Assessment of Statistically Significant Command-Following in Pediatric Patients with Disorders of Consciousness, Based on Visual, Auditory and Tactile Event-Related Potentials

Disorders of Consciousness in Children: Assessment, Treatment, and Prognosis

Children with acquired brain injury may experience prolonged disorders of consciousness (DoC); research on children with DoC lags behind adult literature. Rigorous evaluation of assessment tools used in children with DoC is lacking, though recent developments may contribute to improvements in care, particularly for assessment of young children and those without overt command following. Literature on prognosis continues to grow, reinforcing that early signs of consciousness suggest better long-term outcome. Although large clinical trials for children with DoC are lacking, single-site and multisite programmatic data inform standards of care and treatment options for children with DoC.

Pediatric disorders of consciousness: Considerations, controversies, and caveats

Pediatric disorders of consciousness (PedDOC) encompass conditions that may occur following very severe traumatic or other forms of acquired brain injury sustained during childhood. As in adults, PedDOC is described as a disturbance of awareness and/or responsiveness. PedDOC is a complex condition that requires specialized care, infrastructures, and technologies. PedDOC poses many challenges to healthcare providers and caregivers during recovery and throughout development. In this commentary, we intend to highlight some considerations, controversies, and caveats on the diagnosis, prognosis and treatment of PedDOC.

Scoping Review on the Diagnosis, Prognosis, and Treatment of Pediatric Disorders of Consciousness

BACKGROUND AND OBJECTIVES

Comprehensive guidelines for the diagnosis, prognosis, and treatment of disorders of consciousness (DoC) in pediatric patients have not yet been released. We aimed to summarize available evidence for DoC with >14 days duration to support the future development of guidelines for children, adolescents and young adults aged 6 months-18 years.

METHODS

This scoping review was reported based on Preferred Reporting Items for Systematic reviews and Meta-Analyses-extension for Scoping Reviews guidelines. A systematic search identified records from 4 databases: PubMed, Embase, Cochrane Library, and Web of Science. Abstracts received 3 blind reviews. Corresponding full-text articles rated as "in-scope" and reporting data not published in any other retained article (i.e., no double reporting) were identified and assigned to 5 thematic evaluating teams. Full-text articles were reviewed using a double-blind standardized form. Level of evidence was graded, and summative statements were generated.

RESULTS

On November 9, 2022, 2,167 documents had been identified; 132 articles were retained, of which 33 (25%) were published over the past 5 years. Overall, 2,161 individuals met the inclusion criteria; female patients were 527 of 1,554 (33.9%) cases included, whose sex was identifiable. Of 132 articles, 57 (43.2%) were single case reports and only 5 (3.8%) clinical trials; the level of evidence was prevalently low (80/132; 60.6%). Most studies included neurobehavioral measures (84/127; 66.1%) and neuroimaging (81/127; 63.8%); 59 (46.5%) were mainly related to diagnosis, 56 (44.1%) to prognosis, and 44 (34.6%) to treatment. Most frequently used neurobehavioral tools included the Coma Recovery Scale-Revised, Coma/Near-Coma Scale, Level of Cognitive Functioning Assessment Scale, and Post-Acute Level of Consciousness scale. EEG, event-related potentials, structural CT, and MRI were the most frequently used instrumental techniques. In 29/53 (54.7%) cases, DoC improvement was observed, which was associated with treatment with amantadine.

DISCUSSION

The literature on pediatric DoCs is mainly observational, and clinical details are either inconsistently presented or absent. Conclusions drawn from many studies convey insubstantial evidence and have limited validity and low potential for translation in clinical practice. Despite these limitations, our work summarizes the extant literature and constitutes a base for future guidelines related to the diagnosis, prognosis, and treatment of pediatric DoC.

Objective Neurophysiologic Markers of Cognition After Pediatric Brain Injury

Background and Objectives

Following brain injury, clinical assessments of residual and emerging cognitive function are difficult and fraught with errors. In adults, recent American Academy of Neurology (AAN) practice guidelines recommend objective neuroimaging and neurophysiologic 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 years, clinically classified according to cognitive recovery state: N = 8 in disorders of consciousness (DoC), N = 7 in confusional state, N = 19 cognitively impaired, and N = 13 typically developing 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 3 participants with DoC, EEG markers of active attempted command following revealed cognitive function that clinical assessment had failed to detect. These same 3 individuals could also be distinguished from the rest of their group by 2 event-related potentials that correlate with sensory processing and orienting attention in the oddball paradigm. Considered across the whole participant group, magnitudes of these 2 ERP markers significantly increased as cognitive recovery progressed (ANOVA: each p < 0.001); viewed jointly, the 2 ERP markers cleanly delineated the 4 cognitive states.

Discussion

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 3 individuals who meet the criteria for cognitive-motor dissociation. To diagnose, prognose, and track cognitive recovery accurately, such markers should be used in pediatrics.

Neuroimaging and neurophysiological diagnosis and prognosis in paediatric disorders of consciousness

The diagnosis and prognosis of disorders of consciousness (DOC) such as coma, unresponsive wakefulness syndrome, or minimally conscious state are especially challenging in children. In some paediatric patients with severe acquired brain injury, medical comorbidities or developmental factors may obscure the detection of signs of consciousness via clinical assessments, thus leading to misdiagnosis. To circumvent these biases, patients benefit from multimodal assessments that combine behavioural, neuroimaging, and neurophysiological measures. In this review, we provide original data for such diagnostic procedures in children. Neuroimaging is largely underdocumented in children and most neurophysiological research consists of a cohort study design aimed at providing prognostic markers for clinical outcomes. The scarcity of available data on complementary diagnostic approaches in children makes it difficult to establish clear paediatric guidelines. Although there is preliminary evidence for the applicability of paradigms involving event-related potentials as support for diagnosis in children, more well-designed studies need to be conducted to promote evidence-based practices in paediatric DOC.

Cognitive-Motor Dissociation Following Pediatric Brain Injury: What About the Children?

Background and Objectives

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 neurophysiologic tests to evaluate 2 adolescents (aged 15 and 18 years) who had shown no clinical evidence of preserved cognitive function following brain injury at age 9 and 13 years, respectively. Clinical evaluations were consistent with minimally conscious state (minus) and vegetative state, respectively.

Results

Both participants' EEG, and 1 participant's fMRI, provided evidence that they could understand commands and make consistent voluntary decisions to follow them. Both participants' EEG demonstrated larger-than-expected responses to auditory stimuli and intact semantic processing of words in context.

Discussion

These converging lines of evidence lead us to conclude that both participants 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.

Brain Data in Pediatric Disorders of Consciousness: Special Considerations

SUMMARY

The diagnosis and management of disorders of consciousness in children continue to present a clinical, research, and ethical challenge. Though the practice guidelines for diagnosis and management of disorders of consciousness in adults are supported by decades of empirical and pragmatic evidence, similar guidelines for infants and children are lacking. The maturing conscious experience and the limited behavioral repertoire to report consciousness in this age group restrict extrapolation from the adult literature. Equally challenging is the process of heightened structural and functional neuroplasticity in the developing brain, which adds a layer of complexity to the investigation of the neural correlates of consciousness in infants and children. This review discusses the clinical assessment of pediatric disorders of consciousness and delineates the diagnostic and prognostic utility of neurophysiological and neuroimaging correlates of consciousness. The potential relevance of these correlates for the developing brain based on existing theoretical models of consciousness in adults is outlined.

Choosing Strategies to Deal with Artifactual EEG Data in Children with Cognitive Impairment

Rett syndrome is a disease that involves acute cognitive impairment and, consequently, a complex and varied symptomatology. This study evaluates the EEG signals of twenty-nine patients and classify them according to the level of movement artifact. The main goal is to achieve an artifact rejection strategy that performs well in all signals, regardless of the artifact level. Two different methods have been studied: one based on the data distribution and the other based on the energy function, with entropy as its main component. The method based on the data distribution shows poor performance with signals containing high amplitude outliers. On the contrary, the method based on the energy function is more robust to outliers. As it does not depend on the data distribution, it is not affected by artifactual events. A double rejection strategy has been chosen, first on a motion signal (accelerometer or EEG low-pass filtered between 1 and 10 Hz) and then on the EEG signal. The results showed a higher performance when working combining both artifact rejection methods. The energy-based method, to isolate motion artifacts, and the data-distribution-based method, to eliminate the remaining lower amplitude artifacts were used. In conclusion, a new method that proves to be robust for all types of signals is designed.

EEG Assessment in a 2-Year-Old Child with Prolonged Disorders of Consciousness: 3 Years' Follow-up

A 2-year-old girl, diagnosed with traumatic brain injury and epilepsy following car trauma, was followed up for 3 years (a total of 15 recordings taken at 0, 2, 3, 4, 5, 6, 7, 9, 10, 11, 12, 14, 19, 26, and 35 months). There is still no clear guidance on the diagnosis, treatment, and prognosis of children with disorders of consciousness. At each appointment, recordings included the child's height, weight, pediatric Glasgow Coma Scale (pGCS), Coma Recovery Scale-Revised (CRS-R), Gesell Developmental Schedule, computed tomography or magnetic resonance imaging, electroencephalogram, frequency of seizures, oral antiepileptic drugs, stimulation with subject's own name (SON), and median nerve electrical stimulation (MNS). Growth and development were deemed appropriate for the age of the child. The pGCS and Gesell Developmental Schedule provided a comprehensive assessment of consciousness and mental development; the weighted Phase Lag Index (wPLI ) in the β-band (13–25 Hz) can distinguish unresponsive wakefulness syndrome from minimally conscious state and confirm that the SON and MNS were effective. The continuous increase of delta-band power indicates a poor prognosis. Interictal epileptiform discharges (IEDs) have a cumulative effect and seizures seriously affect the prognosis.

A Novel Method for Sleep-Stage Classification Based on Sonification of Sleep Electroencephalogram Signals Using Wavelet Transform and Recurrent Neural Network

INTRODUCTION

Visual sleep-stage scoring is a time-consuming technique that cannot extract the nonlinear characteristics of electroencephalogram (EEG). This article presents a novel method for sleep-stage differentiation based on sonification of sleep-EEG signals using wavelet transform and recurrent neural network (RNN).

METHODS

Two RNNs were designed and trained separately based on a database of classical guitar pieces and Kurdish tanbur Makams using a long short-term memory model. Moreover, discrete wavelet transform and wavelet packet decomposition were used to determine the association between the EEG signals and musical pitches. Continuous wavelet transform was applied to extract musical beat-based features from the EEG. Then, the pretrained RNN was used to generate music. To test the proposed model, 11 sleep EEGs were mapped onto the guitar and tanbur frequency intervals and presented to the pretrained RNN. Next, the generated music was randomly presented to 2 neurologists.

RESULTS

The proposed model classified the sleep stages with an accuracy of >81% for tanbur and more than 93% for guitar musical pieces. The inter-rater reliability measured by Cohen's kappa coefficient (κ) revealed good reliability for both tanbur (κ = 0.64, p < 0.001) and guitar musical pieces (κ = 0.85, p < 0.001).

CONCLUSION

The present EEG sonification method leads to valid sleep staging by clinicians. The method could be used on various EEG databases for classification, differentiation, diagnosis, and treatment purposes. Real-time EEG sonification can be used as a feedback tool for replanning of neurophysiological functions for the management of many neurological and psychiatric disorders in the future.