Susan T. Herman

American Clinical Neurophysiology Society's Standardized Critical Care EEG Terminology: 2012 version.

Continuous EEG Monitoring is becoming a commonly used tool in assessing brain function in critically ill patients. However, there is no uniformly accepted nomenclature for EEG patterns frequently encountered in these patients such as periodic discharges, fluctuating rhythmic patterns, and combinatio

Distribution of partial seizures during the sleep–wake cycle Differences by seizure onset site

Objective: To evaluate the effects of sleep on partial seizures arising from various brain regions. Methods: The authors prospectively studied 133 patients with localization-related epilepsy undergoing video-EEG monitoring over a 2-year period. Seizure type, site of onset, sleep/wake state at onset, duration, and epilepsy syndrome diagnosis were recorded. Periorbital, chin EMG, and scalp/sphenoidal electrodes were used. A subset of 34 patients underwent all-night polysomnography with scoring of sleep stages. Results: The authors analyzed 613 seizures in 133 patients. Forty-three percent (264 of 613) of all partial seizures began during sleep. Sleep seizures began during stages 1 (23%) and 2 (68%) but were rare in slow-wave sleep; no seizures occurred during REM sleep. Temporal lobe complex partial seizures were more likely to secondarily generalize during sleep (31%) than during wakefulness (15%), but frontal lobe seizures were less likely to secondarily generalize during sleep (10% versus 26%; p < 0.005). Conclusions: Partial-onset seizures occur frequently during NREM sleep, especially stage 2 sleep. Frontal lobe seizures are most likely to occur during sleep. Patients with temporal lobe seizures have intermediate sleep seizure rates, and patients with seizures arising from the occipital or parietal lobes have rare sleep-onset seizures. Sleep, particularly stage 2 sleep, promotes secondary generalization of temporal and occipitoparietal, but not frontal, seizures. These findings suggest that the hypersynchrony of sleep facilitates both initiation and propagation of partial seizures, and that effects of sleep depend in part on the location of the epileptic focus.

The ACNS subcommittee on research terminology for continuous EEG monitoring: proposed standardized terminology for rhythmic and periodic EEG patterns encountered in critically ill patients.

Continuous EEG monitoring is becoming a commonly usedtool in the assessment of brain function in critically illpatients. However, there is no uniformly accepted nomencla-ture for the EEG patterns frequently encountered in thesepatients, such as periodic discharges, fluctuating rhythmicpatterns, and combinations thereof. Similarly, there is noconsensus regarding which patterns are associated with on-going neuronal injury, which needs to be treated, or howaggressively to treat them. The first step in addressing theseissues is to standardize terminology to allow multicenterresearch projects and to facilitate communication. To thisend, we gathered a group of electroencephalographers withparticular expertise or interest in this area to develop stan-dardized terminology to be used primarily in the researchsetting. One of the main goals was to eliminate terms withclinical connotations, intended or not, such as “triphasicwaves,” a term that implies a metabolic encephalopathy withno relationship to seizures. We also decided to avoid the useof “ictal,” “interictal,” and “epileptiform” for the equivocalpatterns that are the primary focus of this report.A standardized method of quantifying interictal dis-charges is also included for the same reasons, with no attemptto alter the existing definition of epileptiform discharges(sharpwavesandspikes Noachtaretal.,1999 .Similarly,weare not necessarily suggesting abandonment of prior termssuch as periodic lateralized epileptiform discharges (PLEDs)and triphasic waves for clinical use.This is a proposal subject to future modifications basedon use and feedback from others.

ELECTROENCEPHALOGRAPHIC MONITORING DURING HYPOTHERMIA AFTER PEDIATRIC CARDIAC ARREST

Background: Hypoxic ischemic brain injury secondary to pediatric cardiac arrest (CA) may result in acute symptomatic seizures. A high proportion of seizures may be nonconvulsive, so accurate diagnosis requires continuous EEG monitoring. We aimed to determine the safety and feasibility of long-term EEG monitoring, to describe electroencephalographic background and seizure characteristics, and to identify background features predictive of seizures in children undergoing therapeutic hypothermia (TH) after CA. Methods: Nineteen children underwent TH after CA. Continuous EEG monitoring was performed during hypothermia (24 hours), rewarming (12–24 hours), and then an additional 24 hours of normothermia. The tolerability of these prolonged studies and the EEG background classification and seizure characteristics were described in a standardized manner. Results: No complications of EEG monitoring were reported or observed. Electrographic seizures occurred in 47% (9/19), and 32% (6/19) developed status epilepticus. Seizures were nonconvulsive in 67% (6/9) and electrographically generalized in 78% (7/9). Seizures commenced during the late hypothermic or rewarming periods (8/9). Factors predictive of electrographic seizures were burst suppression or excessively discontinuous EEG background patterns, interictal epileptiform discharges, or an absence of the expected pharmacologically induced beta activity. Background features evolved over time. Patients with slowing and attenuation tended to improve, whereas those with burst suppression tended to worsen. Conclusions: EEG monitoring in children undergoing therapeutic hypothermia after cardiac arrest is safe and feasible. Electrographic seizures and status epilepticus are common in this setting but are often not detectable by clinical observation alone. The EEG background often evolves over time, with milder abnormalities improving and more severe abnormalities worsening. BS = burst suppression; CA = cardiac arrest; CPR = cardiopulmonary resuscitation; DD = developmental delay; FEN = fentanyl; FOS = fosphenytoin; HIE = hypoxic ischemic encephalopathy; LEV = levetiracetam; LZP = lorazepam; MDZ = midazolam; NCS = nonconvulsive seizures; NCSE = nonconvulsive status epilepticus; NPV = negative predictive value; PB = phenobarbital; PED = periodic epileptiform discharge; PICU = pediatric intensive care unit; PPV = positive predictive value; SE = status epilepticus; SIDS = sudden infant death syndrome; sz = seizures; TH = therapeutic hypothermia; VEC = vecuronium; VPA = valproic acid; VT = ventricular tachycardia.

Consensus Statement on Continuous EEG in Critically Ill Adults and Children, Part I: Indications

Introduction: Critical Care Continuous EEG (CCEEG) is a common procedure to monitor brain function in patients with altered mental status in intensive care units. There is significant variability in patient populations undergoing CCEEG and in technical specifications for CCEEG performance. Methods: The Critical Care Continuous EEG Task Force of the American Clinical Neurophysiology Society developed expert consensus recommendations on the use of CCEEG in critically ill adults and children. Recommendations: The consensus panel recommends CCEEG for diagnosis of nonconvulsive seizures, nonconvulsive status epilepticus, and other paroxysmal events, and for assessment of the efficacy of therapy for seizures and status epilepticus. The consensus panel suggests CCEEG for identification of ischemia in patients at high risk for cerebral ischemia; for assessment of level of consciousness in patients receiving intravenous sedation or pharmacologically induced coma; and for prognostication in patients after cardiac arrest. For each indication, the consensus panel describes the patient populations for which CCEEG is indicated, evidence supporting use of CCEEG, utility of video and quantitative EEG trends, suggested timing and duration of CCEEG, and suggested frequency of review and interpretation. Conclusion: CCEEG has an important role in detection of secondary injuries such as seizures and ischemia in critically ill adults and children with altered mental status.

Essential services, personnel, and facilities in specialized epilepsy centers-Revised 2010 guidelines

This document was developed by the members of the Committee to Revise the Guidelines for Services, Personnel, and Facilities at Specialized Epilepsy Centers. After discussions with the general membership they were adopted by the Board of the National Association of Epilepsy Centers. The Guidelines will be reviewed and updated when considered necessary by the Board.

Neurologic recovery after therapeutic hypothermia in patients with post-cardiac arrest myoclonus

Early myoclonus in comatose survivors of cardiac arrest, even when it is not myoclonic status epilepticus (MSE), is considered a sign of severe global brain ischemia and has been associated with high rates of mortality and poor neurologic outcomes. We report on three survivors of primary circulatory cardiac arrests who had good neurologic outcomes (two patients with a CPC score=1 and one patient with a CPC score=2) after mild therapeutic hypothermia, despite exhibiting massive myoclonus within the first 4h after return of spontaneous circulation. The concept that early myoclonus heralds a uniformly poor prognosis may need to be reconsidered in the era of post-cardiac arrest mild therapeutic hypothermia.

Consensus Statement on Continuous EEG in Critically Ill Adults and Children, Part II: Personnel, Technical Specifications and Clinical Practice

Introduction: Critical Care Continuous EEG (CCEEG) is a common procedure to monitor brain function in patients with altered mental status in intensive care units. There is significant variability in patient populations undergoing CCEEG and in technical specifications for CCEEG performance. Methods: The Critical Care Continuous EEG Task Force of the American Clinical Neurophysiology Society developed expert consensus recommendations on the use of CCEEG in critically ill adults and children. Recommendations: The consensus panel describes the qualifications and responsibilities of CCEEG personnel including neurodiagnostic technologists and interpreting physicians. The panel outlines required equipment for CCEEG, including electrodes, EEG machine and amplifier specifications, equipment for polygraphic data acquisition, EEG and video review machines, central monitoring equipment, and network, remote access, and data storage equipment. The consensus panel also describes how CCEEG should be acquired, reviewed and interpreted. The panel suggests methods for patient selection and triage; initiation of CCEEG; daily maintenance of CCEEG; electrode removal and infection control; quantitative EEG techniques; EEG and behavioral monitoring by non-physician personnel; review, interpretation, and reports; and data storage protocols. Conclusion: Recommended qualifications for CCEEG personnel and CCEEG technical specifications will facilitate standardization of this emerging technology.

Neonatal seizure detection using multichannel display of envelope trend

We aimed to determine whether analysis of EEG envelope trend aids bedside detection of neonatal seizures. Five neonatal EEGs with multiple seizures were used to determine optimal trend parameters for seizure detection. Using these parameters, envelope trends were generated on eight additional EEGs, evaluated by experienced and inexperienced users, and compared to traditional EEG interpretation. Seizures were best detected using envelope trend of 2–6 Hz activity over 20‐s epochs. Experienced and inexperienced users identified 88% and 55% of prolonged seizures, respectively, 40% and 6% of brief seizures, and 20% and 0% of slowly evolving seizures. All users identified less than two false positives per hour. Thus, an experienced envelope trend user accurately identified longer seizures but did not identify brief or slowly evolving seizures. Less experienced users were less accurate. Trending may be a useful tool for seizure detection in some neonates.

Continuous EEG monitoring: a survey of neurophysiologists and neurointensivists.

Continuous EEG monitoring (cEEG) of critically ill adults is being used with increasing frequency, and practice guidelines on indications for cEEG monitoring have recently been published. However, data describing the current practice of cEEG in critically ill adults is limited. We aimed to describe the current practice of cEEG monitoring in adults in the United States.