Noninvasive Neuromonitoring Modalities in Children Part I: Pupillometry, Near-Infrared Spectroscopy, and Transcranial Doppler Ultrasonography.

BACKGROUND: Noninvasive neuromonitoring in critically ill children includes multiple modalities that all intend to improve our understanding of acute and ongoing brain injury. METHODS: In this article, we review basic methods and devices, applications in clinical care and research, and explore potential future directions for three noninvasive neuromonitoring modalities in the pediatric intensive care unit: automated pupillometry, near-infrared spectroscopy, and transcranial Doppler ultrasonography. RESULTS: All three technologies are noninvasive, portable, and easily repeatable to allow for serial measurements and trending of data over time. However, a paucity of high-quality data supporting the clinical utility of any of these technologies in critically ill children is currently a major limitation to their widespread application in the pediatric intensive care unit. CONCLUSIONS: Future prospective multicenter work addressing major knowledge gaps is necessary to advance the field of pediatric noninvasive neuromonitoring.

Ketamine for Management of Neonatal and Pediatric Refractory Status Epilepticus.

BACKGROUND AND OBJECTIVES: Few data are available regarding the use of anesthetic infusions for refractory status epilepticus (RSE) in children and neonates, and ketamine use is increasing despite limited data. We aimed to describe the impact of ketamine for RSE in children and neonates. METHODS: Retrospective single-center cohort study of consecutive patients admitted to the intensive care units of a quaternary care children's hospital treated with ketamine infusion for RSE. RESULTS: Sixty-nine patients were treated with a ketamine infusion for RSE. The median age at onset of RSE was 0.7 years (interquartile range 0.15-7.2), and the cohort included 13 (19%) neonates. Three patients (4%) had adverse events requiring intervention during or within 12 hours of ketamine administration, including hypertension in 2 patients and delirium in 1 patient. Ketamine infusion was followed by seizure termination in 32 patients (46%), seizure reduction in 19 patients (28%), and no change in 18 patients (26%). DISCUSSION: Ketamine administration was associated with few adverse events, and seizures often terminated or improved after ketamine administration. Further data are needed comparing first-line and subsequent anesthetic medications for treatment of pediatric and neonatal RSE. CLASSIFICATION OF EVIDENCE: This study provides Class IV evidence on the therapeutic utility of ketamine for treatment of RSE in children and neonates.

Variability in Pediatric Brain Death Determination Protocols in the United States.

OBJECTIVE: To determine the variability in pediatric death by neurologic criteria (DNC) protocols between US pediatric institutions and compared to the 2011 DNC guidelines. METHODS: Cross-sectional study of DNC protocols obtained from pediatric institutions in the United States (US) via regional organ procurement organizations. Protocols were evaluated across five domains: general DNC procedures, prerequisites, neurologic examination, apnea testing and ancillary testing. Descriptive statistics compared protocols to each other and the 2011 guidelines. RESULTS: One hundred and thirty protocols were analyzed with 118 dated after publication of the 2011 guidelines. Of those 118 protocols, identification of a mechanism of irreversible brain injury was required in 97%, while 67% required an observation period after acute brain injury before DNC evaluation. Most protocols required guideline-based prerequisites such as exclusion of hypotension (94%), hypothermia (97%), and metabolic derangements (92%). On neurologic examination, 91% required a lack of responsiveness, 93% no response to noxious stimuli, and 99% loss of brainstem reflexes. 84% of protocols required the guideline-recommened two apnea tests. CO2 targets were consistent with guidelines in 64%. Contrary to guidelines, fifteen percent required ancillary testing for all patients and 15% permitted ancillary studies that are not validated in pediatrics. CONCLUSIONS: and Relevance: Variability exists between pediatric institutional DNC protocols in all domains of DNC determination, especially with respect to apnea and ancillary testing. Better alignment of DNC protocols with national guidelines may improve the consistency and accuracy of DNC determination.

Axon degeneration induces glial responses through Draper-TRAF4-JNK signalling.

Draper/Ced-1/MEGF-10 is an engulfment receptor that promotes clearance of cellular debris in C. elegans, Drosophila and mammals. Draper signals through an evolutionarily conserved Src family kinase cascade to drive cytoskeletal rearrangements and target engulfment through Rac1. Glia also alter gene expression patterns in response to axonal injury but pathways mediating these responses are poorly defined. We show Draper is cell autonomously required for glial activation of transcriptional reporters after axonal injury. We identify TNF receptor associated factor 4 (TRAF4) as a novel Draper binding partner that is required for reporter activation and phagocytosis of axonal debris. TRAF4 and misshapen (MSN) act downstream of Draper to activate c-Jun N-terminal kinase (JNK) signalling in glia, resulting in changes in transcriptional reporters that are dependent on Drosophila AP-1 (dAP-1) and STAT92E. Our data argue injury signals received by Draper at the membrane are important regulators of downstream transcriptional responses in reactive glia.

dSarm/Sarm1 is required for activation of an injury-induced axon death pathway.

Axonal and synaptic degeneration is a hallmark of peripheral neuropathy, brain injury, and neurodegenerative disease. Axonal degeneration has been proposed to be mediated by an active autodestruction program, akin to apoptotic cell death; however, loss-of-function mutations capable of potently blocking axon self-destruction have not been described. Here, we show that loss of the Drosophila Toll receptor adaptor dSarm (sterile α/Armadillo/Toll-Interleukin receptor homology domain protein) cell-autonomously suppresses Wallerian degeneration for weeks after axotomy. Severed mouse Sarm1 null axons exhibit remarkable long-term survival both in vivo and in vitro, indicating that Sarm1 prodegenerative signaling is conserved in mammals. Our results provide direct evidence that axons actively promote their own destruction after injury and identify dSarm/Sarm1 as a member of an ancient axon death signaling pathway.

The Drosophila cell corpse engulfment receptor Draper mediates glial clearance of severed axons.

Neuron-glia communication is central to all nervous system responses to trauma, yet neural injury signaling pathways remain poorly understood. Here we explore cellular and molecular aspects of neural injury signaling in Drosophila. We show that transected Drosophila axons undergo injury-induced degeneration that is morphologically similar to Wallerian degeneration in mammals and can be suppressed by the neuroprotective mouse Wlds protein. Axonal injury elicits potent morphological and molecular responses from Drosophila glia: glia upregulate expression of the engulfment receptor Draper, undergo dramatic changes in morphology, and rapidly recruit cellular processes toward severed axons. In draper mutants, glia fail to respond morphologically to axon injury, and severed axons are not cleared from the CNS. Thus Draper appears to act as a glial receptor for severed axon-derived molecular cues that drive recruitment of glial processes to injured axons for engulfment.