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Chapter 26: Disorders of Consciousness

Samuel Alperin; Melissa Squires,

INTRODUCTION

Consciousness is defined by 2 components, wakefulness and awareness, requiring arousal (pontine tegmentum and thalamus) and awareness (cerebral and subcortical structure).1,2 A spectrum of disease states exists for disorders of consciousness (DOC) including coma, vegetative state/unresponsiveness wakefulness syndrome (UWS), minimally conscious syndrome (MCS), emergence from MCS, and locked-in state. Assessment of DOC in children is complicated by age and developmental stage, and more formal diagnostic tools and outcome assessments in children continue to be needed,3 as DOCs are estimated to affect more than 130,000 children per year in the United States.4

DEFINITIONS

See Table 26–1 for definitions of DOCs.

Table 26–1.Definitions of disorders of consciousness.
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Table 26–1. Definitions of disorders of consciousness.
Disorder Definition Presentation
Coma Sustained loss of wakefulness and loss of awareness due to (1) dysfunction of RAS, (2) dysfunction of cerebral hemispheres (both), (3) bilateral thalamic dysfunction, and/or (4) toxic/metabolic causes.3,5 Eyes closed, completely unarousable, and nonresponsive to all stimuli except reflex responses. Absent sleep-wake cycles. Requires alteration for at least 4 weeks. May evolve to diagnoses below.
Unresponsive wakefulness syndrome (previously vegetative state) Arousal with lack of awareness, sleep-wake cycling, Nonpurposeful motor function, respiratory function/ without pain sensation.1,4 1 month after coma. Eyes may be open without visual fixation. No external evidence of pain. May make sounds, facial expressions, or body movements. Not sustained.
Minimally conscious state (MCS) Present arousal and partial awareness, sleep-wake cycling.6 Usually split into MCS, or MCS without depending on presence or absence of receptive/expressive language, respectively. May follow commands, yes/no, purposeful behaviors (vocalization, reaching objects, visual pursuit, gestures).
Cognitive-motor dissociation Signs of mental activity based on neuroimaging or electrophysiologic paradigms, but unable to outwardly show this with behavioral signs of consciousness.7 Differentiated from locked-in syndrome where there are some willful movements (usually vertical eye movements). Completely unable to move or follow commands with motor activities, but signs of cognition are present when using fMRI or EEG.
Stupor Appears sleeping. Arousable only when noxious stimulus is applied with eye opening and nonverbal communication.
Obtundation Aroused but appears drowsy; reduced alertness. Slowed responses; requires frequent stimuli to stay awake.
Lethargy Mild sleepiness. Confusion and sleepiness.
Delirium Waxing and waning mental status resulting in periods of confusion.2 Disoriented, irritable, fearful, with sensory misperceptions (visual or auditory hallucinations).
Confusion Impaired ability to think and reason clearly.2 Awake and alert but not oriented, with difficulty with cognitive processes and making new memories.

EEG, electroencephalogram; fMRI, functional magnetic resonance imaging; RAS, reticular activating system.

Causes of DOC unique to children can include acute/acquired traumatic brain injury; genetic/perinatal, metabolic, or degenerative causes; status epilepticus; or unknown/undefined causes. One study of over 5000 children with UWS and MCS found that 15.2% had acquired brain injury, 43.2% had perinatal/genetic conditions, and 2.1% had ...

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