ESSENTIALS OF DIAGNOSIS & TYPICAL FEATURES
Severe head injury: Glasgow coma scale (GCS) of < 9.
Moderate head injury: GCS of 9–13.
Mild head injury: GCS of 13–15.
Various estimates indicate that there are up to 500,000 pediatric traumatic brain injuries in the United States every year, resulting in 37,000–50,000 hospitalizations. Mortality rates vary significantly by region (relative risk 1.19–4.2 nationally), but, overall, pediatric brain injuries result in 2000–3000 deaths annually. The cost of these injuries is significant, particularly when also considering that survivors of pediatric brain injury may have long-term deficits with lifetime needs.
Brain injury is classically divided into two categories based on the timing of the pathologic findings: primary and secondary injury.
Primary injury occurs at the time of trauma, causing focal and diffuse mechanical damage to both the neurons and glia as well as the vasculature and is typically irreversible. Focal damage includes skull fracture, parenchymal bruising or contusion, extraparenchymal or intraparenchymal hemorrhage, blood clots, tearing of blood vessels, or penetrating injury. Diffuse damage includes diffuse axonal injury and edema. Consequences of primary injury, either focal or diffuse, include cellular disruption with release of excitatory amino acids, opiate peptides, and inflammatory cytokines.
Secondary injury is the loss of cellular function accompanying primary injury that results in loss of cerebrovascular regulation, altered cellular homeostasis, or cell death and functional dysregulation. Mitochondrial dysfunction due to dysregulation of Ca++ and other cations and anions leads to depletion of ATP to drive homeostatic cellular pumps. This leads to oxidation of cellular DNA, protein and lipids causing among other things cell death. These multiple mechanisms can also lead to increased extracellular glutamate resulting in excess depolarization further stressing compromised cells. A primary injury can initiate the processes of secondary programmed cell death (apoptosis), which further exacerbates the primary injury. Secondary injury may develop hours or days after the initial insult. It appears to be precipitated by elevated intracranial pressure, cerebral edema, and release of neurochemical mediators. Current treatment paradigms are focused on treating and preventing secondary injury.
Classification & Assessment of Injury Severity
Traumatic brain injury is usually categorized as open or closed. Open injuries are the result of penetration of the skull by missile or sharp object or deformation of the skull with exposure of the underlying intracranial tissues. Closed injuries are the result of blunt trauma to the head, which causes movement (intracranial acceleration or deceleration and rotational forces) and compression of brain tissue. Brain contusions are referred to as coup (occurring at the site of injury) or contra-coup (occurring on the side of the brain opposite the injury). Rating the severity of injury and eventual outcomes is important in medical management. Included below are the two most commonly used scales relevant to clinical care of these injuries in rehabilitation medicine.
A. Glasgow Coma Scale (GCS)
The GCS is the most commonly used system to assess the depth and duration of impaired consciousness in the acute setting. The score is derived from three areas of evaluation: motor responsiveness (maximum score 6), verbal performance (maximum score 5), and eye opening to stimuli (maximum score 6). The scale has been modified for use in infants and children younger than 5 years, allowing for their lack of verbal responsiveness and understanding. Cumulative scores define injury as mild (13–15), moderate (9–12), and severe (≤ 8). The concept of posttraumatic amnesia is used to gauge severity of injury and is an adjunct to the GCS. Posttraumatic amnesia is the period after an injury during which new memory cannot be incorporated and the person appears confused or disoriented. Amnesia can be retrograde, anterograde, or both.
B. Rancho Los Amigos Levels of Cognitive Function
The Rancho Los Amigos Levels of Cognitive Function (LCFS or “Rancho”) is used to gauge the overall severity of cognitive deficit and can be used serially during recovery as a rough gauge of improvement. The scale has 10 levels of functioning ranging from “no response” to “purposeful, appropriate.”
Common Sequelae of Brain Injury
Depending on the severity of brain injury, there may be deficits in cognition and behavior, as well as physical impairments. Injuries can also produce changes in sensory and motor function, emotional stability, social behavior, speed of mental processing, memory, speech, and language. The consequences of mild brain injuries may be difficult to discern. Small intraparenchymal injuries, easily identified by computed tomographic (CT) or magnetic resonance imaging (MRI) scans, may not cause obvious signs or symptoms. The following are common problems associated with brain injury.
Seizures occurring in the first 24 hours after injury are referred to as immediate seizures. Those occurring during the first week are early seizures, and those starting more than 1 week after injury are referred to as late seizures. Seizure prophylaxis with medications is recommended in the first week after brain injury in children at high risk for seizures and in very young children. Seizure prophylaxis is also recommended for 1 week after any penetrating brain trauma. Seizure prophylaxis is probably not effective for prevention of late-onset seizures; these may require long-term treatment.
B. Neuromotor Deficits/Movement Disorders
Neuromotor deficits after brain injury include movement disorders, spasticity, paralysis, and weakness. The type of disorder will be influenced by the areas damaged. The most common movement disorders are tremors and dystonias. These deficits can result in impaired ambulation, coordination, impaired ability to use upper extremities, and speech problems. Physical therapy is the primary means of treating these problems.
C. Communication Disorders
Language and communication disorders are common. Aphasia, difficulty in understanding and producing written and spoken language, is categorized as fluent, nonfluent, or global. Individuals with fluent aphasia or Wernicke-type disorder can produce speech but have little content associated. The nonfluent aphasias or Broca’s type have a paucity of speech and may have word finding difficulties. Global aphasias have extensive injuries and the most severe language disorders.
D. Paroxysmal Sympathetic Hyperactivity
Severe brain injuries may be associated with excessive sympathetic outflow and results in a constellation of symptoms known as paroxysmal sympathetic hyperactivity (PSH). Symptoms of PSH are tachycardia, tachypnea, sweating, hyperthermia, hypertension, agitation, and posturing. Common medications used to treat PSH include dopamine agonists (eg, bromocriptine), β-blockers (eg, propranolol), and α-agonists (eg, clonidine).
E. Cognitive and Behavioral Deficits
After brain injury, cognitive and behavioral deficits are a frequent occurrence. Cognitive disorders depend on the location and severity of the injury. Damage to the frontal lobes can disrupt executive function along with initiation delays. Neuropsychiatric sequelae are common, and depression, anxiety disorders, and posttraumatic stress disorders (PTSD) are present in one-third of those injured. Testing by a neuropsychologist may help to identify problem areas, allowing for development of accommodations in school and use of behavioral strategies.
F. Hypothalamic-Pituitary-Adrenal Axis Dysfunction
Dysfunction of the hypothalamic-pituitary-adrenal axis is common after head injury. The syndrome of inappropriate secretion of antidiuretic hormone (SIADH) and diabetes insipidus (DI) from a posterior pituitary injury can result in significant electrolyte and osmolality imbalance. Amenorrhea that typically resolves spontaneously is common in females. Injury near the onset of puberty can complicate normal development, and endocrine status should be monitored closely.
G. Cranial Nerve Injuries
The sensory and motor components of the cranial nerves are often damaged, resulting in a wide variety of deficits not centrally mediated. The most commonly injured nerves are I, IV, VII, and VIII. Hyposmia or anosmia (cranial nerve I) can occur if the shearing forces at the cribriform plate disrupt the afferent olfactory nerves. Injury to cranial nerves IV (trochlear) is common as it has the longest intracranial length. Superior oblique injuries typically cause a head tilt and vertical diplopia. Facial nerve injuries (cranial nerve VII) are common especially with temporal bone fractures. This impacts the ability to use the facial muscles, causes dryness in the eye and salivary glands along with decreasing taste in the anterior part of the tongue. The cochlear nerve (VIII) is also frequently damaged in temporal bone fractures and can result in vertigo and dizziness.
Much of what we know of traumatic brain injury is based on adult experience. The confounding effects of age and the etiologies unique to the pediatric population (eg, child abuse) make care of the pediatric head-injured patient very complex.
The assumption that younger children will fare better than older children or adults after a brain injury is a myth. The fact that in a child a significant amount of development and synaptic reorganization has yet to occur does not guarantee an improved chance for functional recovery. Indeed, disruption of developmental processes, especially in very young infants or neonates, may be catastrophic. These processes often cannot be recapitulated.
The mechanism of injury plays an important role in determining the severity of brain injury in very young children. Mechanisms associated with nonaccidental injury such as shaking often result in global diffuse damage. The weak neck musculature, large head-body mass ratio, immature blood-brain barrier, and high intracranial fluid-brain mass ratio all contribute to widespread damage.
During puberty, major hormonal changes have an impact on the outcome of brain injury. Behavioral problems may be pronounced in brain-injured adolescents. Precocious puberty and precocious development of sexual activity may occur in preadolescents and should be carefully monitored.
Careful consideration should be given to the developmental progress of the brain-injured child and adolescent. Delays can be anticipated after moderate and severe brain injuries related to abnormalities of cognition and behavior. Educational programs should include an individualized educational program (IEP) to support the child with significant remediation and assistance during their school years. Programs should also include a 504 plan (Section 504 of the Rehabilitation Act and the Americans with Disabilities Act). The 504 plan identifies the accommodations necessary in regular school settings for students with lesser disabilities so that they may be educated in a setting with their peers.
The primary goal of rehabilitation after childhood brain injury is to maximize functional independence. Rehabilitative care can be divided into three phases: acute, subacute, and long term. The acute and subacute phases typically occur in the inpatient setting while the long-term phase is an outpatient endeavor.
Therapy in the acute phase consists mainly of medical, surgical, and pharmacologic measures to decrease brain edema, treat increased intracranial pressure, and normalize laboratory values. Nutrition is essential for the healing process, and either parenteral nutrition or supplemental enteral feedings are employed. Current research suggests that transitioning to enteral nutrition (eg, nasogastric tube feeding) as soon as possible after brain injury is associated with improved outcomes. Placement of a gastrostomy tube for supplemental enteral feeding is often performed in patients with severe brain injuries when recovery will be protracted, and swallowing function is inadequate for safe oral feeding.
Therapy in the subacute phase is characterized by early, intensive participation in rehabilitative therapies promoting functional recovery. Treatment should be planned after consultation with physical therapy, occupational therapy, speech-language specialists, and neuropsychologists. Nursing staff members are a primary interface with the patient and often serve as educators for family-directed care. Pharmacologic approaches may be used to enhance arousal and focus in patients with traumatic brain injury to enable them to more fully participate in therapies or to deal with other subacute sequelae such as agitation. Most children and adolescents with brain injuries can be discharged home to continue with treatment on an outpatient basis.
Long-term follow-up starts immediately after discharge. Annual multidisciplinary evaluation, including neuropsychological testing is important as the child approaches school age so strategies to deal with noted deficits can be implemented to improve outcomes within the educational environment.
Medication is often required for cognitive and behavioral issues. Attention deficit and fatigue may be amenable to treatment with stimulants such as methylphenidate and modafinil. Dopaminergic agents such as amantadine, levodopa, and bromocriptine can be useful in improving cognition, processing speed, and agitation. Antidepressants such as selective serotonin reuptake inhibitors can be helpful in treating depression and mood lability. Anticonvulsants can be used as mood stabilizers and in treating agitation and aggression. Tegretol and valproic acid are typical agents for this purpose.
Attention and arousal can also be successfully addressed by utilizing behavioral techniques to reinforce desired behaviors and by identifying environmental situations to facilitate success. Gains made in the behavioral realm often have a positive impact on therapies designed to address physical issues.
Directly after brain injury, poor pupillary reactivity, low blood pH, absence of deep tendon reflexes, and low GCS all correlate with poor outcome. Coalescing lesions noted on imaging and increased depth and duration of coma suggest more severe injury and poor functional recovery. Children younger than 1 year tend to have worse outcomes.
Functional outcome assessment is important for judging the efficacy of rehabilitation therapy. Global multidomain measures (eg, FIM/WeeFIM) are used to provide a functional “snapshot in time” of select functions—motor function and mobility, self-care, cognition, socialization, and communication. Simpler, single-domain, functional assessment tools such as the Glasgow Outcome Scale (GOS) and its pediatric cousin, the Kings Outcome Scale for Childhood Head Injury (KOSCHI), may also be of use. The National Institute of Neurological Disorders & Stroke (NINDS) is coordinating an effort to validate and promote the use of “common data elements” for evaluating outcomes of brain injury (www.commondataelements.ninds.nih.gov). The goal of this effort is to promote the use of common measures that will facilitate comparison of results across studies and generalizable conclusions.
Outcome associated with mild brain injury is often quite favorable. Most patients recover normal function within a short time. A small percentage develop persistent problems such as chronic headache, poor focusing ability, altered memory, and vestibular abnormalities which may last for many weeks or months. Differentiating between musculoskeletal and central nervous system (CNS) etiologies of persistent symptoms such as headache is important and can influence prognosis and care planning.
In children, recovery may not be fully achieved for many months or years after the initial injury. The impact of the injury on developmental processes and its future consequences are difficult to predict. Long-term follow-up is required, particularly as the child approaches school age.
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