Neurologic Evaluation

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Chapter 584 Neurologic Evaluation

A comprehensive neurologic evaluation—including history, physical examination, and the judicious use of ancillary studies—allows the clinician to localize and determine the etiology of central and peripheral nervous system pathology.

History

A detailed history is the cornerstone of any neurologic assessment. Although parents may be the primary informants, most children older than 3-4 yr are capable of contributing to their history and should be questioned directly.

The history should begin with the chief complaint, as well as a determination of the complaint’s relative significance within the context of normal development (Chapters 7–14). The latter step is critical because a 13 mo old who cannot walk may be perfectly normal, whereas a 4 yr old who cannot walk might have a serious pathology.

Next, the history of present illness should provide a chronological outline of the patient’s symptoms, with attention paid to location, quality, intensity, duration, associated features, and alleviating or exacerbating factors. It is essential to perform a review of systems, because abnormalities of the central nervous system (CNS) often manifest with vague, nonfocal symptoms that may be misattributed to other organ systems (e.g., vomiting, constipation, urinary incontinence). A detailed history might suggest that vomiting is due to increased intracranial pressure (ICP) rather than gastritis or that constipation and urinary incontinence are due to a spinal cord tumor rather than behavioral stool withholding.

Following the chief complaint and history of present illness, the physician should obtain a complete birth history, particularly if a congenital disorder is suspected. The birth history should begin with a review of the pregnancy, including specific questions about common complications, such as pregnancy-induced hypertension, preeclampsia, gestational diabetes, vaginal bleeding, infections, and falls. It is important to quantify any cigarette, alcohol, or drug (prescription, herbal, illicit) use. Inquiring about fetal movement might provide clues to an underlying diagnosis, because decreased or absent fetal activity can be associated with chromosomal anomalies and CNS or neuromuscular disorders. Finally, any abnormal ultrasound or amniocentesis results should be noted.

A labor history should address the gestational age at delivery and mode of delivery (spontaneous vaginal, vacuum- or forceps-assisted, cesarean section) and should comment on the presence or absence of fetal distress. If delivery was by cesarean section, it is essential to record the indication for surgery.

The birth weight, length, and head circumference provide useful information about the duration of a given problem, as well as insights into the uterine environment. Parents can usually provide a reliable history of their child’s postnatal course; however, if the patient was resuscitated or had a complicated hospital stay, it is often helpful to obtain the hospital records. The physician should inquire about the infant’s general well-being, feeding and sleeping patterns, activity level, and the nature of his or her cry. If the infant had jaundice, it is important to determine both the degree of jaundice and how it was managed. Historical markers of neurologic dysfunction include full-term infants who are unable to breathe spontaneously; have poor, uncoordinated sucks; need an inordinate amount of time to feed; or require gavage feeding. Again, it is important to consider the developmental context, because all of these issues would be expected in premature infants, particularly those with very low birth weights.

The most important component of a neurologic history is the developmental assessment (Chapters 6 and 14). Careful evaluation of a child’s social, cognitive, language, fine motor, and gross motor skills is required to distinguish normal development from either isolated or global (i.e., in two or more domains) developmental delay. An abnormality in development from birth suggests an intrauterine or perinatal cause, but a loss of skills (regression) over time strongly suggests an underlying degenerative disease of the CNS, such as an inborn error of metabolism. The ability of parents to recall the precise timing of their child’s developmental milestones is extremely variable. It is often helpful to request old photographs of the child or to review the baby book, where the milestones may have been dutifully recorded. In general, parents are aware when their child has a developmental problem, and the physician should show appropriate concern. Table 584-1 outlines the upper limits of normal for attaining specific developmental milestones. A comprehensive review of developmental screening tests and their interpretation is listed in Chapter 14.

Table 584-1 SCREENING SCHEME FOR DEVELOPMENTAL DELAY: UPPER RANGE

Family history is extremely important in the neurologic evaluation of a child. Most parents are extremely cooperative in securing medical information about family members, particularly if it might have relevance for their child. The history should document the age and history of neurologic disease, including developmental delay, epilepsy, migraine, stroke, and inherited disorders, for all first- and second-degree relatives. It is important to inquire directly about miscarriages or fetal deaths in utero and to document the sex of the embryo or fetus, as well as the gestational age at the time of demise. When available, the results of postmortem examinations should be obtained, as they can have a direct bearing on the patient’s condition. The parents should be questioned about their ethnic backgrounds, because some genetic disorders occur more commonly within specific populations (e.g., Tay-Sachs in the Ashkenazi Jewish population). They should also be asked if there is any chance that they could be related to each other, because the incidence of metabolic and degenerative disorders of the CNS is increased significantly in children of consanguineous marriages.

The social history should detail the child’s current living environment, as well as his or her relationship with other family members. It is important to inquire about recent stressors, such as divorce, remarriage, birth of a sibling, or death of a loved one, because they can affect the child’s behavior. If the child is in daycare or school, one should document his or her academic and social performance, paying particular attention to any abrupt changes. Academic performance can be assessed by asking about the child’s latest report card, and peer relationships can be evaluated by having the child name his or her “best friends.” Any child who is unable to name at least 2 or 3 playmates might have abnormal social development. In some cases, discussions with the daycare worker or teacher provide useful ancillary data.

Neurologic Examination

The neurologic examination begins at the outset of the interview. Indirect observation of the child’s appearance and movements can yield valuable information about the presence of an underlying disorder (Chapters 6 and 14). For instance, it may be obvious that the child has dysmorphic facies, an unusual posture, or an abnormality of motor function manifested by a hemiparesis or gait disturbance. The child’s behavior while playing and interacting with his or her parents may also be telling. A normal child usually plays independently early in the visit but will rapidly engage in the interview process. A child with attention-deficit/hyperactivity disorder might display impulsive behavior in the examining room, and a child with neurologic impairment might exhibit complete lack of awareness of the environment. Finally, note should be made of any unusual odors about the patient, because some metabolic disorders produce characteristic scents (e.g., the “musty” smell of phenylketonuria or the “sweaty feet” smell of isovaleric acidemia). If such an odor is present, it is important to determine whether it is persistent or transient, occurring only with illnesses.

The examination should be conducted in a nonthreatening, child-friendly setting. The child should be allowed to sit where he or she is most comfortable, whether it be on a parent’s lap or on the floor of the examination room. The physician should approach the child slowly, reserving any invasive or painful tests (e.g., measurement of head circumference, gag reflex) for the end of the examination. In the end, the more that the examination seems like a game, the better the child will cooperate. Because the neurologic examination of an infant requires a somewhat modified approach from that of an older child, the two groups are considered separately (Chapters 7, 8, and 88).

Mental Status

Age aside, the neurologic examination should include an assessment of the patient’s mental status in terms of both level of arousal and interaction with the environment. Premature infants born at <28 wk of gestation do not have consistent periods of alertness, whereas slightly older infants arouse from sleep with gentle physical stimulation. Sleep-wake patterns are well developed at term. Because the level of alertness of a neonate depends on many factors, including the time of the last feeding, room temperature, and gestational age, serial examinations are critical when evaluating for changes in neurologic function. Older children’s mental status can be assessed by watching them play. Having them tell a story, draw a picture, or complete a puzzle can also be helpful in assessing cognitive function. Memory can be evaluated informally as patients recount their personal information, as well as more formally by asking them to register and recall three objects or perform a digit span.

Head

Correct measurement of the head circumference is important. It should be performed at every visit for patients younger than 3 yr and should be recorded on a suitable head growth chart. To measure, a nondistensible plastic measuring tape is placed over the mid-forehead and extended circumferentially to include the most prominent portion of the occiput. If the patient’s head circumference is abnormal, it is important to document the head circumferences of the parents and siblings. Errors in the measurement of a newborn skull are common owing to scalp edema, overriding sutures, and the presence of cephalohematomas. The average rate of head growth in a healthy premature infant is 0.5 cm in the 1st 2 wk, 0.75 cm in the 3rd wk, and 1.0 cm in the 4th wk and every week thereafter until the 40th wk of development. The head circumference of an average term infant measures 34-35 cm at birth, 44 cm at 6 mo, and 47 cm at 1 yr of age (Chapters 7 and 8).

If the brain is not growing, the skull will not grow; therefore, a small head reflects a small brain, or microcephaly. Conversely, a large head may be associated with a large brain, or macrocephaly, which is most commonly familial but may be due to a disturbance of growth, neurocutaneous disorder (e.g., neurofibromatosis), chromosomal defect (e.g., Kleinfelter syndrome), or storage disorder. Alternatively, the head size may be increased secondary to hydrocephalus (Fig. 584-1) or chronic subdural hemorrhages. In the latter case, the skull tends to assume a square or boxlike shape, because the long-standing presence of fluid in the subdural space causes enlargement of the middle fossa.

Figure 584-1 Congenital hydrocephalus. Note the enlarged cranium and prominent scalp veins.

The shape of the head should be documented carefully. Plagiocephaly, or flattening of the skull, can be seen in normal infants but may be particularly prominent in hypotonic or weak infants, who are less mobile. A variety of abnormal head shapes can be seen when cranial sutures fuse prematurely, as in the various forms of inherited craniosynostosis (Chapter 585.12).

An infant has two fontanels at birth: a diamond-shaped anterior fontanel at the junction of the frontal and parietal bones that is open at birth, and a triangular posterior fontanel at the junction of the parietal and occipital bones that can admit the tip of a finger or may be closed at birth. If the posterior fontanel is open at birth, it should close over the ensuing 6-8 wk; its persistence suggests underlying hydrocephalus or congenital hypothyroidism. The anterior fontanel varies greatly in size, but it usually measures approximately 2 × 2 cm. The average time of closure is 18 mo, but the fontanel can close normally as early as 9 mo. A very small or absent anterior fontanel at birth might indicate craniosynostosis or microcephaly, whereas a very large fontanel can signify a variety of problems. The fontanel is normally slightly depressed and pulsatile and is best evaluated by holding the infant upright while he or she is asleep or feeding. A bulging fontanel is a reliable indicator of increased ICP, but vigorous crying can cause a protuberant fontanel in a normal infant.

Inspection of the head should include observation of the venous pattern, because increased ICP and thrombosis of the superior sagittal sinus can produce marked venous distention. Dysmorphic facial features can indicate a neurodevelopmental aberration. Likewise, cutaneous abnormalities, such as cutis aplasia or abnormal hair whorls, can suggest an underlying brain malformation or genetic disorder.

Palpation of a newborn’s skull characteristically reveals molding of the skull accompanied by overriding sutures—a result of the pressures exerted on the skull during its descent through the pelvis. Marked overriding of the sutures beyond the early neonatal period is cause for alarm, because it suggests an underlying brain abnormality. Palpation additionally might reveal bony bridges between sutures (craniosynostosis), cranial defects, or, in premature infants, softening of the parietal bones (craniotabes).

Auscultation of the skull is an important adjunct to the neurologic examination. Cranial bruits may be noted over the anterior fontanel, temporal region, or orbits and are best heard using the diaphragm of the stethoscope. Soft symmetric bruits may be discovered in normal children <4 yr of age or in association with a febrile illness. Demonstration of a loud or localized bruit is usually significant and warrants further investigation, because they may be associated with severe anemia, increased ICP, or arteriovenous malformations of the middle cerebral artery or vein of Galen. It is important to exclude murmurs arising from the heart or great vessels, because they may be transmitted to the cranium.

Cranial Nerves

Olfactory Nerve (Cranial Nerve I)

Anosmia, loss of smell, most commonly occurs as a transient abnormality in association with an upper respiratory tract infection or allergies. Permanent causes of anosmia include head trauma with damage to the ethmoid bone or shearing of the olfactory nerve fibers as they cross the cribiform plate, tumors of the frontal lobe, intranasal drug use, and exposure to toxins (acrylates, methacrylates, cadmium). Occasionally, a child who recovers from purulent meningitis or develops hydrocephalus has a diminished sense of smell. Rarely, anosmia is congenital, in which case it can occur as an isolated deficit or as part of Kallman syndrome, a familial disorder characterized by hypogonadotropic hypogonadism and congenital anosmia. Although not a routine component of the examination, smell can be tested reliably as early as the 32nd wk of gestation by presenting a stimulus and observing for an alerting response, withdrawal, or both. Care should be taken to use appropriate stimuli, such as coffee or peppermint, as opposed to strongly aromatic substances (e.g., ammonia inhalants) that stimulate the trigeminal nerve. Each nostril should be tested individually by pinching shut the opposite side.

Optic Nerve (Cranial Nerve II)

Assessment of the optic disc and retina is a critical component of the neurologic examination. Although the retina is best visualized by dilating the pupil, most physicians do not have ready access to mydriatic agents at the bedside; therefore, it may be necessary to consult an ophthalmologist in some cases. Mydriatics should not be administered to patients whose pupillary responses are being followed as a marker for impending herniation or to patients with cataracts. When mydriatics are used, both eyes should be dilated, because unilateral papillary fixation and dilation can cause confusion and worry in later examiners unaware of the pharmacologic intervention. Examination of an infant’s retina may be facilitated by providing a nipple or soother and by turning the head to one side. The physician gently strokes the patient to maintain arousal, while examining the closer eye. An older child should be placed in the parent’s lap and should be distracted by bright objects or toys. The color of the optic nerve is salmon-pink in a child but may be gray-white in a newborn, particularly if he or she has fair coloring. This normal finding can cause confusion and can lead to the improper diagnosis of optic atrophy.

Disc edema refers to swelling of the optic disc, and papilledema specifically refers to swelling that is secondary to increased intracranial pressure. Papilledema rarely occurs in infancy because the skull sutures can separate to accommodate the expanding brain. In older children, papilledema may be graded according to the Frisen scale (Fig. 584-2). Disc edema must be differentiated from papillitis, or inflammation of the optic nerve. Both conditions manifest with enlargement of the blind spot, but visual acuity and color vision tend to be spared in early papilledema in contrast to what occurs in optic neuritis.

Figure 584-2 Stages of papilledema (Frisen scale). A, Stage 0: Normal optic disc. B, Stage 1: Very early papilledema with obscuration of the nasal border of the disc only, without elevation of the disc borders. C, Stage 2: Early papilledema showing obscuration of all borders, elevation of the nasal border, and a complete peripapillary halo. D, Stage 3: Moderate papilledema with elevation of all borders, increased diameter of the optic nerve head, obscuration of vessels at the disc margin, and a peripapillary halo with finger-like extensions. E, Stage 4: Marked papilledema characterized by elevation of the entire nerve head and total obscuration a segment of a major blood vessel on the disc. F, Stage 5: Severe papilledema with obscuration of all vessels and obliteration of the optic cup. Note also the nerve fiber layer hemorrhages and macular exudate.

(Photographs courtesy of the University of Rochester Eye Institute.)

Retinal hemorrhages occur in 30-40% of all full-term newborn infants. The hemorrhages are more common after vaginal delivery than after cesarean section and are not associated with birth injury or with neurologic complications. They disappear spontaneously by 1-2 wk of age. The presence of retinal hemorrhages beyond the early neonatal period should raise a concern for nonaccidental trauma.

Because hearing is integral to normal language development, the physician should inquire directly about hearing problems. Parents’ concern is often a reliable indicator of hearing impairment and warrants a formal audiologic assessment with either audiometry or brainstem auditory evoked potential testing (Chapter 629). Even in the absence of parents’ concern, certain children warrant formal testing within the first month of life, including those with a family history of early life or syndromic deafness or a personal history of prematurity, severe asphyxia, exposure to ototoxic drugs, hyperbilirubinemia, congenital anomalies of the head or neck, bacterial meningitis, and congenital TORCH (toxoplasmosis, other infections, rubella, cytomegalovirus, herpes simplex virus) infections. For all other infants and children, a simple bedside assessment of hearing is usually sufficient. Newborns might have subtle responses to auditory stimuli, such as changes in breathing, cessation of movement, or opening of the eyes and/or mouth. If the same stimulus is presented repeatedly, normal neonates cease to respond, a phenomenon known as habituation. By 3-4 mo of age, infants begin to orient to the source of sound. Hearing-impaired toddlers are visually alert and appropriately responsive to physical stimuli but might have more frequent temper tantrums and abnormal speech and language development.

Glossopharyngeal Nerve (Cranial Nerve IX)

The glossopharyngeal nerve conveys motor fibers to the stylopharyngeus muscle; general sensory fibers from the posterior third of the tongue, pharynx, tonsil, internal surface of the tympanic membrane, and skin of the external ear; special sensory (taste) fibers from the posterior third of the tongue; parasympathetic fibers to the parotid gland; and general visceral sensory fibers from the carotid bodies. The nerve is tested by stimulating one side of the lateral oropharynx or soft palate with a tongue blade and observing for symmetric elevation of the palate (gag reflex). An isolated lesion of CN IX is rare, because it runs in close proximity to CN X. Potential causes of injury include birth trauma, ischemia, mass lesions, motor neuron disease, retropharyngeal abscess, and Guillain-Barré syndrome.

Vagus Nerve (Cranial Nerve X)

The vagus nerve has 10 terminal branches: meningeal, auricular, pharyngeal, carotid body, superior laryngeal, recurrent laryngeal, cardiac, pulmonary, esophageal, and gastrointestinal. The pharyngeal, superior laryngeal, and recurrent laryngeal branches contain motor fibers that innervate all of the muscles of the pharynx and larynx, with the exception of the stylopharyngeus (CN IX) and tensor veli palatini (CN V) muscles. Thus, unilateral injury of the vagus nerve results in weakness of the ipsilateral soft palate and a hoarse voice; bilateral lesions can produce respiratory distress as a result of vocal cord paralysis, as well as nasal regurgitation of fluids, pooling of secretions, and an immobile, low-lying soft palate. Isolated lesions to the vagus nerve may be a complication of thoracotomies or in neonates with type II Chiari malformations. If such a lesion is suspected, it is important to visualize the vocal cords. In addition to motor information, the vagus nerve carries somatic afferents from the pharynx, larynx, ear canal, external surface of the tympanic membrane, and meninges of the posterior fossa; visceral afferents; taste fibers from the posterior pharynx; and preganglionic parasympathetics.

Accessory Nerve (Cranial Nerve XI)

The accessory nerve innervates the sternocleidomastoid (SCM) and trapezius muscles. The left SCM acts to turn the head to the right side and vice versa; acting together, the SCMs flex the neck. The trapezius acts to elevate the shoulder. Lesions to the accessory nerve result in atrophy and paralysis of the ipsilateral sternocleidomastoid and trapezius muscles, with resultant depression of the shoulder. Because several cervical muscles are involved in head rotation, unilateral SCM paresis might not be evident unless the patient is asked to rotate the head against resistance. Skull base fractures or lesions, motor neuron disease, myotonic dystrophy, and myasthenia gravis commonly produce atrophy and weakness of these muscles; congenital torticollis is associated with SCM hypertrophy.

Hypoglossal Nerve (Cranial Nerve XII)

The hypoglossal nerve innervates the tongue. Examination of the tongue includes assessment of its bulk and strength, as well as observation for adventitious movements. Malfunction of the hypoglossal nucleus or nerve produces atrophy, weakness, and fasciculations of the tongue. If the injury is unilateral, the tongue deviates toward the side of the injury; if it is bilateral, tongue protrusion is not possible and the patient can have difficulty swallowing (dysphagia). Werdnig-Hoffmann disease (infantile spinal muscular atrophy, or SMA type 1) and congenital anomalies in the region of the foramen magnum are the principal causes of hypoglossal nerve dysfunction.

Motor Examination

The motor examination includes assessment of muscle bulk, tone, and strength, as well as observation for involuntary movements that might indicate central or peripheral nervous system pathology.

Bulk

Decreased muscle bulk (atrophy) may be secondary to disuse or to diseases of the lower motor neuron, nerve root, peripheral nerve, or muscle. In most cases, neurogenic atrophy is more severe than myogenic atrophy. Increased muscle bulk (hypertrophy) is usually physiologic (e.g., body builders). Pseudohypertrophy refers to muscle tissue that has been replaced by fat and connective tissue, giving it a bulky appearance with a paradoxical reduction in strength, as in Duchenne muscular dystrophy.

Tone

Muscle tone, which is generated by an unconscious, continuous, partial contraction of muscle, creates resistance to passive movement of a joint. Tone varies greatly based on a patient’s age and state. At 28 wk of gestation, all 4 extremities are extended and there is little resistance to passive movement. Flexor tone is visible in the lower extremities at 32 wk and is palpable in the upper extremities at 36 wk; a normal term infant’s posture is characterized by flexion of all four extremities.

There are 3 key tests for assessing postural tone in neonates: the traction response, vertical suspension, and horizontal suspension (Fig. 584-3; Chapters 88 and 91). To evaluate the traction response, the physician grasps the infant’s hands and gently pulls the infant to a sitting position. Normally, the infant’s head lags slightly behind his or her body and then falls forward upon reaching the sitting position. To test vertical suspension, the physician holds the infant by the axillae without gripping the thorax. The infant should remain suspended with his or her lower extremities held in flexion; a hypotonic infant will slip through the physician’s hands. With horizontal suspension, the physician holds the infant prone by placing a hand under the infant’s abdomen. The head should rise and the limbs should flex, but a hypotonic infant will drape over the physician’s hand, forming a U-shape. Assessing tone in the extremities is accomplished by observing the infant’s resting position and passively manipulating his or her limbs. When the upper extremity of a normal term infant is pulled gently across the chest, the elbow does not quite reach the midsternum (scarf sign), whereas the elbow of a hypotonic infant extends beyond the midline with ease. Measurement of the popliteal angle is a useful method for documenting tone in the lower extremities. The examiner flexes the hip and extends the knee. Normal term infants allow extension of the knee to ∼80 degrees. Similarly, tone can be evaluated by flexing the hip and knee to 90 degrees and then internally rotating the leg, in which case the heel should not pass the umbilicus.

Figure 584-3 Normal tone in a full-term neonate. A, Flexed resting posture. B, Traction response. C, Vertical suspension. D, Horizontal suspension.

Abnormalities of tone include spasticity, rigidity, and hypotonia. (Paratonia, which is rarely seen in the pediatric population, is not discussed here.) Spasticity is characterized by an initial resistance to passive movement, followed by a sudden release, referred to as the clasp-knife phenomenon. Because spasticity results from upper motor neuron dysfunction, it disproportionately affects the upper extremity flexors and lower extremity extensors and tends to occur in conjunction with disuse atrophy, hyperactive deep tendon reflexes, and extensor plantar reflexes (Babinski sign). In infants, spasticity of the lower extremities results in scissoring of the legs upon vertical suspension. Older children can present with prolonged commando crawling or toe-walking. Rigidity, seen with lesions of the basal ganglia, is characterized by resistance to passive movement that is equal in the flexors and extensors regardless of the velocity of movement (lead pipe). Patients with either spasticity or rigidity might exhibit opisthotonos, defined as severe hyperextension of the spine due to hypertonia of the paraspinal muscles (Fig. 584-4), though similar posturing can be seen in patients with Sandifer syndrome (gastroesophageal reflux or hiatal hernia associated with torsional dystonia). Hypotonia refers to abnormally diminished tone and is the most common abnormality of tone in neurologically compromised neonates. A hypotonic infant is floppy and often assumes a frog-leg posture at rest. Hypotonia can reflect pathology of the cerebral hemispheres, cerebellum, spinal cord, anterior horn cell, peripheral nerve, neuromuscular junction, or muscle.

Figure 584-4 Opisthotonus in a brain-injured infant.

Strength

Older children are usually able to cooperate with formal strength testing, in which case muscle power is graded on a scale of 0-5 as follows: 0 = no contraction; 1 = flicker or trace of contraction; 2 = active movement with gravity eliminated; 3 = active movement against gravity; 4 = active movement against gravity and resistance; 5 = normal power. An examination of muscle power should include all muscle groups, including the neck flexors and extensors and the muscles of respiration. It is important not only to assess individual muscle groups but also to determine the pattern of weakness (i.e., proximal vs. distal; segmental vs. regional). Testing for pronator drift can be helpful in localizing the lesion in a patient with weakness. This test is accomplished by having the patient extend his or her arms away from the body with the palms facing upward and the eyes closed. Together, pronation and downward drift of an arm indicate a lesion of the contralateral corticospinal tract.

Because infants and young children are not able to participate in formal strength testing, they are best assessed with functional measures. Proximal and distal strength of the upper extremities can be tested by having the child reach overhead for a toy and by watching him or her manipulate small objects. In infants <2 mo old, the physician can also take advantage of the palmar grasp reflex in assessing distal power and the Moro reflex in assessing proximal power. Infants with decreased strength in the lower extremities tend to have diminished spontaneous activity in their legs and are unable to support their body weight when held upright. Older children may have difficulty climbing or descending steps, jumping, or hopping. They might also use their hands to “climb up” their legs when asked to rise from a prone position, a maneuver called Gowers sign (Fig. 584-5).

Figure 584-5 A-D, Gowers sign in a boy with hip girdle weakness due to Duchenne muscular dystrophy. When asked to rise from a prone position, the patient uses his hands to walk up his legs to compensate for proximal lower extremity weakness.

Involuntary Movements

Patients with lower motor neuron or peripheral nervous system lesions might have fasciculations, which are small, involuntary muscle contractions that result from the spontaneous discharge of a single motor unit and create the illusion of a “bag of worms” under the skin. Because most infants have abundant body fat, muscle fasciculations are best observed in the tongue in this age group.

Most other involuntary movements including tics, dystonia, chorea, and athetosis stem from disorders of the basal ganglia. Tremor seems to be an exception, as it is thought to be mediated by the cerebellum. Further detail on the individual movement disorders is provided elsewhere in this text (Chapter 590).

Sensory Examination

The sensory examination is difficult to perform on an infant or uncooperative child and has a relatively low yield in terms of the information that it provides. A gross assessment of sensory function can be achieved by distracting the patient with an interesting toy and then touching him or her with a cotton swab in different locations. Normal infants and children indicate an awareness of the stimulus by crying, withdrawing the extremity, or pausing briefly; however, with repeated testing, they lose interest in the stimulus and begin to ignore the examiner. It is critical, therefore, that any areas of concern are tested efficiently and, if necessary, re-examined at an appropriate time.

Fortunately, isolated disorders of the sensory system are less common in the very young pediatric population than in the adult population, so detailed sensory testing is rarely warranted. Furthermore, most patients who are old enough to voice a sensory complaint are also old enough to cooperate with formal testing of light touch, pain, temperature, vibration, proprioception, and corticosensation (e.g., stereognosis, two-point discrimination, extinction to double simultaneous stimulation). A notable exception is when the physician suspects a spinal cord lesion in an infant or young child and needs to identify a sensory level. In such situations, observation might suggest a difference in color, temperature, or perspiration, with the skin cool and dry below the level of injury. Lightly touching the skin above the level can evoke a squirming movement or physical withdrawal. Other signs of spinal cord injury include decreased anal sphincter tone and strength and absence of the superficial abdominal, anal wink, and cremasteric reflexes.

Reflexes

Deep Tendon Reflexes and the Plantar Response

Deep tendon reflexes are readily elicited in most infants and children. In infants, it is important to position the head in the midline when assessing reflexes, because turning the head to one side can alter reflex tone. Reflexes are graded from 0 (absent) to 4+ (markedly hyperactive), with 2+ being normal. Reflexes that are 1+ or 3+ can be normal as long as they are symmetrical. Sustained clonus is always pathologic, but infants <3 mo old can have 5-10 beats of clonus, and older children can have 1-2 beats of clonus provided that it is symmetrical.

The ankle jerk is hardest to elicit, but it can usually be obtained by passively dorsiflexing the foot and then tapping on either the Achilles tendon or the ball of the foot. The knee jerk is evoked by tapping the patellar tendon. If this reflex is exaggerated, extension of the knee may be accompanied by contraction of the contralateral adductors (crossed adductor response). Hypoactive reflexes reflect lower motor neuron or cerebellar dysfunction, whereas hyperactive reflexes are consistent with upper motor neuron disease. The plantar response is obtained by stimulation of the lateral aspect of the sole of the foot, beginning at the heel and extending to the base of the toes. The Babinski sign, indicating an upper motor neuron lesion, is characterized by extension of the great toe and fanning of the remaining toes. Too vigorous stimulation may produce withdrawal, which may be misinterpreted as a Babinski sign. Plantar responses have limited diagnostic utility in neonates, because they are mediated by several competing reflexes and can be either flexor or extensor, depending on how the foot is positioned. As with adults, asymmetry of the reflexes or plantar response is a useful lateralizing sign in infants and children.

Primitive Reflexes

Primitive reflexes appear and disappear at specific times during development (Table 584-2), and their absence or persistence beyond those times signifies CNS dysfunction. Although many primitive reflexes have been described, the Moro, grasp, tonic neck, and parachute reflexes are the most clinically relevant. The Moro reflex is elicited by supporting the infant in a semierect position and then allowing his or her head to fall backwards onto the examiner’s hand. A normal response consists of symmetric extension and abduction of the fingers and upper extremities, followed by flexion of the upper extremities and an audible cry. An asymmetric response can signify a fractured clavicle, brachial plexus injury, or hemiparesis. Absence of the Moro reflex in a term newborn is ominous, suggesting significant dysfunction of the CNS. The grasp response is elicited by placing a finger in the open palm of each hand; by 37 wk of gestation, the reflex is strong enough that the examiner can lift the infant from the bed with gentle traction. The tonic neck reflex is produced by manually rotating the infant’s head to one side and observing for the characteristic fencing posture (extension of the arm on the side to which the face is rotated and flexion of the contralateral arm). An obligatory tonic neck response, in which the infant becomes “stuck” in the fencing posture, is always abnormal and implies a CNS disorder. The parachute reflex, which occurs in slightly older infants, can be evoked by holding the infant’s trunk and then suddenly lowering the infant as if he or she were falling. The arms will spontaneously extend to break the infant’s fall, making this reflex a prerequisite to walking.

Table 584-2 TIMING OF SELECTED PRIMITIVE REFLEXES

Coordination

Ataxia refers to a disturbance in the smooth performance of voluntary motor acts and is usually the result of cerebellar dysfunction. Lesions to the cerebellar vermis result in unsteadiness while sitting or standing (truncal ataxia). Affected patients might have a wide-based gait or may be unable to perform tandem gait testing. Lesions of the cerebellar hemispheres cause appendicular ataxia, which may be apparent as the patient reaches for objects and performs finger-to-nose and heel-to-shin movements. Other features of cerebellar dysfunction include errors in judging distance (dysmetria), inability to inhibit a muscular action (rebound), impaired performance of rapid alternating movements (dysdiadochokinesia), intention tremor, nystagmus, scanning dysarthria, hypotonia, and decreased deep tendon reflexes. Acute ataxia suggests an infectious or postinfectious, endocrinologic, toxic, traumatic, vascular, or psychogenic process, and chronic symptoms suggest a metabolic, neoplastic, or degenerative process.

Station and Gait

Observation of a child’s station and gait is an important aspect of the neurologic examination. Normal children can stand with their feet close together without swaying; however, children who are unsteady may sway or even fall. On gait testing, the heels should strike either side of an imaginary line, but children with poor balance tend to walk with their legs farther apart to create a more stable base. Tandem gait testing forces patients to have a narrow base, which highlights subtle balance difficulties.

There are a variety of abnormal gaits, many of which are associated with a specific underlying etiology. Patients with a spastic gait appear stiff legged like a soldier. They may walk on tiptoe due to tightness or contractures of the Achilles tendons, and their legs may scissor as they walk. A hemiparetic gait is associated with spasticity and circumduction of the leg, as well as decreased arm swing on the affected side. Cerebellar ataxia results in a wide-based, reeling gait like a drunk person, whereas sensory ataxia results in a wide-based steppage gait, in which the patient lifts the legs up higher than usual in the swing phase and then slaps the foot down. A myopathic, or waddling, gait is associated with hip girdle weakness. Affected children often develop a compensatory lordosis and have other signs of proximal muscle weakness, such as difficulty climbing stairs. During gait testing, the examiner might also note hypotonia or weakness of the lower extremities; extrapyramidal movements, such as dystonia or chorea; or orthopedic deformities, such as pelvic tilt, genu recurvatum, varus or valgus deformities of the knee, pes cavus (high arches) or pes planus (flat feet), and scoliosis.

General Examination

Examination of other organ systems is essential because myriad systemic diseases affect the nervous system. Dysmorphic features can indicate a genetic syndrome (Chapter 102). Heart murmurs may be associated with rheumatic fever (Sydenham’s chorea), cardiac rhabdomyoma (tuberous sclerosis), cyanotic heart disease (cerebral abscess or thrombosis), and endocarditis (cerebral vascular occlusion). Hepatosplenomegaly can suggest an inborn error of metabolism, storage disease, HIV, or malignancy. Cutaneous lesions may be a feature of a neurocutaneous syndrome (Chapter 589).

Special Diagnostic Procedures

Lumbar Puncture and Cerebrospinal Fluid Examination

Examination of the cerebrospinal fluid (CSF) is essential in confirming the diagnosis of meningitis, encephalitis, and pseudotumor cerebri, and it is often helpful in assessing subarachnoid hemorrhage; demyelinating, degenerative, and collagen vascular diseases; and intracranial neoplasms. Having an experienced assistant who can position, restrain, and comfort the patient is critical to the success of the procedure.

The patient should be situated in a lateral decubitus or seated position with the neck and legs flexed to enlarge the intervertebral spaces. As a rule, sick neonates should be maintained in a seated position to prevent problems with ventilation and perfusion. Regardless of the position chosen, it is important to make sure that the patient’s shoulders and hips are straight to prevent rotating the spine.

Once the patient is situated, the physician identifies the appropriate interspace by drawing an imaginary line from the iliac crest downward perpendicular to the vertebral column. In adults, lumbar punctures are usually performed in the L3-L4 or L4-L5 interspaces. Next, the physician dons a mask, gown, and sterile gloves. The skin is thoroughly prepared with a cleansing agent, and sterile drapes are applied. The skin and underlying tissues are anesthetized by injecting a local anesthetic (e.g., 1% lidocaine) at the time of the procedure or by applying a eutectic mixture of lidocaine and prilocaine (EMLA) to the skin 30 minutes before the procedure. A 22-gauge, to 3 in, sharp, beveled spinal needle with a properly fitting stylet is introduced in the midsagittal plane and directed slightly cephalad. The physician should pause frequently, remove the stylet, and assess for CSF flow. Although a pop can occur as the needle penetrates the dura, it is more common to experience a subtle change in resistance.

Once CSF has been detected, a manometer and three-way stopcock can be attached to the spinal needle to obtain an opening pressure. If the patient was seated as the spinal needle was introduced, he or she should be moved carefully to a lateral decubitus position with the head and legs extended before the manometer is attached. Normal opening pressures are 90-120 mm H₂O in newborns, 60-180 mm H₂O in young children, and 12-120 mm H₂O in older children and adults. The 90th percentile in children has been reported to be 250 mm of H₂O. The most common cause of an elevated opening pressure is an agitated patient. Sedation and high body mass index (BMI) can also increase the opening pressure.

Contraindications to performing a lumbar puncture include suspected mass lesion of the brain, especially in the posterior fossa or above the tentorium and causing shift of the midline; suspected mass lesion of the spinal cord; symptoms and signs of impending cerebral herniation in a child with probable meningitis; critical illness (on rare occasions); skin infection at the site of the lumbar puncture; and thrombocytopenia with a platelet count <20 × 10⁹/L. If disc edema or focal findings suggest a mass lesion, a head CT should be obtained before proceeding with lumbar puncture to prevent uncal or cerebellar herniation as the CSF is removed. In the absence of these findings, routine head imaging is not warranted. The physician should also be alert to clinical signs of impending herniation, including alterations in the respiratory pattern (e.g., hyperventilation; Cheyne-Stokes respirations, ataxic respirations, respiratory arrest), abnormalities of pupil size and reactivity, loss of brainstem reflexes, and decorticate or decerebrate posturing. If any of these signs are present or the child is so ill that the lumbar puncture might induce cardiorespiratory arrest, blood cultures should be drawn and supportive care, including antibiotics, should be initiated. Once the patient has stabilized, it may be possible to perform a lumbar puncture safely.

Normal CSF contains up to 5/mm³ white blood cells (WBCs), and a newborn can have as many as 15/mm³. Polymorphonuclear (PMN) cells are always abnormal in a child, but 1-2/mm³ may be present in a normal neonate. An elevated PMN count suggests bacterial meningitis or the early phase of aseptic meningitis (Chapter 595). CSF lymphocytosis can be seen in aseptic, tuberculous, or fungal meningitis; demyelinating diseases; brain or spinal cord tumor; immunologic disorders, including collagen vascular diseases; and chemical irritation (following myelogram, intrathecal methotrexate).

Normal CSF contains no red blood cells (RBCs); thus, their presence indicates a traumatic tap or a subarachnoid hemorrhage. Progressive clearing of the blood between the first and last samples indicates a traumatic tap. Bloody CSF should be centrifuged immediately. A clear supernatant is consistent with a bloody tap, whereas xanthochromia (yellow color that results from the degradation of hemoglobin) suggests a subarachnoid hemorrhage. Xanthochromia may be absent in bleeds <12 hr old, particularly when laboratories rely on visual inspection rather than spectroscopy. Xanthochromia can also occur in the setting of hyperbilirubinemia, carotenemia, and markedly elevated CSF protein.

The normal CSF protein is 10-40 mg/dL in a child and as high as 120 mg/dL in a neonate. The CSF protein falls to the normal childhood range by 3 mo of age. The CSF protein may be elevated in many processes, including infectious, immunologic, vascular, and degenerative diseases, as well as tumors of the brain and spinal cord. With a traumatic tap, the CSF protein is increased by ∼1 mg/dL for every 1,000 RBCs/mm³. Elevation of CSF immunoglobulin G (IgG), which normally represents ∼10% of the total protein, is observed in subacute sclerosing panencephalitis, in postinfectious encephalomyelitis, and in some cases of multiple sclerosis. If the diagnosis of multiple sclerosis is suspected, the CSF should be tested for the presence of oligoclonal bands.

The CSF glucose content is about 60% of the blood glucose in a healthy child. To prevent a spuriously elevated blood:CSF glucose ratio in a case of suspected meningitis, it is advisable to collect the blood glucose before the lumbar puncture when the child is relatively calm. Hypoglycorrhachia is found in association with diffuse meningeal disease, particularly bacterial and tubercular meningitis. Widespread neoplastic involvement of the meninges, subarachnoid hemorrhage, fungal meningitis, and, occasionally, aseptic meningitis can produce low CSF glucose as well.

A Gram stain of the CSF is essential if there is a suspicion for bacterial meningitis; an acid-fast stain and India ink preparation can be used to assess for tuberculous and fungal meningitis, respectively. CSF is then plated on different culture media depending on the suspected pathogen. When indicated by the clinical presentation, it can also be helpful to assess for the presence of specific antigens (e.g., latex agglutination for Neisseria meningitidis, Haemophilus influenzae type b, or Streptococcus pneumoniae) or to obtain antibody or PCR studies (e.g., HSV-1 and -2, West Nile virus, enteroviruses). In noninfectious cases, levels of CSF metabolites, such as lactate, amino acids, and enolase, can provide clues to the underlying metabolic disease.

Neuroradiologic Procedures

Skull roentgenograms have limited diagnostic utility. They can demonstrate fractures, bony defects, intracranial calcifications, or indirect evidence of increased ICP. Acutely increased ICP causes separation of the sutures, whereas chronically increased ICP is associated with erosion of the posterior clinoid processes, enlargement of the sella turcica, and increased convolutional markings.

Cranial ultrasonography is the imaging method of choice for detecting intracranial hemorrhage, periventricular leukomalacia, and hydrocephalus in infants with patent anterior fontanels. Ultrasound is less sensitive than either CT or MRI for detecting hypoxic-ischemic injury, but the use of color Doppler or power Doppler sonography, both of which show changes in regional cerebral blood flow, improve its sensitivity. In general, ultrasound is not a useful technique in older children, though it can be helpful intraoperatively when placing shunts, locating small tumors, and performing needle biopsies.

CT is a valuable diagnostic tool in the evaluation of many neurologic emergencies, as well as some nonemergent conditions. It is a noninvasive, rapid procedure that can usually be performed without sedation. CT scans use conventional x-ray techniques, meaning that they produce ionizing radiation. Because children <10 yr of age are several times more sensitive to radiation than adults, it is important to consider the whether imaging is actually indicated and, if so, whether an ultrasound or MRI might be a more appropriate study. In the emergency setting, a noncontrast CT scan can demonstrate skull fractures, pneumocephalus, intracranial hemorrhages, hydrocephalus, and impending herniation. If the noncontrast scan reveals an abnormality and an MRI cannot be performed in a timely fashion, nonionic contrast should be used to highlight areas of breakdown in the blood-brain barrier (e.g., abscesses, tumors) and/or collections of abnormal blood vessels (e.g., arteriovenous malformations). CT is less useful for diagnosing acute infarcts in children, because radiographic changes might not be apparent for up to 24 hr. Some subtle signs of early (<24 hr) infarction include sulcal effacement, blurring of the gray-white junction, and the hyperdense middle cerebral artery (MCA) sign (increased attenuation in the MCA that is often associated with thrombosis). In the routine setting, CT imaging can be used to demonstrate intracranial calcifications or, with the addition of three-dimensional reformatting, to evaluate patients with craniofacial abnormalities or craniosynostosis. Although other pathologic processes may be visible on CT scan, MR is generally preferred because it provides a more-detailed view of the anatomy without exposure to ionizing radiation (Table 584-3).

Table 584-3 PREFERRED IMAGING PROCEDURES IN NEUROLOGIC DISEASES

ISCHEMIC INFARCTION* OR TRANSIENT ISCHEMIC ATTACK

CT or CTA (head and neck) ± CT perfusion for patients who are unstable

Otherwise, MRI or MRA (head and neck) with diffusion-weighted images for strokes 1-24 hr old

If the examination findings localize to the anterior circulation, carotid ultrasound should be performed rather than neck CTA or MRA

Obtain an MRV if the infarct does not follow an arterial distribution

CT or MRI can detect infarcts >24 hr old, though MRI is generally preferred to avoid exposure to ionizing radiation.

INTRAPARENCHYMAL HEMORRHAGE

CT if <24 hr; MRI if >24 hr

MRI or MRA to assess for underlying vascular malformation, tumor, etc.

Catheter angiography if MRA is nondiagnostic

ARTERIOVENOUS MALFORMATION

CT for acute hemorrhage; MRI or MRA as early as possible

Catheter angiography if noninvasive imaging is nondiagnostic

CEREBRAL ANEURYSM

CT for acute subarachnoid hemorrhage

CTA or catheter angiography to identify the aneurysm

TCD to detect vasospasm

HYPOXIC-ISCHEMIC BRAIN INJURY

Ultrasound in infants

If ultrasound is negative or there is a discrepancy between the clinical course and the sonogram, obtain an MRI

In older children, CT if unstable; otherwise, MRI

MRS is more sensitive than MRI on day 1 of life and can be useful for prognostication in older children

METABOLIC DISORDERS

MRI, particularly T2-weighted and FLAIR images

Diffusion-weighted images may be useful in distinguishing acute and chronic changes

MRS, SPECT, and PET may be useful in certain disorders.

HYDROCEPHALUS

Ultrasound (in infants), CT, or MR for diagnosis of communicating hydrocephalus

MR for diagnosis of noncommunicating hydrocephalus

Ultrasound (in infants) or CT to follow ventricular size in response to treatment

HEADACHE

CT or MRI if a structural disorder is suspected

HEAD TRAUMA

CT initially

MRI after initial assessment and treatment

EPILEPSY

MRI

PET

SPECT

BRAIN TUMOR

MRI without and with contrast

MULTIPLE SCLEROSIS

MRI without and with contrast

Obtain sagittal FLAIR images

MENINGITIS OR ENCEPHALITIS

CT without and with contrast before lumbar puncture if there are signs of increased ICP on examination

MRI without and with contrast after initial assessment and treatment for patients with complicated meningitis or encephalitis

BRAIN ABSCESS

MRI without and with contrast

Diffusion-weighted images and MRS can help to differentiate abscess from necrotic tumor

If the patient is unstable, CT without and with contrast followed by MRI without and with contrast when feasible.

MOVEMENT DISORDERS

MRI

PET

CTA, computed tomographic angiography; FLAIR, fluid-attenuated inversion recovery; ICP, intracranial pressure; MRA, magnetic resonance angiography; MRS, magnetic resonance spectroscopy; MRV, magnetic resonance venography; PET, positron emission tomography; SPECT, single-photon emission computed tomography; TCD, transcranial Doppler ultrasonography.

* Choice of studies differs from that in the adult population because tissue plasminogen activator (tPA) is not approved for use in children <18 yr of age.

CT angiography (CTA) is a useful tool for visualizing vascular structures and is accomplished by administering a tight bolus of iodinated contrast through a large-bore intravenous catheter and then acquiring CT images as the contrast passes through the arteries.

Magnetic resonance imaging (MRI) is a noninvasive procedure that is well suited for detecting a variety of abnormalities, including those of the posterior fossa and spinal cord. MR scans are highly susceptible to patient motion artifact; therefore, most children <8 yr require sedation to ensure an adequate study. Because the American Academy of Pediatrics recommends that infants be kept NPO for ≥4 hr and older children for ≥6 hr before deep sedation, it is often difficult to obtain an MRI on an infant or young child in the acute setting. MRI can be used to evaluate for congenital or acquired brain lesions, migrational defects, dysmyelination or demyelination, post-traumatic gliosis, neoplasms, cerebral edema, and acute stroke (see Table 584-3). Paramagnetic MR contrast agents (e.g., gadolinium-DTPA) are efficacious in identifying areas of disruption in the blood-brain barrier, such as those occurring in primary and metastatic brain tumors, meningitis, cerebritis, abscesses, and active demyelination. MR angiography (MRA) and MR venography (MRV) provide detailed images of major intracranial vasculature structures and assist in the diagnosis of conditions such as stroke, vascular malformations, and cerebral venous sinus thrombosis. MRA is the procedure of choice for infants and young children owing to the lack of ionizing radiation and contrast; however, CTA may be preferable in older children because it is faster and can eliminate the need for sedation.

Functional MRI (fMRI) is a noninvasive technique used to map neuronal activity during specific cognitive states and/or sensorimotor functions. Data are usually based on blood oxygenation, though they can also be based on local cerebral blood volume or flow. Functional MRI is useful for presurgical localization of critical brain functions and has several advantages over other functional imaging techniques. Specifically, fMRI produces high-resolution images without exposure to ionizing radiation or contrast, and it allows coregistration of functional and structural images.

Proton MR spectroscopy (MRS) is a molecular imaging technique in which the unique neurochemical profile of a preselected brain region is displayed in the form of a spectrum. Many metabolites can be detected, the most common of which are N-acetylaspartate (NAA), creatine and phosphocreatine, choline, myoinositol, and lactate. Changes in the spectral pattern of a given area can yield clues to the underlying pathology, making MRS useful in the diagnosis of inborn errors of metabolism as well as the preoperative and post-therapeutic assessment of intracranial tumors. MRS can also detect areas of cortical dysplasia in patients with epilepsy, because these patients have low NAA:creatine ratios. Finally, MRS may be useful in detecting hypoxic-ischemic injury in newborns in the first day of life, because the lactate peak enlarges and the NAA peak diminishes before MRI sequences become abnormal.

Catheter angiography is the gold standard for diagnosing vascular disorders of the CNS, such as arteriovenous malformations, aneurysms, arterial occlusions, and vasculitis. A 4-vessel study is accomplished by introducing a catheter into the femoral artery and then injecting contrast media into each of the internal carotid and vertebral arteries. Because catheter angiography is invasive and requires general anesthesia, it is typically reserved for treatment planning of endovascular or open procedures and for cases in which noninvasive imaging results are not diagnostic.

Positron emission tomography (PET) provides unique information on brain metabolism and perfusion by measuring blood flow, oxygen uptake, and/or glucose consumption. PET is an expensive technique that is gaining a following in some pediatric centers, particularly those with active epilepsy surgery programs. Single-photon emission CT (SPECT) using ^99mTc hexamethyl propylenamine oxime (Tc 99m-HMPAO) is a sensitive and inexpensive technique to study regional cerebral blood flow. SPECT is particularly useful in assessing for vasculitis, herpes encephalitis, dysplastic cortex, and recurrent brain tumors.