Neurological and neurobehavioral evaluation

What skill sets do neonates possess?

Bursts of developmental motor skills (i.e., rolling and subsequent sitting and walking) emerge around 4 months corrected age and serve as predictors for the infant’s developmental trajectory. This emergence of developmental skills enables fairly quick assessment of whether an infant is on target or falling behind. However, neonates also possess more subtle, spontaneous behaviors and responses that serve as the building blocks for later function. Making observations on whether developmental milestones have been achieved later in infancy may be simple, compared to the identification of early markers of alteration that are observed during the perinatal period, which often require specialized training and experience to detect.

Many early neurobehavioral assessment components evaluate the presence of reflexes that are essential to normal development and prepare the child for progressive skills. ^, Through the process of reflex integration, primitive (spinal and brain stem) reflexes gradually diminish in appearance as higher-order patterns of righting, equilibrium reactions, and voluntary responses manifest. Early primitive reflexes do not fully disappear but instead are inhibited by the cerebral cortex. Subsequently, if inhibitory control of higher centers is disrupted later in life (e.g., stroke, traumatic brain injury), these primitive reflex patterns may re-emerge. When there are alterations in reflex patterns during the perinatal period, it can impact necessary sensory experiences. The infant’s early sensory experiences also influence later motor function, including how the infant moves their extremities (i.e., through adequate range to prevent muscle shortening and loss of joint motion) and the development of balanced flexor and extensor muscle groups necessary for postural control and fluid movement. All of these factors can impact the achievement of developmental milestones, affect parent-infant bonding, impact reciprocal responses with others, and affect the development of healthy relationships.

Beyond reflexes, infants demonstrate a wide range of behaviors, responses, and interactions. For example, a particular marker of infant neural maturity is the extent to which the infant reacts and habituates to environmental stimuli. Other behaviors include the infant’s use of the auditory and visual systems to interact with the environment. Further, how the infant responds to and interacts with caregivers is an important component of early neurobehavior. Alterations in any of these behaviors, responses, and/or interactions can indicate a departure from normal development, signaling alterations in brain development, and potentially indicating the need for therapeutic interventions.

With medical advancements in neonatal care, there has been an increased rate of survival of premature infants and other high-risk populations. However, alterations in brain structure and adverse neurodevelopmental outcomes are often observed in high-risk newborns. ^, This is evidenced by significant abnormalities of grey and white matter in the brain, as well as reduced overall brain size. Subsequently, high-risk infants demonstrate neurobehavioral deficits including poorer postural control, midline behavior, exploratory behaviors, and visual motor skills as compared to their full-term counterparts. High-risk infants can experience various developmental delays including motor, cognitive, or behavioral impairment(s). ^, Long-term motor, behavioral, and cognitive deficits may persist throughout childhood and even into adulthood. Medical factors associated with prematurity, such as low birth weight, respiratory support, infection, and brain injury, may further exacerbate developmental deficits. Consequently, there is a greater need for addressing immediate and long-term developmental outcomes. The clinician can detect alterations in the neurodevelopmental trajectory during the perinatal period, prior to discharge from the NICU, through the neurological or neurobehavioral exam. ^, Such exams can be done at the infant’s bedside and have been shown to impose less stress on the infant than typical nursing care.

Overview of the history of neurological and neurobehavioral assessment

The neurological exam can be traced back to the turn of the 20th century; however, the first systemized neonatal neurological exam was reported as early as 1960, conducted by Andre Thomas. Also in the 1960s, Albrecht Peiper identified an extensive portfolio of the development of reflexes and responses, which aided our understanding of neonatal behaviors, with foundational information that has been incorporated into the modern-day neurological exam. Further to his work, Lily and Victor Dubowitz developed a scale to determine gestational age of the newborn in the 1970s, which led to the pioneering development of a neurological scale for neonates in the early 1980s. Ground-breaking work by Prechtl and colleagues aided an understanding of early movement patterns during the perinatal period, including identifying a change in movement patterns that occurs in the first couple months of life (corrected) and continues through 20 weeks corrected age. Refinements in the neurological exam continue to occur, as more evidence emerges and as new interventions, such as hypothermia for the infant with hypoxic-ischemic encephalopathy, are integrated into clinical care.

The difference between neurological exams and neurobehavioral assessments can be clouded, as there can be significant overlap. The purpose of the neurological exam is to test the function of the brain, spinal cord, and nerves, and the neurobehavioral exam expands upon that to the understanding of infant behavior. The use of neurobehavioral assessments can be traced back to at least 1956 when Graham and colleagues developed the Graham Scale and later the Graham-Rosenblith Scale ^, to better understand the behavioral differences of infants in their care. Prechtl and Beintema differentiated between behavioral states and noted that responses to the same stimulus varied based on the infant’s state. Beginning in the 1950s and continuing through the 1990s, several scholars developed scales to aid in quantifying early behavior including Graham and Rosenblith, ^, Yang, Prechtl and Beintema, Scanlon, Parmelee, and Amiel-Tison. Brazelton’s work, on which many of the modern-day assessments are based, recognized the complexity of newborn infants’ skills and began developing formal assessments in an effort to capture this complexity as well as to chart an individual infant’s development. The first version of the Neonatal Behavioral Assessment Scale (NBAS), called the Cambridge Neonatal Scales, was published in 1971 and set the stage for a deeper understanding of neonates as social beings able to respond to and interact with their environment and their caregivers. Other pioneers, including Als, Lester, and Tronick, developed the Assessment of Preterm Infant Behavior and the NICU Network Neurobehavioral Scales. These tools have similarities and differences in the items and scoring represented on the original NBAS. Additional variations of the neurobehavioral exam continue to emerge, with tools that can be used in infants at very young postmenstrual ages or with infants who are on significant respiratory support, tools that can aid in the identification of behaviors that are specific to the age of the infant, and tools that target different areas of complex behavior or motoric responses.

The neurological exam

General features

Observation is critical in each domain of the systematic neurological examination of the newborn. Observations must be made in context of physical features, such as appearance of the skin, due to the relationships between the neurological system and ectoderm. Physical clues, such as sacral dimples, may relate to neurological integrity and can be put in the context of findings from the neurological evaluation. Head circumference can be measured with a tape measure, with a full-term infant measuring an average of 35 (+2) cm. The outward head circumference is informative, as it is reflective of underlying brain structure and development.

Mental status

Timing of the examination is a careful consideration in the newborn so that the neurological evaluation can be captured when the infant is in a quiet and calm state. More than one assessment may be more informative than an isolated assessment at one moment in time. One of the best times to undertake the evaluation is between feedings. It is also important to ensure that the infant is not distressed in any other way, such as following a painful procedure or when affected by medications such as sedatives or analgesics. The best way to study mental state is by observation of the newborn infant’s spontaneous behavior with minimal handling. Careful observation of eye opening, spontaneous movements of the face and extremities, and the extent of any response to stimulation can be informative. The state of arousal is defined by both the combination of eye opening and spontaneous movements. It is important to note that there are also developmental changes that occur from preterm birth to term equivalent. As the newborn matures toward term equivalency, there is increasing duration, frequency, and quality of alertness. After 28 weeks postmenstrual age, stimulation consistently results in the infant waking for several minutes. By 32 weeks postmenstrual age, no stimulation is needed for arousal. After 36 weeks postmenstrual age, increased alertness is readily observed, as are well-formed sleep-wake cycles. Abnormalities in mental status are recognized as alterations in the levels of arousal and alertness. These neurologic abnormalities are among the most common noted during the newborn period but often are subtle, so careful attention is needed. The general descriptions of mental status alterations include hyperalertness, lethargy, stupor, and coma. In the hyperalert state, the infant is often noted to have “wide eyes” and more frequent tremulous type movements, with reflexes that may be excessive or hyper-responsive. The hyperalert infant will often not organize to feed well and often will not easily move into a sleep state. In contrast, the lethargic infant is “sleepy” and difficult to arouse or open their eyes, even when stimulated or hungry. The lethargic infant may also be noted to have low tone and reduced movements, both spontaneously and when stimulated. Stupor and coma describe an infant who cannot be aroused to open their eyes. Lack of responsiveness often results in the infant being intubated and ventilated. In the term born infant, the distinction between stupor and coma relates specifically to the quality of the movements. In coma, all movements are reflexive withdrawal from painful stimuli, with no decrement in the withdrawal reflex response.

Cranial nerves

There are 12 cranial nerves (CNs), and they can all be examined in the newborn but are often overlooked. CN I is olfaction and can be tested by introducing a smell (such as peppermint extract), which elicits a sucking arousal or withdrawal response in an infant from 30 to 32 weeks postmenstrual age. Breast milk scent has also been demonstrated to induce an olfactory response. CN II and III (optic and oculomotor nerves) can be tested by observing eye blinking in response to light, which can begin from 25 to 26 weeks postmenstrual age. These CNs can further be evaluated through consistent visual fixation on a target (e.g., human face or red object) by 34 weeks postmenstrual age and subsequently through tracking of the stimulus in a 180-degree arc by term equivalency. Random eye movements may be observed in the newborn, particularly if the infant is in a drowsy state or stressed by light in the environment. Shielding direct light from the infant may produce different results. One can detect the eyes moving conjugately in the opposite direction to head movement from 26 to 28 weeks postmenstrual age. Facial sensation (CN V—trigeminal nerve) can be tested with pinprick and by observing facial grimace or observation of the movement with mastication and sucking. It can also be tested with the corneal reflex, which should be present starting at 26 weeks postmenstrual age. Facial motility represents the function of CN VII (facial nerve) and is best assessed by observation of the symmetry and movement of the face in both the quiet alert state and during movement with crying. Hearing (CN VIII—vestibulocochlear nerve) can be tested with any loud noise and by observing the infant’s response. Such responses may be subtle and include visual blinking to the sudden, loud noise starting at 28 weeks postmenstrual age. To test CN V, VII, and XII (trigeminal, facial, and hypoglossal nerves), the newborn can be observed sucking on a pacifier to identify sucking, swallowing, and coordination with breathing. Synchronous swallowing does not occur until approximately 34 weeks postmenstrual age, and sucking is not fully coordinated with breathing until 36 to 37 weeks postmenstrual age. Cranial nerve XI (accessory nerve) controls the sternocleidomastoid muscle function, which controls flexion and rotation of the neck. This is best assessed by observation for any atrophy or fixed posture. Cranial nerve XII (hypoglossal nerve) can be examined by observing the tongue for atrophy or fasciculations.

Motor examination

The major features of the motor examination of the newborn include the descriptions of muscle bulk, muscle tone, posture of the limbs, spontaneous and elicited movements, and muscle power, as well as deep tendon and primitive reflexes. Examination of the muscle bulk as well as the presence of any contractures should be identified. Tone is best evaluated by observing the resting posture and passively manipulating the limbs. It is important to avoid head turning (keep the head in midline), as it can elicit a tonic neck reflex and give false asymmetries in tone. Flexer tone tends to develop first in the lower extremities and proceed cephalad. At 28 weeks postmenstrual age, the infant lies in extended positioning with minimally flexed extremities and has minimal resistance to passive movement. By 32 weeks, distinct flexor tone begins in the lower extremities with more resistance present to passive movement. By 36 weeks, flexor tone is prominent in the lower extremities and palpable in the upper extremities with flexion at the elbows. In addition to passive tone, the nature of both the quality and the quantity of the infant’s spontaneous movements matures from 28 weeks to term equivalent. For example, the more immature infant at 28 to 30 weeks postmenstrual age will have more twisting-type symmetric movements of the extremities. By term, movements may best be described as large-amplitude, slow, and asymmetric movements that are fluid and elegant and rotate around the major joints in an unpredictable (not cramped) fashion. For muscular power, one can assess the strength of lower or upper extremity withdrawal to stimulation and the infant’s ability to hold their head upright when held prone in the midline.

Sensory examination

While use of pinprick to elicit sensory responses has been used for many decades, the response to touch can provide much information without noxious stimuli. Many early reflexes are elicited through a touch stimulus, such as palmar and plantar grasp, galant, and rooting. Eliciting these responses can tell you a lot about sensory processing. The time of greatest focus on the sensory examination is related to concerns for a spinal injury, which may produce a dermatome or spinal level where sensation is lost. This can be assessed by using a blunt end of a cotton applicator to scratch or indent the skin from the lower limbs through the truncal region and monitoring for a grimace, which indicates sensation.

Reflexes

The deep tendon reflexes in the pectoralis, biceps, and brachioradialis as well as reflexes in the knee and ankle can be elicited in the infant from 32 to 34 weeks postmenstrual age and should be assessed, even if they are hard to elicit, which is not uncommon. Following the evolution of the reflexes can be very helpful, especially following a brain injury, as they evolve over days to weeks. Symmetric ankle clonus of 5 beats, with decrement, can be a normal finding in a healthy full-term newborn.

Primitive reflexes

There are five major primitive reflexes that provide useful information: the Moro reflex, palmar and plantar grasp, tonic neck responses, placing reflex, and stepping reflex. The Moro reflex is the most commonly tested primitive reflex and is elicited by dropping the infant’s head in relation to the body. A full reflex consists of bilateral hand opening with upper extremity extension and abduction followed by flexion. The Moro emerges from 28 weeks postmenstrual age to 37 weeks postmenstrual age (with disappearance by 4 months corrected age). The palmar grasp reflex is tested by stimulating the palm with a finger. It is present from 28 weeks postmenstrual age and increases in strength. By 37 weeks postmenstrual age, the palmar grasp is strong enough to lift the baby off the bed. The palmar grasp integrates by 2 months corrected age. The asymmetric tonic neck reflex is elicited by rotating the head to one side, resulting in elbow extension occurring to the side the head is turned and elbow flexion on the other side. It appears after 35 weeks postmenstrual age, is well established at 1 month, and is integrated by 5 to 7 months corrected age. For the placing reflex, the infant is held under the axilla in an upright position, and the dorsal aspect of the foot is brushed against an edge, producing hip and knee flexion, with the infant appearing to take a step.

Beyond the neuro exam: The neurobehavioral assessment

The definition of neurobehavioral assessment includes evaluation of a person’s neurological state by observing his or her behavior; establishing relationships between the nervous system and behavior; and connecting how the brain influences emotion, behavior, and learning. Neurobehavioral assessment is an expansion of the neurological exam, which traditionally involves elicitation of a response and an observation of that response. In addition to motoric and reflexive responses, the neurobehavioral assessment further aims to identify behaviors such as capacity for self-regulation, stress reactions and responses to interactions, habituation, and an expansion of other behavioral responses and observations of orientation, posture, reflexes, and movement.

State regulation

State regulation refers to how an infant achieves and maintains an appropriate state to learn from and interact with the environment. An awake quiet state is well-understood to be the best state for learning. The infant who is unable to achieve this (their state is too low or state is too high) is unable to optimally take in and process important sensory information for appropriate behavioral outputs. The clinician can understand an infant’s state regulatory capacity by identifying how well the infant transitions between states of arousal and maintains an appropriate state in the midst of environmental stimuli. How the infant copes with stressors can also provide powerful information about infant self-regulatory capacity. State regulation is an important construct influencing the neurological and neurobehavioral exam, because many items must be assessed in a particular state (e.g., awake quiet state, drowsy). For example, it is inappropriate to assess tone in a crying or sleeping infant, and orientation cannot be assessed in an infant unable to achieve an awake state. For many neurobehavioral exams, state regulation is assessed throughout the exam (or as part of a naturalistic observation during a caregiving task) as the infant shows their ability to rouse from sleep and make smooth transitions from state to state. Self-soothing or calming can also be noted when the infant becomes stressed or disorganized or demonstrates a crying response. Subsequently, whether the infant copes with the stressor on their own or needs assistance from the caregiver (and how much assistance is needed to re-achieve a stable state for interaction) can be identified.

Stress/responses to interactions

Infants can demonstrate different responses to stressors within the environment. The stressor need not be a painful stimulus but may also include necessary hospital-based tasks such as increasing lighting, picking up the infant to hold, or changing the diaper. Stress responses can come in the form of autonomic/physiological (e.g., heart rate drop, color change, stooling), motor (e.g., facial grimace, back arching, finger splaying), state (e.g., going into a diffuse sleep state), or attentional (e.g., gaze aversion away from an interaction) responses. How quickly an infant demonstrates stress during the exam or caregiving interaction, what strategies they use to cope (e.g., sucking, foot bracing, or hand clasping), and if and how quickly they recover can provide important information on stress thresholds and maturity of the central nervous system.

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