Approach to the Comatose Child

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Background

Definitions

• Consciousness: A state of being aware. A state of general wakefulness and responsiveness to environment. Note that in infants, consciousness can be defined operationally.  For example, crying when hungry or uncomfortable suggests awareness of self, or soothing to a mother’s voice suggests awareness of the environment.

• Coma: A state of deep, unarousable, sustained, pathologic unconsciousness in which the person shows no meaningful response to environmental stimuli.

• Consciousness – Coma continuum: Consciousness and coma are two extremes of an awareness scale as indicated here:

Background Physiology

Consciousness requires two components:

• Arousal or wakefulness, which is dependent on the function of the Reticular Activating System (RAS), a network of neurons located in the core of the brainstem extending from mid pons through the midbrain/hypothalamus to thalamus.

• Awareness, which is mediated through cerebral cortical neurons and their reciprocal projections to and from the major subcortical nuclei.  Awareness requires arousal, but not vice versa.

• Following from the above, coma will result if there is either RAS or cerebral cortical dysfunction. RAS dysfunction, mostly caused by structural lesions in the brain stem tend to present with focal neurologic findings while cerebral cortical dysfunction is often caused by Toxic/Metabolic processes and present with non-focal neurologic findings.

Questions to ask

Timing

• Acute onset – Suggests intracranial hemorrhage, non-convulsive status seizures, ischemic stroke, or acute trauma
• Onset of minutes to hours – Suggests a metabolic cause, infection, or progressive injury from trauma
• Onset of hours to days – Suggests a shunt blockage, hydrocephalus, or tumor

Associated symptoms

• Fever – Infections
• Preceding headache – Increased ICP
• Preceding somnolence – Toxic/Metabolic
• Ataxia, confusion or loss of milestones in recent weeks – Neoplasm

*** Always be cautious of a history that is inconsistent with presentation, as this might suggest non-accidental injury (e.g. shaken baby syndrome)

Differential diagnosis

Classification of the different causes of coma can be broadly divided into structural-intrinsic or metabolic-toxic.

Table 1: Selected Etiologies of Impaired Consciousness and Coma

Structural/Intrinsic	Metabolic-toxic
Traumaconcussion, contusion, epidural or subdural hematomas, diffuse axonal injury, non-accidental injury	Hypoxia-ischemiashock, near drowning, cardiac or pulmonary failure, CO poisoning, strangulation
NeoplasmParticularly tumors blocking CSF drainage and causing hydrocephalus/herniation	Metabolic disordershypoglycemia, DKA, hepatic encephalopathy, uremia, vitamin deficiency, fluid electrolyte imbalance
Vascularcerebral infarct, cerebral hemorrhage, vasculitis, congenital abnormality of blood supply	Exogenous toxins and poisonsnarcotics, MAOI, antidepressants, antiepilepsy meds, cyanide, heavy metals, EtOH, cocaine, heroin
Focal infectionempyema, abscess, cerebritis	InfectionsBacterial (e.g. Rickettsia), viral
HydrocephalousShunt blockage, tumor	Paroxysmal disordersepilepsy, migraine

*** The mnemonic “TIPS VOWELS” (AEIOU) is commonly used to remember the causes of coma.

T       Trauma

I        Infection (systemic and neurologic)

P        Psychiatric

S       Space occupying lesion, stroke

A       Alcohol and drugs/toxins

E       Endocrine, environment

I        Insulin (hypo/hyperglycemia)

O       Oxygen (hypoxia), Opiates

U       Uremia

Physical Examination

Primary survey

Airway (with C-spine precautions)

• The tongue is the most common cause of obstruction in the unconscious child. Intubation is needed for:
• GCS less than 9 (link to pediatric GCS)
• Poor airway or impending loss of airway
• Raised ICP (to optimally ventilate)
• Precaution during transport or CT scanning

Breathing – must assure adequate oxygenation and ventilation

Circulation – Is the patient in shock?  Check pulses, BP, HR, perfusion, temperature. Is Cushing response (↑BP, ↓HR, abnormal breathing pattern due to ↑ICP) present? Establish IV access.

Disability– Glascow Coma Scale and Glascow Coma Scale-modification for children (link to pediatric GCS) are useful for objective evaluation and quantification of the consciousness-coma continuum.  Note, however, it does not account for the important brainstem reflexes (pupillary, oculocephalic, oculovestibular, corneal).

Secondary survey

Head and Neck

• Bruises, cephalohematoma, swelling suggest cranial trauma.
• Bleeding or clear fluid from nose or ears suggest basilar skull fracture.
• Check fundi for papilledema (increased ICP) and hemorrhage (occult trauma).
• Many metabolic/toxic causes for coma result in symmetrically small pupils with preserved reactivity to light. Hypoxic-ischemic injury produces symmetric dilated pupils that may not respond to light.
• Passive resistance to neck flexion suggests meningeal irritation, tonsillar herniation.
• Positive Kernig’s and Brudzinski’s sign can also indicate meningeal irritation.

Cranial Nerve Exam:

• II, IV, VI – Extra ocular movement (brainstem integrity)
  • Note that the Oculocephalic reflex should not be done if neck injury is suspected
• V, VII  -Corneal reflexes. A normal response is bilateral closure of eyelids after unilateral stimulation of the cornea. Metabolic causes tend to produce bilateral loss of response.
• IX, X -Gag reflex

Sensory and Motor reflexes

• Sensation is grossly tested through the GCS evaluation (link to pediatric GCS)
• Deep tendon reflex (DTR) and/or motor tone asymmetry are important focal findings.

Posturing indicates level of disease in midbrain with reference to the red nucleus:

• Flexor (previously called decorticate): Arms flexed and hands towards midline; legs extended. Indicates damage above the level of the red nucleus in midbrain.
• Extensor (previously called decerebrate): Arms and legs extended; teeth clenched. Indicates severe disease involving central midbrain below the level of the red nucleus.

Cardiovascular

Congenital heart disease or endocarditis may be sources of intracranial thrombi.

Skin

• Cyanosis – poor oxygenation
• Jaundice – liver failure
• Extreme pallor – anemia or shock
• Cherry red skin – CO poisoning
• Rashes – may be seen with certain infections such as meningococcemia
• Increased pigmentation – Addison’s Disease
• Neuro-cutaneous lesions – e.g. tuberous sclerosis may suggest intracranial tumor

Odor of exhaled breath

• EtOH intoxication
• DKA (sweet fruity)
• Uremia (urine like)
• Hepatic coma (musty)

Investigations

Laboratory investigations

• CBC + differential
• Electrolytes
• Bilirubin
• Albumin
• Coagulation profiles
• Liver enzymes
• Creatinine
• BUN
• Ca2+, Mg2+, PO4
• Ammonia
• Lactate
• Tox. Screen
• Glucose

Imaging Studies

• CT/MRI when patient is medically stable.  CT offers faster results, but MRI may be better for herpes simplex encephalopathy, or for acute disseminated encephalomyelitis.
• Lumber puncture should be performed if ICP is not elevated and there is a suspicion of CNS infection.
• EEG is essential to diagnose nonconvulsive status epilepticus.  May also be useful in serial assessment of persistent coma or status epilepticus.
• Neurosurgical consult if appropriate.

References

Bergman I and Painter MJ.  “Neurology” in Nelson Essentials of Pediatrics, 4th Ed (2002).  Pages 776-783.  Saunders, Philadelphia.

www.UptoDate.com, online version 13.1.  Myer E.  “Acute toxic-metabolic encephalopathy”.  Hampers L.  “Approach of the injured child”.

DiMario FJ.  “The nervous system” in Rudolph’s Fundamentals of Pediatrics, 3rd Ed.  Pages 818-822. McGraw-Hill, New York.

Taylor TA and Ashwal S.  “Impairment of Consciousness and Coma” in Pediatric Neurology, Principles and Practice 3rd Ed (1999).  Pages 861-872.  Mosby, St. Louis.

Acknowledgements

Written by: Jimmy S. Lee

Edited by: Elmine Statham