Approach to Managing Periodic Discharges

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.

Macroperiodic Oscillations Are Associated With Seizures Following Acquired Brain Injury in Young Children

PURPOSE

Seizures occur in 10% to 40% of critically ill children. We describe a phenomenon seen on color density spectral array but not raw EEG associated with seizures and acquired brain injury in pediatric patients.

METHODS

We reviewed EEGs of 541 children admitted to an intensive care unit between October 2015 and August 2018. We identified 38 children (7%) with a periodic pattern on color density spectral array that oscillates every 2 to 5 minutes and was not apparent on the raw EEG tracing, termed macroperiodic oscillations (MOs). Internal validity measures and interrater agreement were assessed. We compared demographic and clinical data between those with and without MOs.

RESULTS

Interrater reliability yielded a strong agreement for MOs identification (kappa: 0.778 [0.542-1.000]; P < 0.0001). There was a 76% overlap in the start and stop times of MOs among reviewers. All patients with MOs had seizures as opposed to 22.5% of the general intensive care unit monitoring population ( P < 0.0001). Macroperiodic oscillations occurred before or in the midst of recurrent seizures. Patients with MOs were younger (median of 8 vs. 208 days; P < 0.001), with indications for EEG monitoring more likely to be clinical seizures (42 vs. 16%; P < 0.001) or traumatic brain injury (16 vs. 5%, P < 0.01) and had fewer premorbid neurologic conditions (10.5 vs. 33%; P < 0.01).

CONCLUSIONS

Macroperiodic oscillations are a slow periodic pattern occurring over a longer time scale than periodic discharges in pediatric intensive care unit patients. This pattern is associated with seizures in young patients with acquired brain injuries.

How to evaluate and assess the epileptogenic/seizure potential of periodic discharges along the ictal-interictal continuum?

The ictal–interictal continuum (IIC) is a concept used for those particular EEG patterns that do not meet the strict criteria for status epilepticus but may be associated with neuronal injury. The aim of this article is to review equivocal periodic patterns and to discuss their clinical significance along the IIC. The risk of seizures increases when the frequency of periodic discharges exceeds 2 Hz and when the pattern has features of superimposed rhythmic, sharp, or fast activity (plus modifier). Lateralized periodic discharges (LPDs) are one of the best examples of the IIC. Criteria have been proposed for identifying patterns along the IIC that we called “peri-ictal” LPDs. There is ongoing debate about when to treat patients with these EEG patterns along this spectrum. The term IIC is only an EEG description, and does not in itself reflect a clinical diagnosis, hence management is based on EEG alone. The decision to intensify treatment is based on the combination of EEG, the underlying etiology, the level of consciousness, comorbidities, imaging, and other surrogates of “damage.”

Lateralized Periodic Discharges Detected and Described via Intraoperative Neuromonitoring

This case report details lateralized periodic discharges (LPDs) detected and described via intraoperative neuromonitoring during tumor resection. Descriptions and quantifications were made according to the American Clinical Neurophysiology Society's Standardized Critical Care EEG Terminology: 2021 Version. Further, this case illustrates quantitative changes to the LPDs observed in real time as the tumor was removed.

Seizures and epilepsy after intracerebral hemorrhage: an update

Seizures are common after intracerebral hemorrhage, occurring in 6-15% of the patients, mostly in the first 72 h. Their incidence reaches 30% when subclinical or non-convulsive seizures are diagnosed by continuous electroencephalogram. Several risk factors for seizures have been described including cortical location of intracerebral hemorrhage, presence of intraventricular hemorrhage, total hemorrhage volume, and history of alcohol abuse. Seizures after intracerebral hemorrhage may theoretically be harmful as they can lead to sudden blood pressure fluctuations, increased intracranial pressure, and neuronal injury due to increased metabolic demand. Some recent studies suggest that acute symptomatic seizures (occurring within 7 days of stroke) are associated with worse functional outcome and increased risk of death despite accounting for other known prognostic factors such as age and baseline hemorrhage volume. However, the impact of seizures on prognosis is still debated and it remains unclear if treating or preventing seizures might lead to improved clinical outcome. Thus, the currently available scientific evidence does not support the routine use of antiseizure medication as primary prevention among patients with intracerebral hemorrhage. Only prospective adequately powered randomized-controlled trials will be able to answer whether seizure prophylaxis in the acute or longer term settings is beneficial or not in patients with intracerebral hemorrhage.

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.

Electroencephalogram Monitoring in Critical Care

Seizures are common in critically ill patients. Electroencephalogram (EEG) is a tool that enables clinicians to provide continuous brain monitoring and to guide treatment decisions-brain telemetry. EEG monitoring has particular utility in the intensive care unit as most seizures in this setting are nonconvulsive. Despite the increased use of EEG monitoring in the critical care unit, it remains underutilized. In this review, we summarize the utility of EEG and different EEG modalities to monitor patients in the critical care setting.

Monitoring the Burden of Seizures and Highly Epileptiform Patterns in Critical Care with a Novel Machine Learning Method

INTRODUCTION

Current electroencephalography (EEG) practice relies on interpretation by expert neurologists, which introduces diagnostic and therapeutic delays that can impact patients' clinical outcomes. As EEG practice expands, these experts are becoming increasingly limited resources. A highly sensitive and specific automated seizure detection system would streamline practice and expedite appropriate management for patients with possible nonconvulsive seizures. We aimed to test the performance of a recently FDA-cleared machine learning method (Claritγ, Ceribell Inc.) that measures the burden of seizure activity in real time and generates bedside alerts for possible status epilepticus (SE).

METHODS

We retrospectively identified adult patients (n = 353) who underwent evaluation of possible seizures with Rapid Response EEG system (Rapid-EEG, Ceribell Inc.). Automated detection of seizure activity and seizure burden throughout a recording (calculated as the percentage of ten-second epochs with seizure activity in any 5-min EEG segment) was performed with Claritγ, and various thresholds of seizure burden were tested (≥ 10% indicating ≥ 30 s of seizure activity in the last 5 min, ≥ 50% indicating ≥ 2.5 min of seizure activity, and ≥ 90% indicating ≥ 4.5 min of seizure activity and triggering a SE alert). The sensitivity and specificity of Claritγ's real-time seizure burden measurements and SE alerts were compared to the majority consensus of at least two expert neurologists.

RESULTS

Majority consensus of neurologists labeled the 353 EEGs as normal or slow activity (n = 249), highly epileptiform patterns (HEP, n = 87), or seizures [n = 17, nine longer than 5 min (e.g., SE), and eight shorter than 5 min]. The algorithm generated a SE alert (≥ 90% seizure burden) with 100% sensitivity and 93% specificity. The sensitivity and specificity of various thresholds for seizure burden during EEG recordings for detecting patients with seizures were 100% and 82% for ≥ 50% seizure burden and 88% and 60% for ≥ 10% seizure burden. Of the 179 EEG recordings in which the algorithm detected no seizures, seizures were identified by the expert reviewers in only two cases, indicating a negative predictive value of 99%.

DISCUSSION

Claritγ detected SE events with high sensitivity and specificity, and it demonstrated a high negative predictive value for distinguishing nonepileptiform activity from seizure and highly epileptiform activity.

CONCLUSIONS

Ruling out seizures accurately in a large proportion of cases can help prevent unnecessary or aggressive over-treatment in critical care settings, where empiric treatment with antiseizure medications is currently prevalent. Claritγ's high sensitivity for SE and high negative predictive value for cases without epileptiform activity make it a useful tool for triaging treatment and the need for urgent neurological consultation.

Poststroke seizures as stroke mimics: Clinical assessment and management

Epileptic seizures with postictal negative symptoms represent 20% of all suspected strokes and should be considered in the differential diagnosis of stroke in any patient presenting with an acute neurological deficit, mostly in absence of convulsions. Seizures may also occur at stroke onset, and the latter need to be promptly recognized in order to timely administer reperfusion therapies and reduce the risk of irreversible brain injury. Neuroimaging is essential in differentiating between postictal negative symptoms and deficits due to stroke. After the acute phase, poststroke seizures may worsen or cause the reappearance of neurological deficits and consciousness impairment; they can be also misinterpreted as stroke recurrence and lead to delayed treatment with antiepileptic drugs. It is mandatory to maintain a low threshold for suspecting epileptic seizures, and require appropriate electroencephalographic and neuroimaging investigations to promptly ascertain the etiology of any unexplained change in the neurological status and provide the most adequate treatment. This article is part of the Special Issue "Seizures & Stroke".

The EEG Ictal-Interictal Continuum-A Metabolic Roar But a Whimper of a Functional Outcome

Lateralized Periodic Discharges Frequency Correlates With Glucose Metabolism Subramaniam T, Jain A, Hall LT, Cole AJ, Westover MB, Rosenthal ES, Struck AF. Neurology. 2019;92(7):e670-e674.

OBJECTIVE

To investigate the correlation between characteristics of lateralized periodic discharges (LPDs) and glucose metabolism measured by (18)F-fluorodeoxyglucose (FDG)-positron emission tomography (PET).

METHODS

We retrospectively reviewed medical records to identify patients who underwent FDG-PET during electroencephalography (EEG) monitoring with LPDs present during the FDG uptake period. Two blinded board-certified neurophysiologists independently interpreted EEGs. (18)F-fluorodeoxyglucose uptake was measured using standardized uptake value (SUV). Structural images were fused with PET images to aid with localization of SUV. Two PET readers independently measured maximum SUV. Relative SUV values were obtained by normalization of the maximum SUV to the SUV of pons (SUVRpons). Lateralized periodic discharge frequency was analyzed both as a categorical variable and as a continuous measure. Other secondary variables included duration, amplitude, presence of structural lesion, and "plus" EEG features such as rhythmic or fast sharp activity.

RESULTS

Nine patients were identified and 7 had a structural etiology for LPDs. Analysis using frequency as a categorical variable and continuous variable showed an association between increased LPD frequency and increased ipsilateral SUVRpons (P = .02). Metabolism associated with LPDs (0.5 Hz as a baseline) increased by a median of 100% at 1 Hz and for frequencies >1 Hz increased by a median of 309%. There were no statistically significant differences in SUVRpons for other factors including duration (P = .10), amplitude (P = .80), structural etiology (P = .55), or "plus" features such as rhythmic or fast sharp activity (P = .84).

CONCLUSIONS

Metabolic activity increases monotonically with LPD frequency. Lateralized periodic discharge frequency should be a measure of interest when developing neuroprotection strategies in critical neurologic illness. Continuous Electroencephalography After Moderate to Severe Traumatic Brain Injury Lee H, Mizrahi MA, Hartings JA, Sharma S, Pahren L, Ngwenya LB, Moseley BD, Privitera M, Tortella FC, Foreman B. Crit Care Med. 2019;47(4):574-582.

OBJECTIVES

After traumatic brain injury, continuous electroencephalography is widely used to detect electrographic seizures. With the development of standardized continuous electroencephalography terminology, we aimed to describe the prevalence and burden of ictal-interictal patterns, including electrographic seizures after moderate to severe traumatic brain injury, and to correlate continuous electroencephalography features with functional outcome.

DESIGN

Post hoc analysis of the prospective, randomized controlled phase 2 multicenter INTREPID study ( ClinicalTrials.gov : NCT00805818). Continuous electroencephalography was initiated upon admission to the intensive care unit. The primary outcome was the 3-month Glasgow Outcome Scale-Extended. Consensus electroencephalography reviews were performed by raters certified in standardized continuous electroencephalography terminology blinded to clinical data. Rhythmic, periodic, or ictal patterns were referred to as "ictal-interictal continuum"; severe ictal-interictal continuum was defined as greater than or equal to 1.5 Hz lateralized rhythmic delta activity or generalized periodic discharges and any lateralized periodic discharges or electrographic seizures.

SETTING

Twenty US level I trauma centers.

PATIENTS

Patients with nonpenetrating traumatic brain injury and postresuscitation Glasgow Coma Scale score of 4 to 12 were included.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Among 152 patients with continuous electroencephalography (age = 34 ± 14 years; 88% male), 22 (14%) had severe ictal-interictal continuum including electrographic seizures in 4 (2.6%). Severe ictal-interictal continuum burden correlated with initial prognostic scores, including the International Mission for Prognosis and Analysis of Clinical Trials in Traumatic Brain Injury (r = 0.51; P = .01) and Injury Severity Score (r = 0.49; P = .01), but not with functional outcome. After controlling clinical covariates, unfavorable outcome was independently associated with absence of posterior dominant rhythm (common odds ratio, 3.38; 95% confidence interval, 1.30-9.09), absence of N2 sleep transients (3.69; 1.69-8.20), predominant delta activity (2.82; 1.32-6.10), and discontinuous background (5.33; 2.28-12.96) within the first 72 hours of monitoring.

CONCLUSIONS

Severe ictal-interictal continuum patterns, including electrographic seizures, were associated with clinical markers of injury severity but not functional outcome in this prospective cohort of patients with moderate to severe traumatic brain injury. Importantly, continuous electroencephalography background features were independently associated with functional outcome and improved the area under the curve of existing, validated predictive models.