Nursing role in the recognition of neurologic complications of critical illness

The recognition of new neurologic deficit(s) relies on the ability of the medical team to recognize changes in the neurologic exam which occur in approximately 30% of children during their ICU stay. Nurses play a critical role in this process with their frequent physical examinations and attention to bedside monitors. Interventions to treat or attenuate neurologic insults—whether seizures, ischemia, or increasing intracranial pressure (ICP)—are more likely to be successful if initiated early in the process of injury. This means that effective neurologic monitoring in the PICU does not rely solely on the availability of an intensivist, neurologist, electroencephalography (EEG), or neuroimaging. Standardized ICU nursing neurologic assessments using a modification of the Glasgow Coma Scale (GCS) score enables crude but reliable detection of neurologic decline.

Anticipatory planning for new neurologic deficits

The ability to recognize changes in the neurologic exam is an essential component of brain-directed critical care for children. Reliance on technology alone is insufficient. Management should include anticipation of specific changes in the patient’s exam, an understanding of the pathophysiology causing that change, and a predetermined plan to intervene to address that mechanism. Representative examples include new irritability in the patient with acute liver failure (ALF), right leg weakness in a patient with right anterior cerebral artery stroke, or hypophonia in the patient with acute inflammatory demyelinating polyneuropathy. Each example (progression of hepatic encephalopathy; compression of the left anterior cerebral artery caused by increased edema in the right frontal lobe; progression to involve bulbar weakness) requires an escalation in care and cannot currently be identified by bedside monitors other than an examiner with an understanding of the disease process and the implications of these findings.

An improving exam despite deterioration in other modalities—such as EEG, transcranial Doppler (TCD), ICP, or neuroimaging—may change the treatment plan. Similarly, deterioration in the neurologic exam may occur without changes in these other measures. The ability to detect and react to such change requires a consensus on the admission neurologic exam, consensus on criteria for “decline” or “improvement” for each specific patient, and anticipatory planning for management of changes in exam. The examiner should first discuss the neurologic findings with the bedside nurse and other members of the medical team. If possible, abnormal findings should be demonstrated to the members of the team. There should be a consensus on the key findings and the approach to be taken for evaluation and management if the neurologic exam changes. The improvement in outcome for children with severe TBI associated with introduction of a multidisciplinary care team and adherence to management guidelines suggests that an emphasis on consistent care following established protocols can improve outcome without the need for additional technology (see Chapter 118 ).

History and assessment of risk factors

For children in the PICU, the medical history may provide essential information about the mechanisms and timing of neurologic insult. This information is needed for the interpretation of the neurologic exam and assessment of potential mechanisms of neurologic injury. These data are then used to assess the risk for progression of neurologic injury, to prioritize therapeutic interventions, and to determine the need for and timing of additional evaluations, including imaging, EEG, and laboratory studies. In many cases, decisions to treat (or not treat) a neurologic injury in the PICU must be empiric and based on a careful assessment of risk factors, potential mechanisms of injury, and weighing of the risks and benefits of such intervention. For example, the approach to evaluation of altered mental status presenting to the PICU will be different for children with an established complex partial seizure disorder, sickle cell disease, or a stem cell transplant recipient on immunosuppressive drugs. Before examining the patient, knowledge of salient details of the medical history allows the examiner to begin to formulate a diagnostic approach and to prepare the early steps in management. The patient with a history of epilepsy in the example presented earlier would likely require an emergent EEG to rule out nonconvulsive seizures, while the patient with sickle cell disease and risk factors of vascular injury with the same symptoms may require an imaging study and the immunosuppressed patient a lumbar puncture. The presenting neurologic symptoms may be similar, but the history dictates the assessment based on the likely mechanisms producing the deficits found on neurologic examination.

Iatrogenic complications of pharmacotherapy

A review of medications should be part of the neurologic assessment of any patient with new neurologic symptoms. The initial assessment of the patient should include attention to medications that cross the blood-brain barrier or that may interfere with the renal or hepatic metabolism of centrally active drugs. In patients in renal or liver failure, or requiring dialysis, the side effects of a centrally acting drug must be considered in the differential diagnosis for any neurologic symptom. This may occur even in the presence of “normal” doses of drugs or levels of anticonvulsants, as off-target drug toxicities may be due to metabolites, not the drug itself. Common examples in the PICU include immunophilin-associated seizures, encephalopathy and hypertension, oculogyric crisis, drug-induced delirium, and prolonged sedation and paralysis following neuromuscular blockade. In many cases, the attribution of the symptoms to a drug side effect (excess level, too rapid withdrawal, idiosyncratic reaction, impairment of clearance) will be a diagnosis of exclusion. Nevertheless, a review of medications and recent changes should be a routine component of the neurologic assessment.

Vital signs

Vital signs are an essential component of the neurologic exam, including recording of temperature. The prevention of hyperthermia may significantly reduce secondary neurologic injury. The results of randomized controlled trials of therapeutic hypothermia in children for severe TBI ^, and out-of-hospital cardiac arrest ^, suggest that early hypothermia, irrespective of ICP, does not improve outcome and, in the case of TBI, may increase the risk of death. ^{, ,} Despite this, the prevention of hyperthermia can be regarded as a safe and effective intervention. Therefore, as a general principal for ICU patients with known or suspected central nervous system (CNS) injury, fever should be aggressively avoided.

In contrast to adults, there are limited data on the optimum ranges for blood pressure, ICP, and cerebral perfusion pressure (CPP) for children. In adults, there are goal-directed protocols aimed at improving outcome following TBI. The targets of ICP less than 20 mm Hg and CPP above 60 mm Hg are based on a number of studies. Data for children with TBI are limited. ^, Guidelines suggest an ICP threshold of 20 mm Hg for all ages and a CPP threshold of 40 to 65 mm Hg as an “age-related continuum.” Although children with TBI younger than 2 years of age have a high mortality rate compared with older children, no thresholds for ICP or CPP have been established for this age group. Accordingly, blood pressure, temperature, and oxygenation must be interpreted in the context of the underlying neurologic insult or risk for further injury. Hyperthermia with the attendant increased cerebral metabolic demand should be treated aggressively whatever the primary injury.

General physical exam

An accurate head circumference is essential in infants and young children and should be documented on admission. This may serve as a baseline for following the development of hydrocephalus in the at-risk infant. In older children, an abnormal (large or small) head circumference may be a previously overlooked sign of pathology. In the infant, the open fontanelle should be palpated and the findings on the exam agreed on in a quiet, resting state. A bulging fontanelle is an important finding of meningeal irritation or increased ICP. Examination of skin for the cardinal features of the phakomatoses may identify café-au-lait spots characteristic of neurofibromatosis, or shagreen patches, hypopigmented macules and angiomyofibromas characteristic of tuberous sclerosis. The physical findings associated with inflicted trauma may be subtle, including unusual patterns of bruising, blood in the oropharynx, and burn or belt marks (see Chapter 121 ).

Importance of observation in the neurologic exam

The elements of the neurologic examination in the PICU comprise the same features of the neurologic exam for noncritically ill patients and are detailed in eTable 60.1 . The assessment of mental status, cranial nerves, motor function, reflexes, sensation, and cerebellar function must be adapted to each patient, but the structure of the neurologic exam in the PICU is no different from the outpatient examination. If possible, sedating drugs and paralytic agents should be reduced prior to the exam. If this is not feasible, the exam must be interpreted in the context of these confounding factors.

The assessment of mental status begins with observation. The examiner should first confirm the drugs used for sedation, if any, and recent changes in dosing. It is not possible to give precise dose ranges for typical sedating agents associated with a mental status exam. For commonly used agents in the PICU (benzodiazepines, opiates, dexmedetomidine), the effects of the drug on arousal and responsiveness will vary with the age of the patient, duration of exposure, nature of the neurologic insult, effect of other drugs on metabolism, and genetically determined ability to clear these drugs. This complex set of interactions underscores the importance of experience in the examination of these patients to determine what is an acceptable level of arousal and the need for serial neurologic examinations.

The observations of the nurses and parents should first be solicited. The examiner should enquire about evidence for changes in arousal or awareness, such as spontaneous eye opening, evidence of a sleep-wake cycle, change in activity, or response to interventions such as suctioning. If family members are present, their observations of response to their presence or voice are important and may represent the first signs of awareness on the part of the patient. It is appropriate to have a family member carry out part of the exam, asking the patient to follow commands, as young children are more likely to respond to their family in that circumstance than to a stranger.

The pattern of breathing rate and rhythm should be observed. Specific patterns may help localize the site of neurologic dysfunction but not the mechanism involved (see eTable 60.1 ). The crescendo-decrescendo pattern alternating with periods of apnea, characteristic of Cheyne-Stokes respiration, may be due to dysfunction either of the cerebral hemispheres, thalamus, or hypothalamus with preserved brainstem function, but can also be found in patients with congestive heart failure or primary respiratory disease. Similarly, the sustained, deep breathing pattern of central neurogenic hyperventilation may be due to either structural injury to the midbrain, sepsis, pulmonary disease, or compensated metabolic acidosis.

The conventional neurologic examination proceeds from mental status, cranial nerves, motor (bulk, tone, and strength), reflexes, and sensation to cerebellar exam and gait. In children, in the PICU in particular, the exam is often best performed out of sequence. It is easier to assess tone and reflexes in the asleep, relaxed patient before waking the patient up to assess mental status. While the exam is discussed in the standard order later, it may be more informative to begin the hands-on part of the exam with assessment of tone and reflexes. Once awake and agitated, subtle asymmetries of tone and reflexes, which may be key findings of the exam, may be obscured.

First, the child is observed. The state of arousal (awake, asleep), and responsiveness, (interactive, verbal, nonresponsive), position (tone and asymmetry of limb position), movement (purposeful, spontaneous, dystonic, choreic, asymmetry of movement) can all be reliably assessed by observation. In a nonintubated, nonsedated patient, the examiner may proceed directly with a standard mental status exam adjusted for age. In the young child who is able to cooperate, the specific cognitive and language skills expected for age can be assessed ( eTable 60.2 ).

Assessment of level of consciousness and mental status

For children with depressed consciousness, the precise stimulus required to elicit a response and the nature of this response should be specified. It is not helpful to describe the patient as “lethargic” or “obtunded.” First, the child is called by name to determine whether there is a response. If this is not effective, the examiner may ask a family member to speak to the child. Next, the stimulus is increased. It is most helpful to describe the patient’s response to specific stimuli and to use the same stimuli for serial examinations. The GCS score, while of limited use in preverbal children ( Table 60.3 ) is a rapid, quantitative measure. If the patient’s eyes open to voice, the response to commands is tested next. This is discussed in more detail later, but the commands should be increased in complexity in one to two or three steps. If there is no response to voice, a painful stimulus is applied. Note that in patients with sensory deficits due to neuropathy, spinal cord, or CNS lesions or with focal limb weakness, the extremity or dermatome selected for testing should have intact sensory or motor function. In the sedated or severely impaired patient, the response may comprise only increase in heart rate. It is important that the stimulus and the specific response, rather than vague descriptors (“lethargic, drowsy, sleepy”) are documented, as this will be more helpful in assessing serial examinations. The infusion rate of sedating drugs or recent administration of sedating drugs should be documented with this exam.

The assessment of higher cognitive function and the early recognition of compromise of cognitive function is a challenge at any time when evaluating young children. In the ICU—where the additional confounding factors of sedation, other organ dysfunction, sleep disturbance, and anxiety must be accounted for—this evaluation is somewhat more challenging. Of course, this is usually the most important component of the exam, and the technologies used for neurologic monitoring in the ICU all serve the same goal of the bedside exam, of detecting compromised cerebral function to enable directed therapeutic intervention.

In the older, awake child, a complete mental status exam can be performed. This must be adjusted for age (see eTable 60.2 ) but should include assessment of language (fluency and comprehension) and the ability to name, repeat, write, read, and respond to written commands. Simple mathematical problems should be adjusted to the child’s age-dependent ability. Praxis can be assessed quickly even in the PICU by demonstration of learned behaviors even in the young child (brush your teeth, brush your hair). Other components of the mental status exam—including memory, fund of knowledge, and reasoning—can be assessed by holding a conversation with the patient.

Most importantly, the examiner needs to have an appropriate index of suspicion for these subtle neurologic deficits of attention, memory, praxis, language comprehension, and reading comprehension, which may be the early signs of new neurologic injury. This is particularly true for patients with metabolic (often liver or renal failure), infectious or iatrogenic (sedation, immunophilins) risk factors for CNS dysfunction and may easily be missed if not specifically investigated. Again, serial examinations by examiners familiar with the patient’s exam while sedated are the key to reliable detection of new deficits of higher cortical function in the ICU.

Fundoscopic examination

Examination of the fundi may reveal hemorrhages or papilledema. Hemorrhages indicate either acute subarachnoid or subdural hemorrhage, cranial trauma from a direct blow or shaking injury, or malignant hypertension. Papilledema indicates raised ICP from any cause. Usually, papilledema develops hours after the onset of the elevated ICP. Acute severe increases, however, as with subarachnoid hemorrhage (SAH) from a ruptured saccular aneurysm, can result in almost instantaneous papilledema. Sometimes, papilledema never develops despite prolonged severe elevations of ICP.

Cranial nerve examination

The pupillary reaction to light is abolished only by structural damage to the midbrain or third cranial nerve. Loss of the pupillary reflexes is always an ominous finding. Preservation of pupillary reflexes in the presence of deep coma suggests a metabolic-toxic cause. The interpretation of the patterns of pupil reactivity is summarized in eTable 60.1 .

Measurement of pupil size and light response is a quantifiable measure of brainstem and autonomic nervous system function. Absence of pupil reactivity is a poor prognostic sign after TBI or cardiac arrest. To provide a very precise measure of pupil size and speed of contraction and relaxation, a portable handheld device (pupillometer) illuminates the eye with an infrared light (850 nm) while acquiring images for analysis. The data (pupil size, rate of contraction and relaxation) are stored on the device and can be downloaded to a computer. In a study of healthy volunteers and adult patients with TBI and ICP monitors in place, a discrepancy in pupil size of more than 0.5 mm was associated with ICP above 20 mm Hg. Using the Neurological Pupil Index (algorithmic composite of measures of pupillary reactivity), a single-center study of 28 children with ICP monitored, identified an inverse relationship between increases in ICP and decreases in pupil reactivity. One of the limitations in the use of other neuromonitoring data in children is the lack of data on age and gender differences. These normative data are now available for children and show greater constriction velocities and percentages in males.

Eye movements are assessed first by observation and then elicited in the patient with depressed mental status with the doll’s head maneuver (oculocephalic response) or cold caloric stimulation (oculovestibular response; see eTable 60.1 ). In general, coma produced by metabolic dysfunction is initially associated with roving, dysconjugate movement and may progress to the cessation of movement. Cold caloric stimulation will produce nystagmus with the rapid phase contralateral to the ear that has been stimulated. This rapid phase is the equivalent of saccadic eye movements and indicates intact functioning of the cerebral cortex. The ears are irrigated separately several minutes apart. In comatose patients, the fast “corrective” phase of nystagmus is lost, and the eyes are tonically deflected to the side irrigated with cold water or away from the side irrigated with warm water. These vestibulo-ocular responses are lost or disrupted in brainstem lesions. Versive eye deviation is a common finding suspicious for seizures. In this case, the eye deviation is contralateral to the hemisphere with the ictal focus. Alternatively, stroke in the ipsilateral hemisphere may also produce versive eye deviation toward the side of the stroke.

An abnormal corneal reflex may indicate either fifth nerve afferent disease (ipsilateral stimulation results in neither a direct nor consensual eye blink) or seventh nerve efferent disease (ipsilateral stimulation results in a brisk consensual but no direct response).

Unilateral weakness of eye closure, forehead movement, and mouth movement indicates peripheral seventh cranial nerve palsy, whereas failure to move only the mouth with preservation of upper face movements indicates a central corticospinal tract lesion rostral to the pons. Facial weakness may be noted during grimacing while responses to painful stimuli are evaluated. Voluntary pharyngeal and laryngeal control is tested by asking the patient to speak and say “Ah.” In the absence of voluntary movement, a hypoactive gag indicates medullary or vagal dysfunction and a hyperactive gag indicates interruption of corticospinal inhibition to the medulla. In a comatose patient or one whose consciousness is rapidly sinking, one must quickly determine whether the patient is experiencing raised ICP. Papilledema or third cranial nerve palsy is strong evidence of elevated ICP.

Approach to the motor exam

In the comatose or obtunded patient, asymmetry of resting tone and spontaneous movement are simple signs of paresis, which can be detected by first observing the patient. In children, this is particularly important as a subtle weakness may not be apparent once the child is more awake and uncooperative. An externally rotated, partly flexed abducted leg may indicate an ipsilateral hemiparesis due to an upper motor neuron lesion. Facial weakness should also be first evaluated by observation before attempting formal testing (often impossible or unreliable in young, anxious, or sedated children). Signs of facial weakness at rest may include a widened palpebral fissure, diminished nasolabial fold, or flattened corner of the mouth. Next, the examiner should attend to the initial movement of the face, either spontaneously or in response to a noxious stimulus. Subtle weakness may be apparent only in a delayed response to these stimuli.

Weakness may be due to lesions at any level of the neuraxis. The goal of the examination of the weak patient is to identify the pattern of weakness as coming from the upper or lower motor neuron and thereby identify the most likely mechanisms. The upper motor neuron (UMN) comprises the corticospinal tract and its neurons. The corticospinal tract begins in the motor and premotor cortex anterior to the central sulcus, descends through the central white matter of the cerebral hemispheres, decussates in the lower medulla, and terminates on the anterior horn cells or interneurons closely associated with the anterior horn cells. The innervation of muscles that control movement of the jaw, pharynx, larynx, upper half of the face, neck, thorax, and abdomen is derived from both cerebral hemispheres. Consequently, unilateral cerebral lesions lead only to weakness of the contralateral limbs and lower face. The lower motor neuron (LMN) is composed of the anterior horn cells, motor roots, peripheral nerves, pre- and postsynaptic components of the neuromuscular junction, and the muscles receiving this innervation. Stereotyped reflex movements may be present despite spinal cord injury because these responses are coordinated by local spinal reflexes below the level of the lesion. In contrast, movement is absent following injury to the LMN because it is the final common pathway producing muscle activity. If the patient is not able to cooperate with a complete exam testing all muscle groups, in addition to observing for asymmetric posture, the observation of facial movement, testing for neck flexion, grip strength, pronator drift, and counting the duration (up to 10 seconds) that the patient can maintain a straight leg raise are efficient means of assessment.

A number of key findings on the pattern of weakness can distinguish between UMN and LMN injury, chronic and acute injury, and neuropathy and neuromuscular disorders—including ICU-acquired paresis, myasthenia gravis, and Guillain-Barré syndrome (GBS). Acute UMN lesions result in a hypotonic or flaccid pattern of weakness and may be associated with the Babinski sign in the legs. In contrast, chronic UMN injury results in a hypertonic limb with associated hyperreflexia. An LMN pattern of weakness is more likely to be associated with a decrease in muscle tone and bulk and decreased or absent reflexes. In general, proximal weakness suggests a myopathic process, while a distal pattern of weakness suggests a neuropathy.

The precise incidence of ICU-acquired weakness (ICU-AW) is uncertain in children. In a study of the incidence of weakness in 830 critically ill children, only 1.7% had generalized weakness. This is lower than the incidence of ICU-AW in adults. Extensive data from adult studies have identified ICU-AW—manifesting as a variable combination of weakness, muscle atrophy, hyporeflexia, and sensory deficits—as a common cause of failure of extubation with a high incidence of long-term morbidity. The contribution of the risk factors in adults (sepsis, hyperosmolarity, neuromuscular blockage, prolonged ventilation, and corticosteroids) to pediatric ICU-AW is not known. ICU-AW is primarily a clinical diagnosis, although nerve conduction and electromyography studies may be confirmatory. Management, particularly in children, is empiric but this disorder should be suspected in any critically ill child with diminished reflexes and new weakness or requiring reintubation without identification of other causes.

The two most common neuromuscular disorders that require intensive care in children are GBS and myasthenia gravis (MG; discussed in Chapter 68 ). For patients with known MG admitted to the ICU in crisis, it is essential to note the timing of anticholinesterase treatment and the timing of the neurologic exam in relation to each evaluation of strength. In general, testing should be performed at the nadir of weakness prior to each treatment. This is the only reliable way in which a decline in strength can be detected in these patients. In contrast to GBS, the progression to respiratory failure in MG may be arrested by noninvasive ventilator support with bilevel positive airway pressure (BiPAP). Muscle fatigue in MG is reversible with a combination of anticholinesterase treatment and BiPAP, which may prevent the need for intubation. In the case of GBS, patients who cannot walk unaided should be treated with intravenous immunoglobulin (IVIG). Neither GBS nor MG should alter pupil reactivity. In this case, if the pupils are slow to react or do not react at all in a weak infant, the diagnosis of botulism should be considered.

Posturing due to increased ICP should be distinguished from abnormal movements, including chorea and dystonia. Decorticate posturing consists of adduction and stiff extension of the legs, flexion and supination of the arms, and fisting of the hands. This occurs when the midbrain and red nucleus control body posture without inhibition by the diencephalon, basal ganglia, and cerebral cortex. Decerebrate posturing consists of stiff extension of legs, arms, trunk, and head with hyperpronation of lower arms and plantar flexion of the feet. This indicates pontine and vestibular nucleus control of posture without inhibition from more rostral structures. Lesions below the level of vestibular nuclei lead to flaccidity and abolition of all postures and movements. These movements should be distinguished from dystonia or chorea, which may be seen as side effects of medications, the sequelae of basal ganglia injury, or metabolic or neurotransmitter disorders.

Reflexes

Reflexes may be absent in critically ill children, wax and wane during the course of the day, or be elicited by some examiners but not others. This variability can be diminished by performing the exam when the child is in a quiet, resting state and by focusing on key reflexes. In general, the purpose of the exam is to determine whether there are changes in intensity (a reduction or increase), symmetry, or development of pathologic reflexes.

At a minimum, reflexes to be tested include the tendon jerks in the upper (if available) and lower extremities and the Babinski sign (dorsiflexion of the great toe, sometimes accompanied by fanning of the toes in response to stimulation of the lateral plantar aspect of the foot) as the cardinal screening test for intact functioning of the pyramidal system. If an extensor plantar reflex is present, this reflects injury along the corticospinal tract. The rest of the neurologic exam is used to identify the level at which this injury is present. A number of other techniques (Chaddock, Oppenheim, Gordon, Strumpell, Moniz, Gonda-Allen) may be used to elicit the extensor response, but the Babinski sign is the most reliable.

In patients with decreased or altered mental status, frontal lobe release signs may be tested. These signs reflect diffuse cerebral dysfunction or injury. The grasp reflex involves the patient reflexively gripping the examiner’s finger or hand as the palm is brushed. The palmomental reflex is elicited by scratching the thenar eminence and observing for twitching of ipsilateral lower jaw muscles. The snout reflex is elicited by tapping on the mouth and producing puckering of the lips. To elicit the rooting reflex, the mouth is lightly scratched, resulting in the patient turning to align the mouth with the finger. The glabellar reflex is elicited by tapping the forehead in the midline (this is done from above the head to not confuse the response with the reflex response to visual threat) and observing for repeated blinking each time the forehead above the bridge of the nose is tapped.

Cerebellar function and gait evaluation

Normal coordination requires that both muscle strength and proprioception are intact. The interpretation of the cerebellar exam testing should be done with these systems already evaluated. Abnormal eye movements—including dysmetria (overshoots of the target or a series of ratchet-like undershooting movements to reach the target when the eyes are rapidly brought from fixation on one object to another), gaze-evoked or downbeat nystagmus, or speech (slow, impaired prosody, distorted consonants or vowels, mutism)—may be the only observable manifestations of cerebellar dysfunction in a patient who is sedated or too weak to cooperate with the remainder of the exam. Truncal ataxia can be detected by sitting the patient up in the bed. If possible, gait should be evaluated and observed for a widened base and the ability to perform rapid turns while maintaining normal balance.

Sensory examination

Even in the alert patient, this component of the neurologic examination is the least reliable and the first to be discarded if necessary. Of the components of this exam, vibration and joint position sense are the most sensitive. In the sedated patient or patient with depressed level of consciousness, sensation testing may need to be limited to noting withdrawal or flexion of the stimulated limb or an increase in heart rate. In the cooperative patient, temperature sensation can be evaluated using a tuning fork, which should feel cool. The examiner should be particularly alert to detecting a level at which sensation (pain, temperature, light touch) is lost or diminished in patients with spinal cord injury, TBI (with unrecognized cord injury), inflammatory (transverse myelitis), or demyelinating disorders of childhood (acute disseminated encephalomyelitis [ADEM], multiple sclerosis), which may involve the spinal cord. In patients with cerebral injury, a lack of response to sensory testing should be distinguished from neglect.

Abnormal movements or altered sensorium in the child with static encephalopathy

This is a common issue in the PICU, often because of concern that the patient may be seizing, and may prompt obtaining additional imaging or EEGs since these children have primary neurologic disorders. A stepwise approach is helpful. A limited behavioral repertoire in these patients may mask subtle medical or surgical problems. For a neurologist, this evaluation should also present an opportunity to revisit the diagnosis of cerebral palsy or static encephalopathy, which may be obscuring a diagnosable (and perhaps treatable) disorder such as dopa-responsive dystonia. In such cases, in addition to (often instead of) monitoring for neurologic injury, evaluations should consider other etiologies, including pain from unrecognized trauma, hip subluxation, long-bone fractures, constipation, urinary infection or retention, volvulus, inguinal hernia, corneal abrasion, otitis media, dental pathology, gastric distension, or bowel adhesions. A systematic approach to evaluation of spells in these patients is essential in order to avoid missing these treatable medical conditions in patients with chronic neurologic disorders.

Distinguishing functional deficits from nonorganic pathology in the pediatric intensive care unit

Not all neurologic deficits in the PICU are organic. Conversion disorders also occur in critically ill patients or result in patients being admitted to the PICU. In the latter case, this is most often due to suspicion of nonepileptiform seizures. A number of features of the examination and history may help make this distinction ( Table 60.4 ). Typically, the eyes are open during a seizure. In one series, over 90% of cases with electrographically confirmed seizures occurred with eye opening. The eyes may look straight ahead, deviate to one side contralateral to the hemisphere from which the seizures originate, or exhibit only nystagmus. Seizures are typically a “positive” phenomenon and will have movement associated with them unless there has been injury to the corticospinal tracts, resulting in a paretic limb. Other features of the exam—or description of the spells, including stereotypy, crescendo-decrescendo behavior, and presence of automatisms—may help to distinguish ictal and nonictal behavior. Video EEG monitoring is the definitive method for distinguishing ictal from nonictal events.

Even in the PICU, the examiner should remember that functional deficits may be detectible; a number of motor signs may help identify the origin of functional symptoms. Given the complex pathophysiology of many critically ill patients and the multiple potential mechanisms of neurologic injury, the diagnosis of a functional neurologic deficit should be made only after a thorough evaluation for organic causes. There are a number of elements of the physical exam that may help distinguish between organic and functional neurologic deficits. An inconsistent examination may be the first clue, for example, the patient with apparent weakness during bedside strength testing who can change position during sleep or who can walk despite apparent paresis on bedside testing. These observations often can be very helpful in the assessment of children with weakness thought to be due to a neuromuscular disease. After first observing for inconsistency, the most useful test for functional weakness is the Hoover sign. This test relies on the principle that when flexing one’s hip the natural accompanying movement is to extend the contralateral hip. With the patient supine, the examiner places one hand on the weak leg and the other hand under the ankle of the strong leg. The patient is then asked to perform a straight leg raise of the healthy limb. In a functional pattern of weakness, the examiner will feel no downward pressure from the good leg since there is no effort being applied to raise the ostensibly weak leg. Other tests include the “arm drop,” in which a paretic or plegic arm is dropped over the patient’s face and exact splitting of sensory or vibration deficits in the midline. A number of functional gait disturbances are also characteristic, including a monoplegic dragging gait (the whole limb is dragged without the circumduction present in pyramidal hemiparesis), a “walking on ice” pattern, excessive slowness, or sudden buckling at the knees with recovery. Of these, none are definitively diagnostic of a functional pathology. Thus, in children in particular, they must be interpreted with caution. Importantly, functional and organic deficits may coexist.

Anti- N -methyl- d -aspartate receptor encephalitis is a class of disorder that may mimic psychiatric disorders such as depression, catatonia, or viral encephalitis. It has important complications, including nonconvulsive seizures and autonomic dysfunction requiring ICU care. This disorder is one of a family of antibody-associated inflammatory brain diseases in children. These patients may at first appear to have a functional exam before other characteristic features emerge, including a movement disorder, sleep disturbance, seizures, and cardiac arrhythmia. ^, Early recognition and initiation of immunosuppression with steroids, IVIG, or plasmapheresis is the key to improving long-term outcome.

Goals of the neurologic examination in the pediatric intensive care unit

At the conclusion of the neurologic examination in the ICU, the examiner should be able to identify the location(s) of neurologic dysfunction at the very least in terms of injury to gray (encephalopathy, seizures, neglect, aphasia) or white (weakness, spasticity) matter, posterior circulation (brainstem dysfunction, cranial nerve palsy with contralateral weakness), the presence of signs of increased ICP, spinal cord (sensory or motor level), peripheral nerve (decreased or absent reflexes), neuromuscular junction, or muscle. This should be established either as the baseline exam or compared with previous examinations and therefore assessed as progressing, improving, or stable. Next, the mechanism producing this injury should be assessed and ranked in order of likelihood. In general, this will involve either primary neurologic insult, such as TBI, stroke, CNS infection, neurodegenerative disease, autoimmune or parainfectious processes, or the complications of other common pediatric disorders requiring ICU care, including sepsis, congenital heart disease, liver failure, organ transplantation, diabetic ketoacidosis (DKA), renal disease and dialysis, status epilepticus, or iatrogenic complications of commonly used drugs such as immunophilins or intrathecal chemotherapy.

The goal of the examiner is to combine data from the history, presenting signs, and physical examination (which may need to involve only observing the patient) in order to develop a differential diagnosis for both the site of injury and mechanism. These mechanisms will involve one or more common etiologies, including vascular (ischemia, hemorrhage, large or small vessel, arterial or venous, artery-to-artery or cardioembolic); metabolic (either iatrogenic, often abnormalities of sodium, glucose or ammonia, or the first presentation of a metabolic disorder); autoimmune (CNS lupus, autoimmune encephalopathies and epilepsies); parainfectious (ADEM); iatrogenic (sedation, neuromuscular blockade, immunophilins); toxic (drugs of abuse, drug metabolite accumulation in liver, or renal failure); and infectious (systemic infection with CNS involvement, meningitis or encephalitis, reactivation of a latent CNS infection in the immunosuppressed patient).

Based on the postulated location of the insult, stability of the neurologic examination, mechanism of injury, and risk for progression of neurologic injury, the monitoring modalities can then be selected based on the need to either establish a diagnosis, monitor for secondary neurologic injury, or both.

Neuroimaging

Computed tomography (CT) and magnetic resonance imaging (MRI) each have specific advantages ( eTable 60.5 ) and should be selected for specific purposes (discussed in Chapter 61 ). CT can be performed quickly and is a sensitive means of detection of cerebral edema or intracranial hemorrhage. CT is relatively insensitive to acute ischemic injury and does not provide sufficient resolution in the posterior fossa, where lesions may be missed. Diagnostic CT scans should be performed first without contrast and then with contrast (if not contraindicated). White (hyperdense) lesions on the noncontrast study are either hemorrhage or calcification. In most patients in the PICU, these hyperdense areas represent hemorrhage. Contrast enhancement indicates either local breakdown of the blood-brain barrier or excess vascularity and is associated with neoplasms, infections, inflammatory lesions, and subacute stroke.

eTABLE 60.5

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