Lateralized Rhythmic Delta Activity and Lateralized Periodic Discharges in Critically Ill Pediatric Patients.

PURPOSE: To evaluate the clinical and electrographic characteristics of critically ill pediatric patients with lateralized rhythmic delta activity (LRDA) and compare them with patients with lateralized periodic discharges (LPDs). METHODS: This was a retrospective study examining consecutive critically ill pediatric patients (1 month-18 years) with LRDA or LPDs monitored on continuous electroencephalography. Clinical, radiologic, and electrographic characteristics; disease severity; and acute sequelae were compared between the two groups. RESULTS: Of 668 pediatric patients monitored on continuous electroencephalography during the study period, 12 (1.79%) patients had LRDA and 15 (2.24%) had LPDs. The underlying etiologies were heterogeneous with no difference in the acuity of brain MRI changes between both groups. Lateralized rhythmic delta activity and LPDs were concordant with the side of MRI abnormality in most patients [85.7% (LRDA) and 83.3% (LPD)]. There was no difference in the measures of disease severity between both groups. Seizures were frequent in both groups (42% in the LRDA group and 73% in the LPD group). Patients in the LPD group had a trend toward requiring a greater number of antiseizure medications for seizure control (median of 4 vs. 2 in the LRDA group, p = 0.09), particularly those patients with LPDs qualifying as ictal-interictal continuum compared with those without ictal-interictal continuum (p = 0.02). CONCLUSIONS: Lateralized rhythmic delta activity and LPDs are uncommon EEG findings in the pediatric population. Seizures occur commonly in patients with these patterns. Seizures in patients with LPDs, especially those qualifying as ictal-interictal continuum, showed a trend toward being more refractory. Larger studies are needed in the future to further evaluate these findings.

Evaluating Injury Severity in Neonatal Encephalopathy Using Automated Quantitative Electroencephalography Analysis: A Pilot Study.

Quantitative analysis of electroencephalography (qEEG) is a potential source of biomarkers for neonatal encephalopathy (NE). However, prior studies using qEEG in NE were limited in their generalizability due to individualized techniques for calculating qEEG features or labor-intensive pre-selection of EEG data. We piloted a fully automated method using commercially available software to calculate the suppression ratio (SR), absolute delta power, and relative delta, theta, alpha, and beta power from EEG of neonates undergoing 72 h of therapeutic hypothermia (TH) for NE between April 20, 2018, and November 4, 2019. We investigated the association of qEEG with degree of encephalopathy (modified Sarnat score), severity of neuroimaging abnormalities following TH (National Institutes of Child Health and Development Neonatal Research Network [NICHD-NRN] score), and presence of seizures. Thirty out of 38 patients met inclusion criteria. A more severe modified Sarnat score was associated with higher SR during all phases of TH, lower absolute delta power during all phases except rewarming, and lower relative delta power during the last 24 h of TH. In 21 patients with neuroimaging data, a worse NICHD-NRN score was associated with higher SR, lower absolute delta power, and higher relative beta power during all phases. QEEG features were not significantly associated with the presence of seizures after correction for multiple comparisons. Our results are consistent with those of prior studies using qEEG in NE and support automated qEEG analysis as an accessible, generalizable method for generating biomarkers of NE and response to TH. Additionally, we found evidence of an immature relative frequency composition in neonates with more severe brain injury, suggesting that automated qEEG analysis may have a use in the assessment of brain maturity.

Hypothermic Protection in Neocortex Is Topographic and Laminar, Seizure Unmitigating, and Partially Rescues Neurons Depleted of RNA Splicing Protein Rbfox3/NeuN in Neonatal Hypoxic-Ischemic Male Piglets.

The effects of hypothermia on neonatal encephalopathy may vary topographically and cytopathologically in the neocortex with manifestations potentially influenced by seizures that alter the severity, distribution, and type of neuropathology. We developed a neonatal piglet survival model of hypoxic-ischemic (HI) encephalopathy and hypothermia (HT) with continuous electroencephalography (cEEG) for seizures. Neonatal male piglets received HI-normothermia (NT), HI-HT, sham-NT, or sham-HT treatments. Randomized unmedicated sham and HI piglets underwent cEEG during recovery. Survival was 2-7 days. Normal and pathological neurons were counted in different neocortical areas, identified by cytoarchitecture and connectomics, using hematoxylin and eosin staining and immunohistochemistry for RNA-binding FOX-1 homolog 3 (Rbfox3/NeuN). Seizure burden was determined. HI-NT piglets had a reduced normal/total neuron ratio and increased ischemic-necrotic/total neuron ratio relative to sham-NT and sham-HT piglets with differing severities in the anterior and posterior motor, somatosensory, and frontal cortices. Neocortical neuropathology was attenuated by HT. HT protection was prominent in layer III of the inferior parietal cortex. Rbfox3 immunoreactivity distinguished cortical neurons as: Rbfox3-positive/normal, Rbfox3-positive/ischemic-necrotic, and Rbfox3-depleted. HI piglets had an increased Rbfox3-depleted/total neuron ratio in layers II and III compared to sham-NT piglets. Neuronal Rbfox3 depletion was partly rescued by HT. Seizure burdens in HI-NT and HI-HT piglets were similar. We conclude that the neonatal HI piglet neocortex has: (1) suprasylvian vulnerability to HI and seizures; (2) a limited neuronal cytopathological repertoire in functionally different regions that engages protective mechanisms with HT; (3) higher seizure burden, insensitive to HT, that is correlated with more panlaminar ischemic-necrotic neurons in the somatosensory cortex; and (4) pathological RNA splicing protein nuclear depletion that is sensitive to HT. This work demonstrates that HT protection of the neocortex in neonatal HI is topographic and laminar, seizure unmitigating, and restores neuronal depletion of RNA splicing factor.

Continuous Electroencephalography (EEG) Protocol Improves Seizure Detection in Children on Extracorporeal Membrane Oxygenation.

BACKGROUND / OBJECTIVE: Seizures are a complication for pediatric patients requiring extracorporeal membrane oxygenation (ECMO). There are no standardized guidelines regarding continuous electroencephalography (EEG) monitoring to detect seizures in these patients, and the impact of protocolized monitoring has not been evaluated. Here we examined the effects of continuous EEG protocol implementation in our pediatric ECMO population. METHODS: Retrospective chart reviews were conducted on 57 patients who underwent extracorporeal membrane oxygenation and concurrent continuous EEG out of 165 patients supported on extracorporeal membrane oxygenation. Timing of continuous EEG initiation and seizures detected by continuous EEG was determined for 5 years prior to and 15 months after protocol implementation. RESULTS: Protocol implementation was associated with increased ECMO-supported patients who were concurrently monitored by continuous EEG. Time from ECMO cannulation to continuous EEG initiation was shorter (median 7 hours after versus 16.2 hours before; P < .001). Patients who had ongoing seizures at the start of continuous EEG recording decreased from 64% preprotocol to 0% postprotocol (P < .001), and there was an associated earlier time to break in status epilepticus postprotocol. Seizures were detected past 48 hours after cannulation in 50% of patients in the postprotocol group. CONCLUSIONS: Protocol implementation resulted in earlier continuous EEG initiation and more EEGs initiated before seizure onset with evidence of altered seizure dynamics. Although current recommendations suggest that continuous EEG duration of 24-48 hours results in seizure detection for >90% of critically ill adults, longer monitoring may be needed to reliably detect seizures in children supported with ECMO, particularly if monitoring is initiated earlier in the post-cannulation period.

Intraoperative Neuromonitoring during Peripheral Arteriovenous Malformation Embolization.

PURPOSE: To evaluate whether intraoperative neuromonitoring (IONM), including pre-embolization lidocaine injection challenge ("provocative testing") is associated with reduced risk of irreversible nerve injury during embolization of peripheral arteriovenous malformations (AVMs). MATERIALS AND METHODS: Medical records of patients with peripheral AVMs who underwent embolotherapy with IONM with provocative testing between 2012 and 2021 were reviewed retrospectively. Data collected included patient demographic characteristics, AVM location and size, embolic agent used, IONM signal changes after lidocaine and embolic agent injections, postprocedural adverse events, and clinical outcomes. Decisions regarding whether embolization would proceed at specific locations were based on IONM findings after the lidocaine challenge and as embolization proceeded. RESULTS: A cohort of 17 patients (mean age, 27 years ± 19; 5 women) who underwent 59 image-guided embolization procedures with adequate IONM data was identified. No permanent neurologic deficits occurred. Transient neurologic deficits were observed in 3 patients (4 sessions), comprising skin numbness (2 patients), extremity weakness (1 patient), and extremity weakness and numbness (1 patient). All neurologic deficits resolved by postoperative day 4 without additional treatment. CONCLUSIONS: IONM, including provocative testing, during AVM embolization may minimize potential nerve injury.

EEG Correlates of Qualitative Hypermetabolic FDG-PET in Patients With Neurologic Disorders.

Background and Objectives: Case reports and case series have described fluorodeoxyglucose (FDG)-PET findings in critically ill patients with rhythmic or periodic EEG patterns, with one reporting that metabolic activity increases with increasing lateralized periodic discharge (LPD) frequency. However, larger studies examining the relationship between FDG-PET hypermetabolism and rhythmic or periodic EEG patterns are lacking. The goal of this study was to investigate the association of FDG-PET hypermetabolism with electroencephalographic features in patients with neurologic disorders. Methods: This was a single-center, retrospective study of adult patients admitted with acute neurologic symptoms who underwent FDG-PET imaging and EEG monitoring within 24 hours. Subjects were divided into 2 groups based on their FDG-PET metabolism pattern: hypermetabolic activity vs hypometabolic or normal metabolic activity. Chi-square tests and logistic regression were used to determine the relationship of FDG-PET metabolism and EEG findings. Results: Sixty patients met the inclusion criteria and underwent 63 FDG-PET studies and EEGs. Twenty-seven studies (43%) showed hypermetabolism while 36 studies (57%) showed either hypometabolism or no abnormalities on FDG-PET. Subjects with hypermetabolic FDG-PET were more likely to have electrographic seizures (44% vs 8%, p = 0.001) and LPDs with/without seizures (44% vs 14%, p = 0.007), but not other rhythmic or periodic EEG patterns (lateralized rhythmic delta activity, generalized periodic discharges, or generalized rhythmic delta activity). Subjects with hypermetabolism and LPDs were more likely to have concurrent electrographic seizures (58% vs 0%, p = 0.03), fast activity associated with the discharges (67% vs 0, p = 0.01), or spike morphology (67% vs 0, p = 0.03), compared with subjects with hypometabolic FDG-PET and LPDs. Discussion: Adults admitted with acute neurologic symptoms who had hypermetabolic FDG-PET were more likely to show electrographic seizures and LPDs, but not other rhythmic or periodic EEG patterns, compared with those with hypometabolic FDG-PET. Subjects with hypermetabolic FDG-PET and LPDs were more likely to have LPDs with concurrent electrographic seizures, LPDs with a spike morphology, and LPDs +F, compared with subjects with hypometabolic FDG-PET.

Neuromonitoring detects brain injury in patients receiving extracorporeal membrane oxygenation support.

OBJECTIVE: There is limited evidence on standardized protocols for optimal neurological monitoring methods in patients receiving extracorporeal membrane oxygenation (ECMO). We previously introduced protocolized noninvasive multimodal neuromonitoring using serial neurological examinations, electroencephalography, transcranial Doppler ultrasound, and somatosensory evoked potentials. The purpose of this study was to examine if standardized neuromonitoring is associated with detection of acute brain injury (ABI) and improved patient outcomes. METHODS: A retrospective analysis of ECMO patients who received neurocritical care consultation was performed and outcomes were reviewed. The cohort was stratified according to those who did not receive standardized neuromonitoring (era 1: 2016-2017) and those who received standardized neuromonitoring (era 2: 2017-2020). Multivariable logistic regression was used to evaluate the association between standardized neuromonitoring and ABI. RESULTS: A total of 215 patients (mean age, 54 years; 60% male) underwent ECMO (71% venoarterial-ECMO) in our institution, 70 in era 1 and 145 in era 2. The proportion of patients diagnosed with ABI were 23% in era 1 and 33% in era 2 (P = .12). In multivariable logistic regression, standardized neuromonitoring (odds ratio, 2.24; 95% CI, 1.12-4.48; P = .02) and pre-ECMO cardiac arrest (odds ratio, 2.17; 95% CI, 1.14-4.14; P = .02) were independently associated with ABI. There was a greater proportion of patients with good neurological outcomes when discharged alive in era 2 (54% vs 30%; P = .04). CONCLUSIONS: Standardized neuromonitoring was associated with increased ABIs in ECMO patients. Although neuromonitoring does not prevent ABI from occurring, it might prevent worsening with timely interventions (eg, anticoagulation management, optimizing oxygen delivery and blood pressure), leading to improved neurological outcomes at discharge.

Recent applications of quantitative electroencephalography in adult intensive care units: a comprehensive review.

Quantitative electroencephalography (qEEG) refers to the numerical analysis and/or visual transformations of raw electroencephalography (EEG) signals. Evaluation of qEEG in intensive care units (ICU) faces unique challenges that warrant investigation separate from those conducted in other settings. Additionally, the pathophysiology, management, and EEG patterns of critically ill conditions often significantly differ between adults and children. Thus, it is important to distinguish the literature on qEEGs specifically performed in adult ICUs. The aim of this review is to summarize the studies using qEEG for clinical evaluation of patients in adult ICUs performed over the past decade (since 2010), and to present the state of the art of these techniques. Overall, these studies have reported that qEEG can reveal important information faster than typically possible with traditional methods of reviewing the raw EEG only, with reasonable accuracy. However, it is crucial to emphasize that qEEG must be reviewed in conjunction with raw EEG and in context of understanding the patients' clinical status. Because each qEEG panel only focuses on a few aspects of the entire EEG, different combinations of qEEG panels may be required for optimal analyses of each medical condition and individual patient. Currently in practical terms, qEEG can serve as a complementary, valuable tool for portions of the EEG that require more detailed review. Further multi-center collaborative studies are needed to ultimately develop standardized methods of employing qEEG that are generalizable across institutions. As qEEG techniques continue to advance, including those involving machine learning, qEEG will further benefit from algorithms specifically suited for ICUs.

Quantitative Assessment of Electroencephalogram Reactivity in Comatose Patients on Extracorporeal Membrane Oxygenation.

Objective assessment of the brain's responsiveness in comatose patients on Extracorporeal Membrane Oxygenation (ECMO) support is essential to clinical care, but current approaches are limited by subjective methodology and inter-rater disagreement. Quantitative electroencephalogram (EEG) algorithms could potentially assist clinicians, improving diagnostic accuracy. We developed a quantitative, stimulus-based algorithm to assess EEG reactivity features in comatose patients on ECMO support. Patients underwent a stimulation protocol of increasing intensity (auditory, peripheral, and nostril stimulation). A total of 129 20-s EEG epochs were collected from 24 patients (age [Formula: see text], 10 females, 14 males) on ECMO support with a Glasgow Coma Scale[Formula: see text]8. EEG reactivity scores ([Formula: see text]-scores) were calculated using aggregated spectral power and permutation entropy for each of five frequency bands ([Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text]. Parameter estimation techniques were applied to [Formula: see text]-scores to identify properties that replicate the decision process of experienced clinicians performing visual analysis. Spectral power changes from audio stimulation were concentrated in the [Formula: see text] band, whereas peripheral stimulation elicited an increase in spectral power across multiple bands, and nostril stimulation changed the entropy of the [Formula: see text] band. The findings of this pilot study on [Formula: see text]-score lay a foundation for a future prediction tool with clinical applications.

Continuous Electroencephalography Markers of Prognostication in Comatose Patients on Extracorporeal Membrane Oxygenation.

BACKGROUND: We aimed to identify continuous electroencephalogram (cEEG) markers associated with survival and death in patients with extracorporeal membrane oxygenation (ECMO) support under standardized sedation cessation protocol. METHODS: Prospectively collected records of adult patients (age ≥ 18 years) who were started on ECMO support in July 2016 to December 2020 at a single tertiary center were analyzed. cEEGs were performed on patients on the basis of inclusion and exclusion criteria. Patients receiving sedation that affect cEEG reactivity at the start of cEEG recording, including propofol, ketamine, or benzodiazepines, were excluded. We allowed fentanyl and dexmedetomidine during cEEG monitoring. cEEGs were evaluated for frequency, amplitude, variability, reactivity, and state changes. RESULTS: Of 290 patients, 40 underwent cEEG in the absence of confounding sedation (median age 60 years, 85% venoarterial-ECMO, 15% venovenous-ECMO). The median length of ECMO support and analyzable cEEG were 143 h and 24 h, respectively. A total of 27 patients underwent withdrawal of life-sustaining therapies (WOLST) during ECMO support. Of the 13 who weaned off ECMO, 9 underwent WOLST later in the hospitalization and 4 survived at hospital discharge. Decisions of WOLST were not influenced by cEEG features' results. Proportions of present EEG reactivity, present state changes, and fair/good variability were significantly higher in patients who survived compared with those who died (odds ratios infinity, infinity, and 13.57, respectively; p values < 0.001, < 0.001, and 0.0299, respectively). Sensitivity and specificity for survival at discharge were 100% and 91.67% for intact reactivity, 100% and 97.20% for present state changes, and 75% and 83.3% for fair/good variability. CONCLUSIONS: Although future multicenter studies with larger patient cohorts are certainly warranted, we were able to validate the feasibility of protocolized sedation cessation and cEEG analyses in the absence of a confounding effect from sedating medications. Moreover, we demonstrate some evidence that cEEG features of intact reactivity, present state changes, and fair/good variability in comatose patients on ECMO may be associated with survival at hospital discharge.

Acute Toxicity and Triphasic Waves-The Example of Cefepime.

PURPOSE: Triphasic waves (TWs) have been associated with a host of medication toxicities, and cefepime has emerged recently as a frequently encountered offending agent. This investigation aims to evaluate cefepime-induced encephalopathy and to report the associated clinical, EEG expression with TWs, and the radiologic findings. METHODS: A retrospective multicenter observational study examining adult patients with cefepime-induced encephalopathy with generalized periodic discharges on either routine or continuous EEG between January 2014 and January 2020. Clinical, electrographic, and radiologic data were collected. Patients in whom cefepime was not the sole causative factor for their encephalopathy were excluded. RESULTS: Twenty-seven patients with cefepime-induced encephalopathy marked by generalized periodic discharges with triphasic morphology were identified at both centers, whereas no patients were presenting with generalized periodic discharges without TWs. Patients had a median age of 63 years (interquartile range, 56-73). Fifty-six percent of the cohort (15 patients) were <65 years of age. Eighteen patients (67%) had either acute or chronic kidney impairment (either acute kidney injury or chronic kidney disease or both), whereas 81% had preexisting white matter disease on brain imaging. Of these, 14 patients (51%) were classified as either moderate or severe. In the majority of the patients, TWs were either state-dependent or stimulus-sensitive, and in one third of them presented only as stimulus-induced pattern. All patients improved with discontinuation of cefepime. CONCLUSIONS: Cefepime toxicity should be considered in the differential diagnosis in encephalopathic patients with TWs. The presence of preexisting white matter disease in these patients should heighten the degree of suspicion, especially in younger patients and patients without renal dysfunction.

Anesthesia-Associated Periodic Discharges.

PURPOSE: Anesthetic agents have been widely used in the treatment of refractory status epilepticus and the medical management of increased intracranial pressure whenever the goal is therapeutic burst suppression. Periodic patterns typically consisting of generalized periodic discharges (GPDs) following emergence from anesthesia have been described in several case reports. However, their clinical significance and in particular whether these patterns are epileptiform remains unclear. METHODS: This is a single-center, retrospective, observational study examining EEG patterns following emergence from pharmacologically induced burst suppression. Clinical and EEG data were collected. Patients who developed GPDs following anesthetic wean were compared with those who did not. RESULTS: Over 4.5 years, 14 patients developed GPDs related to anesthetic withdrawal. The GPDs had a frequency between 0.5 and 2.5 Hz. Generalized periodic discharges related to anesthetic withdrawal were transient, with a median duration of 40 hours (interquartile range, 24-48 hours). Notably, in all patients, the pattern was stimulus dependent. When compared with a control group of 19 consecutive patients who did not develop a generalized periodic pattern in the context of the anesthetic wean, there was no significant difference in the status epilepticus relapse between the two groups (29% vs. 44%; P = 0.63). Patients in the GPD group were more likely to be on pentobarbital (93% vs. 58%; P = 0.05) and were more likely to have concomitant systemic infection treated with antibiotics compared with the control group (86% vs. 42%; P = 0.02). CONCLUSIONS: Generalized periodic patterns are common following the wean of intravenous anesthetics (particularly pentobarbital) and likely represent a transitional encephalopathic state in a subset of patients. Their morphology is distinct and can be differentiated from the reemergence of status epilepticus (if the latter was the indication for anesthetic treatment). Failure to recognize this pattern may lead to prolonged unnecessary treatments if it is mistaken for the emergence of seizure activity. The presence of concomitant systemic infection and associated antibiotic treatment may be risk factors for the development of this pattern.

Acute and Long-Term Outcomes of Lateralized Rhythmic Delta Activity (LRDA) Versus Lateralized Periodic Discharges (LPDs) in Critically Ill Patients.

BACKGROUND: To assess the acute and long-term outcomes for patients with lateralized rhythmic delta activity (LRDA) compared to patients with lateralized periodic discharges (LPDs). METHODS: A single-center retrospective study examining consecutive patients older than 10 years who had LRDA, LPDs, or both on continuous electroencephalographic (cEEG) between 12/01/2015 and 12/31/2017. Outcomes included inpatient mortality, functional outcome at follow-up, inpatient electrographic seizures, and the presence of new epilepsy at follow-up. Patients were classified into 4 groups: LRDA-only (without LPDs), LPDs-only (without LRDA), LRDA/LPDs, and control (without LRDA or LPDs). RESULTS: Twenty-nine patients (2.7%) were in the LRDA-only group, 76 (7%) patients were in the LPDs-only group, and 25 (2.3%) patients had both patterns (LRDA/LPDs group). 68 patients were identified as a control group. Only one patient (3%) in the LRDA-only group died during their hospitalization, compared to 21 patients (28%) in the LPDs-only group, 2 (8%) LRDA/LPDs group and 7 (10%) in the control group (p 0.003). Patients in the LPDs-only group had three times higher odds of adjusted mortality compared to the control group (p 0.05), while there was no difference in the mortality odds between the LRDA-only and control groups. Patients with LRDA-only had higher odds of good functional outcome at clinic follow-up (p 0.04). When compared to control, patients with both IIC patterns (LRDA/LPDs group) had 24.3 higher odds of acute electrographic seizures (p < 0.001), followed by patients in LPDs-only (OR 12.6, p < 0.001) and then LRDA-only (OR 9.4, p = 0.002). The odds of developing epilepsy following discharge were not increased in patients with either LRDA or LPDs (p = 0.9). CONCLUSIONS: Patients with LRDA had superior functional outcome compared to a higher mortality for patients with LPDs. Patients with both patterns had the highest odds of acute seizures, followed by those with only LPDs and then patients with only LRDA. There was no difference in the odds of developing new epilepsy compared to control with any IIC pattern. We hypothesize different underlying mechanisms of injury leading to the observed electrographic patterns.

Neurophysiological Findings and Brain Injury Pattern in Patients on ECMO.

Introduction. Brain injury is a major determinant of outcomes in extracorporeal membrane oxygenation (ECMO). Neurologic prognostication in ECMO has not been established. Absent electroencephalogram (EEG) reactivity and absent N20 on somatosensory evoked potential (SSEP) are associated with poor outcome in other types of brain injuries, especially following cardiopulmonary arrest. It is currently known if the same criteria are applicable in patients on ECMO. Methods. Continuous EEG (cEEG) was performed for patients with a Glasgow Coma Scale (GCS) <8 and SSEP data were performed for patients with a motor GCS < 4 in a prospective observational cohort undergoing ECMO at a tertiary center. EEG variables including reactivity were collected. SSEPs were categorized into absence, delay, or presence of N20. Poor outcome was defined as cerebral performance category 3 to 5 at discharge. Results. We present 13 consecutive patients who underwent both cEEG and SSEP. The median time from cannulation to EEG and SSEP were 3 (interquartile range [IQR] = 1-6) and 5 (IQR = 2-7) days, respectively. All patients were in coma and 12 (92%) had poor outcomes. Ten (77%) underwent brain computed tomography, the findings of which explained coma in only 2. Patients (n = 12) with poor outcome had poor variability, absent reactivity, and lack of sleep features with diffusely slow theta-delta background on the EEG. Despite poor outcomes, all had relatively preserved or normal N20 responses. One patient with preserved reactivity and sleep features on the EEG and intact SSEP had a good outcome. Conclusions. Absent EEG reactivity with the preservation of SSEP N20 was associated with poor outcome in comatose ECMO patients. We advise caution in interpreting electrophysiological tests in prognosticating ECMO patients until the patterns and outcomes are better understood.

Lateralized Rhythmic Delta Activity in Patients With Infectious or Autoimmune Insular Lesions.

INTRODUCTION: Lateralized rhythmic delta activity (LRDA) is a rare pattern on the ictal-interictal continuum (IIC) encountered in critically ill patients. Its association with acute seizures is yet to be fully explored. Insular involvement is a common finding in patients with infectious and autoimmune encephalitis. The association between acute insular lesions and the ictal-interictal continuum, particularly LRDA, has not been explored before. METHODS: A case series of 4 patients with either herpetic or autoimmune encephalitis and prominent insular cortex involvement who had LRDA when monitored on continuous EEG is being presented. RESULTS: Two patients had herpetic encephalitis and 2 patients had autoimmune encephalitis. All patients had either clinical or electrographic seizures with 1 patient progressing into new-onset refractory status epilepticus. CONCLUSION: LRDA can be seen in patients with insular cortex acute inflammation. In this group of patients, LRDA may be associated with a higher risk of acute seizures. The presence of this otherwise not clearly epileptiform pattern should raise the clinical suspicion for the development of acute seizures. Patients with LRDA and ipsilateral insular lesions should be carefully monitored for the development of recurrent electrographic or electroclinical seizures and status epilepticus.

Artifact reduction by using alternating polarity stimulus pairs in intraoperative peripheral nerve action potential recording.

Intraoperative nerve action potential (NAP) recording permits direct study of an injured nerve for functional assessment of lesions in continuity. Stimulus artifact contamination often hampers NAP recording and interferes with its interpretation. In the present study, we evaluated the artifact reduction method using alternating polarity in peripheral nerve recording. Our study was conducted under controlled conditions in laboratory animals. NAPs were recorded from surgically exposed median or ulnar nerves. For the artifact reduction method with alternating polarity, two sequential recordings, one with normal and one with reversed stimulus polarity, were acquired and the signals from this recording pair were averaged. Simulation was also performed to further evaluate the effects of alternating polarity on the waveforms. The results are as follows: First, we found that this method worked for recordings with unsaturated electrical stimulus artifacts. Second, slightly unequal latencies occurred in an NAP pair, and this inequality contributed to a minimal loss of NAP amplitudes when averaging the two recordings. Third, perfect artifact cancelation and minimal signal loss were also demonstrated by simulation. Finally, we applied the method during nerve inching and demonstrated its usefulness in intraoperative NAP recordings as the method made the recording more resilient to short conduction distances. Thus, our findings demonstrate that this artifact reduction method can be used as a supplemental tool together with our previously described bridge grounding technique or the nonlifting nerve recording configuration to further improve intraoperative peripheral nerve recording. The method can be applied in clinical settings.

Noninvasive Neurological Monitoring in Extracorporeal Membrane Oxygenation.

Optimal neurologic monitoring methods have not been characterized for patients on extracorporeal membrane oxygenation (ECMO). We assessed the feasibility of noninvasive multimodal neuromonitoring (NMN) to prognosticate outcome. In this prospective observational study, neurologic examinations, transcranial Doppler (TCD), electroencephalography (EEG), and somatosensory evoked potentials (SSEPs) were performed at prespecified intervals. Outcome at discharge was defined as favorable when modified Rankin Scale (mRS) 0-3; unfavorable when mRS >3. Of 20 patients (median age 60 years), 17 had TCDs, 13 had EEGs, and seven had SSEPs. With NMN, 17 (85%) were found to have neurologic complications. Fourteen (70%) had unfavorable outcomes. The unfavorable outcome was associated with absent EEG reactivity, coma, central cannulation, higher transfusion requirement, and higher Acute Physiology and Chronic Health Evaluation II and Sepsis-related Organ Failure Assessment scores. Seven patients had both SSEPs and EEGs and exhibited intact N20 responses despite poor outcomes. Four of these seven showed absent EEG reactivity despite intact N20. Eighteen thromboembolic events were observed, 14 of which had positive microembolic signals (MESs) in TCD. All 10 patients with arterial-sided thrombotic events had positive MES. NMN caused no adverse effects. NMN during ECMO is feasible and found high neurologic complication rate. EEG and TCD showed potential for prognostication of neurologic outcome.

Solutions to the technical challenges embedded in the current methods for intraoperative peripheral nerve action potential recordings.

OBJECTIVE: Intraoperative nerve action potential (NAP) recording is a useful tool for surgeons to guide decisions on surgical approaches during nerve repair surgeries. However, current methods remain technically challenging. In particular, stimulus artifacts that contaminate or mask the NAP and therefore impair the interpretation of the recording are a common problem. The authors' goal was to improve intraoperative NAP recording techniques by revisiting the methods in an experimental setting. METHODS: First, NAPs were recorded from surgically exposed peripheral nerves in monkeys. For the authors to test their assumptions about observed artifacts, they then employed a simple model system. Finally, they applied their insights to clinical cases in the operating room. RESULTS: In monkey peripheral nerve recordings, large stimulus artifacts obscured NAPs every time the nerve segment (length 3-5 cm) was lifted up from the surrounding tissue, and NAPs could not be recorded. Artifacts were suppressed, and NAPs emerged when "bridge grounding" was applied, and this allowed the NAPs to be recorded easily and reliably. Tests in a model system suggested that exaggerated stimulus artifacts and unmasking of NAPs by bridge grounding are related to a loop effect that is created by lifting the nerve. Consequently, clean NAPs were acquired in "nonlifting" recordings from monkey peripheral nerves. In clinical cases, bridge grounding efficiently unmasked intraoperative NAP recordings, validating the authors' principal concept in the clinical setting and allowing effective neurophysiological testing in the operating room. CONCLUSIONS: Technical challenges of intraoperative NAP recording are embedded in the current methods that recommend lifting the nerve from the tissue bed, thereby exaggerating stimulus artifacts by a loop effect. Better results can be achieved by performing nonlifting nerve recording or by applying bridge grounding. The authors not only tested their findings in an animal model but also applied them successfully in clinical practice.