Duration of electroencephalographic recordings in patients with epilepsy

The Utility of 24-h Video-EEG Monitoring in the Diagnosis of Epilepsy in Children

Objectives: Evaluate the diagnostic yield of 24-h video-EEG monitoring in a group of children admitted in our epilepsy monitoring unit (EMU). Methods: 232 children who underwent 24-h video-EEG monitoring was analysed. We divided each patient's monitoring duration into the first 1, 2, 4, 8, 16 h, relative to the whole 24 h monitoring period. The detection of the first interictal epileptiform discharges (IEDs), epileptic seizures (ES), and psychogenic non-epileptic seizures (PNES) were analysed relative to the different monitoring time subdivision. Results: Our findings revealed that: (1) there was no significant difference in the prevalence of detecting initial IEDs between the first 4-h and 24-h monitoring periods (73.7% vs 81%); (2) clinical events detection rate was statistically similar between the first 8-h and 24-h monitoring periods (15.5% vs 19.3%); (4) an 8-h monitoring was sufficient to capture IEDs, ES and PNES in focal epilepsy children; (5) a 1-h monitoring was sufficient to capture IEDs, ES and PNES in generalized epilepsy children; and (6) IEDs were detected within the first 1-h of monitoring in 96.7% self-limited focal epilepsies (SeLFEs) patient. Conclusion: Our study suggests that a 4-h monitoring has more value in increasing the detection rate of IEDs compared to the traditional shorter routine EEG. And in the case of SeLFEs, a 1-h of monitoring might be sufficient in detecting IEDs. A 24-h VEEG monitoring can detect clinical events in 19.3% of patients. Overall, the yield of IEDs and clinical events detection is adequate in children in children undergoing 24-h video-EEG monitoring.

Optimal duration for recording EEG in children and adolescents- a prospective interventional study

PURPOSE

This study aimed to determine the proportion of EEG recordings yielding diagnostic findings leading to a change in diagnosis beyond a 20-minute recording window, striking a balance between diagnostic yield and clinical practicability.

METHODS

At a tertiary care teaching hospital in North India, 225 subjects aged 1 month to 18 years undergoing outpatient EEG were enrolled. Patients with epileptic encephalopathies, nonepileptic phenomena, and breakthrough seizures in the last 24 hours were excluded. Two recording protocols were employed: Category A (n=163, awake recording with activation procedures for 15 minutes followed by an attempt at sleep for 60 minutes) and Category B (n=62, sleep recording for 55 minutes followed by 5 minutes of awake recording for younger children and those with impaired cognition). EEGs were prospectively reported at 20, 30, 40, 50, and 60-minute time points, with no retrospective changes allowed.

RESULTS

Among abnormal EEGs, the final diagnosis was changed beyond 20 minutes in 38.9% and 20.4% in categories A and B, respectively. A significant change in the final diagnosis among abnormal EEGs beyond 20 minutes was seen in - those who achieved sleep compared to those who didn't (45% versus 19%, p=0.03) in category A, and - focal compared to generalised seizures (Category A: 26.1% versus 8.3%, p=0.01; Category B: 23.8% versus 0%, p=0.02).

CONCLUSION

Forty minutes of awake EEGs with/without sleep and 30 minutes of sleep EEGs achieve a final diagnosis in nearly 90%. Prolonging awake records beyond 20 minutes, incorporating sleep, is particularly beneficial in focal epilepsies.

Latencies to the first interictal epileptiform discharges recorded by the electroencephalography in different epileptic patients

PURPOSE

Interictal epileptiform discharges (IEDs) captured in electroencephalography (EEG) have a high diagnostic value for epileptic patients. Extending the recording time may increase the possibility of obtaining IEDs. The purpose of our research was to determine how long it took for various epileptic individuals to receive their first IEDs.

METHODS

We retrospectively analyzed patients who were diagnosed with epilepsy and had no anti-seizure medications (ASMs) between September 2018 and March 2019 in the neurology department of the First Affiliated Hospital of Xi'an Jiaotong University. Each individual underwent a 24-h long-term video electroencephalographic monitoring (VEM) procedure. Clinical information including age, gender, age of seizure onset, frequency of seizures, the interval between last seizure and VEM, and results of neuroimaging were gathered. We also calculated the times from the start of the VEM to the first definite IEDs.

RESULTS

A total of 241 patients were examined, including 191 with focal-onset epilepsy and 50 with generalized epilepsy. In individuals with focal-onset epilepsy, the median latency to the first IED was 63.0 min (IQR 19.0-299.0 min), as compared to 30.0 min (IQR 12.5-62.0 min) in patients with generalized epilepsy (p < 0.001). The latency to the first IED is significantly related to the age of seizure onset (HR = 0.988, p = 0.049), the interval between last seizure and VEM (HR = 0.998, p = 0.013). But it is not correlated with seizure frequency, gender and age.

CONCLUSIONS

IEDs were discovered during 24-h EEG monitoring in 222/241(92.1%) of the epilepsy patients that were included. Compared to focal-onset epilepsy, generalized epilepsy demonstrated a much shorter latency to IED. Patients with late-onset epilepsy or those without recent episodes may require longer EEG monitoring periods.

Spike propagation mapping reveals effective connectivity and predicts surgical outcome in epilepsy

Neurosurgical intervention is the best available treatment for selected patients with drug resistant epilepsy. For these patients, surgical planning requires biomarkers that delineate the epileptogenic zone, the brain area that is indispensable for the generation of seizures. Interictal spikes recorded with electrophysiological techniques are considered key biomarkers of epilepsy. Yet, they lack specificity, mostly because they propagate across brain areas forming networks. Understanding the relationship between interictal spike propagation and functional connections among the involved brain areas may help develop novel biomarkers that can delineate the epileptogenic zone with high precision. Here, we reveal the relationship between spike propagation and effective connectivity among onset and areas of spread and assess the prognostic value of resecting these areas. We analysed intracranial EEG data from 43 children with drug resistant epilepsy who underwent invasive monitoring for neurosurgical planning. Using electric source imaging, we mapped spike propagation in the source domain and identified three zones: onset, early-spread and late-spread. For each zone, we calculated the overlap and distance from surgical resection. We then estimated a virtual sensor for each zone and the direction of information flow among them via Granger causality. Finally, we compared the prognostic value of resecting these zones, the clinically-defined seizure onset zone and the spike onset on intracranial EEG channels by estimating their overlap with resection. We observed a spike propagation in source space for 37 patients with a median duration of 95 ms (interquartile range: 34-206), a spatial displacement of 14 cm (7.5-22 cm) and a velocity of 0.5 m/s (0.3-0.8 m/s). In patients with good surgical outcome (25 patients, Engel I), the onset had higher overlap with resection [96% (40-100%)] than early-spread [86% (34-100%), P = 0.01] and late-spread [59% (12-100%), P = 0.002], and it was also closer to resection than late-spread [5 mm versus 9 mm, P = 0.007]. We found an information flow from onset to early-spread in 66% of patients with good outcomes, and from early-spread to onset in 50% of patients with poor outcome. Finally, resection of spike onset, but not area of spike spread or the seizure onset zone, predicted outcome with positive predictive value of 79% and negative predictive value of 56% (P = 0.04). Spatiotemporal mapping of spike propagation reveals information flow from onset to areas of spread in epilepsy brain. Surgical resection of the spike onset disrupts the epileptogenic network and may render patients with drug resistant epilepsy seizure-free without having to wait for a seizure to occur during intracranial monitoring.

Ambulatory video EEG extended to 10 days: A retrospective review of a large database of ictal events

OBJECTIVE

This work aims to determine the ambulatory video electroencephalography monitoring (AVEM) duration and number of captured seizures required to resolve different clinical questions, using a retrospective review of ictal recordings.

METHODS

Patients who underwent home-based AVEM had event data analyzed retrospectively. Studies were grouped by clinical indication: differential diagnosis, seizure type classification, or treatment assessment. The proportion of studies where the conclusion was changed after the first seizure was determined, as was the AVEM duration needed for at least 99% of studies to reach a diagnostic conclusion.

RESULTS

The referring clinical question was not answered entirely by the first event in 29.6% (n = 227) of studies. Diagnostic and classification indications required a minimum of 7 days for at least 99% of studies to be answered, whilst treatment-assessment required at least 6 days.

CONCLUSIONS

At least 7 days of monitoring, and potentially multiple events, are required to adequately answer these clinical questions in at least 99% of patients. The widely applied 72 h or single event recording cut-offs may be inadequate to adequately answer these three indications in a substantial proportion of patients.

SIGNIFICANCE

Extended duration of monitoring and capturing multiple events should be considered when attempting to capture seizures on video-EEG.

Does the duration of video-EEG recording influence diagnostic yield in pediatric epilepsy: Results from a single center study

AIM

This exploratory study examines the association of the duration of electroencephalography (EEG) recordings to diagnostic yield in children undergoing evaluation for seizures.

METHOD

Clinical and EEG data on three hundred and ten patients (167 males and 143 females) were reviewed retrospectively. 134 (43.2%) children with focal-onset seizures, and 59 (19%) children with generalized-onset seizures. The mean duration of recordings in studies interpreted as "diagnostic" was compared to studies that were interpreted as "non-diagnostic". EMU recordings were also compared to routine EEG studies to identify the relationship between routine EEG and diagnostic studies.

RESULTS

The principal finding of this study indicates that a longer duration of monitoring is more likely to be associated with a positive diagnostic yield. Mean duration of recording in children with a "non-diagnostic study" was 31.05 hours versus 44.27 hours; p < 0.001 in a "diagnostic study". EMU recordings are likely to be diagnostic with longer epilepsy duration (2.6 years vs 3.7 years; p < 0.01). A diagnostic EEG from a prolonged recording is more likely to be achieved in children with abnormal routine EEG and focal-onset seizures. p < 0.001.

INTERPRETATION

Tailoring the optimal duration of EEG recordings and factoring in confounding variables will reduce the need for repeated studies, improving diagnostic utility and permitting efficient utilization of resources.

Routine and sleep EEG: Minimum recording standards of the International Federation of Clinical Neurophysiology and the International League Against Epilepsy

This article provides recommendations on the minimum standards for recording routine ("standard") and sleep electroencephalography (EEG). The joint working group of the International Federation of Clinical Neurophysiology (IFCN) and the International League Against Epilepsy (ILAE) developed the standards according to the methodology suggested for epilepsy-related clinical practice guidelines by the Epilepsy Guidelines Working Group. We reviewed the published evidence using the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) statement. The quality of evidence for sleep induction methods was assessed by the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) method. A tool for Quality Assessment of Diagnostic Studies (QUADAS-2) was used to assess the risk of bias in technical and methodological studies. Where high-quality published evidence was lacking, we used modified Delphi technique to reach expert consensus. The GRADE system was used to formulate the recommendations. The quality of evidence was low or moderate. We formulated 16 consensus-based recommendations for minimum standards for recording routine and sleep EEG. The recommendations comprise the following aspects: indications, technical standards, recording duration, sleep induction, and provocative methods.

Routine and sleep EEG: Minimum recording standards of the International Federation of Clinical Neurophysiology and the International League Against Epilepsy

This article provides recommendations on the minimum standards for recording routine ("standard") and sleep electroencephalography (EEG). The joint working group of the International Federation of Clinical Neurophysiology (IFCN) and the International League Against Epilepsy (ILAE) developed the standards according to the methodology suggested for epilepsy-related clinical practice guidelines by the Epilepsy Guidelines Working Group. We reviewed the published evidence using the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) statement. The quality of evidence for sleep induction methods was assessed by the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) method. A tool for Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) was used to assess the risk of bias in technical and methodological studies. Where high-quality published evidence was lacking, we used modified Delphi technique to reach expert consensus. The GRADE system was used to formulate the recommendations. The quality of evidence was low or moderate. We formulated 16 consensus-based recommendations for minimum standards for recording routine and sleep EEG. The recommendations comprise the following aspects: indications, technical standards, recording duration, sleep induction, and provocative methods.

A retrospective study of the correlation between duration of monitoring in the epilepsy monitoring unit and diagnostic yield

OBJECTIVE

Long-term video-electroencephalographic (LTVEM) monitoring is a valuable tool in the evaluation of paroxysmal clinical events. However, vEEG itself is costly. Hence, we aimed to establish if longer duration of monitoring (DOM) is associated with higher diagnostic yield.

METHOD

A retrospective review of patients admitted into the epilepsy monitoring unit (EMU) for the diagnostic evaluation of paroxysmal events was performed. Patients' demographic, clinical characteristics, and vEEG data were analyzed. In the cohort of patients with DOM > 7 days, the reasons for prolonged DOM were identified and the differences in clinical characteristics and vEEG data between conclusive and inconclusive studies were analyzed.

RESULT

A total of 501 patients were included. Four hundred and thirty-six (87 %) patients had conclusive studies. Of these patients, 67.9 % patients with conclusive studies received diagnosis within the first 7 days of monitoring with the highest on day 7. The likelihood of conclusive studies decreased beyond 7 days. A total of 175 had DOM > 7 days, of which 140 (80 %) had conclusive studies. In the cohort with DOM > 7 days, patients with previous abnormal routine EEG, previous vEEG monitoring, first event recorded before day 5 of admission and ≥1 events recorded during vEEG monitoring were more likely to have conclusive studies. The most common reason for prolonging DOM beyond 7 days was to adequately record multiple semiologically distinctive events (76 %).

CONCLUSION

Our study supports that longer DOM is associated with an increase in diagnostic yield. More than one-third of our cohort were monitored beyond 7 days with majority (80 %) being conclusive. Our findings may guide clinicians in planning the DOM and predicting the likelihood of conclusive vEEG studies in patients with prolonged DOM based on the clinical characteristics and vEEG data.

Detection of interictal epileptiform discharges in an extended scalp EEG array and high-density EEG - A prospective multicenter study

OBJECTIVES

High counts of averaged interictal epileptiform discharges (IEDs) are key components of accurate interictal electric source imaging (ESI) in patients with focal epilepsy. Automated detections may be time-efficient, but they need to identify the correct IED types. Thus, we compared semiautomated and automated detection of IED types in long-term video EEG monitoring (LTM) using an extended scalp EEG array and short-term high-density EEG (hdEEG) with visual detection of IED types and the seizure onset zone (SOZ).

METHODS

We prospectively recruited consecutive patients from four epilepsy centers who underwent both LTM with 40 electrodes scalp EEG and short-term hdEEG with 256 electrodes. Only patients with a single circumscribed SOZ in LTM were included. In LTM and hdEEG, IED types were identified visually, semiautomatically and automatically. Concordances of semiautomated and automated detections in LTM and hdEEG as well as visual detections in hdEEG were compared against visually detected IED types and the SOZ in LTM.

RESULTS

Fifty-two out of 62 patients with LTM and hdEEG were included. The most frequent IED types per patient, detected semiautomatically and automatically in LTM and visually in hdEEG, were significantly concordant with the most frequently visually identified IED type in LTM and the SOZ. Semiautomated and automated detections of IED types in hdEEG were significantly concordant with visually identified IED types in LTM only when IED types with more than 50 detected single IEDs were selected. The threshold of 50 detected IED in hdEEG was reached in half of the patients. For all IED types per patient, agreement between visual and semiautomated detections in LTM was high.

SIGNIFICANCE

Semiautomated and automated detections of IED types in LTM show significant agreement with visually detected IED types and the SOZ. In short-term hdEEG, semiautomated detections of IED types are concordant with visually detected IED types and the SOZ in LTM if high IED counts were detected.

Transcranial alternating current stimulation for treating depression: a randomized controlled trial

Treatment of depression with antidepressants is partly effective. Transcranial alternating current stimulation can provide a non-pharmacological alternative for adult patients with major depressive disorder. However, no study has used the stimulation to treat first-episode and drug-naïve patients with major depressive disorder. We used a randomized, double-blind, sham-controlled design to examine the clinical efficacy and safety of the stimulation in treating first-episode drug-naïve patients in a Chinese Han population. From 4 June 2018 to 30 December 2019, 100 patients were recruited and randomly assigned to receive 20 daily 40-min, 77.5 Hz, 15 mA, one forehead and two mastoid sessions of active or sham stimulation (n = 50 for each group) in four consecutive weeks (Week 4), and were followed for additional 4-week efficacy/safety assessment without stimulation (Week 8). The primary outcome was a remission rate defined as the 17-item Hamilton Depression Rating Scale (HDRS-17) score ≤ 7 at Week 8. Secondary analyses were response rates (defined as a reduction of ≥ 50% in the HDRS-17), changes in depressive symptoms and severity from baseline to Week 4 and Week 8, and rates of adverse events. Data were analysed in an intention-to-treat sample. Forty-nine in the active and 46 in the sham completed the study. Twenty-seven of 50 (54%) in the active treatment group and 9 of 50 (18%) in the sham group achieved remission at the end of Week 8. The remission rate was significantly higher in the active group compared to that in the sham group with a risk ratio of 1.78 (95% confidence interval, 1.29, 2.47). Compared with the sham, the active group had a significantly higher remission rate at Week 4, response rates at Weeks 4 and 8, and a larger reduction in depressive symptoms from baseline to Weeks 4 and 8. Adverse events were similar between the groups. In conclusion, the stimulation on the frontal cortex and two mastoids significantly improved symptoms in first-episode drug-naïve patients with major depressive disorder and may be considered as a non-pharmacological intervention for them in an outpatient setting.

Automated spike detection: Which software package?

PURPOSE

We assessed three commercial automated spike detection software packages (Persyst, Encevis and BESA) to see which had the best performance.

METHODS

Thirty prolonged EEG records from people aged at least 16 years were collected and 30-minute representative epochs were selected. Interictal epileptiform discharges (IEDs) were marked by three human experts and by all three software packages. For each 30-minutes selection and for each 10-second epoch we measured whether or not IEDs had occurred. We defined the gold standard as the combined detections of the experts. Kappa scores, sensitivity and specificity were estimated for each software package.

RESULTS

Sensitivity for Persyst in the default setting was 95% for 30-minute selections and 82% for 10-second epochs. Sensitivity for Encevis was 86% (30-minute selections) and 61% (10-second epochs). The specificity for both packages was 88% for 30-minute selections and 96%-99% for the 10-second epochs. Interrater agreement between Persyst and Encevis and the experts was similar than between experts (0.67-0.83 versus 0.63-0.67). Sensitivity for BESA was 40% and specificity 100%. Interrater agreement (0.25) was low.

CONCLUSIONS

IED detection by the Persyst automated software is better than the Encevis and BESA packages, and similar to human review, when reviewing 30-minute selections and 10-second epochs. This findings may help prospective users choose a software package.

24-Hour video EEG in the evaluation of the first unprovoked seizure

•

In the evaluation of a first seizure, the capture of epileptiform discharges is increased with 24-hour EEG recordings.

•

This likely stems from a combination of increased sampling and robust sleep recording.

•

Subtle seizures were also recorded by prolonging the EEG in a minority of first seizure presentations.

Objective

To assess the gain in detection of epileptiform abnormalities in 24-hour EEG recordings following the first seizure.

Methods

We identified patients who underwent 24-hour video EEG (VEEG) with “first seizure” as an indication. We noted the presence or absence of epileptiform discharges (EDs) in the VEEG study and the latency for the appearance of such discharges. We compared the rate of EDs during the initial 60 min with those occurring only later during the recording.

Results

Data from 25 patients, aged 15 to 59, were included. Of the 11 patients with EDs, eight (73%) appeared only after 60 min of recording. This equates to a 32% absolute increase in the detection of EDs across all patients. The latency to first EDs varied from one to 1080 min with a median of 170 min. In four cases, actual subtle seizures were recorded.

Conclusion

This study suggests an increase in the detection of EDs with the 24-hour studies compared to the traditional shorter recordings, in the context of a first seizure.

Significance

A standard EEG can be performed close to the seizure, followed by a longer up to 24-hour recording if the initial shorter study is unrevealing.

Effect of Transcranial Alternating Current Stimulation for the Treatment of Chronic Insomnia: A Randomized, Double-Blind, Parallel-Group, Placebo-Controlled Clinical Trial

BACKGROUND

Not all adults with chronic insomnia respond to the recommended therapeutic options of cognitive behavioral therapy and approved hypnotic drugs. Transcranial alternating current stimulation (tACS) may offer a novel potential treatment modality for insomnia.

OBJECTIVES

This study aimed to examine the efficacy and safety of tACS for treating adult patients with chronic insomnia.

METHODS

Sixty-two participants with chronic primary insomnia received 20 daily 40-min, 77.5-Hz, 15-mA sessions of active or sham tACS targeting the forehead and both mastoid areas in the laboratory on weekdays for 4 consecutive weeks, followed by a 4-week follow-up period. The primary outcome was response rate measured by the Pittsburgh Sleep Quality Index (PSQI) at week 8. Secondary outcomes were remission rate, insomnia severity, sleep onset latency (SOL), total sleep time (TST), sleep efficiency, sleep quality, daily disturbances, and adverse events at the end of the 4-week intervention and at the 4-week follow-up.

RESULTS

Of 62 randomized patients, 60 completed the trial. During the 4-week intervention, 1 subject per group withdrew due to loss of interest and time restriction, respectively. Based on PSQI, at 4-week follow-up, the active group had a higher response rate compared to the sham group (53.4% [16/30] vs. 16.7% [5/30], p = 0.009), but remission rates were not different between groups. At the end of the 4-week intervention, the active group had higher response and remission rates than the sham group (p < 0.001 and p = 0.026, respectively). During the trial, compared with the sham group, the active group showed a statistically significant decrease in PSQI total score, a shortened SOL, an increased TST, improved sleep efficiency, and improved sleep quality (p < 0.05 or p < 0.001). Post hoc analysis revealed that, in comparison with the sham group, the active group had improved symptoms, except for daily disturbances, at the end of the 4-week intervention, and significant improvements in all symptoms at the 4-week follow-up. No adverse events or serious adverse responses occurred during the study.

CONCLUSION

The findings show that the tACS applied in the present study has potential as an effective and safe intervention for chronic insomnia within 8 weeks.

EEG Abnormalities as a Neurophysiological Biomarker of Severity in Autism Spectrum Disorder: A Pilot Cohort Study

To date, the phenotypic significance of EEG abnormalities in patients with ASD is unclear. In a population affected by ASD we aimed to evaluate: the phenotypic characteristics; the prevalence of EEG abnormalities; the potential correlations between EEG abnormalities and behavioral and cognitive variables. Sixty-nine patients with ASD underwent cognitive or developmental testing, language assessment, and adaptive behavior skills evaluation as well as sleep/wake EEG recording. EEG abnormalities were found in 39.13% of patients. EEG abnormalities correlated with autism severity, hyperactivity, anger outbursts, aggression, negative or destructive behavior, motor stereotypies, intellectual disability, language impairment and self-harm. Our findings confirmed that EEG abnormalities are present in the ASD population and correlate with several associated phenotypic features.

Latencies to first interictal epileptiform discharges in different seizure types during video-EEG monitoring

PURPOSE

Interictal epileptiform discharges (IEDs) have high diagnostic value concerning patients with epilepsy and the instances of obtaining IEDs increase with longer recording times. However, the merit of a single, extended electroencephalography (EEG) recording in detecting IEDs has not been substantiated. We aimed to determine the optimal duration of an EEG required to diagnose epilepsy in different seizure types.

METHODS

Overall, 84 patients-29 with generalised onset epilepsy and 55 with focal onset epilepsy-were evaluated. Long-term video electroencephalographic monitoring (VEM) was analysed to find the first definite IED besides assessing the first seizure and latency.

RESULTS

The median latency of the first IED (12 min, ranging from 1 to 440 min vs. 55 min, ranging from 2 to 7500 min; p =  0.014) and the median duration of a VEM recording (2 d, ranging from 1 to 10 d vs. 3 d, ranging from 1 to 10 d; p =  0.012) were found significantly lower in the generalised epilepsy group compared with that in the focal epilepsy group.

CONCLUSIONS

Generalised onset epilepsy showed a significantly shorter latency to IED and VEM duration compared with focal onset epilepsy. In our data set, all the patients with generalised onset epilepsy had interictal IED within 10 h, but the patients with focal onset epilepsy required monitoring for three days to obtain IED.

Optimal duration of video-electroencephalographic monitoring to capture seizures

We aimed to find the optimal duration of long-term video-electroencephalographic monitoring (VEM) to capture seizures in patients with epileptic seizures (ES) and psychogenic non-epileptic seizures (PNES) by evaluating the time to first clinical event and the diagnostic yield of clinical events and positive cases in each day of VEM. Patients aged ⩾18years who underwent VEM from May 2009 to June 2014 were studied retrospectively. Demographic, clinical and VEM data (including total monitoring length, type and time to first event, total number of ES/PNES) were collected. The difference in time to the first event between ES and PNES was analysed with Mann-Whitney U test. Of 207 VEM studies performed during the 5year period, 108 recordings captured seizures (ES and PNES) (52.2%). Median times to the first ES and PNES were 19.7 and 23.4hours, respectively (p=0.99). A small majority (53.7%) of event-positive patients had their first event on the first day of monitoring. By the end of the fifth day, 98% of all clinical events were captured and 99% of all positive cases were diagnosed. In conclusion, in a patient monitoring program where a diagnosis is reached by capturing seizures, 5days is probably sufficient to capture the greatest number of events and diagnose 99% of those patients.

EEG Duration: The Long and the Short of It

Current American Clinical Neurophysiology Society guidelines require a minimum of 20 minutes of artifact-free EEG recording; however, the optimum duration for routine EEGs is not established. Our hypothesis was that an EEG recording of 40 minutes' duration would yield more information than a 20-minute EEG in capturing epileptiform abnormalities and in obtaining sleep. We retrospectively studied 150 consecutive EEGs of 40 minutes' duration performed at St Christopher's Hospital for Children. Although the majority (89%) of interictal EEG abnormalities can be identified within the first 20 minutes of a routine EEG, extending the time of a routine EEG increases the yield significantly by identifying an additional 11% of abnormal studies (P = .0001), precluding the need for further long-term monitoring in these patients. Forty-three percent of interictal epileptiform abnormalities were found during sleep. We recommend that routine EEGs be performed for 40 minutes, whenever possible, to improve yield in a cost-effective manner.