Normal adult EEG and patterns of uncertain significance

Source Localization of Normal Variants Seen on EEG

PURPOSE

The EEG is an essential neurological diagnostic tool. EEG abnormalities can guide diagnosis and management of epilepsy. There are also distinctive EEG waveforms that are seen in healthy individuals. It is critical not to misinterpret these as abnormal. To emphasize the importance of these waveforms, we analyzed different normal variants via the source localization technology.

METHODS

This is a retrospective analysis of EEGs performed at the Duke University Hospital between June 2014 and Dec 2019. We selected samples of vertex waves, Mu, lambda, POSTS, wickets, and sleep spindles for analysis. EEG were imported to Curry 8 (Compumedics) to calculate the dipole and current density. The averaged head model from the Montreal Neurological Institute database was used for reconstruction.

RESULTS

Thirty-four patient EEG samples were selected including five vertex, six Mu, four wicket, seven lambda, five POSTS, and seven spindles. Results from source localization showed that vertex waves are localized in the frontocentral area, whereas spindles in the deep midline central region. Mu were identified in the ipsilateral somatosensory cortex. Lambda and POSTS, on the other hand, had maximum results over the bilateral occipital region and wickets in the ipsilateral temporal lobe.

CONCLUSIONS

Our results confirm and expand previous hypotheses. This allows us to speculate on the origin of these normal EEG variants. Although this study is limited by small sample size, lack of high-density EEG, and patient-specific MRI, our analysis provides an easily replicable three-dimensional visualization of these waveforms.

Initiation of Antiseizure Medications by US Board-Certified Neurologists After a First Unprovoked Seizure Based on EEG Findings

Background and Objectives

To investigate neurologists' practice variability in antiseizure medication (ASM) initiation after a first unprovoked seizure based on reported EEG interpretations.

Methods

We developed a 15-question multiple-choice survey incorporating a standardized clinical case scenario of a patient with a first unprovoked seizure for whom different EEG reports were provided. The survey was distributed among board-certified neurologists practicing in the United States. Associations between categorical variables were evaluated using the Fisher Exact test. Multivariate analysis was performed using logistic regression.

Results

A total of 106 neurologists responded to the survey. Most responders (75%-95%) would start ASM for definite epileptiform features on EEG, with similar rates between subgroups differing in years of practice, presence of subspecialty EEG training, and self-reported confidence in EEG interpretation. There was greater variability in practice for nonspecific EEG abnormalities, with sharply contoured activity, sharp transients, and focal delta slowing associated with the highest variability and uncertainty. Neurologists with >5 years of practice experience (21% vs 44%, OR 0.35 [95% CI 0.13-0.89], p = 0.021), subspecialty EEG training (15% vs 50%, OR = 0.17 [95% CI 0.06-0.48], p < 0.001), and greater confidence in EEG interpretation (21% vs 52%, OR 0.24 [95% CI 0.09-0.62], p = 0.001) were less likely to start ASM for ≥2 nonspecific EEG abnormalities and reported greater uncertainty. In multivariate analysis, seniority (p = 0.039) and subspecialty EEG training (p = 0.032) were associated with decreased ASM initiation for nonspecific EEG features.

Discussion

There was substantial variability in ASM initiation practices between board-certified neurologists after a first unprovoked seizure with nonspecific EEG abnormalities. These findings clarify specific areas where EEG reporting may be optimized and reinforces the importance of implementing evidence-based practice guidelines.

Hippocampal barques and their manifestation as 14&6 Hz positive spikes during sleep

OBJECTIVE

This study investigates variations in hippocampal barque occurrence during sleep and compares findings to respective variations of their scalp manifestation as 14&6/sec positive spikes.

METHODS

From 11 epilepsy patients, 12 non-epileptogenic hippocampi with barques were identified for this study. Using the first seizure-free whole-night sleep stereo-encephalography (sEEG) recording, we performed sleep staging and measured the occurrence of barques and 14&6/sec positive spikes variants.

RESULTS

Hippocampal barques (total count: 9,183; mean count per record: 765.2 ± 251.2) occurred predominantly during non-rapid eye movement (NREM) II sleep (total: 5,744; mean: 478.6 ± 176.1; 62.2 ± 6.0%) and slow-wave sleep (SWS) (total: 2,950; mean: 245.83 ± 92.9; 32.0 ± 6.2%), with rare to occasional occurrence in NREM I (total: 85; mean: 7.0 ± 2.8; 0.9 ± 0.4%), rapid eye movement (REM) (total: 153; mean: 12.75 ± 4.0; 1.7 ± 0.6) and wakefulness (total: 251; mean: 20.9 ± 6.3; 2.9 ± 0.9%). Barque rate increased during SWS (mean: 2.7 ± 1.0 per min) compared to NREM II (2.2 ± 1.0 per min) and other states (wakefulness: 0.1 ± 0.0 per min; NREM I: 0.3 ± 0.1 per min; REM: 0.1 ± 0.0 per min). The 14&6/sec positive spikes variant (total count: 2,406; mean: 343.7 ± 106.7) was present in NREM II (total: 2,059; mean: 249.1 ± 100.2, 84.9 ± 3.6%) and SWS (total: 347; mean: 49.5 ± 12.8, 15.0 ± 3.6%) stages, and absent from the rest of sleep and wakefulness. While all 14&6/sec positive spikes correlated with barques, only 44.7 ± 6.1% of barques manifested as 14&6/sec positive spikes.

CONCLUSIONS

Hippocampal barques are predominant in NREM II and SWS, and tend to increase their presence during SWS. Their scalp manifestation as 14&6/sec positive spikes is confounded by wakefulness, REM and NREM I stages, and "masked" by the co-occurrence of NREM II and SWS slow waves, and overlapping reactive micro-arousal elements.

SIGNIFICANCE

Our study highlighted the overnight profile of hippocampal barques, in relation to the respective profile of their scalp manifestation, the 14&6/sec positive spikes variant.

Normal variants and artifacts: Importance in EEG interpretation

Overinterpretation of EEG is an important contributor to the misdiagnosis of epilepsy. For the EEG to have a high diagnostic value and high specificity, it is critical to recognize waveforms that can be mistaken for abnormal patterns. This article describes artifacts, normal rhythms, and normal patterns that are prone to being misinterpreted as abnormal. Artifacts are potentials generated outside the brain. They are divided into physiologic and extraphysiologic. Physiologic artifacts arise from the body and include EMG, eyes, various movements, EKG, pulse, and sweat. Some physiologic artifacts can be useful for interpretation such as EMG and eye movements. Extraphysiologic artifacts arise from outside the body, and in turn can be divided into the environments (electrodes, equipment, and cellphones) and devices within the body (pacemakers and neurostimulators). Normal rhythms can be divided into awake patterns (alpha rhythm and its variants, mu rhythm, lambda waves, posterior slow waves of youth, HV-induced slowing, photic driving, and photomyogenic response) and sleep patterns (POSTS, vertex waves, spindles, K complexes, sleep-related hypersynchrony, and frontal arousal rhythm). Breach can affect both awake and sleep rhythms. Normal variants or variants of uncertain clinical significance include variants that may have been considered abnormal in the early days of EEG but are now considered normal. These include wicket spikes and wicket rhythms (the most common normal pattern overread as epileptiform), small sharp spikes (aka benign epileptiform transients of sleep), rhythmic midtemporal theta of drowsiness (aka psychomotor variant), Cigánek rhythm (aka midline theta), 6 Hz phantom spike-wave, 14 and 6 Hz positive spikes, subclinical rhythmic epileptiform discharges of adults (SREDA), slow-fused transients, occipital spikes of blindness, and temporal slowing of the elderly. Correctly identifying artifacts and normal patterns can help avoid overinterpretation and misdiagnosis. This is an educational review paper addressing a learning objective of the International League Against Epilepsy (ILAE) curriculum.

Rhythmic mid-Temporal Theta of Drowsiness Activated by Hyperventilation- Uncommon Trigger of a Rare Benign EEG Variant in Pediatrics. An Educational Review

Distinguishing abnormal electroencephalogram (EEG) waveforms from benign variants is critical for accurate interpretation of EEG. Hyperventilation (HV) is one of the basic procedures during EEG to enable activation of epileptiform activity. Rarely, HV can activate benign EEG rhythms. Herein, we illustrate two pediatric cases with bursts of rhythmic mid-temporal theta of drowsiness (RMTD), activated by hyperventilation. Continued awareness of this EEG phenomenology and its variations in pediatrics is important in avoiding misdiagnosis of epilepsy.

EEG normal variants: A prospective study using the SCORE system

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We analyzed the number of normal variants in a SCORE database of 3050 EEG recordings.

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The most common normal variant was sharp transients.

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We present typical examples and detailed characterization of the normal variants.

Objective

To determine the prevalence and characteristics of normal variants in EEG recordings in a large cohort, and provide readers with typical examples of all normal variants for educational purposes.

Methods

Using the SCORE EEG system (Standardized Computer-Based Organized Reporting of EEG), we prospectively extracted EEG features in consecutive patients. In this dataset, we analyzed 3050 recordings from 2319 patients (mean age 38.5 years; range: 1–89 years).

Results

The distribution of the normal variants was as follows: sharp transients 19.21% (including wicket spikes), rhythmic temporal theta of drowsiness 6.03%, temporal slowing of the old 2.89%, slow fused transients 2.59%, 14-and 6-Hz bursts 1.83%, breach rhythm 1.25%, small sharp spikes 1.05%, 6-Hz spike and slow wave 0.69% and SREDA 0.03%.

Conclusions

The most prevalent normal variants are the sharp transients, which must not be over-read as epileptiform discharges.

Significance

EEG readers must be familiar with the normal variants to avoid misdiagnosis and misclassification of patients referred to clinical EEG recordings.

EEG Essentials

PURPOSE OF REVIEW

EEG is the best study for evaluating the electrophysiologic function of the brain. The relevance of EEG is based on an accurate interpretation of the recording. Understanding the neuroscientific basis for EEG is essential. The basis for recording and interpreting EEG is both brain site-specific and technique-dependent to detect and represent a complex series of waveforms. Separating normal from abnormal EEG lies at the foundation of essential interpretative skills.

RECENT FINDINGS

Seizures and epilepsy are the primary targets for clinical use of EEG in diagnosis, seizure classification, and management. Interictal epileptiform discharges on EEG support a clinical diagnosis of seizures, but only when an electrographic seizure is recorded is the diagnosis confirmed. New variations of normal waveforms, benign variants, and artifacts can mimic epileptiform patterns and are potential pitfalls for misinterpretation for inexperienced interpreters. A plethora of medical conditions involve nonepileptiform and epileptiform abnormalities on EEG along the continuum of people who appear healthy to those who are critically ill. Emerging trends in long-term EEG monitoring to diagnose, classify, quantify, and characterize patients with seizures have unveiled epilepsy syndromes in patients and expanded medical and surgical options for treatment. Advances in terminology and application of continuous EEG help unify neurologists in the diagnosis of nonconvulsive seizures and status epilepticus in patients with encephalopathy and prognosticate recovery from serious neurologic injury involving the brain.

SUMMARY

After 100 years, EEG has retained a key role in the neurologist's toolkit as a safe, widely available, versatile, portable test of neurophysiology, and it is likely to remain at the forefront for patients with neurologic diseases. Interpreting EEG is based on qualitative review, and therefore, the accuracy of reporting is based on the interpreter's training, experience, and exposure to many new and older waveforms.

Normobaric oxygen may correct chronic cerebral ischemia-mediated EEG anomalies

AIMS

To explore the safety and efficacy of normobaric oxygen (NBO) on correcting chronic cerebral ischemia (CCI) and related EEG anomalies.

METHODS

This prospective randomized trial (NCT03745092) enrolled 50 cases of CCI patients, which were divided into NBO (8 L/min of oxygen supplement) group and control group (room air) randomly, and also enrolled 21 healthy volunteers. Two times of 30-min EEG recordings with the interval of 45min of NBO or room air were analyzed quantitatively.

RESULTS

The CCI-mediated EEG presented with two patterns of electrical activities: high-power oscillations (high-power EEG, n = 26) and paroxysmal slow activities under the normal-power background (normal-power EEG, n = 24). The fronto-central absolute power (AP) of the beta, alpha, theta, and delta in the high-power EEG was higher than that in healthy EEG (p < 0.05). The fronto-central theta/alpha, delta/alpha and (delta + theta)/(alpha + beta) ratios in the normal-power EEG were higher than those in healthy EEG (p < 0.05). The high-power EEG in NBO group had higher fronto-central AP reduction rates than those in control group (p < 0.05). NBO remarkably reduced the fronto-central theta/alpha, delta/alpha, and (delta + theta)/(alpha + beta) ratios in the normal-power EEG (p < 0.05).

CONCLUSIONS

NBO rapidly ameliorates CCI-mediated EEG anomalies, including attenuation of the abnormal high-power oscillations and the paroxysmal slow activities associated with CCI.

Alternating hemiparesis in the context of hemolytic uremic syndrome and COVID-19 positivity

Hemiparesis has been reported in hemolytic uremic syndrome (HUS), however electrophysiological findings associated with this syndrome have not been well-characterized, and alternating hemiparesis presentations have not been reported. We present detailed electrophysiological and clinical findings in a case of alternating hemiparesis corresponding to alternating focal contralateral delta slowing on prolonged EEG monitoring in a case of HUS with COVID-19 positivity. A 24-year-old woman was admitted with bloody diarrhea, acute kidney injury, and focal seizures initially presumed due to Escherichia coli 0157:H7 Shiga-like toxin-related hemolytic uremic syndrome (ST-HUS). After admission, the patient tested positive for COVID-19. Continuous EEG monitoring revealed diffuse polymorphic delta slowing. Around 24 hours into the admission, the delta slowing became focal in the right hemisphere and was associated with a left hemiparesis. Around three days later, the clinical and EEG pattern reversed, showing left hemisphere slowing and an associated right hemiparesis. Additionally, 14 Hz positive spikes were observed throughout the recording period. Neuroimaging, including CT and MRI, was negative for acute ischemia throughout. The patient subsequently recovered over several days with no residual neurologic abnormalities.

Magnetoencephalography to confirm epileptiform discharges mimicking small sharp spikes in temporal lobe epilepsy

OBJECTIVE

To determine whether magnetoencephalography (MEG) can identify epileptiform discharges mimicking small sharp spikes (SSSs) on scalp electroencephalography (EEG) in patients with temporal lobe epilepsy (TLE).

METHODS

We retrospectively reviewed simultaneous scalp EEG and MEG recordings of 83 consecutive patients with TLE and 49 with extra-TLE (ETLE).

RESULTS

SSSs in scalp EEG were detected in 15 (18.1%) of 83 TLE patients compared to only two (4.1%) of 49 ETLE patients (p = 0.029). Five of the 15 TLE patients had MEG spikes with concurrent SSSs in EEG, but neither of the 2 ETLE patients. Three of these 5 TLE patients had additional interictal epileptiform discharges (IEDs) in EEG and MEG. Equivalent current dipoles (ECDs) of MEG spikes with concurrent SSSs and IEDs showed no difference in temporal lobe localization and horizontal orientation, whereas ECD moments were smaller in MEG spikes with concurrent SSSs than those with IEDs.

CONCLUSIONS

SSSs were more common in TLE than in ETLE. At least some morphologically diagnosed SSSs are true but low-amplitude epileptiform discharges in TLE which can be identified with simultaneous MEG.

SIGNIFICANCE

Simultaneous MEG is useful to identify epileptiform discharges mimicking SSSs in patients with TLE.

Which Factors Affect the Stress of Intraoperative Orthopedic Surgeons by Using Electroencephalography Signals and Heart Rate Variability?

Can we recognize intraoperative real-time stress of orthopedic surgeons and which factors affect the stress of intraoperative orthopedic surgeons with EEG and HRV? From June 2018 to November 2018, 265 consecutive records of intraoperative stress measures for orthopedic surgeons were compared. Intraoperative EEG waves and HRV, comprising beats per minute (BPM) and low frequency (LF)/high frequency (HF) ratio were gathered for stress-associated parameters. Differences in stress parameters according to the experience of surgeons, intraoperative blood loss, and operation time depending on whether or not a tourniquet were investigated. Stress-associated EEG signals including beta 3 waves were significantly higher compared to EEG at rest for novice surgeons as the procedure progressed. Among senior surgeons, the LF/HF ratio reflecting the physical demands of stress was higher than that of novice surgeons at all stages. In surgeries including tourniquets, operation time was positively correlated with stress parameters including beta 1, beta 2, beta 3 waves and BPM. In non-tourniquet orthopedic surgeries, intraoperative blood loss was positively correlated with beta 1, beta 2, and beta 3 waves. Among orthopedic surgeons, those with less experience demonstrated relatively higher levels of stress during surgery. Prolonged operation time or excessive intraoperative blood loss appear to be contributing factors that increase stress.

The influence of the abundance and morphology of epileptiform discharges on diagnostic accuracy: How many spikes you need to spot in an EEG

OBJECTIVE

The operational definition of interictal epileptiform discharges (IEDs) of the International Federation of Clinical Neurophysiology (IFCN) described six morphological criteria. Our objective was to assess the impact of pattern-repetition in the EEG-recording, on the diagnostic accuracy of using the IFCN criteria. For clinical implementation, specificity over 95% was set as target.

METHODS

Interictal EEG-recordings of 20-minutes, containing sharp-transients, from 60 patients (30 with epilepsy and 30 with non-epileptic paroxysmal events) were evaluated by three experts, who first marked IEDs solely based on expert opinion, and then, independently from the first session evaluated the presence of the IFCN criteria for each sharp-transient. The gold standard was derived from long-term video-EEG recordings of the patientś habitual paroxysmal episodes.

RESULTS

Presence of at least one discharge fulfilling five criteria provided a specificity of 100% (sensitivity: 70%). For discharges fulfilling fewer criteria, a higher number of discharges was needed to keep the specificity over 95% (5 discharges, when only 3 criteria were fulfilled). A sequential combination of these sets of criteria and thresholds provided a specificity of 97% and sensitivity of 80%.

CONCLUSIONS

Pattern-repetition and IED morphology influence diagnostic accuracy.

SIGNIFICANCE

Systematic application of these criteria will improve quality of clinical EEG interpretation.

Criteria for defining interictal epileptiform discharges in EEG: A clinical validation study

Objective

To define and validate criteria for accurate identification of EEG interictal epileptiform discharges (IEDs) using (1) the 6 sensor space criteria proposed by the International Federation of Clinical Neurophysiology (IFCN) and (2) a novel source space method. Criteria yielding high specificity are needed because EEG over-reading is a common cause of epilepsy misdiagnosis.

Methods

Seven raters reviewed EEG sharp transients from 100 patients with and without epilepsy (diagnosed definitively by video-EEG recording of habitual events). Raters reviewed the transients, randomized, and classified them as epileptiform or nonepileptiform in 3 separate rounds: in 2, EEG was reviewed in sensor space (scoring the presence/absence of each IFCN criterion for each transient or classifying unrestricted by criteria [expert scoring]); in the other, review and classification were performed in source space.

Results

Cutoff values of 4 and 5 criteria in sensor space and analysis in source space provided high accuracy (91%, 88%, and 90%, respectively), similar to expert scoring (92%). Two methods had specificity exceeding the desired threshold of 95%: using 5 IFCN criteria as cutoff and analysis in source space (both 95.65%); the sensitivity of these methods was 81.48% and 85.19%, respectively.

Conclusions

The presence of 5 IFCN criteria in sensor space and analysis in source space are optimal for clinical implementation. By extracting these objective features, diagnostic accuracy similar to expert scorings is achieved.

Classification of evidence

This study provides Class III evidence that IFCN criteria in sensor space and analysis in source space have high specificity (>95%) and sensitivity (81%–85%) for identification of IEDs.

Critically ill benign EEG variants: Is there such a thing?

Despite growing use of critical care electroencephalography (ccEEG) to detect seizures and status epilepticus in the intensive care unit (ICU), integrating ccEEG findings with traditionally described benign EEG variants (BEVs) is a relatively new concept. BEV-like waveforms are now increasingly encountered in the ICU, and have also been explicitly included in proposed definitions of brief potentially ictal rhythmic discharges (BIRDs) in the ICU, bringing to the fore the question of if and which EEG patterns in critically ill patients can be safely deemed "benign". Though well-characterized as benign in healthy outpatients at low pre-test risk for neurologic disease, the significance of BEVs in the ICU remains largely unknown. Simultaneously, there has been mounting evidence to suggest that certain BEVs can arise from heterogeneous intracranial sources, including some pathologic generators. We conducted an extensive literature review on all known BEVs to assess what is known of BEVs in the ICU. Here we discuss critically ill BEVs and how to interpret them.

Artifact Mimicking Ictal Epileptiform Activity in EEG

Although the EEG is designed to record cerebral activity, it also frequently records activity from extracerebral sources, leading to artifact. Differentiating rhythmical artifact from true electrographic ictal activity remains a substantial challenge to even experienced electroencephalographers because the sources of artifact able to mimic ictal activity on EEG have continued to increase with the advent of technology. Knowledge of the characteristics of the polarity and physiologic electrical fields of the brain, as opposed to those generated by the eyes, heart, and muscles, allows the electroencephalographer to intuitively recognize noncerebrally generated waveforms. In this review, we provide practical guidelines for the EEG interpreter to correctly identify physiologic and nonphysiologic artifacts capable of mimicking electrographic seizures. In addition, we further elucidate the common pitfalls in artifact interpretation and the costly impact of epilepsy misdiagnosis due to artifact.

Normal Variants Are Commonly Overread as Interictal Epileptiform Abnormalities

Electroencephalographers may misclassify benign variant EEG patterns as epileptiform discharges, resulting in delays in the diagnosis and appropriate treatment of other paroxysmal disorders, such as psychogenic nonepileptic seizures, anxiety/panic disorders, and near syncope. These benign variant patterns include wicket spikes, small sharp spikes, and rhythmic mid-temporal theta of drowsiness. Cautious interpretations of semi-rhythmic sharp transients, usually gradually rising from the EEG background in drowsiness, can help avoid misdiagnosing patients as having seizures. Viewing the EEG as confirmatory for a clear clinical diagnosis is also helpful-elderly patients with syncope, for example, often have microvascular disease and EEG wicket rhythms in drowsiness-a careful review of the clinical history and the paroxysmal EEG pattern usually help distinguish normal variant patterns from interictal sharp waves and spikes and avoid misdiagnosing epilepsy.

Wood and Its Impact on Humans and Environment Quality in Health Care Facilities

The paper presents the application of natural materials, especially wood, which are relevant for human well-being in built environments of health, social, and day care facilities. These properties were tested by a complex methodology in a case study in the wooden waiting room at National Oncology Institute in Bratislava. In this space, experimental tests of physiological responses were further executed on 50 volunteers moving in the waiting room for 20 min. In this article, the EEG (electroencephalograph) (four persons) and emotions from the faces of all our volunteers before entering and after a stay in a wooden waiting room were recorded. Specifically, the ECG (electrocardiograph), heart rate (HR), and respiration activity were measured by using our own designed ECG holter (40 persons), and also blood pressure and cortisol levels were observed. The usage of wooden materials verifies their regenerative and positive impact on the human nervous system, through the appealing aesthetics (color, texture, and structures), high contact comfort, pleasant smell, possibility to regulate air humidity, volatile organic compound emissions (VOC-emissions), and acoustic well-being in the space.

Adult EEG

After more than 85 years of development and use in clinical practice, the electroencephalogram (EEG) remains a dependable, inexpensive, and useful diagnostic tool for the investigation of the electrophysiologic activity of the brain. The advent of digital technology has led to greater sophistication and multiple software applications to extend the utility of EEG beyond the confines of the laboratory. Despite the discovery of new waveforms, basic neurophysiologic principles remain essential to the clinical care of patients. Patterns in the interictal EEG make it possible to clarify the differential diagnosis of paroxysmal neurological events, classify seizure type and epilepsy syndromes, and characterize and quantify seizures when ictal recordings are obtained. EEG can also demonstrate cerebral dysfunction when structural imaging is normal to detect focal or lateralized abnormalities in patients with encephalopathy. High-density EEG with electrical source imaging has improved localization in candidates for epilepsy surgery. Quantitative EEG and broadband EEG are advancing our understanding of the functional processes of the brain itself.

Focal Epileptiform Discharges Can Mimic Electrode Artifacts When Recorded on the Scalp Near a Skull Defect

Breach rhythm, the hallmark of skull defect, is a familiar finding in the electroencephalogram (EEG). A hole in the skull can also give rise to unfamiliar EEG findings. We present 3 patients with a skull defect whose scalp EEG showed focal epileptiform discharges that resembled F4 electrode artifacts—a 23-year-old man with a right-sided craniectomy for traumatic brain injury, a 63-year-old woman with a history of bifrontal craniectomy and meningioma resection, and a 77-year-old woman who had a right hemicraniectomy for a life-threatening subdural hematoma. In all 3 patients, the F4 electrode was directly above or near a skull defect, and scalp EEG showed phase-reversing waves in FP2-F4 and F4-C4 with no clear-cut “physiological field” (even when the EEG was displayed at a higher sensitivity). In the first 2 patients, the technologist tried to eliminate the “electrode artifacts” by cleaning the scalp thoroughly, replacing the F4 electrode, and maintaining electrode impedance between 2 and 5 kΩ. These measures failed to eliminate the “electrode artifacts” so the EEG was recorded from four 10-10 electrode sites around F4. Extending the montage made it clear that what appeared as F4 electrode artifacts were actually focal epileptiform discharges. Correlation with other electroclinical and neuroimaging data was enough to resolve this issue in the third patient, obviating the need to extend the montage. When recording and interpreting the EEG of patients with a craniotomy or craniectomy, EEG professionals should be aware that focal epileptiform discharges can masquerade as electrode artifacts.

Prevalence of benign epileptiform variants during initial EEG examination in French military aircrew

INTRODUCTION

In France, a systematic EEG is performed during initial examination in military aircrew applicants, which may provide an estimation of the prevalence of benign epileptiform variants in healthy adults.

METHODS

We analyzed standard EEG (21 scalp electrodes, 20minutes, 400Hz sampling rate) of military aircrew applicants examined in the French Main Aeromedical Center in 2016. EEGs were analyzed using both bipolar and referential montages. The collected data were EEG abnormalities and benign epileptiform variants. The kappa inter-observer index for the detection of benign epileptiform variants was calculated.

RESULTS

Our population was composed of 495 subjects (86.7% males, mean age 22.5±4.8 years), wishing to become a pilot in 69.7% of cases. None of the applicants reported any neurological disease and none was taking regular medication. EEG was considered as normal for 96.4% of them. Encountered EEG abnormalities were mainly asymmetric and sharp slow wave bursts. Drowsiness was recorded during 13.9% of these EEG. Benign epileptiform variants were present in 7.7% of our population: anterior theta activities (4%), posterior slow waves (2.8%), alpha variants (0.6%) and wicket spikes (0.2%). Hyperventilation induced EEG slowing in 14.1% of cases. During intermittent photic stimulation, physiological photic driving was observed in 15.2% of subjects.

DISCUSSION

Many previous studies have been dedicated to the prevalence of benign epileptiform variants but results are often heterogeneous and based on patients in whom there was an indication for EEG. Our results thus bring data on benign epileptiform variants prevalence in a young adult population characterized by the absence of neurologic disorders. Our study demonstrates that anterior theta activities, posterior slow waves, alpha variants and wicket spikes are the most frequent benign EEG variants in such a young adult population.

The Texting Rhythm: A Novel EEG Waveform Using Smartphones

INTRODUCTION

We report a unique EEG phenomenon in patients with paroxysmal neurological events undergoing video EEG monitoring.

METHODS

Two epilepsy centers analyzed the interictal scalp EEG in patients using personal electronic devices during epilepsy monitoring. The texting rhythm (TR) was defined as a reproducible, stimulus-evoked, generalized frontocentral monomorphic burst of 5-6 Hz theta consistently induced by active text messaging. An independent prospective and retrospective cohort was analyzed and compared from two sites in Florida and Illinois. We assessed age, gender, diagnosis, epilepsy classification, MRI, and EEG to compare patients with a TR. Analysis was performed with statistical significance set at P < 0.05.

RESULTS

We identified 24 of 98 evaluable patients with a TR in a prospective arm at one center and 7 of 31 patients in a retrospective arm at another totaling 31/129 (24.0%). The waveform prevalence was similar at both centers independent of location. TR was highly specific to active texting. A similar waveform during independent cognitive, speech or language, motor activation and audio cellular telephone use was absent (P < 0.0001). It appeared to be increased in patients with epilepsy in one cohort (P = 0.03) and generalized seizures in the other (P = 0.025). Age, gender, epilepsy type, MRI results, and EEG lateralization in patients with focal epileptic seizures did not bear a relationship to the presence of a TR in either arm of the study (P = NS).

CONCLUSIONS

The TR is a novel waveform time-locked to text messaging and associated with active use of smartphones. Electroencephalographers should be aware of the TR to separate it from an abnormality in patients undergoing video EEG monitoring. Larger sample sizes and additional research may help define the significance of this unique cognitive-visual-cognitive-motor network that is technology-related and task-specific with implications in communication research and transportation safety.

Audit of EEG Reporting Temporal Abnormalities

Background:

To ensure the overall quality of our electroencephalogram (EEG) laboratory, we decided to perform an audit of EEGs interpreted at our institution, focusing initially on EEGs reporting temporal abnormalities.

Methods:

Reports of all EEGs performed between January 1st and June 30th, 2006 were reviewed in order to identify tracings mentioning abnormalities in the temporal regions. These records were then independently reviewed by two epileptologists on two distinct occasions, separated by an interval of at least six months. If the recording was considered normal after this process, the cause for misinterpretation was identified and the patient's chart was reviewed to determine if he was epileptic or not based on available evidence until June 2009.

Results:

In the first half of 2006,143 out of 773 EEGs mentioned temporal abnormalities (18.5%). In general, intra- and interrater agreement ratios between our two epileptologists were moderate to substantial for normality, presence of epileptic activity and presence of slowing. Forty-five recordings (31.5%) were reported as normal independently by them on two distinct sittings six months apart. The most common causes for misinterpretation were the presence of benign epileptiform variants, normal sharply contoured patterns of somnolence or hyperventilation. Chart review confirmed that most were non-epileptic patients (60% non-epileptic, 27% epileptic, 13% unknown).

Conclusion:

Moderate to substantial intra- and interrater agreement as well as frequent misinterpretation of physiological variants indicate that some corrective measures need to be implemented to improve the consistency of EEG interpretation amongst our group of electroencephalographers.

Cortical processing during smartphone text messaging

OBJECTIVE

The objective of this study was to report the EEG features of text messaging using smartphones.

METHODS

One hundred twenty-nine patients were prospectively evaluated during video-EEG monitoring (VEM) over 16months. A reproducible texting rhythm (TR) present during active text messaging with a smartphone was compared with passive and forced audio telephone use, thumb/finger movements, cognitive testing/calculation, scanning eye movements, and speech/language tasks in patients with and without epilepsy. Statistical significance was set at p<0.05.

RESULTS

Twenty-seven patients with a TR were identified from a cohort of 129 (93 female, mean age: 36; range: 18-71) unselected VEM patients. Fifty-three out of 129 patients had epileptic seizures (ES), 74/129 had nonepileptic seizures (NES), and 2/129 were dual-diagnosed. A reproducible TR was present in 27/129 (20.9%) specific to text messaging (p<0.0001) and present in 28% of patients with ES and 16% of patients with NES (p=NS). The TR was absent during independent tasks and audio cellular telephone use (p<0.0001). Age, gender, epilepsy type, MRI results, and EEG lateralization in patients with focal seizures were unrelated (p=NS).

CONCLUSIONS

Our results suggest that the TR on scalp EEG represents a novel technology-specific neurophysiological alteration of brain networks. We propose that cortical processing in the contemporary brain is uniquely activated by the use of PEDs.

SIGNIFICANCE

These findings have practical implications that could impact industry and research in nonverbal communication.

Electroencephalography in Normotensive and Hypertensive Pregnancies and Subsequent Quality of Life

OBJECTIVES

To compare electroencephalography (EEG) findings during pregnancy and postpartum in women with normotensive pregnancies and pregnancies complicated by hypertensive disorders. Also the health related quality of life postpartum was related to these EEG findings.

MATERIALS AND METHODS

An observational case-control study in a university hospital in the Netherlands. Twenty-nine normotensive and 58 hypertensive pregnant women were included. EEG's were recorded on several occasions during pregnancy and 6-8 weeks postpartum. Postpartum, the women filled out health related quality of life questionnaires. Main outcome measures were qualitative and quantitative assessments on EEG, multidimensional fatigue inventory, Short Form (36) Health Survey and EuroQoL visual analogue scale.

RESULTS

In women with severe preeclampsia significantly lower alpha peak frequency, more delta and theta activity bilaterally and a higher EEG Sum Score were seen. Postpartum, these women showed impaired mental health, mental fatigue and social functioning, which could not be related to the EEG findings.

CONCLUSIONS

Severe preeclamptic patients show more EEG abnormalities and have impaired mental wellbeing postpartum, but these findings are not correlated.

Rhythmic Midtemporal Discharge in a Youth During Light Sleep

Rhythmic midtemporal discharge (RMTD) is a rare, benign EEG pattern that may have epileptic morphology. Recognizing variations of RMTD is important in order to avoid over- or misinterpretation of EEG findings, which may lead to inappropriate treatment and negative consequences for the patient in question. We present a case report of RTMDs during light sleep where initial erroneous description necessitated repeat EEGs and additional diagnostic exams and led to the postponement of obtaining a drivers licence for this young patient.

The applicability of ambulatory electroencephalography (AEEG) in healthy horses and horses with abnormal behaviour or clinical signs of epilepsy

BACKGROUND

Short-duration electroencephalography (EEG) recordings in horses are helpful in diagnosing intracranial disorders. Potentially, long-duration ambulatory EEG (AEEG) recordings in horses will enhance the chance of detecting abnormal brain activity independent of the presence of an insult.

OBJECTIVE

The objective of this study was to test if AEEG recordings in unsedated horses can be acquired and benefit diagnosing abnormal brain activity.

ANIMALS AND METHODS

Recordings were taken from 8 adult control horses and 10 patients suspected of intracranial abnormalities. Self-adhesive electrodes and the 'Porti-5' recording system were used. Filter settings were 0.5 Hz high pass and 35 Hz low pass. The records were analysed offline at a 50-200 μV/division and 10 seconds/division scale. Abnormal activity was defined as a spike or sharp wave, a period of generalised slow wave rhythmical activity or a generalised fast rhythmical discharge. The recording time ranged from 5 to 49 hours.

RESULTS

In the control group, one horse showed pathological activity. In the patient group, six out of nine horses showed abnormal activity during the recordings. Magnetic resonance imaging confirmed the presence of an intracranial mass in one patient. Long-term recordings of high quality can be obtained in unsedated horses by allowing daily activity using AEEG, resulting in a reasonable chance of recording (inter)ictal abnormal brain activity indicating epileptic or seizure-like activity in the absence of clinical signs or seizures.

CONCLUSIONS

It is concluded that abnormal behaviour can be expressed intermittently, and with the availability of AEEG a useful tool is added to the diagnostic scenario for horses.

Lambda waves and occipital generators

The objective of this study was to identify the relationship between lambda waves (LWs) and other occipital waveforms, in a retrospective analysis of electroencephalograms (EEGs) of clinic and hospitalized patients at a single center. The LWs were correlated with α rhythm, photic driving, and positive occipital sharp transients of sleep (POSTS). A computer-generated cursor quantified amplitude and duration of POSTS and LWs (3 waveforms and both hemispheres). Fisher exact test was used for significance (P ≤ .05). A total of 116 patients were evaluated. Of 111 patients, with interpretable results, 74 (66.67%) had visual scanning during EEG, with 37 (50.0%) having LWs. The LWs (17.69 µV) were consistently smaller than POSTS (31.40 µV) despite similar morphology. Patients with an α rhythm of >8.5 Hz were strongly correlated with the presence of LWs (P < .0001), and those with LWs were strongly predictive of normal EEG (P = .001). Of the 37 patients, 27 (73.0%) with LWs had photic driving (P = .0496). No correlation was found between LWs and POSTS (P = .45). The presence of LWs and a low normal posterior dominant rhythm (PDR) suggests intact electrocerebral health. LWs and the photic driving response suggest similar generators but stimulus-specific networks. POSTS differ from LWs despite similar morphology, suggesting different network activation of occipital generators. LWs have clinical significance in excluding encephalopathy. Occipital generators are differentiated by state and stimulus-dependent network activation and not by location and morphology.

Artifact: recording EEG in special care units

Artifacts may be obtained during routine recording but are more common in special care units (SCUs) outside of the EEG laboratory, where complex electrical currents are present that create a "hostile" environment. Special care units include the epilepsy monitoring unit, neurologic intensive care unit, and operating room, where artifact is present in virtually every recording, increasing with prolonged use. Nonepileptic attacks treated as epileptic seizures have been incorrectly diagnosed and treated due to a misinterpreted EEG. The recent emergence of continuous EEG as a neurophysiologic surrogate for brain function in the neurologic intensive care unit and operating room has also brought a greater amount and new types of EEG artifact. The artifacts encountered in special care units during continuous EEG are becoming more complex and may have adverse therapeutic implications. Our knowledge of artifact needs to parallel our growth in technology to avoid the pitfalls that may be incurred during visual analysis of the EEG.

Positive occipital sharp transients of sleep (POSTS): a reappraisal

OBJECTIVE

Positive occipital sharp transients of sleep (POSTS) are considered a normal variant seen in non-REM sleep; their asymmetrical presentation and relationship with EEG abnormalities have received scarce attention to date. We analyzed these features in a large prospective EEG recordings' sample.

METHODS

In this case-control study, over 6 months we collected consecutive patients showing POSTS on their EEG. They were matched with consecutive control subjects (two for each). Demographical data, asymmetries for POSTS and alpha activity, and lateralized or diffuse occurrence of EEG abnormalities (slowing, epileptiform transients) were compared among these two groups.

RESULTS

Out of 1254 EEG studies, 102 (8%) patients showed POSTS. They were younger (p=0.031), and more likely to show EEG abnormalities (p=0.008) - including epileptiform transients (p=0.002) - than controls. However, this relationship was influenced by age and recording length. Thirty nine POSTS recordings (38%) had a consistent amplitude asymmetry, but this was not associated with specific EEG abnormalities or alpha asymmetry.

CONCLUSION

POSTS are a normal EEG variant, occurring in less than 10% of unselected EEG recordings, mostly in younger adults, without gender predominance. Amplitude asymmetries are found in over one third of subjects.

SIGNIFICANCE

POSTS asymmetry, as opposed to other sleep transients, should be considered as normal.

Errors in EEG interpretation and misdiagnosis of epilepsy. Which EEG patterns are overread?

BACKGROUND/AIMS

The overinterpretation of EEGs is common and is an important contributor to the misdiagnosis of epilepsy. We reviewed our experience in order to clarify which EEG patterns are commonly overread as epileptiform.

METHODS

We identified patients who were seen at our epilepsy clinic and were ultimately diagnosed as having conditions other than epilepsy. We selected those who had previously had an EEG read as showing epileptiform discharges and whose EEG was available for our own re-review.

RESULTS

37 patients met the above criteria. Eventual diagnoses were psychogenic nonepileptic seizures (10), syncope (7), other miscellaneous diagnoses (5) and unexplained nonspecific symptoms (15). None of the EEGs had epileptiform discharges. The descriptions of the abnormalities included 'temporal sharp waves' in 30, 'frontal sharp waves' in 2 and 'generalized spike-wave complexes' in 2. Three had no reports available to identify the alleged abnormality. The benign patterns mistaken for temporal (30) and frontal (2) sharp waves were simple fluctuations of background activity with temporal phase reversals.

CONCLUSIONS

By far the most common patterns overread as epileptiform are nonspecific fluctuations of background in the temporal regions, which are misread as temporal sharp waves.