Neurologic Disorders
Arteriovenous Malformation
Valarie D. Eichler
Background
Congenital abnormality in the connection between arteries and veins without a developed capillary; resembling a “bag of worms.”
Most common cause of hemorrhagic strokes in infants and nontraumatic intracranial hemorrhage (ICH) in children.
Definition
A congenital intracranial malformation distinguished by a persistently abnormal connection between arteries and veins within the brain without an interposed or developed capillary bed.
Etiology/Epidemiology
Uncommon; etiology is largely unknown.
Present at birth; formed during the 3rd week of gestation.
Capillary network fails to develop between the arteries and veins.
Occurs in approximately 1% of the pediatric population.
1:100,000 children have arteriovenous malformations (AVMs); most are asymptomatic.
Majority of AVMs are supratentorial and within the parenchyma of the brain.
Less often, located within the brainstem, thalamus, basal ganglia, and cerebellum.
Infrequently, familial.
Can be associated with several inherited disorders such as Sturge-Weber syndrome, neurofibromatosis, and von Hippel-Lindau syndrome.
Pathophysiology
Occurs during fetal development; failed capillary bed development between the cerebral arteries and veins.
Abnormally high-blood-flow state shunts blood, producing enlarged and engorged vessels.
Normally the capillary bed dampens the high-velocity flow of blood from the artery to the vein.
The cluster of veins and arteries is referred to as the nidus or core.
Because of the high flow state, the AVM steals blood from the surrounding healthy brain tissue, leading to mild hypoxia, progressive neurologic deficits, and more angiogenesis. This is referred as “the steal phenomenon.”
Size can range from 1 mm to >10 cm.
Smaller defects, usually <2 cm, bleed more often than larger ones and are usually located in the basal ganglia or thalamus.
Vein of Galen.
A distinctive AVM in the infant population that is responsible for more than 30% of AVMs in the general pediatric population.
Spinal AVMs.
Rare.
Often associated with cutaneous angiomas such as port-wine stains and hereditary hemorrhagic telangiectasia as seen in Osler-Weber-Rendu syndrome.
Suspect intracranial AVM when a port-wine stain spans the cutaneous distribution of the trigeminal cranial nerve (CN V).
Clinical Presentation
Commonly presents between the second and fourth decades of life.
Usually in healthy children or adolescents.
TABLE 6.1 Cranial Nerves
Cranial
Nerve
Function
I
Olfactory
Conveys impulses related to smell.
II
Optic
Conveys impulses related to sight.
Visual acuity.
III
Oculomotor
Supplies four extraocular muscles: the medial rectus, superior rectus, inferior rectus, and inferior oblique, which adduct, depress, and elevate the eye.
Supplies the levator palpebrae superioris muscle, which controls eye-lid opening.
Pupil constriction.
IV
Trochlear
Controls movement of the superior oblique muscle which intorts the eye.
V
Trigeminal
Three branches: maxillary, mandibular, and ophthalmic.
Controls chewing movements.
Delivers impulses related to touch, pain, and temperature in the facial area.
Corneal reflex (with CN VII).
VI
Abducens
Supplies the lateral rectus muscle that abducts the eye.
VII
Facial
Controls the muscles of facial expression including eye-lid closure.
Sensation and taste of the anterior two third of the tongue.
Controls the tear and salivary glands.
Corneal reflex (with CN V).
VIII
Vestibulocochlear
Transmits impulses related to equilibrium and hearing.
IX
Glossopharyngeal
Sensation and taste in the posterior one third of the tongue.
Controls swallowing.
Controls the salivary glands.
Controls viscera in the thorax and abdomen.
X
Vagus
Controls the skeletal muscle movements in the pharynx, larynx, and palate.
XI
Accessory
Controls swallowing.
Controls movement of the head.
XII
Hypoglossal
Controls muscles involved in speech and swallowing.
Often associated with a high morbidity and mortality.
Associated with ICH ˜80% of the time.
Signs and symptoms of increased intracranial pressure (ICP) due to associated mass effect.
Headache (acute or intermittent).
Nausea/vomiting.
Seizures.
Focal neurologic deficits, depending on location of AVM.
Infant presentation is usually with vein of Galen.
With or without hydrocephalus.
With or without macrocephaly.
High output cardiac failure.
Audible intracranial bruit.
Cardiomegaly.
Diagnostic Evaluation
Computed tomography (CT) is the initial diagnostic tool.
Presence of hyperdense tubular structures with calcifications surrounding the AVM.
If a hemorrhage is present, the primary AVM may be obliterated or compressed by the hematoma.
Evaluates for associated hydrocephalus, cerebral edema (with or without mass effect), and signs of herniation.
CT angiography.
Provides more vascular detail of the AVM.
Magnetic resonance imaging (MRI)/magnetic resonance angiography (MRA) (once clinically stable).
Identifies the structure of the feeding vessels, nidus, draining veins, hemorrhage, hematomas, and presence of vasospasm.
FIGURE 6.1 • Cranial Nerves Labeled.
Cerebral angiography.
Radiologic study of choice or “gold standard.”
Identifies the dilated feeding arteries, the nidus, and large draining veins.
Definitively reveals the origin or morphology of the AVM.
When evaluating a ruptured AVM, the child should be clinically stable and ideally in “cooling off” period to allow for resorption of the hematoma.
If performed too early, the hematoma and surrounding edema may block or hide the vasculature (Figure 6.2).
Management
Overall goal is complete elimination of the AVM.
Presentation with a ruptured AVM is a medical emergency secondary to the likelihood of cerebral edema and increased ICP.
Goal is prevention of secondary injury.
Emergent treatment is the same as any patient presenting with signs and symptoms of increased ICP.
ABCs and controlling increased ICP by positioning, hyperosmolar therapy, mild hyperventilation (Paco2 ˜33-35 mmHg), temperature control, seizure control, sedation/analgesia, and pharmacologic paralysis as needed.
FIGURE 6.2 • AVM on Cerebral Angiogram. Angiogram demonstrates anteroposterior view of left cerebellar arteriovenous malformation (AVM). Dashed arrow points to AVM nidus.
Further tiered therapy includes placement of an external ventricular drain for cerebrospinal fluid (CSF) removal and barbiturate coma.
In some cases, a decompressive craniectomy may be performed to allow more room for the brain to swell during the acute phase.
Surgical excision.
Approach depends on the location of the AVM, and usually involves microsurgery and complete obliteration of the AVM.
In emergent cases, may be performed to evacuate the hematoma.
An angiography or MRA is often performed immediately postoperatively to confirm removal of the AVM.
Endovascular embolization (with cerebral angiography).
Usually a multistage approach and is an adjunct to surgery.
Embolization with beads, coils, and glue to reduce the size of the nidus and overall flow to the AVM.
Goal is to decrease the morbidity associated with both the AVM and the surgical procedure.
Stereotactic radiosurgery (Gamma Knife).
Used for lesions located deep in the brain parenchyma or when near critical areas such as the basal ganglia, brainstem, or thalamus.
A high-dose focused beam of radiation targets the precise area of the AVM while reducing the risk of injury to adjacent tissue.
PEARLS
AVMs are congenital occurrences; informing caregivers that they could not have prevented the incident will sometimes help alleviate anxiety.
Ruptured AVMs are medical emergencies.
Assume increased ICP and treat accordingly.
Interprofessional approach with neurosurgery, interventional radiology, critical care, neurology, radiation oncology, and physical medicine and rehabilitation is needed.
Botulism
Cathy Haut
Background/Definition
A progressive descending neurologic disorder caused by the Clostridium botulinum bacteria, which causes general muscle weakness that can result in respiratory failure.
Etiology
The botulinum toxin is a protein that is naturally produced by certain strains of spore-forming Clostridium bacteria.
Clostridia are soil-dwelling organisms that occasionally make their way into food products, especially unpasteurized honey.
Infants <6 months of age are most often affected.
Pathophysiology
Botulinum spores are ingested or inhaled from soil, vacuum cleaner dust, honey, or other foods.
Bacteria multiply, colonize the intestines, and produce toxin, which affects the neuromuscular junction, blocking the release of acetylcholine from nerve endings, resulting in paralysis.
Clinical Presentation
Symptoms include constipation, poor feeding, lethargy, and increasing weakness.
Physical examination reveals hypotonia and symmetrical CN palsies.
Infants have weak cry, expressionless face, ptosis, and sluggish pupillary responses. Gag, suck, and swallow reflexes are diminished or may be absent.
Diagnostic Evaluation
Presence of botulinum toxin in stool sample.
Management
Supportive care, monitoring, possibility of intubation, and ventilation.
Administration of human botulism immune globulin intravenous (BIG-IV).
Obtained only through the California Health Department.
PEARL
Botulism should be suspected of any infant that presents with hypotonia and difficulty with sucking, feeding, swallowing, or crying.
Brain Abscess
Cathy Haut
Background/Definition
A rare, life-threatening condition in children that has decreased in incidence over time.
Can occur through spread of septic emboli, by direct extension of oropharyngeal infection, or as a result of head trauma.
Classification of abscess is determined by the mechanism of infection, anatomic area affected and organism causing the infection.
Etiology
Majority of brain abscesses occur as a result of a suppurative infection in a local area such as sinusitis, mastoiditis, and, occasionally, otitis media.
Small percentage (10%) associated with trauma.
Associated with spread from a distant source (e.g., congenital heart disease, AVM, pulmonary infection, skin infections, endocarditis, abdominal and pelvic infections).
Anaerobic and microaerophilic cocci and gram-negative and gram-positive anaerobic bacilli are the most common isolates, including Staphylococcus aureus, Enterobacter, and Streptococcus species.
Pathophysiology
Infectious lesion in the intracranial space occurring as a result of a local or distant infection from circulating vascular or cerebrospinal fluid or trauma.
Clinical Presentation
Presentation can vary, but may include (in order of occurrence) headache, mental status changes, focal neurologic deficits, fever, seizures, nausea and vomiting, nuchal rigidity, and papilledema.
Localized neurologic signs are related to the area of the lesion (e.g., brainstem lesion will present with facial weakness, headache, fever, vomiting, dysphagia, and hemiparesis).
Diagnostic Evaluation
Imaging, primarily MRI or CT, of head (Figure 6.3).
Laboratory evaluation: complete blood count (CBC) with differential, blood culture, erythrocyte sedimentation rate, C-reactive protein (CRP), specific serology.
In some cases, evaluation of CSF is warranted.
Culture of involved area via surgical aspiration or stereotactic CT.
 FIGURE 6.3 • Pediatric Brain Abscess MRI. Brain abscess. A: Axial T2-weighted image showing a hyperintense lesion with hypointense rim and surrounding vasogenic edema in the posterior left frontal lobe. B: Sagittal postcontrast T1-weighted image demonstrating hypointense central portion and rim enhancement of the mass. C: The lesion is very bright on the axial diffusion-weighted image. D: Corresponding apparent diffusion coefficient map revealing the low signal intensity of the mass, consistent with restricted diffusion of water molecules. Surrounding vasogenic edema is hyperintense due to increased diffusion. |
Management
Antimicrobial therapy with good penetration of the intracranial spaces.
Control of increased ICP, if present.
Surgical resection, aspiration, or drainage, especially if more than one area is involved.
Consultation with a neurosurgeon and infectious disease specialist.
PEARL
Clinical manifestations are typically nonspecific; so intracranial lesions can go undiagnosed.
Cerebrovascular Accidents
Michele Grimason
Definition
A cerebrovascular accident, also known as stroke, is the result of a sudden interruption of arterial or venous blood flow to a focal region of the brain.
Types
Ischemic: A decrease or disruption of blood flow, leading to dysfunction of brain tissue, caused by systemic hypoperfusion, embolism, thrombus, and sinus venous thrombosis.
Hemorrhagic: A vessel or aneurysm ruptures and leaks into the surrounding tissue and cells.
Etiology
About 20% of neonatal and approximately 50% of nonneonatal pediatric strokes are arterial ischemic and the remainder are hemorrhagic or secondary to cerebral sinus thrombosis.
Most common risk factors for arterial ischemic stroke in children are:
Congenital and acquired heart disease.
Arteriopathies (e.g., arterial dissection, Moyamoya disease, vasculitis).
Sickle cell disease.
Hypercoagulable conditions.
Clinical Presentation
Ischemic.
Neonates: seizures, decreased responsiveness, focal weakness.
Children: focal neurologic deficits such as hemiparesis, aphasia, visual disturbances, and headache.
Hemorrhagic.
May present with signs of increased ICP such as headache and vomiting.
Other signs: irritability, seizures, and hemiparesis.
Diagnostic Evaluation
National stroke guidelines are available from the American Heart Association.
Head CT or MRI with diffusion-weighted imaging to assess for ischemic and hemorrhagic infarct.
Initial CT (hours after infarct) could be negative; thus, serial imaging may be necessary.
Consider CT angiography or MRA if concern for dissection; consider CT venography or magnetic resonance venography if concerned for venous thrombosis (Figure 6.4).
Management
Supportive care.
Prevention of fever.
Maintenance of normoglycemia.
Normovolemia to maintenance of adequate substrate delivery.
Ischemic strokes.
Heparin (unfractionated or low molecular weight) may be administered for as long as 1 week.
Acetylsalicylic acid (aspirin) 3 to 5 mg/kg has been used for ischemic stroke prophylaxis.
Hemorrhagic stroke.
Neurosurgical evaluation for ICP monitoring.
PEARLS
Average time from initial symptoms to diagnosis of stroke is 35 hours; consequently, the patient may have experienced significant ischemia and cell death at the time of diagnosis.
Should be high on the differential when a patient presents with symptoms of headache, seizure, or focal weakness.
Delirium
Keshava Gowda
Tageldin M. Ahmed
Definition/Background
A state of acute brain dysfunction.
Studies have indicated that children who have prolonged ICU stays are more vulnerable to developing delirium.
Other associated factors include neurologic disorders, including acute brain injury, medications, infection, autoimmune disorders, and multiorgan system failure.
Postanesthetic emergence delirium is considered another type of delirium, often associated with anxiety in the preoperative period.
Iatrogenic risk factors include sleep deprivation, restraint use, tubes, catheters, pain, and use of psychoactive medications.
May occur in as many as 30% of critically ill infants and children.
Etiology/Types
Hyperactive delirium, often referred as ICU psychosis, manifests as agitated behavior, restlessness, or inattention.
Risk increases with duration of length of mechanical ventilation and hospitalization.
Hypoactive delirium manifests as withdrawal, flat affect, apathy, and lethargy.
Mixed delirium is a combination of above types.
Long-term outcomes remain uncertain.
Pathophysiology
A number of environmental, pharmacologic, and biochemical mechanisms can lead to the final common pathway of delirium.
There are also patient factors and iatrogenic factors.
Disruption in the balance of stimulatory and inhibitory neurotransmitters (e.g., dopamine, acetylcholine, gamma-aminobutyric acid).
 FIGURE 6.4 • Pediatric Stroke CT and MRI. A 2-year-old girl who awoke with left hemiparesis and right-gaze preference. A: A wedge-shaped area of hypodensity is seen on axial CT. MRI shows B: T2 hyperintensity and C: corresponding diffusion restriction, indicative of an ischemic stroke in the distribution of the right middle cerebral artery. |
Presentation
Sleep-wake disturbances, disorientation, inattention, purposeless actions, labile mood or affect, inconsolability, autonomic dysregulation.
Variation between pediatric and adult presentation emphasizes the benefit to employing a pediatric screening tool.
Diagnostic Evaluation
Requires complete physical examination including a neurologic evaluation and mental status assessment.
Evaluate for other causes of brain dysfunction (e.g., hypoxemia, new infection, deliriogenic medications, metabolic derangements, pain).
FIGURE 6.5 • pCAM Pediatric Confusion Assessment. (Copyright © 2008 Heidi A.B. Smith M.D. and Monroe Carell Jr. Children’s Hospital at Vanderbilt. All rights reserved.)
Use of screening tools including pediatric Confusion Assessment Method for the Intensive Care Unit (pCAM-ICU) or Richmond Agitation Sedation Scale will assist in identifying patients with delirium in PICU (Figure 6.5).
pCAM-ICU screening tool.
Rapid; <2 minutes to complete screening.
Specificity 99%; sensitivity 83% in diagnosing delirium in children >5 years of age.
Screens for the most fundamental signs of delirium first.
Delirium is not present if the child does not display any acute change or fluctuation in mental status or inattention.
Richmond Agitation Sedation Scale screening tool.
Tool to assist in the evaluation of level of consciousness (LOC).
Scale from unarousable (-5) to combative (+4).
Electroencephalogram (EEG) can be utilized for assistance with diagnosis indicating slowing or disorganization.
Limitations in evaluation include developmental and cognitive changes in childhood.
Management
Recognition of the importance of routine delirium evaluation by the interprofessional team.
Implementation of screening tool (e.g., pCAM-ICU).
Very little research is available to support therapy.
Combination of psychosocial and pharmacologic therapies, along with removing or minimizing causative factors, is the best management.
Minimize known risk factors such as sleep disruption, noise, and environmental disturbances.
Maintain continuity of care.
Provide calm, soothing, reassuring environment (e.g., limit extraneous sounds, encourage familiar music/pictures/personal items in child’s room).
Establish day/night routine (as allowed by clinical status) and periods for uninterrupted sleep.
Encourage family to be present with the child.
Avoid trigger medications including benzodiazepines.
Pharmacologic management with haloperidol, droperidol, and risperidone.
Involve child life therapists/hospital teachers.
Encephalopathy
Michele Grimason
Background
The brain requires adequate perfusion, acid-base balance, normothermia, as well as a delicate balance of substrates, neurotransmitters, water, and electrolytes, to function correctly.
Derangement in this milieu can cause disruption of neurotransmitter signals, disturbances of electrical impulses within the brain, and injury to brain cells.
Definition
Encephalopathy is defined as global brain dysfunction leading to an altered mental state.
Types
Acute toxic/metabolic encephalopathy.
Global cerebral dysfunction resulting in altered consciousness, behavior changes, and/or seizures.
Excludes primary structural brain disease, infection, and traumatic brain injury.
Etiologies include electrolyte imbalance, medication, environment, organ dysfunction, and inborn errors of metabolism.
Hypoxic-ischemic encephalopathy.
Occurs after an event such as cardiac arrest.
Deprives the brain of adequate perfusion or oxygenation, resulting in cerebral ischemia, hypoxia, and cell death.
Other acute encephalopathies.
Infectious.
Postinfectious.
Vascular disorders.
Static encephalopathy.
Cerebral dysfunction that is permanent and nonprogressive.
Etiologies include prematurity, infection, and ischemia.
Progressive encephalopathies.
Most commonly associated with neurodegenerative disorders.
May also be associated with autoimmune disorders (e.g., Hashimoto thyroiditis, NMDA receptor antibody encephalitis).
These disorders present with progressive deterioration of neurologic dysfunction, sometimes in a previously healthy child, and are the result of specific biochemical or genetic abnormalities, infections, or other unknown causes.
Clinical Presentation
Mental status changes.
Infant: irritability, lethargy, poor feeding.
Child: personality or behavioral changes, cognitive decline, concentration problems.
Other symptoms: seizures, nystagmus, tremor, myoclonus, abnormal movements.
Diagnostic Evaluation
Since multiple mechanisms (toxins, infection, electrolyte abnormality, cerebral ischemia, or medications) may produce encephalopathy, the diagnostic approach may be broad and is adjusted according to each patient’s specific risk factors.
Laboratory.
General: CBC with differential, comprehensive metabolic panel, liver function test, ammonia, coagulation panel, blood gas analysis.
Infectious: blood, urine, and CSF cultures.
Metabolic: serum amino acids, urine organic acids, lactate, thyroid function tests.
Toxic: toxicology screen, medication drug levels, lead level.
Inflammatory: CSF for oligoclonal bands; serum for antibodies (thyroid, NMDA).
CT or MRI.
EEG to identify seizures and background organization.
Medications should be reviewed to assess if they are contributing to encephalopathy.
Management
Electrolyte imbalances should be corrected.
Antimicrobial, antifungal, and antiviral agents, if indicated, should be initiated promptly.
Antiepileptics should be administered to treat seizures.
Steroids should be considered with a postinfectious or autoimmune encephalopathy.
Guillain-Barré Syndrome/Acute Inflammatory Demyelinating Polyradiculoneuropathy
Kelly K. Marcoux
Background
Both axonal and demyelinating forms have been described.
Definition
Acute inflammatory peripheral neuropathy.
Etiology/Types
Specific cause unknown.
Autoimmune disease triggered by infectious process (particularly viral) as well as immunizations; often preceded by a viral illness or upper respiratory tract infection (URI).
Clinical Presentation
Progressive extremity weakness, may progress to paralysis, usually ascending; begins distally and progresses to proximal muscles (respiratory, trunk, cranial muscles), maximum weakness usually occurs 1 to 2 weeks after onset of symptoms.
Areflexia.
Numbness.
CN palsies.
Hypoventilation due to weak respiratory muscles.
With or without altered LOC.
With or without ataxia.
Autonomic instability can occur, including wide fluctuations in blood pressure (BP), diaphoresis, vasoconstriction, pupil dilation and constriction, and cardiac arrhythmias.
Diagnostic Evaluation
Lumbar puncture (diagnostic): CSF demonstrates elevated protein (>45 mg/dL) and absence of pleocytosis.
Electromyogram (EMG): diffuse demyelination and delayed motor conduction consistent with lower motor neuron disease.
Management
Intravenous immunoglobulin (IVIG).
IVIG may work via several mechanisms, including blocking macrophage receptors, inhibiting antibody production, inhibiting complement binding, and neutralizing pathologic antibodies.
Plasmapheresis.
Removal of circulating humoral factors (e.g., immunoglobulins and antibodies) responsible for demyelination.
Supportive care (e.g., airway protection, skin care, physical therapy).
Assess functional vital capacity, negative inspiratory force serially (assists in determining trajectory and need for mechanical ventilation).
Evaluate BP for autonomic dysfunction.
Hypoxic-Ischemic Encephalopathy
Kelly K. Marcoux
Background
There are many types of encephalopathy which encompass disorders with acute global brain dysfunction resulting in altered mental status.
Primary processes leading to hypoxic-ischemic encephalopathy are brain hypoxia and ischemia due to hypoxemia, reduced cerebral blood flow, or both.
Definition
Type of toxic/metabolic encephalopathy occurring before, during, or after birth due to lack of oxygen or inadequate perfusion, resulting in cerebral ischemia and hypoxia.
Etiology/Types
Associated with trauma, asphyxiation, congenital abnormality, stroke, medications, and prematurity.
In older children, can also result from submersion injury, chronic hypoxia from pulmonary disease, respiratory or circulatory arrest, systemic hemorrhage, or carbon monoxide poisoning.
Clinical Presentation
History:
Infants: irritability, poor feeding, change in mental status.
Older children: change in mental status, personality or cognitive changes, such as inability to concentrate.
Examination:
Abnormal reflexes.
Disorientation.
Depressed mental status.
Abnormal pupillary response.
Abnormal motor response (e.g., tremors, asymmetry, hypotonia, hemiparesis, posturing).
Abnormal heart rhythm or perfusion.
May have apnea.
Diagnostic Evaluation
Laboratory evaluation:
CBC with differential; comprehensive chemistry, liver function tests with bilirubin, ammonia; coagulation studies; blood gas analysis; toxicology screen; blood, urine, and CSF cultures with viral polymerase chain reaction (PCR).
Consider serum amino acids and urine organic acid panels if inborn error of metabolism suspected.
If endocrine disorder suspected, consider thyroid function tests and cortisol levels.
Radiologic evaluation.
CT brain: initial diagnostic study to evaluate acute hemorrhage, calcifications, mass lesion, cerebral edema.
MRI/MRA brain: to identify vascular or hemorrhagic disease.
EEG: to evaluate seizure activity, particularly subclinical seizures.
Management
Supportive care aimed at restoration of adequate oxygenation and ventilation; prevention of secondary injury and increased ICP.
ABCs; consider endotracheal intubation for airway protection.
Monitor for increased ICP.
Correct glucose and electrolyte imbalances; avoid hypo- and hyperosmolar states.
Hypothermia therapy (e.g., cool cap in neonates).
Appropriate antibiotic, antiviral, and/or antifungal agents; if indicated, prompt administration.
Antiepileptic agents to control seizure activity.
Specialty consultation: neurology, critical care, neurosurgery, cardiology, nephrology, endocrinology, rheumatology, pulmonology, genetics, and rehabilitation medicine.
Intracranial Hypertension
Cathy Haut
Definition/Background
Three main components inside the skull: brain (80%), CSF (10%), and blood (10%).
After birth, the skull becomes relatively inflexible, leaving a fixed space in the skull.
An increase in any of the three components in the skull requires a decrease in another component (e.g., Monro-Kellie doctrine).
ICP limits due to fixed space.
The normal range for ICP varies with age, and the values for children are not well established.
Typically, accepted normal values are <20-25 cm H2O in older children and <15-20 mmHg in children <1 year of age.
ICP can be subatmospheric in newborns, especially in the presence of open fontanels.
ICP generally peaks 24 to 72 hours after a traumatic injury.
Cerebral perfusion pressure (CPP) = Mean arterial pressure (MAP) – ICP.
Goals: infant >40 mmHg, children >50 mmHg, and adolescents >60 mmHg.
Net pressure gradient supplying blood flow to the brain depends on MAP and ICP.
MAP is equal to one third systolic BP and two third diastolic BP. Therefore, CPP can be decreased from an increase in ICP, decrease in systemic BP, or a combination of both.
TABLE 6.2 Causes of Increased Intracranial Pressure
Intracranial (Primary)
Extracranial (Secondary)
Postoperative
Brain tumor.
Trauma (epidural and subdural hematoma, cerebral contusions).
Nontraumatic intracerebral hemorrhage.
Ischemic stroke.
Hydrocephalus.
Idiopathic or benign intracranial hypertension (pseudotumor cerebri).
Other (e.g., pseudotumor cerebri, pneumoencephalus, abscesses, cysts).
Airway obstruction or hypoventilation (hypoxia and hypercarbia).
Hypertension or hypotension.
Posture (head rotation).
Hyperpyrexia.
Seizures.
Drug and metabolic (e.g., tetracycline, lead intoxication).
Others (e.g., high-altitude cerebral edema, hepatic failure).
Mass lesion (hematoma).
Edema.
Increased cerebral blood volume (vasodilation).
Disturbances of CSF.
Low CPP has been associated with poor outcomes in trauma literature.
ICP can change easily based on many factors, including intracranial, extracranial, and postoperative situations.
Idiopathic intracranial hypertension, also known as pseudotumor cerebri, causes increased ICP without evidence of space-occupying lesion or vascular abnormality.
Pathophysiology
Intracranial hypertension occurs when there is an increase in the volume of any of the intracranial compartments which necessitates a decrease in another, or an increase in ICP will occur (known as Monro-Kellie doctrine).
The body has various mechanisms by which it keeps the ICP stable, with CSF pressures varying by approximately 1 mmHg in healthy patients through shifts in production and absorption of CSF.
ICP changes based on normal body functions such as coughing and hyperthermia, but severe changes resulting from trauma or cerebral edema can cause ICP which may be difficult to control, thus contributing to intracranial hypertension and secondary brain injury.
Persistent increase in ICP can lead to brain herniation and death.
Cerebral edema may be the result of intracellular swelling (cytotoxic edema), capillary endothelial cell dysfunction, or interstitial edema.
Clinical Presentation
Traumatic brain injury is the most common problem leading to increased ICP.
Symptoms of increased ICP include loss of consciousness or altered LOC, vomiting, increased head circumference (especially infant) and tense fontanel, seizures or status epilepticus, coma.
Cushing triad is an indication of increased ICP with irregular respirations, widening pulse pressure, and bradycardia, indicating impending herniation. These signs indicate a medical emergency.
Diagnosis
Head CT is the initial diagnostic study; rapid with definitive results of cerebral edema and other underlying pathology.
Increased ICP or intracranial hypertension can be diagnosed and monitored via a ventriculostomy or ICP monitor.
For more information on ICP monitoring, see Diagnostic Testing later in this section (Figure 6.6).
 FIGURE 6.6 • Cerebral Edema Noncontrast CT. Axial noncontrast CT scan shows diffuse edema manifested as sulcal effacement and low attenuation of the cerebral cortex, resulting in loss of cortical-white matter contrast. |
 FIGURE 6.7 • Management of Increased ICP. From Simon, D. W., Da Silva, Y. S., Zuccoli, G., & Clark, R. S. B. (2013). Acute encephalitis. Critical Care Clinics, 29, 259-277. |
Management
Insert ICP monitoring device, either external ventriculostomy device or parenchymal catheter.
Maintain adequate CPP.
Infants >40 mmHg.
Children >50 mmHg.
Adolescents >60 mmHg.
Elevations in ICP typically peak 24 to 72 hours following injury.
Monitor ICP; if increased, control extrinsic factors, and/or drain CSF (if ventriculostomy drain present).
Medical management should include sedation, drainage of CSF, and osmotic diuresis with either mannitol or hypertonic saline.
Position with head of bed elevated and midline.
Mild hyperventilation is helpful in decreasing ICP, with goal CO2 30 to 35 mmHg.
If evidence of cerebral ischemia and no contraindications, consider hypothermia.
For intracranial hypertension refractory to initial medical management, barbiturate coma, hypothermia, or decompressive craniectomy should be considered (Figure 6.7).
Pseudotumor Cerebri: Idiopathic Intracranial Hypertension
Cathy Haut
Clinical Presentation
Often presents in obese or overweight adolescent females with persistent headache and visual loss or diplopia.
These patients are often referred from primary care providers who have evaluated papilledema as an accompanying physical feature.
Diagnosis
Opening-pressure evaluation with lumbar puncture.
Imaging, usually MRI, which is completed to document normal results.
Ophthalmology examination with visual fields.
Associated conditions or risk factors: obesity, hypernatremia, medications such as tetracyclines, fluoroquinolones, oral contraceptives, vitamin A, isotretinoin, sulfamethoxazole, growth hormone, lithium.
Management
Medications for the management of headache symptoms and acetazolamide (Diamox).
Draining CSF with repeated lumbar punctures, surgery.
Identify/Address any secondary cause.
Main goal of treatment is to prevent or reverse visual loss.
Bacterial Meningitis
Denise C. Schiel
Definition/Background
Inflammation of the membranes lining the brain and spinal cord.
Infectious etiologies include acute bacterial, viral, fungal, parasitic.
Usually purulent and involves the fluid in the subarachnoid space.
Most common acute central nervous system (CNS) infection.
More than two third of cases involve children <15 years of age.
Peak incidence in 3 to 12 months of age, with decreasing incidence after age 2 years.
Peak season is late fall and early winter.
Risk Factors
Males > females.
Urban areas, crowded living conditions, poverty.
Underlying chronic illness/immunosuppression, asplenia.
Routes of CNS Invasion
Causative agent varies with age and route of infection.
Hematogenous dissemination.
Sinuses, middle ear, mastoid, other pericranial structures.
Congenital or acquired defects in the skull or spinal cord (Table 6.3).
Pathophysiology
Colonization and penetration of the nasopharyngeal epithelium or direct extension from a distant site of infection.
Hematogenous dissemination.
Bacteria enter the CNS and circulate to CSF/subarachnoid space.
Bacterial-/endotoxin-induced local inflammation of the meninges, CSF, and ventricles.
Polymorphonuclear infiltration of the subarachnoid space.
Mechanism of CNS Injury
Alterations in CBF.
Initial hyperemia followed by a reduction of CBF with progressive infection/inflammation.
Impaired delivery of metabolic substrate (e.g., oxygen and glucose) to the brain tissue with resultant ischemia and infarction.
TABLE 6.3 Age-Associated Pathogens for Meningitis | ||||||||||
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