Objective:Following brain injury, clinical assessments of residual and emerging cognitive function are difficult and fraught with errors. In adults, recent AAN practice guidelines recommend objective neuroimaging and neurophysiological measures to support diagnosis. Equivalent measures are lacking in pediatrics—an especially great challenge due to the combined heterogeneity of both brain injury and pediatric development. Therefore, we aim to establish quantitative, clinically practicable measures of cognitive function following pediatric brain injury.Methods:Participants with and without brain injury were aged 8–18, clinically classified according to cognitive recovery state: N=8 in disorders of consciousness (DoC), N=7 in confusional state (CS); N=19 cognitively impaired (CI); N=13 typically-developing (TD) uninjured controls. We prospectively measured electroencephalographic markers of sensory processing and attention in an auditory “oddball'' paradigm, and of covert movement attempts in a command-following paradigm.Results:In three DoC participants, EEG markers of active attempted command-following revealed cognitive function that clinical assessment had failed to detect. These same three individuals could also be distinguished from the rest of their group by two event-related potentials (ERPs) that correlate with sensory processing and orienting attention in the oddball paradigm. Considered across the whole subject group, magnitudes of these two ERP markers significantly increased as cognitive recovery progressed (ANOVA: each p<0.001); viewed jointly, the two ERP markers cleanly delineated the four cognitive states.Conclusion:Despite heterogeneity of brain injuries and brain development, our objective EEG markers reflected cognitive recovery independent of motor function. Two of these markers required no active participation. Together, they allowed us to identify, for the first time in pediatrics, three individuals who meet the criteria for cognitive motor dissociation. To diagnose, prognose and track cognitive recovery accurately, such markers should be employed in pediatrics.

Objective:Following severe brain injury, up to 16% of adults showing no clinical signs of cognitive function nonetheless have preserved cognitive capacities detectable via neuroimaging and neurophysiology; this has been designated cognitive-motor dissociation (CMD). Pediatric medicine lacks both practice guidelines for identifying covert cognition, and epidemiologic data regarding CMD prevalence.Methods:We applied a diverse battery of neuroimaging and neurophysiological tests to evaluate two adolescents (aged 15 and 18) who had shown no clinical evidence of preserved cognitive function following brain injury at age 9 and 13 respectively. Clinical evaluations were consistent with minimally conscious state (minus) and vegetative state, respectively.Results:Both subjects’ EEG, and one subject’s fMRI, provided evidence that they could understand commands and make consistent voluntary decisions to follow them. Both subjects’ EEG demonstrated larger-than-expected responses to auditory stimuli, and intact semantic processing of words in context.Interpretation:These converging lines of evidence lead us to conclude that both subjects had preserved cognitive function dissociated from their motor output. Throughout the 5+ years since injury, communication attempts and therapy had remained uninformed by such objective evidence of their cognitive abilities. Proper diagnosis of CMD is an ethical imperative. Children with covert cognition reflect a vulnerable and isolated population; the methods outlined here provide a first step in identifying such persons to advance efforts to alleviate their condition.