Intermittent Photic Stimulation Research Articles

Utility of Various Activation Procedures in Provoking Ictal and Interictal Patterns, during Routine Electroencephalogram (rEEG) Recording.

Activation procedures (APs) are adopted during routine electroencephalography (rEEG) to provoke interictal epileptiform abnormalities (EAs). This study aimed to observe interictal and ictal (EAs) of different EEG patterns, provoked by various APs. This cross-sectional study was performed in the neurology department of King Fahd hospital of university, Saudi Arabia. The EEGs and medical records of patients who presented for EEG recordings were screened initially, then 146 EEGs provoked EAs due to utilization of APs, were included for analysis. Among all EEGs with provoked EAs, Non-rapid eye movement sleep (NREM) provoked EAs in 93 (63.7%) patients with following patterns, focal spike wave discharges (FSWDs) 45 (P= 0.01), focal spike wave discharges with bilateral synchrony (FSWDBS) 27 (P=0.03) and generalized spike wave discharges (GSWDs) 46 (P=0.01). Intermittent photic stimulation (IPS) most significantly provoked FSWDs in 07 patient (P =0.01) and GSWDs in 30 patients (P=<0.001) 7 patients (P = 0.01) and GSWDs in 30 patients (P < 0.001). Hyperventilation (HV) was associated with a higher occurrence of GSWDs in 37 patients (P =0.01). Female sex 7 (P = 0.02), provoked GSWDs 3 (P = 0.03), NREM sleep 8 (P = 0.04), prolonged EEG record 3 (P = 0.02), clinical events during recording 5 (P ≤ 0.01), diagnosis of genetic 05 (P = 0.03), and immune-mediated epilepsies 2 (P = 0.001) were associated with the provocation of ictal EAs; however, in multiple logistic regression analysis, no statistically significant association of these variables (P ≥ 0.05 each) was noted. The provocation of EAs in rEEG with different APs varies according to circumstances, including seizure types, epilepsy etiology, and the type of AP applied. These clinical and procedural parameters affect the diagnostic yield of rEEG and need careful consideration during rEEG recordings. APs adopted during rEEG recording can induce FSWDs, FSWDBS, and GSWDs in the form of either interictal or ictal EAs in various etiologies of epilepsy. Ictal EAs may appear in the form of GSWDs, during NREM sleep, in prolonged EEG records; however, their independent association needs to be evaluated in larger sample studies. Further, prospective cohort studies with adequate sample sizes are warranted.

Burst-Suppression EEG Reactivity to Photic Stimulation-A Translational Biomarker in Hypoxic-Ischemic Brain Injury.

The reactivity of an electroencephalogram (EEG) to external stimuli is impaired in comatose patients showing burst-suppression (BS) patterns following hypoxic-ischemic brain injury (HIBI). We explored the reactivity of BS induced by isoflurane in rat models of HIBI and controls using intermittent photic stimulation (IPS) delivered to one eye. The relative time spent in suppression referred to as the suppression ratio (SR) was measured on the contralateral fronto-occipital cortical EEG channel. The BS reactivity (BSR) was defined as the decrease in the SR during IPS from the baseline before stimulation (SRPRE). We found that BSR increased with SRPRE. To standardize by anesthetic depth, we derived the BSR index (BSRi) as BSR divided by SRPRE. We found that the BSRi was decreased at 3 days after transient global cerebral ischemia in rats, which is a model of brain injury after cardiac arrest. The BSRi was also reduced 2 months after experimental perinatal asphyxia in rats, a model of birth asphyxia, which is a frequent neonatal complication in humans. Furthermore, Oxytocin attenuated BSRi impairment, consistent with a neuroprotective effect in this model. Our data suggest that the BSRi is a promising translational marker in HIBI which should be considered in future neuroprotection studies.

Visual Electroencephalography Assessment in the Diagnosis and Prognosis of Cognitive Disorders.

Electroencephalography (EEG) is a noninvasive diagnostic tool that can be of diagnostic value in patients with cognitive disorders. In recent years, increasing emphasis has been on quantitative EEG analysis, which is not easily accessible in clinical practice. The aim of this study was to assess the diagnostic and prognostic value of visual EEG assessment to distinguish different causes of cognitive disorders. Patients with cognitive disorders from a specialized memory clinic cohort underwent routine workup including EEG, neuropsychological testing and brain imaging. Electroencephalography parameters including posterior dominant rhythm, background activity, and response to photic stimulation (intermittent photic stimulation) were visually scored. Final diagnosis was made by an expert panel. A total of 501 patients were included and underwent full diagnostic workup. One hundred eighty-three patients had dementia (111 Alzheimer disease, 30 vascular dementia, 15 frontotemporal dementia, and 9 dementia with Lewy bodies), 66 patients were classified as mild cognitive impairment, and in 176, no neurologic diagnosis was made. Electroencephalography was abnormal in 60% to 90% of patients with mild cognitive impairment and dementia, most profoundly in dementia with Lewy bodies and Alzheimer disease, while frontotemporal dementia had normal EEG relatively often. Only 30% of those without neurologic diagnosis had EEG abnormalities, mainly a diminished intermittent photic stimulation response. Odds ratio of conversion to dementia was 6.1 [1.5-24.7] for patients with mild cognitive impairment with abnormal background activity, compared with those with normal EEG. Visual EEG assessment has diagnostic and prognostic value in clinical practice to distinguish patients with memory complaints without underlying neurologic disorder from patients with mild cognitive impairment or dementia.

Factors Affecting the Activation and Appearances of Epileptiform Abnormalities in Routine Electroencephalography by Different Provocation Methods

Objective: The objective of this study was to observe the effects of various clinical factors on the activation and appearance of epileptiform abnormalities (EAs) in routine electroencephalography (rEEG) by different provocation methods. Methods: This observational study involved a review of 136 patients presented for EEG recording due to various indications and their EEG showing EAs during various provocation methods. Results: Generalized spike-wave discharges (GSWDs) were the most frequent activated epileptiform pattern observed in, 81 (59.1%) recordings. This pattern was seen mainly in females 49 (P = 0.00), in patients with generalized seizures 48 (P = 0.00), in prolonged EEG records 3 (P = 0.03), and in both genetic 35 (P = 0.00) and lesional epilepsies 21 (P = 0.00). Focal sharp waves with bilateral synchrony (FSWSBS) were the most activated ictal pattern (P = 0.00). Ictal EAs after hyperventilation (HV) (P = 0.03) and intermittent photic stimulation (IPS) (P = 0.01) were mainly observed in patients with uncontrolled seizures (P = 0.00), and immune-mediated epilepsy (P = 0.02). Females sex (odds ratio [OR]: 1.33, confidence interval [CI]: 0.6–2.6; P = 0.25), bilateral tonic–clonic seizures (OR: 1.17, CI: 0.5–2.4; P = 0.31) and lesional epilepsies (OR: 1.45, CI: 0.7–2.9; P = 0.20) had risk of activation of EAs by provocation methods; however this risk was not statistically significant. While sleep deprivation (SD) (OR: 6.33, CI: 2.2–18.2; P = 0.00), nonrapid eye movement sleep (NREM) (OR: 2.41, CI: 1.0–5.4; P = 0.00), and prolong EEG recording (OR: 1.91, CI: 0.9–3.9; P = 0.04) were leading to a statistically significant risk of activation and appearances of EAs due to provocation. Conclusion: Different provocation methods can activate and augment the variety of EEG patterns of diverse clinical significance. Detection of activated ictal EAs is dependent on various patient factors, including seizure control, and the provocation method applied. Further larger prospective cohort studies with adequate sample sizes are warranted.

Seizure provocation in EEG recordings: A data-driven approach.

Recording seizures on video-EEG has a high diagnostic value. However, bilateral convulsive seizures constitute a risk for the patients. Our aim was to investigate the diagnostic yield and associated risks of provocation methods in short-term video-EEGs. We extracted data on seizures and provocation methods from a large database of short-term video-EEGs with standardized annotations using SCORE (Standardized Computer-based Organized reporting of EEG). 2742 paroxysmal clinical episodes were recorded in 11 919 consecutive EEGs. Most epileptic seizures (54%) were provoked. Hyperventilation provoked most of typical absence seizures (55%), intermittent photic stimulation (IPS) provoked myoclonic seizures (25%) and most of bilateral convulsive seizures (55%), while 43% of focal seizures were precipitated by sleep. All but one of the 16 bilateral convulsive seizures were provoked by IPS or sleep. Latency between start of generalized photoparoxysmal EEG response and bilateral convulsive seizures were ≤3 s in all but one patient. The large, structured database provides evidence for the diagnostic utility of various provocation methods in short-term video-EEGs. The risk of bilateral convulsive seizures is relatively small, but it cannot be prevented by stopping IPS after 3 s. A priori knowledge about seizure semiology helps planning patient-tailored provocation strategy in short-term video-EEGs.

Acute effect of transcranial direct current stimulation on photoparoxysmal response

IntroductionTranscranial direct current stimulation (tDCS) is a non-invasive technique, used to modify the excitability of the central nervous system. The main mechanism of tDCS is to change the excitability by subthreshold modulation by affecting neuronal membrane potentials in the direction of depolarization or repolarization. tDCS was previously investigated as an alternative adjunctive therapy in patients with epilepsy. We aimed here to investigate the acute effect of tDCS on the photoparoxysmal response (PPR) in EEG. MethodsWe enrolled 11 consecutive patients diagnosed with idiopathic generalized epilepsy who had PPR on at least 2 EEGs. Three different procedures, including sham, anodal, and cathodal tDCS were applied to the patients at intervals of one week by placing the active electrode over Oz, for 2 mA, 20 minutes. Spike-wave indices (SWI) were counted by two researchers independently and were compared during intermittent photic stimulation (IPS) on EEGs both before and after the application. ResultsAfter cathodal tDCS, SWI increased compared to baseline EEG and sham EEG in 3 patients, and after anodal tDCS, SWI increased in 2 patients. Although the SWI values did not change significantly, 8 patients reported subjectively that the applications were beneficial for them and that they experienced less discomfort during photic stimulation after the sessions. There were no side effects except transient skin rash in one patient, only. ConclusionsIn our sham controlled tDCS study with both cathodal and anodal stimulation, our data showed that there was no significant change in SWI during IPS, despite subjective well-being. tDCS’ modulatory effect does not seem to act in the acute phase on EEG parameters after photic stimulation.

Video-EEG in the first 24 hours after the first unprovoked seizure in patients with normal neurological examination and head CT scan

Purpose: to determine the yield of Video-Electroencephalogram (VEEG) in the first 24 h in patients with a first unprovoked seizure and normal neurological examination, laboratory findings, and cranial CT scans. Methods: we analyzed retrospectively the yield of VEEG performed in these patients in the emergency department. All the patients were subsequently seen in the Epilepsy Clinic, and the epilepsy diagnosis was confirmed. Results: we included 19 patients who met the inclusion criteria; all of them underwent VEEG with the 10–20 system within the first 24 h after the seizure. The duration of the recordings averaged at 108.53 min and may or may not have included intermittent photic stimulation and sleep recording; 74% of the recordings were abnormal, with 26% being normal. Among the abnormal cases, epileptogenic activity was found in 47% and seizures in 26% of the patients; because both findings could be present in the same VEEG, 63% of all the VEEG showed epileptogenic alterations or seizures. The VEEG anomalies were recorded before the 20th minute (standard VEEG duration) in 58% of patients who exhibited epileptogenic activity and/or seizures, and after the 20th minute in 42%. Conclusion: conducting approximately 100-minute VEEGs within the first 24 h after a first unprovoked seizure can enhance the diagnostic yield in patients with epilepsy. However, the study has the limitations of its sample size and retrospective nature.

Diagnostic Value of Intermittent Photic Stimulation Among Adult Patients in a Tertiary Referral Epilepsy Center: A Retrospective Study.

Photosensitivity is a phenomenon that may be elicited by standardized intermittent photic stimulation during EEG recording and is detected more frequently in children and adolescents. Nevertheless, at our Epilepsy Center, we routinely assess photosensitivity in all newly referred adult patients. In this investigation, we sought to address the diagnostic yield under the prerequisites described. We reanalyzed all routine EEG recordings among referrals to the department of adults during the first six months of 2019, including a simultaneous video that is always coregistered in our center. The prevalence of abnormal findings during photic stimulation was assessed. Intermittent photic stimulation was performed on 344 patients. Photoparoxysmal response were detected in five subjects (1.5%). All patients were female. Four patients were diagnosed with idiopathic generalized epilepsy, and one with Doose syndrome. Photomyogenic responses were recorded in 1.1% and only in patients with psychogenic nonepileptic seizures. In two subjects with psychogenic nonepileptic seizures, the typical seizure was provoked by intermittent photic stimulation (8.7% of all subjects with psychogenic nonepileptic seizures in this cohort). Photoparoxysmal response was not detected in any subject with focal epilepsy, syncope, or other nonepileptic paroxysmal events. In every case of photoparoxysmal responses, increased photosensitivity had already been reported before recording. In our study, photoparoxysmal responses was a rare phenomenon among adults with a preponderance of females and idiopathic generalized epilepsies. Intermittent photic stimulation may be helpful in provoking typical psychogenic nonepileptic seizures and thus abbreviate the diagnostic process. Provided a careful history, routine intermittent photic stimulation in adults with epilepsy does not appear to be mandatory.

Photosensitive occipital lobe epilepsy: Delineation of an under-recognized reflex epilepsy syndrome according to the new ILAE criteria and long-term follow-up.

Photosensitive occipital lobe epilepsy (POLE) should be suspected in patients with occipital lobe seizures triggered by photic stimuli, who have normal motor-mental development and brain imaging. We aimed to examine the clinical, electrophysiological, and prognostic features of POLE, which is a rare and under-investigated syndrome. Archives from two tertiary epilepsy centers were retrospectively scanned and patients with normal neurological examination and cranial imaging were identified with POLE if they had: (1) seizures consistently triggered by photic stimuli; (2) non-motor seizures with visual symptoms; and (3) photosensitivity documented on EEG. The clinical and electrophysiological features and prognostic factors were evaluated for patients who had follow-up ≥5 years. We identified 29 patients diagnosed with POLE with a mean age of 20.1± 7.6 years. In one-third of the patients, POLE syndrome overlapped with genetic generalized epilepsy (GGE). The overlap group had higher rates of febrile seizure history and self-induction; when compared to pure POLE patients, their EEGs showed more frequent interictal generalized epileptic discharges and posterior multiple spikes during intermittent photic stimulation. During long-term follow-up, the remission rate for POLE was 80%, but EEG photosensitivity persisted in three quarters of patients despite clinical remission, and more than half had relapsed after clinical remission. This first long-term follow-up study, utilizing newly suggested criteria of the International League Against Epilepsy, showed that POLE syndrome shows a notable overlap with GGE but also has distinctive features. POLE has a good prognosis; however, relapses are common, and photosensitivity persists as an EEG finding in the majority of patients.

Electroclinical characteristics of photosensitive epilepsy: A retrospective study of 31 Chinese children and literature review.

The objective of this study was to better understand the clinical features of photosensitive epilepsy (PSE) in Chinese children. Thirty-one children with PSE were screened out of 398 children with epilepsy who were consecutively diagnosed by the video-electroencephalogram (VEEG) monitoring method and by using an intermittent photic stimulation (IPS) test. Their EEGs and clinical features were retrospectively analyzed, and their treatment outcomes were followed up. PSE accounted for 7.79% (31/398) of children with epilepsy during the observation period in our single epilepsy center. The male to female ratio of PSE was 1:3.43, and the average seizure onset age was 7.8 ± 3.28 years. The highest range of frequency sensitivity of the IPS test for the induction of EEG epileptic discharge or electroclinical seizures was within 10-20 Hz. Electroclinical seizures were induced in 41.94% (13/31) of PSE patients by using the IPS test, while EEG discharge without clinical seizures was induced in 58.06% (18/31) of PSE patients. Among all PSE patients, an IPS-positive reaction in the eye-closure state was induced in 83.87% of patients, and this rate was significantly higher than that in the eye-opened state (41.94%) or eye-closed state (35.48%). (Eye-closure IPS stimulation means: make the subjects close their eyes at the beginning of each stimulation, open their eyes at the end of the stimulation, and close their eyes again at the beginning of the next stimulation, and so on. While Eye-closed IPS stimulation means the stimulation is started after 5 s of eye closure, and the subjects are kept closed throughout the whole process.) The common and effective drugs used for single or combined therapy in PSE children were valproic acid and levetiracetam. This study provides some useful information about electroclinical characteristics in a cohort of 31 PSE children. It may be beneficial for pediatric neurologists in terms of paying more attention to PSE and correctly dealing with it.

The patent foramen ovale may alter migraine brain activity: A pilot study of electroencephalography spectrum and functional connectivity analysis.

A link has been shown between patent foramen ovale (PFO) and migraine, particularly migraine with aura. However, it is unknown if PFO might cause migraine by altering cortical excitability and neural network, which may lower the threshold of cortical spreading depression (CSD). This study aims to compare the spectrum power and functional connectivity of the alpha and beta bands of electroencephalography (EEG) across migraine patients with and without PFO. Thirty-five migraine patients with PFO (PFO +), 35 migraine patients without PFO (PFO -) and 20 PFO patients without migraine (control) were enrolled in this cross-sectional analysis. 19-channel EEG was recorded for all patients under resting state and intermittent photic stimulation. Power spectrum density (PSD) and phase lag index (PLI) of alpha and beta bands were then calculated and compared between the three groups. During photic stimulation, the beta band PSD at the occipital area was substantially higher in PFO + migraine patients compared to PFO-migraine patients (p < 0.05, Bonferroni corrected). Subgroup analysis showed that both migraine with and without aura patients with PFO had increased PSD in the alpha and beta bands at the occipital region during photic stimulation (p < 0.05, Bonferroni corrected). Meanwhile, the beta band PLI during photic stimulation was significantly elevated (adjusted p = 0.008, utilizing the network-based statistic technique) in PFO + group compared to PFO-group. Furthermore, although failed to pass the correction, the beta band power in the occipital area during photic stimulation at 20 Hz on O1 (R = 0.392, p = 0.024) and O2 channel (R = 0.348, p = 0.047) was prone to positively correlated with MIDAS score, and during photic stimulation at 12 Hz on O2 channel (R = 0.396, p = 0.022) and 20 Hz (R = 0.365, p = 0.037) on O1 channel was prone to positively correlated to HIT-6 score in PFO+ migraineurs, whereas no similar correlation was found in the PFO-group patients. The outcomes of this investigation suggested that PFO may change the cortical excitability in the occipital lobe of both migraineurs with and without aura. Meanwhile, the beta band PSD on the occipital area during photic stimulation might be an objective measure of severity in migraineurs with PFO.

Data Augmentation Effects on Highly Imbalanced EEG Datasets for Automatic Detection of Photoparoxysmal Responses.

Photosensitivity is a neurological disorder in which a person's brain produces epileptic discharges, known as Photoparoxysmal Responses (PPRs), when it receives certain visual stimuli. The current standardized diagnosis process used in hospitals consists of submitting the subject to the Intermittent Photic Stimulation process and attempting to trigger these phenomena. The brain activity is measured by an Electroencephalogram (EEG), and the clinical specialists manually look for the PPRs that were provoked during the session. Due to the nature of this disorder, long EEG recordings may contain very few PPR segments, meaning that a highly imbalanced dataset is available. To tackle this problem, this research focused on applying Data Augmentation (DA) to create synthetic PPR segments from the real ones, improving the balance of the dataset and, thus, the global performance of the Machine Learning techniques applied for automatic PPR detection. K-Nearest Neighbors and a One-Hidden-Dense-Layer Neural Network were employed to evaluate the performance of this DA stage. The results showed that DA is able to improve the models, making them more robust and more able to generalize. A comparison with the results obtained from a previous experiment also showed a performance improvement of around 20% for the Accuracy and Specificity measurements without Sensitivity suffering any losses. This project is currently being carried out with subjects at Burgos University Hospital, Spain.

The seizures that wake up with the patient: The effect of sleep deprivation and short sleep on epilepsy with eyelid myoclonia

ObjectiveIn this study, our aim was to demonstrate the effect of sleep deprivation, short sleep, and awakening on photoparoxysmal responses (PPR) and eyelid myoclonia (EM) in patients with Epilepsy with Eyelid Myoclonia (E-EM). MethodsE-EM patients with at least 1 year of follow-up in our clinic were included in the study. Video EEG(v-EEG) analyses were divided into three periods of wakefulness, sleep, and awakening. The PPR and onset of EMs were investigated. Results32 patients met the study criteria, of which 56.3% (n = 18) were male. The mean age at disease onset was 7.7 ± 4.1 years. The mean age at EEG recording was 12.4 ± 4.0 years. EM was observed only on awakening in 78.1% of patients (n = 22), of which it was seen only during intermittent photic stimulation (IPS) in 43.7% (n = 14). Eye closure (EC) sensitivity was detected in all patients. The proportion of patients with a PPR was significantly higher on awakening than before sleep (p = 0.01). ConclusionsThis study showed that EM is most prominent and sometimes can only be detected in the awakening period in E-EM. In order to detect E-EM, v-EEG recordings including both pre-sleep and post-sleep wakefulness periods should be recorded, with intermittent photic stimulation performed in both periods.

Brivaracetam or levetiracetam in status epilepticus?: Lessons from the photosensitivity model

First, a short history is given of the use of the EEG as a biomarker of efficacy in anti-seizure medication (ASM) development. The generalized epileptiform EEG response to Intermittent Photic Stimulation (IPS), the photoparoxysmal EEG response or PPR, in particular, is a reliable reproducible measure since the 1950s.Over time, a “Photosensitivity Model”, testing within the same patients the impact of potential new oral ASMs, along with dose-ranging data, on PPRs, has been developed successfully. The classical Photosensitivity Model consists of IPS and blood sampling for ASM measurement performed hourly between 8 AM and 5 PM over three consecutive days. This single-blind, placebo-controlled, pharmacokinetic-pharmacodynamic (PK/PD) Model is now commonly utilized as a Proof-of-Concept Phase 2a trial.For Generalized Tonic-Clonic Status Epilepticus (GTCSE), it is especially relevant to know the time for CNS entry and effect minutes after i.v. ASM treatment, since “time is brain”. We, therefore, adapted successfully the Model to a time-efficient Model with the determination of photosensitivity ranges in minutes after equivalent doses of iv brivaracetam (BRV) and levetiracetam (LEV). This modified design allows one to monitor the time to CNS effect (i.e., PPR elimination) of a quickly-acting FDA-approved ASM given i.v., a crucial element in status epilepticus treatment. This paper was presented at the 8th London-Innsbruck Colloqium on Status Epilepticus and Acute Seizures held in September 2022.

Role of Electroencephalogram (EEG) and Magnetic Resonance Imaging (MRI) Findings in Early Recognition and Diagnosis of Neuronal Ceroid Lipofuscinosis Type 2 Disease.

Neuronal ceroid lipofuscinosis type 2 (CLN2) disease is a very rare neurodegenerative lysosomal storage disorder. Progression is rapid and irreversible, making early diagnosis crucial for timely treatment. A group of pediatric neurologists and neuroradiologists with expertise in CLN2 convened to discuss early electroencephalogram (EEG) and magnetic resonance imaging (MRI) findings in CLN2 diagnosis. Of 18 CLN2 cases, 16 (88.9%) had background slowing and 16 (88.9%) had epileptiform discharges on initial EEG. Seven of 17 (41.2%) patients who received intermittent low-frequency photic stimulation had a photoparoxysmal response. Initial MRIs showed subtle cerebellar (n = 14, 77.8%) or cerebral (n = 9, 50.0%) atrophy, white matter abnormalities (n = 11, 61.1%), and basal ganglia T2 hypointensity (n = 6, 33.3%), which became more apparent on follow-up MRI. The recognition of even subtle cerebellar atrophy and white matter signal changes in children aged 2-5 years who present with language delay, new-onset seizures, and an EEG with epileptiform discharges and background slowing should prompt investigation for CLN2. Because these early signs are not unique to CLN2, genetic testing is essential early in the diagnostic journey.

Photo-Dependent Reflex Seizures-A Scoping Review with Proposal of Classification.

Children and adolescents are the largest at-risk group for the appearance of reflex seizures or epilepsy syndromes with a photoparoxysmal response. The aim of this study was to present an overview of the literature regarding photo-dependent reflex seizures. Epilepsy with seizures provoked by intermittent light stimulation is a distinct group of epilepsies; therefore, we focused on reflex seizures provoked by different factors whose common feature is the patient’s response to intermittent photic stimulation. A qualitative search of PubMed/MEDLINE, Scopus, EBSCO, and Cochrane Library electronic databases for selected terms was carried out for scientific articles published up to May 2020 outlining the outcomes of control, observational, and case studies. This scoping review was developed and followed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews. The review of the qualitative evidence for the synthesis of photosensitive epilepsy allowed us to distinguish the following categories: light-induced seizures and light-deprived seizures. Differentiating between intermittent photic stimulation-related epilepsy syndromes and seizures is essential in order to determine the length of appropriate treatment. Photo-dependent reflex seizures make up the majority of this type of disorder among reflex seizures. Since there are many seizures provoking factors in the world around us, it is important to distinguish amongst them in order to be able to protect the patient exposed to this factor. It is recommended that the photostimulation procedure be performed during a routine electroencephalogram study.

A Preliminary Study on Photic Driving in the Electroencephalogram of Children with Autism across a Wide Cognitive and Behavioral Range

Intermittent photic stimulation (IPS) is a useful technique in electroencephalography (EEG) to investigate the neurophysiological anomalies of brain activity. Although not an active task, IPS has also been explored in ASD; it is thought to capture local potential oscillators at specific frequencies and perhaps tap into rhythmic activity in a way that general resting-state recordings cannot. Previous studies suggest that individuals with ASD showed photic driving reactivity predominantly at lower frequencies of stimulation. In our study we used IPS to measure rhythmic oscillatory activity in a sample of 81 ASD children. We found a significant correlation linking ASD children with photic driving activation only at low frequencies (δθ band) and increased severity of “restricted behavior”. This suggests that ASD children with higher severity of restricted behaviors could have a hypersynchronous θ power and an impaired resonance synchronization at middle-ranged frequencies (α). Furthermore, we found some evidence of hemispherical oscillatory asymmetry linked particularly to behavioral impairments. This result is in line with the EEG pattern model indicating a “U-shaped profile” of electrophysiological power alterations with excess power in low- and high-frequency bands and a reduction of power in the middle-ranged frequencies. IPS technique in electroencephalography is confirmed to reveal EEG biomarkers in autistic children, with a focus on spectral power, coherence, and hemisphere asymmetries.

P.073 Diagnostic utility of specific abnormal EEG patterns in children

Background: CTS and PPR are common EEG findings that are classically associated with CECTS and GGE respectively. PPD and sleep spindles are physiologic phenomenon that occur in respond to intermittent photic stimulation and sleep respectively. Methods: We reviewed EEG studies with CTS, PPR, asymmetric PPD, or asymmetric sleep spindles. For CTS, we determined sensitivity, specificity, PPV and NPV for a diagnosis of CECTS. For PPR, we determined the same diagnostic outcome measures for a diagnosis of GGE or JME. For each of asymmetric PPD and asymmetric sleep spindles, we determined the same diagnostic outcome measures for the presence of a structural abnormality on brain MRI. Results: CTS had 83% specificity and 75% PPV in children with normal neurological examination. PPR had high specificity of 92% and NPV 92% for GGE; for JME, PPR also had high sensitivity (92%). Asymmetric PPD had low sensitivity for structural brain abnormalities (17%), with specificity 80%. In contrast, asymmetric sleep spindles had higher sensitivity and specificity, 44% and 97%, respectively. Conclusions: CTS are seen with CECTS and other conditions. PPR is highly indicative of a GGE, though may be seen other conditions. Relative attenuation of sleep spindles is a more reliable indicator of structural brain malformation than asymmetric PPD.

A Computational Biomarker of Photosensitive Epilepsy from Interictal EEG

People with photosensitive epilepsy (PSE) are prone to seizures elicited by visual stimuli. The possibility of inducing epileptiform activity in a reliable way makes PSE a useful model to understand epilepsy, with potential applications for the development of new diagnostic methods and new treatments for epilepsy. A relationship has been demonstrated between PSE and both occipital and more widespread cortical hyperexcitability using various types of stimulation. Here we aimed to test whether hyperexcitability could be inferred from resting interictal electroencephalographic (EEG) data without stimulation. We considered a cohort of 46 individuals with idiopathic generalized epilepsy who underwent EEG during intermittent photic stimulation: 26 had a photoparoxysmal response (PPR), the PPR group, and 20 did not, the non-PPR group. For each individual, we computed functional networks from the resting EEG data before stimulation. We then placed a computer model of ictogenicity into the networks and simulated the propensity of the network to generate seizures in silico [the brain network ictogenicity (BNI)]. Furthermore, we computed the node ictogenicity (NI), a measure of how much each brain region contributes to the overall ictogenic propensity. We used the BNI and NI as proxies for testing widespread and occipital hyperexcitability, respectively. We found that the BNI was not higher in the PPR group relative to the non-PPR group. However, we observed that the (right) occipital NI was significantly higher in the PPR group relative to the non-PPR group. Other regions did not have significant differences in NI values between groups.

Brain Dynamics in Response to Intermittent Photic Stimulation in Epilepsy

Purpose: Routine electroencephalogram (EEG) examinations uses intermittent photic stimulation (IPS) for investigation of the visual cortex EEG responses during resting time. This study aimed to discover brain dynamics effects of IPS in 28 generalized epilepsy patients and 28 healthy subjects. Methodology: Signal processing techniques were used in feature extraction by Fast Fourier transform (FFT), feature dimension reduction by t-test (significant, p&lt;0.05) and classification by nearest neighbor (k-NN) and support vector machine (SVM). Results: The epilepsy group had higher level of amplitude in Theta waves compared to the healthy group. The Alpha waves in the resting time and for all IPS frequencies were observed with lower level of amplitude in healthy subjects compared to the epilepsy group. The k-NN (85.7% accuracy) classifier had the best discrimination of epilepsy from healthy group for resting time versus during IPS at 18 Hz IPS. However, using SVM (75.0% accuracy), IPS at 25 Hz yielded the best discrimination between resting time versus IPS in epilepsy where the healthy group responded similarly in all IPS frequencies. Conclusions: This study shows that IPS at 18 Hz and 25 Hz are suitable IPS frequencies for k-NN and SVM, respectively, to discriminate non-photosensitive generalized epilepsy from normal subjects during interictal.