The neurological examination of the neonate presents the clinician with numerous challenges. First, it tests the examiner's powers of observation. Most of the neurological examination is carried out by observing the neonate's baseline state. The baseline state changes based on the gestational age of the neonate, level of arousal, and recent experiences (eg, postmedical procedures such as IV placement). Second, the patient is unable to respond to verbal commands. And, last, the examiner uses subjective methods of evaluating the neonate's response to various stimuli and cues. This necessitates a high level of experience and knowledge to obtain a thorough and accurate assessment of the neonate's neurological status. This section is designed to briefly review the complete neurological examination of the neonate. The rationale for each portion of the examination will be reviewed, as will the potential differential diagnosis for abnormal findings. The examination is laid out in a systematic manner beginning with simple observation and proceeding to active evaluation of tone and responses to various stimuli. The examination is performed in this manner to maximize the clinician's time at the bedside while thoroughly examining the neonate's neurological status (Figure 28-1).
The first step to a thorough examination is to review the maternal history (age, gravity, parity, pregnancy health status, fetal growth) and the history of the neonate's birth (route of delivery, anesthesia/analgesia, APGAR scores, need for resuscitation) and hospital course from the neonate's chart. Particular attention should be focused on the gestational age of the neonate (as measured by examination—see Figure 28-1). The examiner should also review the neonate's weight, head circumference, and length. It is very important to start with these physical parameters to have the proper context for the remainder of the examination. For example, infants of diabetic mothers will typically be large for gestational age for weight and length with a normal head circumference. These infants may have problems associated with hypocalcemia and hypoglycemia, which may be evident on the neurological examination with findings of jitteriness, agitation, and seizures.1 The head circumference may also present the examiner with clues to underlying neuropathology. Neonates with microcephaly may have a congenital infection (CMV, rubella, toxoplasmosis), genetic abnormality (trisomy 13, 18, 21), somatic anomalies or syndromes (CHARGE association, Meckel-Gruber syndrome, Smith-Lemli-Opitz syndrome, Cornelia de Lange syndrome, Prader-Willi syndrome), in utero drug exposure (cocaine, heroin, ethanol, inhalation of mixed solvent vapor), hormonal disorders (congenital hypothyroidism), congenital developmental abnormality (holoprosencephaly, lissencephaly, polymicorgyria, shizencephaly), or microcephaly vera. Conversely, neonates with macrocephaly may have an underlying ventricular enlargement (aqueductal stenosis, Dandy-Walker syndrome, Arnold-Chiari malformation, vein of Galen malformation) or other etiologies (Soto syndrome, Beckwith-Wiedemann syndrome, fragile X syndrome, cranial mass, familial macrocephaly).
After completing a thorough review of the history, the examiner should simply observe the neonate. With keen observation, the examiner can gain many details about the neonate's neurological status without disturbing the neonate.
The level of alertness is perhaps the most sensitive of all neurological functions since it is dependent on the integrity of several different levels of the central nervous system.2 Before 28 weeks gestation, the newborn states of wakefulness and sleep are difficult to distinguish, and the neonate requires persistent stimulation to arouse eye opening and alertness for a period of seconds. At 28 weeks, a change occurs, and the neonate is aroused with gentle shaking with periods of alertness lasting several minutes. By 32 weeks, stimulation is no longer necessary; the eyes remain open for long periods of time with observed sleep –waking alterations. By 36 weeks, increased alertness is observed, with vigorous crying during periods of wakefulness. By term, the infant exhibits periods of attention to visual and auditory stimuli. It is important to note that the level of alertness varies depending on the time of the neonate's last feed, environmental stimuli, and recent experiences (such as placement of IV). Several disturbances of arousal can be noted on the examination. An irritable neonate is one who is agitated and cries with minimal stimulation and is unable to be comforted.3 A lethargic or stuporous neonate will have a sluggish response to sensory stimuli, while a comatose neonate will not be arousable and will have no response to sensory input.
The examiner should focus on the resting posture of the unswaddled neonate. This observation can reveal the symmetry and maturity of the passive tone with the tone changing as a function of gestational age (Figure 28-1). Flexor tone first develops in the lower extremities and proceeds cephalad correlating with increasing myelination of the subcortical motor pathways, which originate in the brainstem.3 The examiner should also note any abnormal movements, such as choreathetoid movements, that may indicate an underlying structural or metabolic problem.3 The normal term neonate displays fisting of the hand (adduction and infolding of the thumbs [cortical thumbs]) with intermittent hand opening.
Visual Inspection and Palpation
The head should be visualized and palpated for ridges along the sutures, the size and fullness of the anterior fontanel, excessive head molding or cephalohematomas, and any depressions in the skull. The spine should be carefully inspected for any patches or tufts of hairs, pits, hemangiomas, or lipomas. The entire body should be observed for birthmarks, port wine stains, ash leaf spots, or macules (Figure 28-2). Each of these findings may lead the examiner to consider underlying pathology associated with these skin findings.
Various birthmarks and skin lesions in the newborn. Salmon patches, also called "stork bites" (A) and Mongolian spots (B) are among the most common birthmarks. Café au lait spots (C) may be benign, but can also be a sign of neurofibromatosis. Port wine stains (D) and hemangiomas (E, F) may be located anywhere on the skin. Papules (G, H) and macules (I, J) may be benign as in the case of neonatal acne (G), erythema toxicum (I), or transient neonatal pustular melanosis (J), but may also be an indication of serious infection such as herpes simplex (H).(A, C, E, F, G, I, Jreproduced with permission from Wolff K, et al., eds. Fitzpatrick's Dermatology in General Medicine. 7th ed. New York; McGraw-Hill; 2008.Breproduced with permission from Wolff K, et al., eds. Fitzpatrick's Color Atlas & Synopsis of Clinical Dermatology. 5th ed. New York: McGraw-Hill; 2005.D reproduced with permission from Wolff K, et al., eds. Fitzpatrick's Dermatology in General Medicine. 7th ed. New York: McGraw-Hill; 2008:online edition. H used with permission from Alvin H. Jacobs, MD.)
The major features to be evaluated in the motor examination are muscle tone and motility. Development of tone proceeds in a caudal-rostral progression, particularly flexor tone, with maturation.2,4 A 28-week neonate has minimal resistance to passive movement in all limbs, but by 32 weeks, there is distinct flexor tone in the lower extremities. At 36 weeks, flexor tone is prominent in the lower extremities and resistance to movement is present in the upper extremities, while at term, there is strong flexor tone in all extremities.
Parallel to development of tone described above, the quality of neonatal movements advances. The 28-week neonate will have writhing movements of the extremities, while the 32-week neonate will have predominately flexor movement of the hips and knees. At 36 weeks, the active flexor movements in the lower extremities are stronger and prominent flexor movements of the upper extremities are appreciated. At 40 weeks, the neonate moves all limbs in an alternating manner. Neck flexor power also becomes apparent. This is illustrated by pulling the neonate to a sitting position using the upper extremities. During this maneuver, the head is held in the same plane as the body for several seconds.2,4
Even though the neonate's interaction with the examiner is limited, essentially all the cranial nerves can be evaluated. Cranial nerve (CN) I, given its rare involvement in diseases and the difficulty in evaluating the neonate's response, is not usually evaluated. CN II and III can be tested by the pupillary reflex, which appears consistently at 32 to 35 weeks of gestation.3 Shining a light in the neonate's eyes will elicit a blink response, first appreciated at 28 weeks, testing CN II and VII. By 34 weeks, 90% of infants will fix and follow a fluffy ball of red wool, thus testing CN II, III, IV, and VI.5 The doll's-eye maneuver can be elicited as early as 25 weeks of gestation and further tests CN III, IV, and VI. It is important to note that spontaneous roving eye movements are common at 32 weeks of gestation, as are dysconjugate eye movement in the term infant when not fixing on an object.3 Smooth visual tracking movements do not become present until 3 months of life.6 Facial sensation (CN V) can be tested with a pinprick to different areas of the face with the neonate responding with a facial grimace or change in sucking. CN VII can be tested by observing the face at rest with particular attention to the vertical width of the palpebral fissures, the nasolabial fold, and the position of the corner of the mouth. Changes in these structures should then be observed during crying. With a facial nerve palsy, the corner of the mouth on the affected side droops and the mouth is drawn to the normal side. A coordinated suck and swallow involves the function of CN V, VII, IX, X, and XII. A suck and swallow can be noted as early as 28 weeks, but the synchrony with breathing and feeding is not well developed. As the brain matures, coordination improves at 32 to 34 weeks but is not fully achieved until at least 37 weeks.7
Deep tendon reflexes (DTRs) in the neonate are elicited in a manner similar to the older pediatric patients. During testing of the DTRs, the head should be maintained in a neutral position to prevent the induction of an asymmetrical tonic neck response, which can produce asymmetrical reflex activity with stimulation. The examiner can readily elicit reflexes in the biceps, brachioradialis, and ankle, although the upper extremity reflexes are often more difficult to elicit than the lower extremities. Testing of the DTRs in the neonate can also induce clonus, which is physiologically normal (5-10 beats) if unsustained.2 The plantar response is considered of limited value since four competing reflexes lead to movement of the toes, depending on how the examination is performed.2
The developmental reflexes (Figure 28-3) are a set of reflexes that are found in the neonate and disappear at regular developmental periods as the neonatal brain develops. Volpe has commented that these reflexes are more valuable in assessment of disorders of the lower motor neuron, nerve, and muscle than of the upper motor neuron.2
The neonatal developmental reflexes are (A) the Moro or startle reflex, (B) the asymmetric tonic neck reflex, (C) the grasp reflex, and (D) the stepping reflex.
The Moro reflex (Figure 28-3A) consists of bilateral hand opening with upper extremity extension and abduction followed by anterior flexion ("embracing") of the upper extremities, then an audible cry. The reflex is elicited by dropping the head in relation to the neonate's body. The Moro reflex can be first appreciated in a rudimentary form at 28 weeks of gestation with the neonate responding with hand opening. The reflex disappears by 6 months of age.
The tonic neck response (Figure 28-3B) can be elicited by rotating the head to one side. The neonate responds to this action with what has been described as a fencing posture: an extension of the upper extremity on the side to which the face is rotated, and flexion of the upper extremity on the side of the occiput. The response first appears at 35 weeks of gestation and disappears by approximately 6 to 7 months of age.
The palmar grasp (Figure 28-3C) is elicited by stimulating the palm of the neonate's hand with an object. The reflex is present at 28 weeks of gestation, strong at 32 weeks, and strong enough to lift the neonate off the bed by 37 weeks. This reflex disappears by 2 months of age, which coincides with the development of voluntary grasp.
The placing and stepping reflexes (Figure 28-3D) are elicited by contacting the dorsum of the foot against a flat surface. The neonate will respond by flexing the hip and knee and will appear to be taking a step. This reflex is useful if asymmetry occurs and may indicate a lesion in the basal ganglia, brainstem, or spinal cord, although it is difficult to perform in a sick neonate.