Evaluation of the Comatose Child

Nicholas S. Abend

Daniel J. Licht

Coma is a not a specific diagnosis but instead describes an altered state of consciousness which may be the consequence of a range of insults to the brain. The estimated incidence of nontraumatic coma is 30/100,000 children per year (1), and the estimated incidence of severe traumatic coma is 5.6/100,000 (2). Morbidity and mortality are highly dependent on the coma etiology (1,3). The comatose child requires immediate evaluation and medical stabilization, followed by a history and physical examination directed at identifying the underlying etiology of coma, which will direct specific management. Coma is the most severe form of the acute encephalopathy spectrum. All types of acute encephalopathy are serious disorders that involve the same differential diagnosis and management approach. This chapter aims to (a) define coma and distinguish it from other states of encephalopathy and altered consciousness; (b) review coma pathophysiology; (c) discuss a differential diagnosis of etiologies; and (d) outline an approach to evaluation of a comatose child.

DEFINITIONS

Consciousness, as defined by Plum and Posner (4), is a state of wakefulness and awareness of self and surroundings. Coma is a state of altered consciousness with loss of both wakefulness (arousal, vigilance) and awareness of self and environment. Sleep-wake cycles are absent. Coma is characterized by sustained, pathologic, eyes-closed, unarousable unresponsiveness (4). Coma is a transitory state that can evolve toward recovery of consciousness, a minimally conscious state, a vegetative

state, or brain death.

TABLE 57.1 STATES OF ALTERED CONSCIOUSNESS

▪ STATE	▪ AROUSAL	▪ AWARENESS	▪ SLEEP-WAKE CYCLING	▪ MOTOR FUNCTION	▪ RESPIRATORY FUNCTION
Brain death	–	–	–	None or Spinal reflexes	–
Coma	–	–	–	Non-purposeful	Variable
Vegetative state (unresponsive wakefulness syndrome)	+	–	+	Non-purposeful	+
Minimally conscious state	+	Partial	+	Intermittently purposeful or Absent but nonmotor evidence of responsiveness	+

Between normal consciousness and coma is a spectrum of diminished consciousness, conventionally subdivided into lethargy, obtundation, and stupor. Lethargy is a state of reduced wakefulness with attentional deficits. Obtundation is characterized by blunted alertness and diminished interaction with the environment. Stupor is a state of unresponsiveness with little or no spontaneous movement, resembling deep sleep, but differs from coma because vigorous stimulation induces temporary arousal. The descriptive terms listed above are not defined uniformly in the literature, nor are they defined consistently by the physicians involved in a given patient’s care. Thus, since tracking changes in the patient’s state is important in the acute setting, a description of the patient’s examination along with these terms may convey more information than these one word descriptors alone.

Other chronic states of altered neurologic function may resemble coma but must be differentiated from coma (Table 57.1). A patient in the persistent vegetative state has sleep-wake cycles but is unaware of self and environment.
Although such patients may make sounds, facial expressions, or body movements, detailed testing does not demonstrate reproducible purposeful responses to stimulation. Since patients in whom coma is due to head trauma may recover consciousness after a longer period than those in whom coma is nontraumatic, the diagnosis of a persistent vegetative state may be made 3 months following nontraumatic brain injury, but not until 12 months following traumatic brain injury (5,6). Of children in the vegetative state 1 month after head injury, 1-year outcome was death (9%), persistent vegetative state (29%), and recovery of consciousness (62%). However, outcome was worse when the etiology was nontraumatic, with death (22%), persistent vegetative state (65%), and recovery of consciousness (usually with severe cognitive disabilities) in only 13% (7). A patient in a minimally conscious state has severely altered consciousness but has behavioral evidence of self or environmental awareness, such as following simple commands or making simple nonreflexive gestures. Recent functional neuroimaging and electrophysiological studies have indicated that some patients considered to be in the vegetative state demonstrate reproducible physiologic changes in response to tasks, indicating there may be some awareness despite the absence of behavioral signs of responsiveness (8,9,10). These findings have prompted the use of more neutral and descriptive terms (11,12). The vegetative state may be referred to as the unresponsive wakefulness syndrome. The minimally conscious state may be subdivided into the minimally conscious positive state (high-level behavioral responses, such as following commands or intelligible verbalizations) and the minimally conscious negative state (lower level behavioral responses, such as visual pursuit or contextually-appropriate crying or smiling) (11).

Akinetic mutism is a condition of extreme slowing or absence of bodily movement with loss of speech. Wakefulness and awareness are preserved, but cognition is slowed. Causes include extensive bihemispheric disease and lesions involving the bilateral inferior frontal lobes, paramedian mesencephalic reticular formation, or the posterior diencephalon. Frontal release signs may be evident, and electroencephalogram (EEG) may show background slowing. The locked-in syndrome is a state of preserved cognition with complete paralysis of the voluntary motor system. Cortical function is intact as indicated by normal EEG patterns. Eye movements, most commonly vertical eye movements, may be preserved, allowing for some communication. It may result from lesions of the corticospinal and corticobulbar pathways at or below the pons or severe peripheral nervous system disease such as Guillain-Barré syndrome, botulism, and critical illness polyneuropathy. Psychogenic unresponsiveness may also mimic coma. Coma must also be distinguished from brain death, which is the permanent absence of all brain activities, including brainstem function (13). Delirium is an acute confusional state characterized by changes in level of consciousness, impaired attention, and a fluctuating course.

ANATOMY

Maintaining consciousness depends on interactions between the reticular activating system (RAS), thalamus, posterior hypothalamus, and cerebral hemispheres (Fig. 57.1). The RAS constitutes the central core of the brainstem and extends from the caudal medulla to the thalamus and the basal forebrain. The RAS receives input stimulation from all sensory pathways and projects to vast areas of the cerebral cortex. The RAS activates the cortex and participates in feedback control that regulates incoming signals. This may account for the ability of certain signals to cause more arousal than other signals of equal electrical intensity. The RAS can be partitioned into medial and lateral zones. The medial RAS contains a mixture of large and small neurons. The most prominent cells in this region are the giant neurons that have long ascending and descending axons. The ascending portions of the medial RAS emanate from the Raphe nuclei, which regulate sleep cycles and utilize serotonin as their major neurotransmitter. The descending pathways regulate automatic motor functions, including the automatic rhythms of breathing. The lateral RAS projects to the reticular nucleus of the thalamus, which relays signals to the cortex, forming the ascending RAS, which maintains wakefulness. These projections are both cholinergic and noradrenergic. A second cholinergic pathway ascends through the hypothalamus to influence basal forebrain structures, including the limbic system, which influences conscious behavior. Noradrenergic pathways originating in the locus ceruleus have an excitatory effect on most of the brain, mediating arousal and priming the brain’s neurons to be activated by stimuli. The RAS extends to the posterior portion of the hypothalamus and the thalamus. The thalamus (intralaminar and medial nuclei) rely information from the RAS diffusely throughout the cerebral hemispheres via thalamocortical projections. In general, wakefulness is maintained by the RAS and thalamus, whereas awareness is dependent on the cortex.

FIGURE 57.1. Key structures in maintaining an awake and alert state.

ETIOLOGIES OF COMA

The main causes of coma are listed in Table 57.2. Coma subdivisions have occurred along several lines including (a) traumatic or nontraumatic and (b) structural or nonstructural. A population-based study of 600,000 children evaluated 345 episodes of coma (1). Infection was the most common cause of nontraumatic coma, accounting for 38% of cases. Intoxication, epilepsy, and complications of congenital abnormalities each accounted for 8%-10% of cases. Nontraumatic accidents (such as smoke inhalation and drowning) and metabolic
causes each accounted for 6% of cases. Approximately onequarter of children with traumatic brain injury present with coma (2). Importantly, multiple interrelated factors crossing these subdivisions may be present in one patient. For example, status epilepticus may occur in the setting of encephalitis; infection inducing a catabolic state may produce decompensation in a child with an inborn error of metabolism; and hyponatremia or other electrolyte dysfunctions may accompany brain injury and contribute to cerebral dysfunction.

TABLE 57.2 ETIOLOGIES OF COMA

*Traumatic Etiologies (Accidental or Abusive)*
Cerebral contusion
Intracranial hemorrhage
	Epidural hematoma
	Subdural hematoma
	Subarachnoid hemorrhage
	Intraparenchymal hematoma
Diffuse axonal injury
*Nontraumatic Etiologies*
Hypoxic-ischemic encephalopathy
	Shock
	Cardiopulmonary arrest
	Cardiac or pulmonary failure
	Near drowning
	Carbon monoxide poisoning
	Cyanide poisoning
Vascular
	Intracranial hemorrhage (subdurale, epidural, subarachnoid, parenchymal)
	Arterial ischemic infarct
	Venous sinus thromboses
	Vasculitis
	Carotid or vertebral artery dissection (cervical or intracranial)
Mass lesions
	Primary neoplasms
	Brain metastases
	Abscess
	Granuloma
Hydrocephalus
Infections
	Meningitis and encephalitis: bacterial, viral, rickettsial, fungal, protozoal
	Abscess
Inflammatory/Autoimmune/Postinfectious
	Acute disseminated encephalomyelitis
	Multiple sclerosis
	Sarcoidosis
	Sjogren disease
	Cerebritis (e.g., systemic lupus erythematosus)
	Sepsis-associated encephalopathy
	Autoimmune-mediated encephalitis
Paroxysmal neurologic disorders
	Seizures, status epilepticus, nonconvulsive seizures, postictal state
	Acute confusional migraine
Hypertensive encephalopathy
Posterior reversible encephalopathy syndrome
Systemic metabolic disorders
	Substrate deficiencies
		Hypoglycemia
		Cofactors: thiamine, niacin, pyridoxine, folate, B12
	Electrolyte and acid-base imbalance: sodium, magnesium, calcium
	Hypoglycemia
	Diabetic ketoacidosis
	Endocrine
		Acute hypothyroidism
		Addison disease
		Acute panhypopituitarism
	Uremic encephalopathy
	Hepatic encephalopathy
	Reye syndrome
	Sepsis-associated encephalopathy
	Porphyria
	Inborn errors of metabolism
		Urea cycle disorders
		Aminoacidopathies
		Organic acidopathies
		Mitochondrial disorders
Toxins
	Medications: narcotics, sedatives, antiepileptics, antidepressants, analgesics, aspirin, valproic acid encephalopathy
	Environmental toxins: organophosphates, heavy metals, cyanide, mushroom poisoning
	Illicit substances: alcohol, heroine, amphetamines, cocaine, and many others
Drug induced
	Neuroleptic malignant syndrome
	Serotonin syndrome
	Malignant hyperthermia
Psychiatric
	Conversion disorder
	Catatonia
Other
	Hypothermia

EVALUATION OF THE COMATOSE CHILD

Coma is often a manifestation of life-threatening condition. The initial evaluation of the child begins with evaluation and stabilization of vital functions and identification of immediately

reversible etiologies. Medical stabilization must occur as the coma etiology is being investigated to prevent development of secondary brain injury. An algorithm for initial evaluation of coma is outlined in Table 57.3 and discussed below. The Pediatric Accident and Emergency Research Group of the Royal College of Paediatrics and Child Health and the British Association for Emergency Medicine have published guidelines for practice on the basis of an extensive literature review and expert consensus (www.nottingham.ac.uk/paediatric- guideline) (14). Other literature reviews are also available (15,16,17).

Patient History

Historical information must be gathered as quickly as possible since it may be crucial in identifying the cause of coma. The history must include a detailed description of events leading
to coma, with particular attention to timing, exposures, and accompanying symptoms. Preceding somnolence or headaches suggests metabolic, toxic or infectious etiologies, hydrocephalus, or expanding mass lesions. Sudden onset of coma without trauma suggests seizure, intracranial hemorrhage, or hypoxicischemic encephalopathy caused by a cardiac event. A slowly progressive loss of consciousness suggests hydrocephalus, an expanding mass lesion, or indolent infection. Fluctuations in mental status may occur with metabolic etiologies, seizure, or subdural hemorrhage. Preceding headache aggravated with positional changes or Valsalva maneuver implies increased intracranial pressure from hydrocephalus or a mass lesion. Headache with neck pain or stiffness suggests meningeal irritation from inflammation, infection, or hemorrhage. Fever suggests infection but its absence does not rule it out, particularly in infants younger than 3 months of age, or immunocompromised children. Recent fevers or illnesses suggest autoimmune processes such as acute disseminated encephalomyelitis (ADEM) or possibly Reye-like illness although this is uncommon. Questions about possible toxic ingestions should include a survey of medications and poisons kept in the places that the child has been.

TABLE 57.3 INITIAL EVALUATION OF COMA

▪ Resuscitation and medical stabilization
	▪ Airway, breathing, and circulation assessment and stabilization ▪ Ensure adequate ventilation and oxygenation ▪ Determine whether hypertension is reactive (maintaining cerebral perfusion pressure) or problematic
▪ Bedside glucose assessment ▪ Draw blood for glucose, electrolytes, ammonia, arterial blood gas, liver and renal function tests, complete blood count, lactate, pyruvate, and toxicology screen ▪ Neurological assessment
	▪ GCS (modified for children) or FOUR score or coma description ▪ Assess for evidence of raised intracranial pressure and herniation ▪ Assess for abnormalities suggesting focal neurologic disease
▪ Head CT scan (and possibly MRI when stable) ▪ Identify and treat critical elevations in intracranial pressure
	▪ Neutral head position, elevated head by 20 degrees, sedation ▪ Consider hyperosmolar therapy (mannitol or hypertonic saline) ▪ Hyperventilation as temporary measure ▪ Consider need for intracranial monitoring and/or neurosurgical intervention
▪ Lumbar puncture if concern for infection or coma etiology unknown
	▪ Generally head CT scan first and defer lumbar puncture if concern for elevated intracranial pressure ▪ If there is concern for infection and lumbar puncture must be delayed, then provide broad-spectrum infection coverage ( including bacterial, viral, and possibly fungal) Only gold members can continue reading. Log In or Register to continue Share this: Click to share on Twitter (Opens in new window) Click to share on Facebook (Opens in new window) Related Related posts: Picu Organization and Physical Design Communication and Information Technology in the Picu Learning From the Data—Discovery Informatics for Critically Ill Children Rehabilitation Recognition and Initial Management of Shock Blood Products and Transfusion Therapy Stay updated, free articles. Join our Telegram channel Tags: Rogers' Textbook of Pediatric Intensive Care Jun 4, 2016 \| Posted by drzezo in CRITICAL CARE \| Comments Off on Evaluation of the Comatose Child Full access? Get Clinical Tree Get Clinical Tree app for offline access Get Clinical Tree app for offline access