Continuous EEG monitoring in the intensive care unit

It is now feasible and desirable to continuously monitor brain function with EEG in critically ill patients. Nonconvulsive seizures are more common than previously recognized and may contribute to impaired mental status and brain injury. Alerting stimuli commonly elicit periodic or ictal-appearing EEG patterns. Cerebral ischemia can be detected at a reversible stage with continuous EEG monitoring (cEEG). With the current availability of treatments for acute ischemia, this early detection has great potential for the prevention of stroke, but is only now beginning to be utilized for this purpose. The intensive care unit poses many technical difficulties for EEG acquisition, and artifact recognition is more important than ever. Recording synchronized video with EEG is essential for maximizing the efficiency and accuracy of cEEG interpretation, and quantitative EEG analysis can be quite helpful. The role of the EEG technologist is particularly important in these patients to aid in recognizing and minimizing artifact, to enhance communication between electroencephalographers and clinicians, to assess the effect of alerting stimuli, and to note possible subtle clinical correlates of electrographic seizures.     

Continuous electroencephalogram monitoring in critically ill patients

The past few years have witnessed remarkable advances in continuous EEG monitoring (cEEG). The indications and applications for cEEG are broadening, including detection of nonconvulsive seizures, spell characterization, and prognostication. Seizures are common in the critically ill, are usually nonconvulsive, and can easily be missed without cEEG. Interpretation and clinical management of the complex periodic and rhythmic EEG patterns commonly identified in these patients require further study. With the use of quantitative analysis techniques, cEEG can detect cerebral ischemia very early, before permanent neuronal injury occurs. This article reviews the indications and recent advances in cEEG in critically ill patients. Continuous brain monitoring with cEEG is rapidly becoming the standard of care in critically ill patients with neurologic impairment.     

Multimodal brain monitoring in the neurological intensive care unit: where does continuous EEG fit in?

Continuous EEG (cEEG) is a vital component of patient monitoring in the neurologic intensive care unit, allowing the intensivist to diagnose nonconvulsive seizure activity. Though still in its infancy, Fourier-transformed cEEG data are also increasingly being used in ICUs to monitor global cerebral activity and cortical function. In conjunction with other components of multimodality neurologic monitoring, including intracranial pressure, cerebral blood flow, brain tissue oxygen tension monitoring, transcranial Doppler, and microdialysis monitoring, cEEG provides unique data regarding the electrical activity of the brain. The main challenge for clinicians and researchers will be to understand how these different aspects of multimodality monitoring relate to each other, and how physiologic variables such as blood pressure, osmolality, and temperature can be manipulated to optimize cerebral function and tissue survival in the setting of acute injury.     

Predictors of nonconvulsive seizures among critically ill children

Purpose: Continuous electroencephalography (EEG) monitoring is a valuable tool for the detection of seizures among critically ill children, in particular when these seizures occur without clinical signs: termed nonconvulsive seizures. Continuous EEG monitoring is a limited resource in many centers. We sought to identify which critically ill children most frequently experience nonconvulsive seizures, and thus may particularly benefit from continuous EEG monitoring. Methods: Single‐center review was undertaken of consecutive diagnostic continuous EEG (cEEG) recordings performed in our pediatric and neonatal intensive care units (ICUs). We examined the indications for monitoring, the clinical characteristics of monitored patients, the occurrence and timing of seizures, and clinical and EEG characteristics associated with nonconvulsive seizures. Key Findings: One hundred twenty‐one patients underwent diagnostic continuous EEG monitoring, for a mean duration of 26 h. Seizures were detected in 32% of these patients, of which 90% experienced some nonconvulsive seizures, and 72% experienced exclusively nonconvulsive seizures. Patients with nonconvulsive seizures had significantly greater odds of having acute epilepsy, acute structural brain injury, prior in‐hospital convulsive seizures, and the presence of interictal epileptiform abnormalities on EEG. Significance: Seizures are common among critically ill children undergoing diagnostic cEEG monitoring. The great majority of these seizures are nonconvulsive, requiring EEG for their detection. Predictors of nonconvulsive seizures include acute epilepsy, acute structural brain injury, prior in‐hospital convulsive seizures, and interictal epileptiform abnormalities on EEG. These findings can help inform future allocation of limited cEEG monitoring resources to those patients at greatest risk for nonconvulsive seizures.     

Continuous EEG Monitoring in the Intensive Care Unit

In the past 15 years, the increased availability and use of continuous electroencephalography (cEEG) in critically ill patients has substantially changed our understanding of the injured brain. We have become increasingly aware that electrographic seizures in this population may have only subtle or no clinical signs and that cEEG greatly increases the likelihood of detecting these seizures. This review highlights the rationale behind using cEEG rather than routine EEG for detection of nonconvulsive seizures and nonconvulsive status epilepticus in critically ill patients and defines which patients are at greatest risk. It also describes other applications of cEEG in the intensive care unit and how it may play an important role in monitoring brain function.     

Continuous EEG monitoring for the detection of seizures in traumatic brain injury, infarction, and intracerebral hemorrhage: "to detect and protect".

Brain injury results in a primary pathophysiologic response that enables the brain to have seizures. Seizures occur frequently after traumatic and nontraumatic intracerebral bleeding. These seizures can be nonconvulsive, and if one does not monitor for seizures, one will not know they are occurring. The use of continuous EEG monitoring (cEEG) to detect brain arrhythmias after a primary insult, much in way that cardiac arrhythmias are detected after myocardial infarction, can influence treatment decisions and mitigate some of the pathophysiologic natural history of brain injuries. Seizures after brain injury worsen clinical outcome and need to be treated. In summary, cEEG is a valuable clinical instrument "to detect and protect," i.e., to detect seizures and protect the brain from seizure-related injury in critically ill patients, whose brains are often in a particularly vulnerable state.     

Continuous EEG monitoring in the evaluation of non-convulsive seizures and status epilepticus

Non-convulsive seizures (NCSzs) and non-convulsive status epilepticus (NCSE) occur in a substantial proportion of patients with acute brain injury. These acute seizure disorders are often unrecognized and under-diagnosed. Seizure semiology of NCSz is too subtle clinically to be noticed. Most often, mental status impairment is the presenting feature. Changes in the functions of the thalamo-cortical system in patients with impaired consciousness can be detected by continuous EEG (cEEG) monitoring. cEEG monitoring allows detection of the changes at a reversible stage, often when there are no clinical indications of such phenomena. In addition EEG provides reasonable spatial resolution and excellent temporal resolution. This makes cEEG an excellent method for supplementing single or serial recordings in the detection of NCSzs and NCSE. Recent advances in digital EEG have made cEEG monitoring in the neurological intensive care unit (NICU) technically feasible. Current evidence suggests that the common clinical denominator associated with electrographic seizures or NCSzs is mental status impairment. In NCSE, the duration of ictal activity and the time of delay to diagnosis are independent predictors of poor outcome. It will be prudent to do cEEG monitoring in any patient with impaired consciousness either in the setting of acute brain injury or with no clear explanation to detect NCSzs/NCSE. Early recognition and timely intervention is likely to be associated with good outcomes.     

Continuous EEG monitoring in patients with subarachnoid hemorrhage.

Patients with subarachnoid hemorrhage (SAH) are at risk for seizures and delayed cerebral ischemia, both of which can be detected with continuous EEG monitoring (cEEG). Ischemia can be detected with EEG at a reversible stage. CEEG may be most useful in patients with poor grade SAH, as the neurological exam is of limited utility in these stuporous or comatose patients. Seizures have been detected in 19% of SAH patients undergoing cEEG, with the vast majority (95%) of these seizures being nonconvulsive and without any detectable clinical correlate. Applying quantitative analysis to the cEEG (relative alpha variability, post-stimulation alpha/delta ratio) allows reliable detection of ischemia from vasospasm, with EEG changes often preceding changes in the clinical exam and other non-continuous monitoring techniques by up to two days. In patients at risk for developing vasospasm, cEEG monitoring, preferably with quantitative EEG analysis, should be started as early as possible and carried out for up to 14 days after the SAH. CEEG findings may lead to therapeutic (e.g., antiepileptic medication, hypertensive therapy, angioplasty) or additional diagnostic interventions such as angiography, CT or MRI.     

Continuous electroencephalogram monitoring in the critically III

The use of continuous electroencephalogram (cEEG) monitoring in the intensive care unit is becoming more widespread, with improvements in data storage capability and networking and the increasing awareness of nonconvulsive seizures. Current and potential uses for this technology include seizure detection, ischemia detection, and prognostication. Nonconvulsive seizures are common in the critically ill, particularly those with acute brain injury and those who are comatose. The implications of some of the electrographical patterns observed in critically ill patients are not yet clear. This article discusses findings with cEEG to date, pitfalls in performing and interpreting these studies, and where we should turn our attention with this underutilized brain monitoring technique.     

The Use of Continuous EEG Monitoring in Intensive Care Units in The Netherlands: A National Survey

Background

Currently, continuous electroencephalographic monitoring (cEEG) is the only available diagnostic tool for continuous monitoring of brain function in intensive care unit (ICU) patients. Yet, the exact relevance of routinely applied ICU cEEG remains unclear, and information on the implementation of cEEG, especially in Europe, is scarce. This study explores current practices of cEEG in adult Dutch ICU departments focusing on organizational and operational factors, development over time and factors perceived relevant for abstaining its use.

Methods

A national survey on cEEG in adults among the neurology and adult intensive care departments of all Dutch hospitals (n?=?82) was performed.

Results

The overall institutional response rate was 78%. ICU cEEG is increasingly used in the Netherlands (in 37% of all hospitals in 2016 versus in 21% in 2008). Currently in 88% of university, 55% of teaching and 14% of general hospitals use ICU cEEG. Reasons for not performing cEEG are diverse, including perceived non-feasibility and lack of data on the effect of cEEG use on patient outcome. Mostly, ICU cEEG is used for non-convulsive seizures or status epilepticus and prognostication. However, cEEG is never or rarely used for monitoring cerebral ischemia and raised intracranial pressure in traumatic brain injury. Review and reporting practices differ considerably between hospitals. Nearly all hospitals perform non-continuous review of cEEG traces. Methods for moving toward continuous review of cEEG traces are available but infrequently used in practice.

Conclusions

cEEG is increasingly used in Dutch ICUs. However, cEEG practices vastly differ between hospitals. Future research should focus on uniform cEEG practices including unambiguous EEG interpretation to facilitate collaborative research on cEEG, aiming to provide improved standard patient care and robust data on the impact of cEEG use on patient outcome.

     

Electrophysiologic Monitoring in Acute Brain Injury

To determine the optimal use and indications of electroencephalography (EEG) in critical care management of acute brain injury (ABI). An electronic literature search was conducted for articles in English describing electrophysiological monitoring in ABI from January 1990 to August 2013. A total of 165 studies were included. EEG is a useful monitor for seizure and ischemia detection. There is a well-described role for EEG in convulsive status epilepticus and cardiac arrest (CA). Data suggest EEG should be considered in all patients with ABI and unexplained and persistent altered consciousness and in comatose intensive care unit (ICU) patients without an acute primary brain condition who have an unexplained impairment of mental status. There remain uncertainties about certain technical details, e.g., the minimum duration of EEG studies, the montage, and electrodes. Data obtained from both EEG and EP studies may help estimate prognosis in ABI patients, particularly following CA and traumatic brain injury. Data supporting these recommendations is sparse, and high quality studies are needed. EEG is used to monitor and detect seizures and ischemia in ICU patients and indications for EEG are clear for certain disease states, however, uncertainty remains on other applications.     

Continuous Electroencephalography (cEEG) Changes Precede Clinical Changes in a Case of Progressive Cerebral Edema

Background

Continuous electroencephalogram (cEEG) is tightly linked to cerebral metabolism and is sensitive to cerebral ischemia and hypoxia. The severity of cerebral ischemia can be seen on cEEG as changes in morphology, amplitude, or frequency, and cEEG may detect neuronal dysfunction at a reversible stage.

Methods

Case report and imaging.

Results

We present a case of focal cerebral edema with changes seen on cEEG 24 h before clinical signs of increased intracranial pressure. cEEG showed developing asymmetry in the left hemisphere followed by burst suppression. The right hemisphere showed similar progression to burst suppression. Complete suppression of both hemispheres was noted 6 h before clinical signs of herniation. Computed tomography (CT) head confirmed a large left parietal intracerebral hematoma with mass effect.

Conclusions

cEEG has applications in monitoring cerebral dysfunction in addition to detecting seizure activity in the intensive care unit. It may serve a vital role in multi-modality monitoring for early recognition of neurological complications from brain injuries that may not be noticed clinically, which is paramount to early intervention.     

Prognostic value of electroencephalography (EEG) for brain injury after cardiopulmonary resuscitation

Cardiac arrest (CA) patients can experience neurological sequelae or even death after successful cardiopulmonary resuscitation (CPR) due to cerebral hypoxia- and ischemia–reperfusion-mediated brain injury. Thus, it is important to perform early prognostic evaluations in CA patients. Electroencephalography (EEG) is an important tool for determining the prognosis of hypoxic–ischemic encephalopathy due to its real-time measurement of brain function. Based on EEG, burst suppression, a burst suppression ratio >0.239, periodic discharges, status epilepticus, stimulus-induced rhythmic, periodic or ictal discharges, non-reactive EEG, and the BIS value based on quantitative EEG may be associated with the prognosis of CA after successful CPR. As measures of neural network integrity, the values of small-world characteristics of the neural network derived from EEG patterns have potential applications.     

Stimulus-induced rhythmic, periodic, or ictal discharges (SIRPIDs): a common EEG phenomenon in the critically ill

PURPOSE: To describe an underrecognized EEG phenomenon in critically ill patients undergoing continuous EEG monitoring (cEEG). We named these EEG patterns stimulus-induced rhythmic, periodic, or ictal discharges (SIRPIDs). METHODS: We reviewed 150 consecutive patients undergoing cEEG during a 9-month period and compared those with and without SIRPIDs. SIRPIDs were defined as periodic, rhythmic, or ictal-appearing discharges that were consistently induced by alerting stimuli. RESULTS: We identified 33 patients with SIRPIDs (22%). SIRPID patterns included periodic epileptiform discharges in 21 patients (nine lateralized) and rhythmic patterns with evolution that fulfilled criteria for ictal discharges in 18 patients (12 unilateral). Eight patients had prior epilepsy; 24 had acute brain injury. Half the patients (17 of 33) had seizures, clinical or subclinical, during the acute illness in addition to SIRPIDs, and half (16 of 33) did not. No significant difference was found in the incidence of clinical seizures in patients with SIRPIDs (30%) compared with those without (45%). Clinical status epilepticus was more common in patients with focal (43%) or ictal-appearing (33%) SIRPIDs than in those without SIRPIDs (17%). CONCLUSIONS: Rhythmic, periodic, or ictal-appearing EEG patterns are commonly elicited by stimulation in critically ill, encephalopathic patients. Recording video, documenting patient stimulation, or repetitively examining patients during cEEG is necessary to recognize these patterns and to differentiate SIRPIDs from spontaneous seizures. Further research is necessary to determine the pathophysiologic, prognostic, and therapeutic significance of SIRPIDs.     

Somatosensory evoked potentials are of additional prognostic value in certain patterns of brain injury in term birth asphyxia

Objective(a) To relate MRI patterns of brain injury to somatosensory evoked potentials (SEPs), and (b) to determine the prognostic value of SEPs in addition to continuous EEG monitoring (cEEG) and cerebral imaging, in term asphyxiated newborns.MethodsFifty one consecutive neonates were studied. Survivors were followed for at least 2 years. cEEG, started within 24 h, was done for ?24 h and scored. SEPs and MRIs were performed in the first week. Brain injury patterns were classified.ResultsBilaterally abnormal SEPs had a sensitivity of 90% (28/31) and specificity of 85% (17/20) in predicting a poor outcome, defined as death or severe handicap. SEPs were of particular value in predicting outcome in isolated symmetrical white matter injury and predicting the development of hemiparesis in isolated asymmetrical watershed injury. Binary logistic regression analysis revealed a significant relation to outcome separately for cEEG, deep grey matter injury on MRI and SEPs. SEPs provided additional value when added to cEEG and MRI in the model (p = 0.034).ConclusionsSEPs are of additional prognostic value after term birth asphyxia.SignificanceIn certain patterns of postasphyxial neonatal brain injury like asymmetrical watershed lesions and symmetrical white matter injury, EPs are complementary to information obtained from cEEG and MRI for prognostication.     

Plenary Session II: Neurophysiological Monitoring of the Critically Ill 8:15 a.m.–10:15 a.m.

¹ Ronald Emerson (   ¹ Neurology, Columbia University, New York, NY )
Until recently, functional neurological assessment of neurologically critically ill patients has been limited largely to periodic physical examinations, often compromised by medication effects, along with occasional, brief EEG's. This is changing with the availability of continuous/EEG monitoring, made practical by recent advances in computer and network technology. Indeed, in some centers, continuous EEG monitoring, with or without concurrent video, has become part of routine neuro-critical care. Its greatest initial impact has been on the recognition and management of non-convulsive seizures. The use of EEG monitoring for real-time detection of cerebral ischemia will likely become compelling as effective treatments for acute stroke emerge. Practical implementation of EEG-based cerebral ischemia detection in the ICU, however, awaits development of reliable, robust automated detection algorithms capable of triggering bedside alarms. Concurrent monitoring of other physiological parameters, including blood pressures, intracranial pressure and brain tissue oxygenation along with EEG-derived parameters may provide the basis for development of better treatment models incorporating multivariable feedback systems. Evoked potentials can provide useful prognostic information, with long latency evoked potentials attracting recent attention as possible predictors of recovery of consciousness in comatose patients.     

Electroencephalography Measures are Useful for Identifying Large Acute Ischemic Stroke in the Emergency Department

Background: Early diagnosis of stroke optimizes reperfusion therapies, but behavioral measures have incomplete accuracy. Electroencephalogram (EEG) has high sensitivity for immediately detecting brain ischemia. This pilot study aimed to evaluate feasibility and utility of EEG for identifying patients with a large acute ischemic stroke during Emergency Department (ED) evaluation, as these data might be useful in the prehospital setting. Methods: A 3-minute resting EEG was recorded using a dense-array (256-lead) system in patients with suspected acute stroke arriving at the ED of a US Comprehensive Stroke Center. Results: An EEG was recorded in 24 subjects, 14 with acute cerebral ischemia (including 5 with large acute ischemic stroke) and 10 without acute cerebral ischemia. Median time from stroke onset to EEG was 6.6 hours; and from ED arrival to EEG, 1.9 hours. Delta band power (P = .004) and the alpha/delta frequency band ratio (P = .0006) each significantly distinguished patients with large acute ischemic stroke (n = 5) from all other patients with suspected stroke (n = 19), with the best diagnostic utility coming from contralesional hemisphere signals. Larger infarct volume correlated with higher EEG power in the alpha/delta frequency band ratio within both the ipsilesional (r = ?0.64, P = .013) and the contralesional (r = ?0.78, P = .001) hemispheres. Conclusions: Within hours of stroke onset, EEG measures (1) identify patients with large acute ischemic stroke and (2) correlate with infarct volume. These results suggest that EEG measures of brain function may be useful to improve diagnosis of large acute ischemic stroke in the ED, findings that might be useful to pre-hospital applications.     

Emergency EEG and continuous EEG monitoring in acute ischemic stroke.

There is physiologic coupling of EEG morphology, frequencies, and amplitudes with cerebral blood flow. Intraoperative continuous electroencephalographic monitoring (CEEG) is an established modality that has been used for 30 years to detect cerebral ischemia during carotid surgery. These facts have generated interest in applying EEG/CEEG in the intensive care unit to monitor cerebral ischemia. However, its use in acute ischemic stroke (AIS) has been limited, and its value has been questioned in comparison with modern MRI imaging techniques and the clinical neurologic examination. This review presents evidence that EEG/CEEG adds value to early diagnosis, outcome prediction, patient selection for treatment, clinical management, and seizure detection in AIS. Research studies correlating EEG/CEEG and advanced imaging techniques in AIS are encouraged. Improvements in real-time ischemia detection systems are needed for EEG/CEEG to have wider application in AIS.     

Continuous electroencephalography in pediatric traumatic brain injury: Seizure characteristics and outcomes

BackgroundTraumatic brain injury (TBI) is a major cause of pediatric morbidity and mortality. Secondary injury that occurs as a result of a direct impact plays a crucial role in patient prognosis. The guidelines for the management of severe TBI target treatment of secondary injury. Posttraumatic seizure, one of the secondary injury sequelae, contributes to further damage to the injured brain. Continuous electroencephalography (cEEG) helps detect both clinical and subclinical seizure, which aids early detection and prompt treatment.ObjectiveThe aim of this study was to examine the relationship between cEEG findings in pediatric traumatic brain injury and neurocognitive/functional outcomes.MethodsThis study focuses on a subgroup of a larger prospective parent study that examined children admitted to a level-1 trauma hospital. The subgroup included sixteen children admitted to the pediatric intensive care unit (PICU) who received cEEG monitoring. Characteristics included demographics, cEEG reports, and antiseizure medication. We also examined outcome scores at the time of discharge and 4–6 weeks postdischarge using the Glasgow Outcome Scale — Extended Pediatrics and center-based speech pathology neurocognitive/functional evaluation scores.ResultsSixteen patients were included in this study. Patients with severe TBI made up the majority of those that received cEEG monitoring. Nonaccidental trauma was the most frequent TBI etiology (75%), and subdural hematoma was the most common lesion diagnosed by CT scan (75%). Fifteen patients received antiseizure medication, and levetiracetam was the medication of choice. Four patients (25%) developed seizures during PICU admission, and 3 patients had subclinical seizures that were detected by cEEG. One of these patients also had both a clinical and subclinical seizure. Nonaccidental trauma was an etiology of TBI in all patients with seizures. Characteristics of a nonreactive pattern, severe/burst suppression, and lack of sleep architecture, on cEEG, were associated with poor neurocognitive/functional outcome.ConclusionContinuous electroencephalography demonstrated a pattern that associated seizures and poor outcomes in patients with moderate to severe traumatic brain injury, particularly in a subgroup of patients with nonaccidental trauma. Best practice should include institution-based TBI cEEG protocols, which may detect seizure activity early and promote outcomes. Future studies should include examination of individual cEEG characteristics to help improve outcomes in pediatric TBI.     

Continuous EEG predictors of outcome in patients with altered sensorium

PurposeTo evaluate EEG predictors of outcome in patients with altered sensorium suspected to have seizure and to assess whether short term EEG is as effective as long term continuous EEG (cEEG) in predicting the outcome of patients with altered sensorium due to neurological causes.MethodsWe identified 99 consecutive critically ill patients with altered sensorium in whom nonconvulsive seizures were suspected. They underwent cEEG. Functional outcome was assessed with the modified Rankin Scale (mRS) at 4 weeks, discharge or death. We compared efficacy of short term EEG and long term continuous EEG in recording the abnormal patterns on EEG. Logistic regression analysis was performed to identify EEG findings associated with poor outcome, defined as mRS 4–6 (dead or moderately to severely disabled).ResultsPoor outcome was associated with nonconvulsive seizures (NCS), nonconvulsive status epilepticus (NCSE), periodic lateralized epileptiform discharges (PLEDS), PLEDS plus, generalized periodic epileptiform discharges (GPEDS) and abnormal EEG background. Short term EEG can detect seizure activity and other electrographic markers of poor outcome but the values are statistically insignificant.ConclusioncEEG monitoring provides independent prognostic information in patients with altered sensorium and suspected seizures. Unfavorable findings include nonconvulsive seizures, periodic epileptiform discharges and abnormal background. Short term EEG is ineffective in detecting seizures on EEG in patients with altered sensorium and should not be used as substitute for Long term EEG