725CHAPTER 60 Neurologic Assessment and Monitoring 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[.]
CHAPTER 60 Neurologic Assessment and Monitoring 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 used43 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 725 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, longbone 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,44 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 TABLE Clinical Features of Seizures and Nonepileptic 60.4 Spells Seizures Nonepileptic spells Eyes Open Closed Automatisms Common Rare Stereotypical behavior Common Rare Onset is gradual Rare Common Waxing and waning course Rare Common Thrashing movements Rare Common 726 S E C T I O N V I Pediatric Critical Care: Neurologic 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.45 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.45 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.46–48 This disorder is one of a family of antibody-associated inflammatory brain diseases in children.49 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.50,51 Early recognition and initiation of immunosuppression with steroids, IVIG, or plasmapheresis is the key to improving longterm outcome.52 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 MRI stimulates tissue with a specific radiofrequency pulse, after which the tissue returns to its preexcited state by processes known as T1 or T2 relaxation Small infarcts, infections, inflammatory areas, and demyelinating plaques are much more readily detected on MRI than on CT In the T1 sequences, which measure T1 relaxation, cerebrospinal fluid (CSF) appears dark; in the T2 sequences, it appears bright T1 sequences are useful for anatomic evaluation (Fig 60.1A) T2 sequences are useful for evaluating for pathology, particularly for lesions with edema (Fig 60.1B) Fluid-attenuated inversion recovery (FLAIR) imaging uses T2weighted sequences and attenuates the CSF signal This makes normal CSF signal appear dark and draws greater attention to areas of pathology versus T2 alone (Fig 60.1C) For detection of ischemia, diffusion-weighted images (DWI) are more sensitive than CT scans in the detection of acute cytotoxic edema This sequence can identify acute ischemic strokes as bright lesions within minutes of their occurrence (Fig 60.1D) Bright lesions on DWI 726.e1 eTABLE Neuroimaging Advantages and Limitations 60.5 Plain CT MRI CT Angiogram MR Angiogram Conventional Angiogram Purpose Detection of edema or blood Higher anatomic resolution; DWI can detect early ischemic changes Evaluate large cerebral arteries Evaluate large cerebral arteries Gold standard Obtain if CTA or MRA negative and dissection or vasculitis suspected Advantage Fast, widely available DWI can detect acute ischemia Better detection of intracranial stenosis and occlusion than MRA Detects large vessel arteriopathy Most sensitive to small vessel disease, dissection, vasculitis Limitations May not detect acute ischemia; insensitive to posterior fossa lesions Less available on emergent basis; patient may need sedation Large radiation dose Not a measure of flow; not sensitive to small-vessel disease 1% risk of complication CT, Computed tomography; CTA, computed tomography angiography; DWI, diffusion-weighted imaging; MR, magnetic resonance; MRA, magnetic resonance angiography; MRI, magnetic resonance imaging CHAPTER 60 Neurologic Assessment and Monitoring A B C D E F 727 • Fig 60.1 Brain magnetic resonance imaging (MRI) sequences from a 2-year-old male with acute lym- phoblastic leukemia who developed rapid obtundation The etiology of his encephalopathy and MRI changes is unclear (A) T1 sagittal view shows narrowing of the aqueduct (B) Axial T2-weighted image shows prominent hyperintense cerebrospinal fluid (CSF) spaces consistent with hydrocephalus (C) Axial T2 fluid-attenuated inversion recovery image shows more clearly transependymal CSF flow and injury to the basal ganglia and thalamus, relative to the prior T2 image (D) Axial diffusion-weighted image showing hyperintensities of the basal ganglia and thalamus, which correspond with the hypointensities on the axial apparent diffusion coefficient map (E) (F) Axial susceptibility-weighted image shows linear hypointensities corresponding to blood vessels within the parenchyma indicate a restriction in the movement of water and thus an increased water content of that region The degree of water proton mobility is quantified by the apparent diffusion coefficient (ADC) On ADC maps, areas of restricted diffusion appear as hypointense (dark) (Fig 60.1E) The reason for early decline in ADC is thought to be cytotoxic edema as a result of cellular energy failure causing a loss of ion homeostasis and subsequent shift of water to the intracellular compartment Not all restricted diffusion is ischemic in origin and may instead be associated with inflammation (infection, demyelination) or metabolic derangement Gradient-recalled echo (GRE) sequences or the more sensitive susceptibility-weighted images are used for detection of blood products on MRI (Fig 60.1F) In these sequences, blood appears dark early (4–6 hours) after hemorrhage and remains dark in all later stages of hemorrhage Magnetic resonance angiography (MRA) and magnetic resonance venography (MRV) are used to detect vascular occlusions in large- and medium-sized vessels in the head and neck, cerebral aneurysms larger than mm and arterial dissection (detects the presence of methemoglobin in the false lumen within the vessel wall) If MRA or CT angiography (CTA) is negative and a dissection is suspected, a conventional angiogram should be obtained Similarly, if small vessel arteriopathy or vasculitis is suspected and MRA or CTA is negative, conventional angiography should also be obtained For traumatic diffuse axonal injury (DAI)—in particular, following TBI—diffusion tensor imaging (DTI) is the most sensitive technique for assessing the structural integrity of white matter and risk for long-term neurologic impairment.53 DAI is thought to be a major contributor to cognitive dysfunction ranging from cognitive difficulty to coma following TBI54,55 but is difficult to diagnose or characterize using clinical criteria alone The cellular mechanisms involved in the long-term sequelae of TBI in children lead to compromise of neuronal metabolism, perfusion, and 728 S E C T I O N V I Pediatric Critical Care: Neurologic axonal function, all components of the neurovascular bundle.56 Advances in imaging technology using DTI MRI have allowed early detection of DAI in patients following TBI and have linked cognitive disability in these patients to white matter signal changes.57 Increased sensitivity of DTI methods can now detect injury to white matter microstructure linked to postconcussive symptoms following mild TBI.58 Magnetic resonance spectroscopy (MRS) can show neuronal injury directly by detecting metabolites involved in secondary brain injury.59 In the acute phase of treatment in the ICU, the use of MRI to guide prognostication is limited by studies with small sample sizes, heterogenous cohorts, attrition bias in long-term outcome studies, and variable clinical outcome measures.60 Given the requirement for transport of the critically ill child, the increased duration of the scan and the availability of the scanner are important in the decision to obtain MRI (compared to CT) One approach is to streamline the use of MRI by only obtaining sequences specific to the insult being evaluated Thus, for suspected ischemia, only DWI and ADC sequences are obtained; for hemorrhage, GRE; hydrocephalus, MR of the ventricles; sinus thrombosis, MR venogram; dissection or large-vessel vasculitis, MR angiogram; metabolic disease, MR spectroscopy; and for cortical dysplasia in epilepsy patients, standard MRI This means that a patient admitted with suspected stroke can complete a study (MR ventricles and DWI/ADC) in a much shorter time window than is otherwise required and the most important initial question (presence or absence of ischemia) is addressed so that therapy can be adjusted Particularly in children, neuroimaging cannot be used as the definitive measure of the presence or absence of intracranial hypertension Rather, the examiner must rely on a combination of assessment of risk factors, clinical examination (and changes in the examination) combined with imaging findings (which may be unremarkable) Intracranial Pressure Monitoring Severe TBI is the best established indication for ICP monitoring in critically ill children (discussed in Chapters 63 and 118), in which the measurement of ICP serves to direct therapy with the goal of preventing the secondary complications of TBI resulting from cerebral hypoperfusion or metabolic stress For children with severe TBI, a CPP between 40 and 65 mm Hg is recommended and CPP of 60 to 70 mm Hg for adolescents.61 Optimal CPP levels for children under years of age have not been established The lack of age-specific CPP thresholds for severe TBI was addressed in a study using an online Internet database, TBI-trac, containing data from trauma centers in New York state.62 The investigators measured the survival rates and relative risks of mortality for 317 children with severe TBI based on predefined, age-specific high and low CPP thresholds (60 and 50 mm Hg for 12 years old or older, 50 and 35 mm Hg for 6–11 years, and 40 and 30 mm Hg for 0–5 years) The results supported age-specific CPP targets above 50 or 60 mm Hg in adults, above 50 mm Hg in 6- to 17-year-old children, and above 40 mm Hg in 0- to 5-year old children The authors assumed that the zero point for the ICP and blood pressure transducers were uniform across institutions and that both were set at the level of the foramen of Monro However, some patients may have had the head of the bed elevated, which may have led to variability in the calculation of CPP Since the threshold for increased mortality in this analysis was based on the lowest CPP that a patient experienced during the monitoring period, comparing these results with the “dose” of abnormal ICP or CPP as proposed by other investigators is not possible.20,63 The limitations of using a uniform threshold, even when modified for age, to direct care was also noted in a study of cerebral blood flow velocity (CBFV) change in 69 children after severe TBI.64 While low CBFV was associated with poor outcome, individual patterns were highly variable, suggesting the need to use monitoring to guide therapy specific to the changing pathophysiology of individual patients after brain injury Whether ICP-directed care can be delivered without measuring ICP and whether such monitoring improves outcome has been challenged.65 A multicenter study of 324 patients ages 13 years or older with severe TBI carried out in Bolivia and Ecuador called into question the benefit of monitoring ICP.66 In this study, patients were randomly assigned to either guidelines-based management using a protocol in which treatment was based on imaging and clinical examination or a protocol for monitoring ICP There was no significant difference in the primary outcome (a composite measure of functional and cognitive status) or in 6-month mortality between groups However, patients not monitored for ICP received more ICP-directed therapies than the monitored group The extent to which these results apply to North American and European practice is uncertain When ICP is monitored for the management of severe TBI, questions have been raised about using a threshold pressure for intervention and the rationale for directing care only by ICP, not other injury mechanisms—including cerebral ischemia and loss of autoregulation.67 A study of adults with severe TBI using a combination of positron emission tomography, jugular venous oxygen saturation, and brain-tissue oximetry found a complex combination of early and late ischemia, regional hyperemia, increased cerebral blood volume, and low cerebral blood flow (CBF).68 The benefits and complications of ICP monitoring are unproven for other conditions in children in which ICP may be increased (e.g., DKA, meningitis, metabolic disorders, ALF, stroke, brain tumors, cardiac arrest, hypoxic-ischemic encephalopathy, drowning) Similarly, data on treatment goals of ICP or CPP specific to each insult are lacking In pediatric ALF, neurologic morbidity is a major determinant of outcome,69 with compromise of astrocyte metabolism postulated as a pivotal mechanism in the development of cerebral edema associated with hepatic encephalopathy.70 A single-center retrospective review reported 14 children with ALF who underwent ICP monitoring Only one developed intracranial hemorrhage,71 suggesting that invasive ICP monitoring can be performed relatively safely in children with ALF The safety of this approach is supported by a single-center study of 37 children (ages 12 years) and adults with ALF and grade hepatic encephalopathy, of whom 24 underwent intraparenchymal monitor insertion.72 The pediatric cases were not analyzed separately but only one patient developed a subdural hemorrhage and five (21%) had a sustained increase in ICP ICP monitoring is used in approximately 7% of patients with meningitis.73 Mortality is higher in patients with meningitis and mean CPP is less than 50 mm Hg.74 Results of a randomized controlled trial of 110 comatose children with acute CNS infection and raised ICP suggest that a CPP goal is superior to the ICP goal.75 This study compared a goal CPP of 60 mm Hg or higher to a goal ICP of less than 20 mm Hg.75 Ninety-day mortality was significantly lower (18.2%) in the CPP group compared with the ICP group (38.2%; relative risk, 2.1) This treatment resulted in systolic blood pressures in the 95th percentile for age In two children with DKA and cerebral edema, invasive multimodal neuromonitoring, combining ICP and partial pressure of oxygen in brain tissue (PbtO2) monitoring was used to guide therapy.76 The ... 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... sensitive than CT scans in the detection of acute cytotoxic edema This sequence can identify acute ischemic strokes as bright lesions within minutes of their occurrence (Fig 60.1D) Bright lesions on... 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