhances the frequency and range of the movements. Such tremulousness may indicate metabolic abnormalities (e.g., electrolyte imbalance), bleeding, congenital CNS defects (structural or functional), infections, or drug withdrawal syndromes. Exaggerated and persistent tremulousness may indicate relative irritability of the cerebral cortex and potential risk for subsequent, significant neurologic dysfunction including seizures.

Deep tendon reflexes are elicited using a reflex hammer and are often brisk in the newborn, although they may be normally absent [Critchley, 1968]. They may be inordinately enhanced by upper motor neuron abnormalities and are further facilitated by crying. CNS depression may be associated with reduced deep tendon reflexes. The examiner should confirm that the deep tendon reflexes are symmetric, because asymmetry may indicate central or peripheral nervous system impairment. If previous examination has suggested the possibility of hemiparesis, deep tendon reflexes should be carefully evaluated for asymmetry; they are usually increased on the affected side. Deep tendon reflex asymmetry in the arms may be associated with upper motor neuron abnormality, but asymmetrically absent deep tendon reflexes suggest peripheral involvement, possibly the result of brachial plexus injury. Nerve conduction studies in newborns may provide an index of neurologic maturity [Dubowitz et al., 1968].

Controversy remains over the significance of the plantar response in the newborn period in term infants. Although some investigators have reported that the Babinski sign is flexor and symmetric in the newborn period [Hogan and Milligan, 1971], this finding is more likely caused by obtaining a plantar grasp than a Babinski response if only the sole of the foot is used to elicit the response. The plantar response is extensor for at least the first month of life and usually through the first year of life. However, at all times, the response should always be bilaterally symmetric. Persistence of extensor toe-sign responses beyond infancy suggests corticospinal tract impairment and may be associated with alterations in tone and other deep tendon reflex abnormalities. Ankle clonus is frequently elicited in the newborn; rarely are there more than eight beats in normal infants. The clonus is enhanced during crying and may be facilitated during hyperexcitable states, such as those associated with metabolic abnormalities, infection, and subarachnoid hemorrhage. Sustained ankle clonus has the same significance in term newborns as in later life and suggests dysfunction of the corticospinal tracts.

A reflex akin to the plantar response has been described for the hand in term and preterm newborns. The examiner strokes the ulnar aspect of the infant’s palm with the thumb, beginning distally and stroking proximally from the small finger to the hypothenar eminence. The normal response is gradual extension of the fingers, beginning with the small finger and continuing to the middle fingers [Modanlou, 1988]. Lack of response or gross alteration of response may be observed in the presence of corticospinal tract dysfunction.

Cranial Nerve Examination

A more detailed discussion of the cranial nerve examination is found in Chapter 2. Cranial nerve I, the olfactory nerve, is infrequently tested but may be evaluated by the use of pleasant but definitive aromatic substances, such as cinnamon and cloves [Sarnat, 1978]. The infant usually manifests an arrest of activity, arousal, and sucking activity when exposed to these aromas. Virtually all neonates born after more than 32 weeks’ gestation respond [Sarnat, 1978].

Evaluation of cranial nerves II, III, IV, and VI involves assessment of the eyes. The pupils should be symmetric, and there should be an equal bilateral response to light. A bright light causes the infant to blink or hold the lids closed. The presence of ptosis or increased height of the palpebral fissure should be evaluated. The examiner should ascertain the presence of heterochromia, although it may not be evident until later.

Examination of the optic fundi may be difficult but is necessary. Numerous changes, including chorioretinitis (i.e., salt-and-pepper pigmentary changes), may be observed. Hemorrhages are commonly detected after vaginal delivery, even in the absence of traumatic delivery. The optic nerve may be hypoplastic, as manifested by a small, pearl-colored optic disc. The color of the optic disc in the newborn infant is grayish white. Retinal hemorrhages may be found in a large percentage of otherwise normal infants who have no history of abnormal delivery and who later prove to be neurologically normal [Besio et al., 1979]. Further discussion of funduscopic characteristics is presented in Chapter 6.

The newborn infant turns toward a light of moderate intensity and fixes on a bright object or the examiner’s face. Most often, the newborn’s eyes are symmetrically open or closed. If one eye is open and the other closed, there should be a shifting from one side to the other. Width of palpebral fissures should be equal; if not, the presence of ptosis should suggest an abnormality of cranial nerve III function, sympathetic innervation dysfunction, neuromuscular junction difficulty, weakness of the levator muscle of the lid, or abnormality of the lid connective tissue. Among the conditions to be considered are congenital myasthenia gravis, myotonic dystrophy, Horner’s syndrome (Figure 4-2), Möbius’ syndrome, congenital myopathies, and Duane’s syndrome. Occasionally, central or peripheral seventh nerve paresis may result in asymmetry of the palpebral fissure.

Fig. 4-2 Horner’s syndrome (left eye).

Miosis and ptosis are plainly evident.

(Courtesy of the Division of Pediatric Neurology, University of Minnesota Medical School.)

Extraocular movements should be monitored while a child is lying quietly. Slight lapses of conjugate gaze are common in the newborn period. Newborn visual acuity is difficult to assess, but black and white-patterned objects can be used. The examiner’s face is often the best “target.” The intended object of focus is moved slowly in the infant’s field of vision, less than a foot from the infant’s eyes. The infant slowly follows with eye movement, particularly in lateral directions. Prolonged gaze may occur in the newborn period [Brazelton et al., 1976]. Opticokinetic nystagmus may be elicited by using a striped, rotating drum or striped cloth strip, which is slowly pulled across the infant’s visual field in the vertical and horizontal directions. The response is the same as in older children (see Chapter 2).

Although small-excursion, lateral-gaze nystagmus may be present in the newborn, the coarser to-and-fro pattern of congenital nystagmus, which is oscillatory in nature, is usually unmistakable. Although unusual, nystagmus associated with mild esotropia or exotropia may be evident in the newborn. Wild, jerky nystagmus of congenital opsoclonus is a startling and readily discernible finding suggesting midbrain involvement.

Doll’s-eye movement is elicited by the examiner gently rotating the infant’s head from one side to the other when the infant is asleep. The eyes move conjugately in the direction opposite to the rotation of the head. Movement of the head in the vertical position (upward and downward) causes similar movements in the vertical plane. Failure of the eyes to move in the expected manner or direction indicates abnormalities of the cranial nerves or brainstem nuclei. Failure of abduction is associated with cranial nerve VI impairment or lateral rectus muscle impairment. Failure of normal movement in the medial direction implicates medial rectus muscle or cranial nerve III impairment.

To gain further information, the infant may be held supine on the examiner’s arm as the examiner rotates and watches the infant’s eyes. This oculovestibular maneuver causes movement so that there is lateral conjugate deviation in the direction of the rotation. When the rotational movement is terminated abruptly, the eye movements reverse. It is possible to assess the integrity of cranial nerves III and VI with this maneuver.

Cranial nerve VII involvement may be the result of the position of the infant in the maternal pelvis and delivery by pressure incurred during forceps delivery, or by agenesis of the motor nucleus of cranial nerve VII. Facial movements are readily observed during crying; an asymmetry of mouth movement may indicate cranial nerve VII involvement. During crying, the angle of the mouth is depressed on the normal side. The syndrome referred to as asymmetric crying facies may manifest this way [Nelson and Eng, 1972]. This syndrome results from weakness of the lower lip caused by hypoplasia of the depressor muscle of the mouth angle. This phenomenon is a congenital abnormality and does not signal cranial nerve VII involvement. This condition also may be associated with somatic atrophy, vertebral and rib abnormalities, renal dysgenesis, and most importantly, cardiac defects (i.e., atrial or ventricular septal defect; cardiofacial syndrome) [Pape and Pickering, 1972].

Hearing in term infants has been evaluated by sophisticated testing techniques that indicate some ability to localize and discriminate. However, meaningful hearing evaluation during routine neurologic examination is difficult to accomplish because of simultaneous visual cues and variable responses. The use of brainstem auditory-evoked potential testing has greatly improved the ability to evaluate hearing response during the neonatal period. Vestibular function can be monitored by the oculovestibular maneuver described previously.

Assessment of cranial nerves IX, X, and XII may be facilitated by evaluating the infant’s cry; however, impairment of crying may occur because of central rather than peripheral abnormalities. An infant with generally depressed CNS function often cries infrequently, and the cry is weak and may be high-pitched. The volume and tone of the cry should be assessed. An irritable child with a hyperexcitable nervous system may have a high-pitched shriek, whereas unusual cries, such as that associated with the cri du chat syndrome, are similar to a cat’s cry.

Observation of the infant during crying is a valuable adjunct to certain portions of the examination. During the lusty segments of crying, the infant’s tongue and palate may be readily inspected. Asymmetry or loss of tongue bulk may indicate abnormalities of cranial nerve XII or its nucleus. The presence of fasciculations may indicate spinal muscular atrophy. More complex forms of Möbius’ syndrome may also involve the tongue. Tongue fasciculations must be identified when the child is quiet and not crying. The fasciculations occur along the lateral margins and underside of the tongue.

Cranial nerves V, VII, IX, X, and XII are involved in sucking and swallowing. Swallowing dysfunction requires close scrutiny to determine which cranial nerve or nerves are involved. The gag reflex is present in term newborns and requires normal function of cranial nerves IX and X.

Tests for pain and sensation are imprecise at this age, and the gross response of infants to stroking and pinprick with withdrawal, crying, and change in sucking rates may be the only information possible. More sophisticated testing can be devised during which heart and respiratory rates are monitored.

If necessary, in the presence of olfactory, gustatory, visual, tactile, or auditory stimuli, sophisticated monitoring and scoring of body activity may be performed [Brazelton et al., 1976]. All such sensory stimuli produce habituation in the newborn [Lipsitt, 1977]. Lack of habituation or failure to respond to these stimuli is abnormal; however, the abnormality may be specific for the sensory mechanism or merely may be a reflection of generalized CNS depression.

General Examination

It is not possible with any great assurance to estimate gestational age from the date of the first day of the mother’s last menstrual period [Lubchenco, 1970]. Nevertheless, a number of physical findings evident during the examination can prove helpful in this evaluation [Farr et al., 1966a, 1966b; Lubchenco, 1970; Usher and McLean, 1969]. Among the most valuable findings are skin texture and color, quantity of breast tissue and ear cartilage, and the stage of development of the external genitalia. No single characteristic can determine the gestational age. The estimate should be based on the average of expected findings (Table 4-3). The combination of findings based on physical characteristics and neurologic examination has proved of value in the estimation of gestational age [Dubowitz et al., 1970]. This method is discussed with the specifics of the neurologic examination.

Electrophysiologic Assessment

Motor nerve conduction velocity studies of the ulnar and posterior tibial nerves may corroborate the clinical estimation of gestational age because nerve velocity becomes more rapid with maturation. Such studies also differentiate infants of short gestation from those with intrauterine growth retardation, including those at high risk and with very low birth weight [Dubowitz et al., 1968; Cruz-Martinez et al., 1983; Miller et al., 1983; Moosa and Dubowitz, 1972].

Electroencephalographic (EEG) patterns also appear to be a function of maturity. Comparison of EEG, anatomic, and clinical criteria provides one means of estimating gestational age [Scher and Barmada, 1987]. EEG correlates are listed in Box 4-1 [Scher and Barmada, 1987] and are further discussed in Chapter 12.

Box 4-1 Selected Gestational Age-dependent Electroencephalographic Patterns Based on Convolutional Measurements

Less than 28 weeks

Prominent occipital theta/alpha

Prominent vertex-central delta brush

Rhythmic occipital delta (<6 seconds)*

Prominent bitemporal attenuation

Diffuse theta/delta slowing

Interburst intervals (<40 seconds)

Brief continuous portions (<1 minute)

28–29 weeks

Prominent occipital delta (<10 seconds)

Appearance of temporal delta brush

Occasional temporal attenuation

Diffuse theta/delta slowing

Interburst intervals (<40 seconds)

Continuous portions (>1 minute)

30–31 weeks

Prominent temporal theta bursts

Prominent temporal delta brushes

Prominent occipital delta brushes (>10 seconds)

Interburst intervals (<30 seconds)

Continuous portions (several minutes)

^* Parentheses contain observed duration of electroencephalographic pattern.

(Adapted from Scher MS, Barmada MA. Estimation of gestational age by electrographic, clinical, and anatomic criteria. Pediatr Neurol 1987;3:256.)

Neurologic Examination

Although estimation of gestational age should be made as soon after birth as possible, the neurologic examination may be postponed for 1–2 days, depending on the condition of the infant and the need for physiologic support. The examination should be performed while the infant is awake and approximately 1 hour before the next scheduled feeding. The child may become fussy shortly before a feeding and often becomes somnolent after a feeding, resulting in decreased muscle tone.

Formal Scale of Gestational Assessment

Using a systematic evaluation of body and neurologic characteristics, Dubowitz and colleagues [1970] were able to achieve a high correlation with gestational age, making this method of assessment most valuable. The evaluation was based on 10 neurologic and 11 external (e.g., skin texture, breast size, ear form) characteristics. The external evaluation was adapted from Farr and colleagues [1966a, 1966b]. The scoring scheme is detailed in Figure 4-3 and Figure 4-4 and in Table 4-4 [Dubowitz et al., 1970].

Fig. 4-3 A, Scoring system for neurologic criteria.

(From Dubowitz L, Dubowitz V, Goldberg C. Clinical assessment of gestational age in the newborn infant. J Pediatr 1970;77:1.)

Fig. 4-3 B, Description of techniques used to assess neurologic signs.

(From Dubowitz L, Dubowitz V Goldberg. Clinical Assessment of gestational age in the newborn infant, J Pediatr 1970; 77:1.)

Fig. 4-4 Graph for reading gestational age from total score obtained from scores derived from Figure 4-3.

(Redrawn from Dubowitz LMS, Dubowitz V, Goldberg C. J Pediatr 1970;77:1.)

Table 4-4 Scoring System for External Criteria

Deep Tendon Reflex Assessment

The assessment of deep tendon reflexes in preterm infants can be of value in the presence of many conditions, such as spinal cord anomalies, peripheral nerve injuries, congenital myopathies, and infantile spinal muscular atrophy. A standard method of deep tendon reflex examination for preterm infants has been proposed [Kuban et al., 1986]. The methods of elicitation are described in Table 4-5 and depicted in Figure 4-5 [Kuban et al., 1986]. Deep tendon reflexes differ in healthy and ill preterm infants of 33 weeks’ gestation; the elicitation rate and intensity of deep tendon reflexes vary with maturity (i.e., less than and greater than 33 weeks’ gestation) [Kuban et al., 1986]. In a study of preterm infants of more than 27 weeks’ postconceptional age, the pectoralis major reflex was elicited in all, regardless of maturity. In 98 percent of the infants of more than 33 weeks’ gestation, the Achilles, patellar, biceps, thigh adductor, and brachioradialis reflexes were obtained. Infants of less than 33 weeks’ gestation had decreased elicitation rates for patellar and biceps reflexes and had overall decreases in reflex intensity compared with their older counterparts. For all infants in the study, the following tendon reflexes were found to be present (in decreasing order): finger flexors, jaw, crossed adductors, and triceps. Contrary to conventional wisdom, head position had no effect on the reflexes [Kuban et al., 1986].

Table 4-5 Deep Tendon Reflexes Evaluated in Preterm Infants

Deep Tendon Reflexes	Innervation	Technique of Elicitation
Jaw	Cranial nerves V and VII	The point of the finger is placed over the chin so that the jaw is slightly open. The hammer strikes the index finger tip
Pectoralis major	Predominantly C7 and C8, lateral pectoral nerve	The examiner’s index finger is firmly placed in a caudad (or cephalad) direction on to the axilla over the pectoralis major
Biceps	C5 and C6, musculocutaneous nerve	The examiner’s index finger is placed on to the biceps tendon in the superomedial aspect of the antecubital fossa with the arm flexed at the elbow
Brachioradialis	C5, C6, radial nerve	The tendon of the muscle is struck directly over the distal third of the radius while slowly flexing and extending the arm
Triceps	C7, C8, radial nerve	The examiner’s finger is placed over the triceps tendon at its distal aspect proximal to the elbow. The triceps tendon also may be struck directly while flexing and extending the arm
Finger flexors	C8, T1, median nerve	The examiner’s finger is placed horizontally across the base of the infant’s fingers to elicit a partial grasp. The examiner’s finger is then struck
Patellar	L3, L4, femoral nerve	The reflex hammer strikes the examiner’s finger placed across the patellar tendon, or the latter is struck directly while flexing and extending the leg at the knee
Thigh adductors and crossed adductors	L3, L4, obturator nerve	The examiner’s index finger to be struck is placed diagonally across the medial aspect at the knee (thigh adductor) with the little finger placed on the contralateral leg to maintain a 45- to 60-degree angle (crossed adductor)
Achilles	L5, S1, tibial nerve	The examiner’s finger to be struck is placed horizontally across the plantar aspect of the infant’s foot, which is partially dorsiflexed

(From Kuban KCK, Skouteli HN, Urion DK, et al. Deep tendon reflexes in premature infants. Pediatr Neurol 1986;2:266.)

Fig. 4-5 Elicitation of deep tendon reflexes in a preterm infant of 32 weeks’ gestation.

A and B, Pectoralis major. C, Brachioradialis. D, Thigh adductors and crossed adductors. E, Achilles.

(From Kuban KCK, Skouteli HN, Urion DK, et al. Deep tendon reflexes in premature infants. Pediatr Neurol 1986;2:266.)

Muscle Tone

Assessment of muscle tone in the preterm infant is requisite to completion of a satisfactory neurologic evaluation [Paro-Panjan et al., 2005; Amiel-Tison, 1968, 2002; Saint-Anne Dargassies, 1966]. The muscle tone of small-for-gestational-age infants differs from that of infants with only a short gestation.

At 26–28 weeks’ gestation, the infant is extremely hypotonic. When held by the examiner in vertical suspension, the infant does not extend the head, limbs, or trunk (Figure 4-6). The change from the hypotonia of the preterm infant to the flexion posture of the term infant manifests first in the legs and then in the arms and head. At 34 weeks’ gestation, the infant lies in the frogleg position while supine; the legs are flexed at the hip and knee, but the arms remain extended and relatively hypotonic (Figure 4-7).

Fig. 4-6 Preterm baby, 26–28 weeks’ gestation.

Notice the hypotonic posture with lack of extension of the spine and head, and lack of flexion of the extremities.

Fig. 4-7 Two weeks after birth.

The frogleg position of a preterm infant of 34 weeks’ gestation.

Measurement of various limb angles offers some objective evidence for the degree of tone. The popliteal angle, measured by maximum extension of the leg at the knee with the hip fully flexed, decreases from 180 degrees at 28 weeks’ gestation (Figure 4-8; see also Figure 4-14) to less than 90 degrees at term [Kato et al., 2005]. Similarly, the adductor and dorsiflexion angle of the foot diminishes to almost 0 degrees at term (Figure 4-9).

Fig. 4-8 The popliteal angle is 180 degrees in a preterm infant of 28 weeks’ gestation.

Fig. 4-14 Measurement of the popliteal angle in an infant who was 8 months old (corrected age).

The popliteal angle is evaluated by bringing the infant’s knees to the chest and by extending the legs with the use of gentle pressure behind the ankles. The popliteal angle was approximately 180 degrees in this case.

(From Kato T, Okumura A, Hayakawa F, et al. Popliteal angle of low birth weight infants during the first year of life. Pediatr Neurol 2004;30:244.)

Fig. 4-9 The adductor angle of the thighs is almost 180 degrees in a preterm infant of 30 weeks’ gestation.

During the traction maneuver, the head lags considerably, with little resistance until after 30 weeks’ gestation. The head extensors develop gradually, followed by the flexors. By 38 weeks, the head follows the trunk, is maintained briefly, and then falls forward when the infant is pulled from a supine to a sitting position during the traction maneuver.

In small preterm infants, the scarf sign, which is elicited by folding the arm across the chest toward the opposite shoulder, is present if the elbow reaches the opposite shoulder (Figure 4-10). In term infants, the elbow cannot be brought beyond the midline.

Fig. 4-10 An infant of 32 weeks’ gestation demonstrates the scarf sign, with the elbow approximating the opposite shoulder.

The extreme hypotonia of preterm infants permits the legs to be flexed at the hip so that the heel can be passively brought to the side of the face (i.e., heel-to-ear maneuver). Understandably, this positioning is restricted in the older infant because of increasing tone (Figure 4-11).

Fig. 4-11 Diminished tone in the very small preterm infant of 30 weeks’ gestation allows the heels to reach the head easily.

The pelvis should be flat on the table.

Tone may also be monitored while postural and righting reflexes are assessed. During the stepping maneuver, the 28-week preterm infant will not support weight (Figure 4-12). However, over the next few weeks, there is gradual support of weight, and by 34 weeks, a good supporting response is present. Tremors and even clonic movements manifest in the small preterm infant but are not normally discernible after 32 weeks’ gestation. Stretching movements of the limbs are common in small preterm infants while they are awake but somewhat less common during sleep. These movements may spread to include the trunk and head.

Fig. 4-12 A preterm infant of 28 weeks’ gestation supports his or her weight briefly.

Toe-walking may be evident.

Serial measurements may indicate the likelihood of developing spasticity. A “tight” (<120 degrees) angle was found at 4 months in infants with birth weights ranging from less than 999 g up to 1999 g. Infants who had birth weights ranging from 2000 to more than 2500 g had only an 8 percent incidence of tight popliteal angle (Table 4-6).

Table 4-6 The Rates of Infants with a Tight Popliteal Angle

Developmental Reflexes

Observation and description of the major reflex changes peculiar to the preterm infant have been undertaken by many investigators (Table 4-7) [Amiel-Tison, 1968, 2002; Fenichel, 1985; Lubchenco, 1970; Saint-Anne Dargassies, 1966].

Table 4-7 Neurologic Maturation

The rooting and sucking reflexes in small preterm infants are perfunctory but become vigorous in infants of 34 weeks’ gestation. The Moro reflex, first present in fragmentary form at 24 weeks, is well developed by 28 weeks, although it fatigues easily and lacks a complete adduction phase. Not until 38 weeks’ gestation is the entire response characteristic of the term infant observed.

At 28 weeks’ gestation, the grasp reflex is evident just in the fingers, and by 32 weeks, the palm and fingers participate. Slightly later, contraction of the muscles of the shoulder girdle and elbows occurs during the traction maneuver when the infant is pulled from a supine to a sitting position.

The tonic reflex is elicited by turning of the head to one side. The arm on the side to which the head is turned extends, and the other arm flexes. The legs may follow suit, but the response is often absent or subtle. This “fencing” position often can be elicited in the 35-week preterm infant.

The crossed-extensor reflex is obtained by stroking the sole of one foot while holding the leg firmly in extension. The response occurs in the opposite leg and comprises rapid flexion at the hips and knees with attendant withdrawal, followed by extension, adduction, and fanning of the toes. The complete response, elicited in infants of about 36 weeks’ gestation, is informative when asymmetric. Otherwise, it only establishes that some degree of primitive function is present.

The stepping response (i.e., automatic walking) is usually present by 37 weeks’ gestation and can be induced by resting the infant’s soles on a mattress and rocking the infant gently from one foot to the other. This procedure usually initiates a walking sequence, which is facilitated by the examiner supporting the infant’s weight and tilting the infant forward. The preterm infant usually walks on the toes, whereas the term infant uses a heel-to-toe sequence. The response manifests at 32–34 weeks’ gestation.

Ongoing neurologic examinations of the preterm infant are most important for the assessment of development and neurologic status. When the preterm infant reaches the equivalent of 40 weeks’ gestation, the neurologic examination results are not the same as those of a term newborn [Illingworth, 1972]. After reaching 40 weeks’ gestation the preterm infant lies with relatively less elevation of the pelvis, and so the prone body profile is flatter than that of the term newborn (Figure 4-13). The preterm infant continues toe-walking and, even at 40 weeks, manifests relative hypotonia, incomplete dorsiflexion of the foot, and a greater popliteal angle compared with the term newborn.

Fig. 4-13 The hips are abducted and the pelvis is low in a prone preterm infant of 32 weeks’ gestation.

Tone can also be evaluated by measurement of the popliteal angle in preterm infants. These data provide useful information in assessing tone (Kato et al., 2004). The angle is assessed as shown in Figure 4-14. Data documenting preterm infants and popliteal angle changes are found in Table 4-6.

Assessment of Head Growth Patterns

It is essential to measure and plot growth data to facilitate early detection of abnormal patterns. The shape of the head changes markedly with growth in preterm infants. The ratio of anteroposterior diameter to biparietal diameter increases rapidly in preterm infants during the first few months of life [Baum and Searls, 1971].

There are known differences between the extrauterine body growth patterns of preterm infants and the extrauterine body growth patterns of the term infant [Babson et al., 1970; Gardner and Pearson, 1971; Lubchenco et al., 1966; Usher and McLean, 1969]. The occipitofrontal circumference of preterm infants often shrinks during the first few days of life. Expected patterns of extrauterine head growth are reasonably well documented, making diagnosis of hydrocephalus or microcephaly in the preterm infant possible. Frequent serial occipitofrontal circumference measurements should be obtained to allow early diagnosis. A standard plotting curve must be used to monitor head growth in the preterm infant. A useful standard plot is depicted in Figure 4-15 [Babson and Benda, 1976]. Conventional symptoms and signs of hydrocephalus are not immediately evident, even though the presence of ventricular dilatation is documented with imaging techniques [Korobkin, 1975; Volpe et al., 1977].

Fig. 4-15 A fetal-infant growth graph for infants of various gestational ages.

This can be used for plotting growth from birth until 1 year of age after term status has been reached.

(From Babson SG, Benda GI. Growth graphs for the clinical assessment of infants of varying gestational age. J Pediatr 1976;89:814.)

The presence of certain characteristics should alert the clinician to the presence of hydrocephalus [Sher, 1982]; these include full fontanel with separation of the cranial sutures, abnormally high rate of occipitofrontal circumference increase, frontal bossing, scaphocephaly, and increased ratio of head size to body length.

The preterm infant’s state of health is a major determinant of head growth [Sher and Brown, 1975a, 1975b]. Mean occipitofrontal circumferences for small and large, healthy, preterm infants and for sick infants are graphed [Sher and Brown, 1975a] for comparison with the data of O’Neill [1961]. Irrespective of gestational age, sick infants were designated as those who were maintained with mechanical ventilation and intravenous therapy for various periods up to 2 weeks [Sher and Brown, 1975a, 1975b]. Infants with easily correctable metabolic abnormalities or minimal degrees of hyperbilirubinemia not requiring exchange transfusion were excluded from the sick group. On the basis of the study of Sher and Brown [1975a, 1975b], some conclusions are possible [Sher, 1982].

The rate of occipitofrontal circumference increase in the healthy preterm infant is approximately double (1.1 cm/week) that of the term infant in the first and second months after delivery (Figure 4-16). The rate of increase of occipitofrontal circumference in the healthy preterm infant is approximately equal (0.5 cm/week) to that of the term infant in the third and fourth months. The average rate of occipitofrontal circumference for ill preterm infants is 0.25 cm/week for the first 3 months.

Fig. 4-16 Head circumference growth record for preterm infants.

Preterm infants with a short gestation have more rapid rates of occipitofrontal circumference increase than infants with a longer gestation. Preterm infants with rates of occipitofrontal circumference increase greater than the expected rate should be evaluated for the presence of hydrocephalus. Preterm infants who are healthy and who fail to achieve the least expected rate of occipitofrontal circumference increase may have intrinsic brain disease.

When comparisons are made based on postconceptional age, the occipitofrontal circumference of preterm infants is greater than that of the term infant, at least for the first 5 postnatal months [Fujimura et al., 1977]. The maximum velocity of head growth in healthy, preterm infants with good caloric intake occurs shortly postpartum and decreases thereafter.

In general, the prognosis for normal development of low birth weight infants is much improved since the advent of focused obstetric practices related to the preterm infant and neonatal intensive care units [Hutson et al., 1986; Kitchen and Murton, 1985]; however, the increase in the number of very low birth weight infants has resulted in an increase in the prevalence of cerebral palsy in this population [Pharoah et al., 1990]. The clinician must be cognizant of the normal, rapid rate of head growth and avoid unnecessary procedures designed to diagnose hydrocephalus.

Caution should be exercised in placing undue emphasis on isolated neurologic findings that deviate from expected findings in preterm infants. Variations from infant to infant and from time to time in the same infant are common. The infant’s general pattern of responses should weigh heavily in the assessment of CNS integrity at any one moment.