30-minute EEG Research Articles

The Clinical Utility of Long-Term Video-EEG Monitoring in Patients Hospitalized for New-Onset Seizures (P6-1.004)

<h3>Objective:</h3> The objective of this study is to evaluate if long-term EEG monitoring (LTM) increases the detection rate of epileptiform abnormalities and seizures as compared to a standard 30-minute EEG in patient’s with first time seizures. <h3>Background:</h3> The usage of LTM has increased in the hospital setting for patients with altered mental status and paroxysmal spells, however, there is limited data regarding the utility of long term EEG monitoring in patients hospitalized for a new-onset seizure. <h3>Design/Methods:</h3> This was a retrospective cohort study including adult patients (&gt;18 years) admitted to two tertiary care hospitals between 1/1/2014 and 12/31/2019. Patients who were given a clinical diagnosis of seizure and were initiated with LTM (monitoring duration of greater than 30 minutes) were included in this study. 295 consecutive patients were initially identified. Patients with a prior diagnosis of seizure/epilepsy or an alternative diagnosis to seizure were excluded. 84 patients qualified for the study. <h3>Results:</h3> 41/84 (49%) patients had EEG recordings of 12–24 hours and 16/84 (19%) had recordings for &gt;24 hours. Drowsy and Sleep states were captured in 82/84 (97.6%). 25/84 (30%) patients were found to have epileptiform activity. Of those, 18/25 (72%) had epileptiform activity occurring within the first 30 minutes. 3/25 (12%) had their first epiletiform activity between 30 and 120 minutes and 4/25 (16%) between 2–12 hours. <h3>Conclusions:</h3> This study raises the possibility of increasing EEG yield with a longer recording period when compared to a 30-minute EEG record. EEG findings that prompted management changes were noted after 30 minutes in just under a third of those found to have epileptiform activity on EEG. This suggests a longer EEG recording period especially in patients with a high clinical suspicion of first-time seizure, may be helpful in determining management. Further prospective studies with a larger sample size, would be of benefit and provide further insight. <b>Disclosure:</b> Dr. Cheng has nothing to disclose. Dr. Rameez has nothing to disclose. Dr. Abbas has nothing to disclose. David E. Burdette, MD has nothing to disclose. Dr. Tank has nothing to disclose. Dr. Chen has nothing to disclose. Rachel Fabris has nothing to disclose. Dr. Okazaki has nothing to disclose. Mohammad Haykal, MD has nothing to disclose.

1230 An unusual presentation of dementia with Lewy bodies in a septuagenarian

Abstract Introduction Dementia with Lewy bodies (DLB) can be associated with degeneration of the hypocretin system and reduced hypocretin levels. However, reports of DLB initially presenting with narcolepsy with cataplexy symptoms are sparse. Report of Case A 77-year-old man presents with two years of new onset hypersomnia, tremors, memory difficulties, and gait instability. Before his sleep evaluation, he was started on levetiracetam for suspected seizures and levodopa for suspected Parkinson’s disease, without improvement. During his evaluation for hypersomnia, he reported loud snoring, witnessed apneas, sleep maintenance difficulty, hypnagogic hallucinations of well-formed images, and vivid dreams with dream enactment behavior occurring almost nightly. He had witnessed episodes of cataplexy described as transient lower extremity weakness with associated bifacial weakness, inability to speak, and no loss of consciousness, self-injury, loss of bowel/bladder control, or post-event symptoms. These events completely resolved after 1-minute, occurred while sitting or standing, and were spontaneous or triggered by anger or anxiety. His Epworth Sleepiness Scale was 18 and Ullanlinna Narcolepsy Scale was 35, suggestive of narcolepsy with cataplexy. Physical examination did not reveal Parkinsonism or resting tremor. He subsequently underwent a baseline polysomnogram that showed an apnea-hypopnea index of 32.7 events/hour. During an in-laboratory titration study, he had REM sleep without atonia. A 30-minute EEG was interpreted as normal and a typical cataplexy-like event captured during continuous EEG monitoring had no ictal correlate. Despite adherence to positive airway pressure therapy, he continued to have hypersomnia, cataplexy, and visual hallucinations during transitions from wake to sleep. He was tapered off levetiracetam and levodopa with a plan for further evaluation of probable DLB. Conclusion Narcolepsy with cataplexy symptoms is an uncommon presentation of probable DLB as seen in this case with two core clinical features of DLB (RBD and visual hallucinations), suggesting neurodegeneration of the hypocretin system.

Prolonged EEGs in adult patients with a first unprovoked seizure: a prospective pilot study.

Definitions of epilepsy have changed to include a first unprovoked seizure with a high (>60%) risk of recurrence in the next 10 years. A single seizure and an epileptiform discharge on an EEG would suffice for this diagnosis. We hypothesized that an extended six-hour EEG in adult patients presenting with a first unprovoked seizure would demonstrate an increased yield of epileptiform discharges in comparison to a standard 30-minute EEG, and therefore higher rates of epilepsy diagnosis. Thirty-eight patients were recruited at Hamilton Health Sciences over six years and 36 underwent extended six-hour EEGs. Two of seven patients demonstrated epileptiform discharges on their EEG after only the first 30 minutes of recording, observed during sleep for both patients. This correlated to an overall increase of 5.56%, or a yield of 29%. A third more patients could benefit from early diagnosis with extended EEGs. The rate of epilepsy diagnosis based on EEG overall was superior to that of brain imaging (19% versus 6%). Given the limitations due to sample size in this study, a larger trial would be beneficial to confirm these findings.

Editors' note: Continuous EEG is associated with favorable hospitalization outcomes for critically ill patients

In “Continuous EEG is associated with favorable hospitalization outcomes for critically ill patients,” Hill et al. retrospectively reviewed national inpatient hospitalization data over a 10-year period and found that continuous EEG (cEEG) use increased >10-fold from 2004 to 2013, but that it was still only used for 0.3% of critically ill patients. They noted that although patients evaluated with cEEG appeared more ill, its use was associated with lower in-hospital mortality for critically ill patients, prompting them to conclude that cEEG may be underused. At a single institution, Sethi found that cEEG use increased >5-fold from 2005 to 2011, but he notes that in some cases, cEEG was unnecessary, and a 30-minute emergent EEG would have been sufficient. He comments that better guidelines are needed on the indications for cEEG vs 30-minute EEG in critically ill patients. Hill et al. agree that it is necessary to further evaluate which subgroups of critically ill patients benefit from cEEG the most to ensure that resources are allocated appropriately. In “Patient-reported outcomes across cerebrovascular event types: More similar than different,” Katzan et al. retrospectively reviewed patient-reported measures in multiple domains over a 2-year period for 2,181 patients with ischemic stroke, TIA, intracerebral hemorrhage (ICH), and subarachnoid hemorrhage (SAH) at a single institution. After adjustment, patients with TIA had worse scores for pain, fatigue, anxiety, depression, and sleep than patients with the various forms of stroke. Spector notes that although the data for ischemic stroke, ICH, and SAH are interesting, the TIA results must be interpreted with caution because (1) there were no premorbid data on these domains, so it is unclear whether symptoms can be attributed to the TIA, and (2) some of the TIAs likely were not even ischemic. Katzan et al. agree with both of these limitations. Both Katzan et al. and Spector feel that further research of the impact of TIA on the aforementioned domains is needed.

Diagnostic Yield of 2-Hour EEG Is Similar With 30-Minute EEG in Patients With a Normal 30-Minute EEG.

Current literature suggests that longer duration of EEG recording increases the yield of detecting interictal epileptiform discharges. However, optimal duration for a repeat study in patients with initially normal 30-minute EEG is not clear. Thus, the purpose of this study is to determine whether a 2-hour EEG has a diagnostic advantage over a routine 30-minute EEG in detecting epileptiform abnormalities in patients who had a first normal 30-minute EEG. This is a single-center, retrospective study done at UT Southwestern Medical Center at Dallas and Parkland Memorial Hospital. The data from 1997 to 2015 were extracted from the existing EEG report database for patients who had a first normal 30-minute EEG recording. EEG was interpreted by board-certified clinical neurophysiologists, who classified each EEG as normal or abnormal, with relevant subsequent subclassification. Over 18 years, a total of 12,425 individual 30-minute EEGs were performed. Of these, 1,023 patients had at least one repeated EEG after the first normal EEG. Among these patients, 763 had a 30-minute EEG as the second study and 260 had a 2-hour EEG as the second study. The yield of epileptiform discharges was 3.3% in the 30-minute EEG group and 4.2% in the 2-hour EEG group (P = 0.5) in the repeating studies. Two-hour EEG has a similar yield as 30-minute EEG to detect epileptiform discharges in patients with a normal 30-minute EEG.

The diagnostic value of continuous EEG for the detection of non-convulsive status epilepticus in neurosurgical patients – A prospective cohort study

ObjectiveTo prospectively compare the diagnostic yields of standard EEG and continuous EEG (cEEG) monitoring for the diagnosis of non-convulsive status epilepticus (NCSE) in neurosurgical patients in the intensive care unit. MethodsWe included 50 consecutive patients with clinical suspicion of NCSE due to unexplained coma or subtle clinical phenomena such as discrete myoclonus. The initial 30-minute EEG recording and the following cEEG were analyzed separately for seizure activity. Data were collected on neurosurgical diagnosis, previous diagnosis of epilepsy, current medication, level of consciousness, and outcome at discharge from the neurosurgical department. ResultsRecurrent electrographic seizure activity was detected in five patients. This was within the first 30 mins for three patients and on the following cEEG for two patients. Antiepileptic treatment had been initiated in three of these patients. Most of the 50 patients had severe newly acquired neurological disability at discharge. ConclusionsThe prospective finding of a 10% seizure incidence was lower than reports from retrospective studies. SignificanceUse of cEEG led to detection of seizure activity in 2 of 50 patients (4%) and was thus a low-yield method in neurosurgical patients with suspicion of NCSE. Specific markers for patient selection for cEEG are needed.

Seizure in Alzheimer's Disease: An Underestimated Phenomenon.

Alzheimer's disease (AD) is considered as a potential risk factor for the development of seizure due to neurodegeneration and imbalance between stimulatory and inhibitory circuits in the brain. Seizure could occur in any point during the course of AD, and its presentation varies from fluctuation in cognitive domains to more typical seizures. The clinical diagnosis of seizure in patients with dementia may be challenging due to difficulty in history taking and clinical assessment. No paraclinic methods other than electroencephalogram (EEG) could provide arguments for the diagnosis of AD-related seizures (neither imaging modalities nor cerebrospinal fluid biomarkers). Standard 30-minute EEG may not be sufficiently sensitive to detect epileptiform discharges. In the present study, we aim to review different aspects of seizure in AD, including seizure prevalence, risk factors, underlying mechanisms, electroencephalographic findings, clinical presentations, impact of seizures on AD, and treatment options.

Seizure incidence in the acute postneurosurgical period diagnosed using continuous electroencephalography.

Delay in diagnosis and subsequent treatment of nonconvulsive seizures can lead to worsened outcomes. The gold standard in detecting nonconvulsive seizures is continuous video-electroencephalography (cEEG). Compared to routine, 30-minute EEG, the use of cEEG increases the likelihood of capturing intermittent nonconvulsive seizures. Studies of critically ill patients in intensive care units demonstrate a particularly high rate of nonconvulsive seizures. Some of these studies included postneurosurgical patients, but often subanalyses of specific populations were not done. In particular, few studies have specifically evaluated postneurosurgical patients by using cEEG in the acute postoperative setting. Therefore, the incidence and predictors of acute postneurosurgical seizures are unclear. In this study, the authors focused on patients who were admitted to the neurological critical care unit following neurosurgery and who underwent cEEG monitoring within 72 hours of surgery. A total of 105 cEEG studies were performed in 102 patients. Twenty-nine patients demonstrated electrographic (subclinical) seizures, of whom 10 had clinical seizures clearly documented either before or during cEEG monitoring. Twenty-two patients had subclinical seizures only detected on cEEG, 19 of whom did not have clinical seizure activity at any point during hospitalization. Those with seizures were more likely to have had a history of epilepsy (p = 0.006). The EEG studies of patients with seizures were more likely to show lateralized periodic discharges (p = 0.012) and lateralized rhythmic delta activity (p = 0.012). The underlying neuropathological disorders most associated with seizure risk were lobar tumor on presentation (p = 0.048), subdural hematoma (SDH) requiring craniotomy for evacuation (p = 0.002), subarachnoid hemorrhage (SAH) (p = 0.026), and perioperative SAH (p = 0.019). In those undergoing craniotomy, the presence of SDH (p = 0.032), particularly if requiring evacuation (p = 0.003), increased the risk of seizures. In those without preoperative intracranial bleeding, perioperative SAH after craniotomy was associated with a higher incidence of seizures (p = 0.014). There was an additive effect on seizure incidence when perioperative SAH as well as concomitant intraparenchymal hemorrhage and/or stroke were present. The clinical examination of the patient, including the presence or absence of altered mental status and the presence or absence of repetitive movements, was not predictive of subclinical seizures. In postneurosurgical patients referred for cEEG monitoring, there is a high rate of both clinical and subclinical seizures in the early postoperative period. Seizures are particularly common in patients with SDH or lobar tumor and perioperative SAH. There was an additive effect on seizure incidence when more extensive brain injury was present. As expected, those with a history of epilepsy also demonstrated higher seizure rates. Further studies are needed to evaluate the time period of maximum seizure incidence after surgery, and the effects acute postneurosurgical seizures have on long-term outcomes.

Disruption of Brain-Heart Coupling in Sepsis.

To investigate heart rate and EEG variability and their coupling in patients with sepsis and determine their relationship to sepsis severity and severity of sepsis-associated brain dysfunction. Fifty-two patients with sepsis were prospectively identified, categorized as comatose (N = 30) and noncomatose (N = 22), and compared with 11 control subjects. In a 30-minute EEG and electrocardiogram recording, heart rate variability and EEG variability (measured by the variability of relative power in a modified alpha band = RAP) and their coupled oscillations were quantified using linear (least-square periodogram and magnitude square coherence) and nonlinear (Shannon entropy and mutual information) measures. These measures were compared between the three groups and correlated with outcome, adjusting for severity of sepsis. Several measures of heart rate variability and EEG variability and of their coupled oscillations were significantly lower in patients with sepsis compared with controls and correlated with outcome. This correlation was not independent when adjusting for severity of sepsis. Sepsis is associated with lower variability of both heart rate and RAP on EEG and reduction of their coupled oscillations. This uncoupling is associated with the severity of encephalopathy. Combined EEG and electrocardiogram monitoring may be used to gain insight in underlying mechanisms of sepsis and quantify brainstem or thalamic dysfunction.

EEG Characteristics in Cooled and Rewarmed Periods in Post-cardiac Arrest Therapeutic Hypothermia Patients.

Continuous video EEG is a tool to assess brain function in injuries, including cardiac arrest (CA). In post-CA therapeutic hypothermia (TH) studies, some EEG features are linked to poor prognosis, but the evolvement of EEG characteristics during two temperature phases and its significance is unclear. We systematically analyzed EEG characteristics in cooled and rewarmed phases of post-CA therapeutic hypothermia patients and investigated their correlation to patient outcome. This is a retrospective study of EEG analyses, from a single academic center, of 20 patients who underwent CA and therapeutic hypothermia. For each patient, three 30-minute EEG segments in cooled and rewarmed phases were analyzed for continuity, frequency, interictal epileptiform discharges, and seizures. Mortality at the time of discharge was used as outcome. Rewarming was associated with the emergence of interictal epileptiform discharges, 2.6 times as likely compared with the cooled period (P = 0.03), and was not affected by systemic factors. Continuity, frequency, and discrete seizures were unaffected by temperature and did not show variance within each temperature phase. There was a trend toward the emergence of interictal epileptiform discharges upon rewarming and mortality, but it was not statistically significant. Increased interictal epileptiform discharges with rewarming in post-CA therapeutic hypothermia patients may suggest poor prognosis, but a larger scale prospective study is needed.

The First-Time Seizure Emergency Department Electroencephalogram Study

Seizures account for 1.2% of all emergency department (ED) visits, with 24% of those representing first-time seizures. Our primary goal is to determine whether obtaining an electroencephalogram (EEG) in the ED after a first-time seizure can identify individuals appropriate for initiation of anticonvulsant therapy on ED discharge. Our secondary goals are to determine the association of historical and clinical seizure features with epileptic EEGs and to determine the interobserver agreement for the EEG interpretation. We conducted a prospective study including patients older than 17 years with either a first-time seizure or previous seizures without a previous EEG, all of whom were candidates for discharge home from the ED without antiepileptic drug treatment. We based seizure diagnosis on provider impression. We excluded patients with laboratory studies or neuroimaging deemed to be the seizure cause. EEG technicians performed a 30-minute EEG in the ED, which was immediately remotely interpreted by an epileptologist, who made a recommendation on antiepileptic drug initiation. We categorized EEGs as normal, abnormal but not epileptic, or epileptic. In accordance with duplicate EEG interpretation by a second, blinded epileptologist, we calculated interrater agreement for EEG interpretation and antiepileptic drug initiation. As a secondary analysis, according to questionnaires completed by patients and seizure observers, we explored the association of aura, focal symptoms, provocation, or historical risk factors with epilepsy. We enrolled 73 patients, 71 of whom had an EEG performed. All EEGs were performed within 11 hours of seizure, with an average of 3.85 hours. Twenty-four percent of patients (95% confidence interval 15% to 36%) received a diagnosis of epilepsy, and all began receiving antiepileptic drug therapy from the ED. Our final study sample size afforded only an exploratory analysis about an association between aura, focal onset, provocation, or historical risk factors with an epilepsy diagnosis. Weighted κ agreement for EEG interpretation was 0.69 (95% confidence interval 0.55 to 0.82). Of the 34 patients who followed up with an epileptologist, 9 had received a diagnosis of epilepsy in the ED, and none had antiepileptic drug medication stopped at initial follow-up. ED EEG performance in adults with first-time seizures results in a substantial yield of an epilepsy diagnosis and immediate initiation of antiepileptic drug treatment. A larger study is required to determine whether historical and clinical seizure features are associated with an ED epilepsy diagnosis.

Absence of early epileptiform abnormalities predicts lack of seizures on continuous EEG

To determine whether the absence of early epileptiform abnormalities predicts absence of later seizures on continuous EEG monitoring of hospitalized patients. We retrospectively reviewed 242 consecutive patients without a prior generalized convulsive seizure or active epilepsy who underwent continuous EEG monitoring lasting at least 18 hours for detection of nonconvulsive seizures or evaluation of unexplained altered mental status. The findings on the initial 30-minute screening EEG, subsequent continuous EEG recordings, and baseline clinical data were analyzed. We identified early EEG findings associated with absence of seizures on subsequent continuous EEG. Seizures were detected in 70 (29%) patients. A total of 52 patients had their first seizure in the initial 30 minutes of continuous EEG monitoring. Of the remaining 190 patients, 63 had epileptiform discharges on their initial EEG, 24 had triphasic waves, while 103 had no epileptiform abnormalities. Seizures were later detected in 22% (n = 14) of studies with epileptiform discharges on their initial EEG, vs 3% (n = 3) of the studies without epileptiform abnormalities on initial EEG (p < 0.001). In the 3 patients without epileptiform abnormalities on initial EEG but with subsequent seizures, the first epileptiform discharge or electrographic seizure occurred within the first 4 hours of recording. In patients without epileptiform abnormalities during the first 4 hours of recording, no seizures were subsequently detected. Therefore, EEG features early in the recording may indicate a low risk for seizures, and help determine whether extended monitoring is necessary.

EEG Infraslow Activity in Absence and Partial Seizures

It is currently assumed that for recording of infraslow activity (ISA) DC-coupled amplifiers are required. This report will demonstrate that this may not be the case and presents some data about its potential clinical usefulness. Archived EEGs of 29 seizures from 6 children with absence attacks, accompanied by 3 Hz classical spike-wave discharges (SW), were compared with 20 partial seizures from 10 adult patients. The data from the children were acquired on a Bio-logic system, those from the adults on a Grass-Telefactor instrument. In the children the original 30-minute routine EEG was used while in the adults stored videomonitored data were excerpted to provide 20-minute segments which included the preictal, ictal and postictal state. All data were analyzed with the BESA software package. The seizures were evaluated separately on conventional filter settings, full band of 0.01-to the upper limit of the instrument, and 0.01-0.1 Hz (infraslow activity, ISA). Filter settings of 0.01-0.1 Hz provided a better assessment of ISA than when the full band was evaluated. Absence seizures showed bilateral essentially synchronous ISA with a negative positive sequence in the frontal areas and opposite polarity in the posterior head regions. In partial seizures when seizure onset was clearly lateralizeable from conventional frequency settings ISA corresponded to that hemisphere, but the electrode position could be displaced to a neighboring one from the one which was maximally involved on conventional settings. Topographic analysis showed two types of ISA: one with focal spread only and the other where there was in addition an element of synchrony especially in the frontal areas. It is concluded that ISA can be recovered from conventional EEG recordings and may be helpful not only in determining the area(s) of seizure onset but can also differentiate truly focal seizures from those where an additional generalized seizure tendency is present. This is likely to be important when epilepsy surgery is performed in absence of a demonstrable structural lesion.