Typical Absence Seizures Triggered by Photosensitivity

Long-term prognosis of patients with photosensitive idiopathic generalized epilepsy

OBJECTIVE

The long-term prognosis of photosensitive idiopathic generalized epilepsy (p-IGE) is generally considered favorable; however, its specific characteristics remain unclear. Our objective was to investigate the extended prognosis of p-IGE.

METHODS

We analyzed the demographics, clinical, and electroencephalographic (EEG) data of consecutive patients who were diagnosed as having p-IGE, who were under follow-up for a minimum of 10 years and exhibited a photoparoxysmal response (PPR) in their EEGs. Prognostic data, epilepsy course types, and electroclinical variables were compared using appropriate statistical methods.

RESULTS

The mean follow-up duration for 108 consecutive patients with p-IGE (74.1 % female) was 16.8 ± 6.5 years. The main syndromes within this cohort included juvenile myoclonic epilepsy (37 %), juvenile absence epilepsy (15.7 %), and epilepsy with eyelid myoclonia (EEM) (14.8 %). In terms of epilepsy course types, 27.8 % were in the relapse-remission group, and 13.9 % had never experienced remission. A low early remission rate (5.6 %) was evident, with the remaining half of the cohort categorized as the late remission group. Several significant poor prognostic factors were identified including self-induction, clinical symptoms accompanying PPR, asynchrony and focal findings in EEG discharges, a wide frequency range of PPR, the coexistence of three seizure types, the presence of accompanying focal seizure features, and a history of convulsive status epilepticus.

CONCLUSIONS

Our long-term follow-up study, conducted within a substantial p-IGE group, unveiled newly proposed course types within this epilepsy category and highlighted significant poor prognostic factors related to photosensitivity. These findings furnish valuable insights for precise prognosis counselling and effective management strategies for patients with p-IGE.

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

Objective

The objective of this study was to better understand the clinical features of photosensitive epilepsy (PSE) in Chinese children.

Methods

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.

Results

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.

Conclusion

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.

Visually sensitive seizures: An updated review by the Epilepsy Foundation

Light flashes, patterns, or color changes can provoke seizures in up to 1 in 4000 persons. Prevalence may be higher because of selection bias. The Epilepsy Foundation reviewed light-induced seizures in 2005. Since then, images on social media, virtual reality, three-dimensional (3D) movies, and the Internet have proliferated. Hundreds of studies have explored the mechanisms and presentations of photosensitive seizures, justifying an updated review. This literature summary derives from a nonsystematic literature review via PubMed using the terms "photosensitive" and "epilepsy." The photoparoxysmal response (PPR) is an electroencephalography (EEG) phenomenon, and photosensitive seizures (PS) are seizures provoked by visual stimulation. Photosensitivity is more common in the young and in specific forms of generalized epilepsy. PS can coexist with spontaneous seizures. PS are hereditable and linked to recently identified genes. Brain imaging usually is normal, but special studies imaging white matter tracts demonstrate abnormal connectivity. Occipital cortex and connected regions are hyperexcitable in subjects with light-provoked seizures. Mechanisms remain unclear. Video games, social media clips, occasional movies, and natural stimuli can provoke PS. Virtual reality and 3D images so far appear benign unless they contain specific provocative content, for example, flashes. Images with flashes brighter than 20 candelas/m² at 3-60 (particularly 15-20) Hz occupying at least 10 to 25% of the visual field are a risk, as are red color flashes or oscillating stripes. Equipment to assay for these characteristics is probably underutilized. Prevention of seizures includes avoiding provocative stimuli, covering one eye, wearing dark glasses, sitting at least two meters from screens, reducing contrast, and taking certain antiseizure drugs. Measurement of PPR suppression in a photosensitivity model can screen putative antiseizure drugs. Some countries regulate media to reduce risk. Visually-induced seizures remain significant public health hazards so they warrant ongoing scientific and regulatory efforts and public education.

Utility of EEG Activation Procedures in Epilepsy: A Population-Based Study

PURPOSE

No previous population-based study has addressed the contribution of activation procedures to the yield of epileptiform abnormalities on serial EEGs. We assessed yield of activation-related epileptiform abnormalities and predictors of finding an activation-related abnormality with multiple EEGs in a population-based study of newly diagnosed epilepsy.

METHODS

We used the resources of the Rochester Epidemiology Project to identify 449 residents of Rochester, Minnesota with a diagnosis of newly diagnosed epilepsy at age 1 year or older, between 1960 and 1994, who had at least one EEG. Information on all activation procedures (i.e., sleep, hyperventilation, and photic activation) and seizure/epilepsy characteristics was obtained by comprehensive review of medical records.

RESULTS

At the first EEG, the yield of epileptiform abnormalities was greatest for individuals 1 to 19 years of age at diagnosis, for each activation procedure. The yield in patients aged 1 to 19 versus ≥20 years was 21.6% versus 10.3% for sleep, 6.5% versus 3.3% for photic stimulation, and 10.3% versus 5% for hyperventilation. Among young people (aged 1-19 years), sleep was associated with an increased likelihood of finding an activation-related abnormality on any EEG. The likelihood of finding an activation-related abnormality on any EEG was decreased for postnatal symptomatic and for unknown etiology.

CONCLUSIONS

Among activation procedures, sleep showed the highest yield of epileptiform abnormalities. There was a low yield for photic stimulation and hyperventilation. Within each activation procedure, younger age at diagnosis had the greatest yield. Sleep is the most effective activation procedure, especially in younger patients, and should be performed when possible.

Impaired Visual Habituation in Idiopathic Generalized Epilepsy with Photosensitivity Patients

Introduction

In this study, our goal was to analyze further the cortical excitability levels in idiopathic generalized epilepsy (IGE) patients with and without photosensitivity.

Methods

Forty-two patients (16 men and 26 women; mean age 30±8 years; range: 18-43 years) with IGE and thirty healthy age-matched control subjects (15 men and 15 women; mean age 35±3 years; range: 20-45 years) were enrolled for the investigation. We investigated the following two groups: 18 subjects with IGE with photosensitivity (IGE+PS), and 24 patients with IGE without photosensitivity (IGE-PS). Pattern reversal and potential inter-peak amplitudes, N75-P100 and P100-N145, as well as the corresponding latencies (N75, P100, and N145) for one hundred responses were measured 6 times. A linear regression slope was used for N75-P100 and P100-N145.

Results

Statistical analysis showed difference between groups where the IGE+PS had reduced N75-P100 compared to IGE-PS and controls. In IGE+PS group, the amplitude of N75-P100 was drastically reduced receiving antiepileptic therapy compared to those not receiving any anti-epileptic treatment (p=0.035).

Conclusion

These results show that the IGE+PS group has a different photoparoxysmal response phenotype driven by an unknown and distinct molecular mechanism. Pre-activation cortical excitability may be increased in IGE+PS patients compared to the IGE-PS or in healthy group. PR-VEP habituation may project the pathophysiological mechanisms underlying photosensitivity and it may be potential biomarker in patients with IGE+PS.

Photosensitivity and epilepsy: Current concepts and perspectives-A narrative review

The authors review the influence of photic stimuli on the generation of epileptic seizures, addressing the first descriptions of the phenomenon and its subsequent exploration. Initially defined in the 1950's, links between intermittent photic stimulation (IPS) and seizures were well understood by the 1970. Since then the increasing exposure to photic stimuli associated with modern life (for instance through TVs, patterns, computer games and electronic instruments with flickering displays) has led to an increased interest in this issue. Diverse stimulation procedures have been described and difference in the effects of stimulation frequencies and types, colour and lighting have been recognised. Approximately 5% of patients with epilepsy have photosensitive epilepsy (PSE). PSE is commoner in younger individuals, more frequent in women, often time-limited, generally easy to treat and closely related to generalised epilepsies, especially Juvenile Myoclonic Epilepsy (JME). Structural and functional studies of PSE indicate abnormalities beyond the frontal lobes and evidence for the role of the visual cortex in human PSE. A reduction in connectivity between prefrontal and frontopolar regions and increased connectivity between occipital cortex and the supplementary motor area may be the basis for triggering motor seizures in JME. Due to the changes observed in such areas, it is hypothesised that photoparoxysmal responses (PPR) could be a final expression of pathogenic phenomena in the striato-thalamocortical system, and possibly a core feature of JME as system epilepsy. The familial transmission of epileptiform responses to IPS is well-recognised, but no clear relation between PSE and specific genes has emerged. Although the influence of ethnic factors on PSE has been widely studied, clear conclusions are still lacking. Pharmacological therapeutic approaches are beyond the scope of this review although preventive measures allowing patients to avoid PS seizure initiation and/or generalisation are discussed. Given the gender/age group most commonly affected by PSE, the risks and benefits of drug treatment need to be carefully weighed up.

Status epilepticus in patients with juvenile myoclonic epilepsy: Frequency, precipitating factors and outcome

Status epilepticus (SE) is rarely described in patients with juvenile myoclonic epilepsy (JME), and little is known about its frequency, subtypes, and predictors and the prognosis of these patients. In this retrospective study, we aimed to analyze the incidence of SE in patients with JME and emphasize the risk factors and long-term outcome of SE in an epilepsy outpatient-based cohort. We included patients with JME with a history of predominant myoclonic seizures and at least one diagnostic EEG with normal background activity and bursts of typical ≥3-Hz generalized spike-polyspike and waves. We investigated the electroclinical features of patients with JME who had experienced SE and compared them with patients with JME without SE. Of the 133 patients with JME, only 5 patients were diagnosed with SE (3.8%) according to new criteria. The most common SE subtype was myoclonic SE (MSE, 4 patients), followed by generalized clonic-tonic-clonic SE (1 patient) and nonconvulsive SE (1 patient). One patient had both MSE and generalized clonic-tonic-clonic SE. In three out of five patients, recurrent episodes of SE were observed. Same seizure precipitants including sleep deprivation, inappropriate antiepileptic drug treatment, and noncompliance were identified in patients with JME with and without SE, not reaching a significant difference between the groups. Myoclonia limited to specific body parts (one arm, face, or head) were significantly more common in patients with JME with SE (p: 0.002). We did not find any significant correlation with drug-resistant course and SE. Status epilepticus is rarely observed in patients with JME, and MSE appears to be the most common subtype. Local myoclonia might predict SE in a subgroup of patients with JME. We may suggest that some patients with JME have a liability to SE, in addition to usual seizure precipitating factors of JME. It seems that SE per se does not affect the outcome of JME and the patients with SE did not have drug-resistant course in the final analysis.

Investigation of the possible association of NEDD4-2 (NEDD4L) gene with idiopathic photosensitive epilepsy

NEDD4-2 alias NEDD4L (neural precursor cell expressed, developmentally downregulated) gene was reported as a candidate gene for epileptic photo-sensitivity. We aimed to investigate this possible association of NEDD4-2 variants with idiopathic photosensitive epilepsy. Consecutive patients who had been followed up at our epilepsy center and diagnosed with idiopathic epilepsy according to ILAE criteria and clear-cut photoparoxysmal responses in their electroencephalograms and 100 ethnically matched healthy subjects were included in the study. The regions around previously reported three variants, namely, S233L, E271A and H515P were tracked with DHPLC and the samples showing variations were sequenced. 81 patients (63 females) aged between 12-63 years (45 had juvenile myoclonic epilepsy, 11 childhood absence epilepsy, 14 juvenile absence epilepsy, 7 late onset idiopathic generalized epilepsy, 1 unclassified idiopathic generalized epilepsy, and 3 patients with idiopathic photosensitive occipital lobe epilepsy) were included in this study. We found only one heterozygous S233L variant in a 23-year-old man who has photosensitive form of juvenile absence epilepsy and pattern sensitivity to striped carpets. Other two variants were not found in any of the other patients and controls. Our results suggest that three screened NEDD4-2 variants do not play a leading role in the pathogenesis of photosensitive epilepsy in the Turkish population.

Pattern sensitivity: a missed part of the diagnosis

RATIONALE

Pattern sensitivity can be diagnosed by presenting a series of visual patterns to the subject in the electroencephalography (EEG) laboratory; however, testing for pattern sensitivity is not routinely done during EEG recording. This work aimed to highlight the incidence of pattern sensitivity among patients referred for routine EEG recording during a 1-year period, identifying the cause of referral, diagnosis, and the characteristics of pattern-sensitive patients.

METHODS

All patients aged 4 years and older who were referred for routine EEG during a 12-month period and had no motor or visual impairment were enrolled in the study. Intermittent photic stimulation and pattern sensitivity were tested for each case. Pattern sensitivity was tested by scanning three different rhythmically moving patterns at reading distance with the patient seated in an illuminated room. A pattern evoking a paroxysmal response was reintroduced after exposure to a blank white card to confirm the findings.

RESULTS

Two hundred twenty-eight patients were studied; twelve patients (5.26%) had pattern sensitivity and their ages ranged from 5 to 12 years. Eight of these patients (66.7%) were referred for seizure disorders, two were referred with the diagnosis of migraine, one with headache and poor scholastic performance and one with recurrent attacks of dizziness for investigation. Seven of the twelve patients (58.3%) had a previous EEG done without testing for pattern sensitivity. Five patients (41.6%) had positive family history for epilepsy, three (25%) for migraine, and two (16.6%) for migraine and epilepsy. Two patients (16.6%) had pattern sensitivity without photosensitivity. Pattern stimulation provoked epileptiform discharges in eight patients (66.6%), focal discharges in one, and unilateral build-up of posterior discharge in three.

CONCLUSION

Diagnosis of pattern sensitivity is often missed as it is not routinely tested for during EEG recording. The result of the study challenges the concept of a consistent association between photosensitivity and pattern sensitivity; it also raises questions about the incidence of pattern sensitivity among children who do not suffer from epilepsy and in particular those with migraine, headache and scholastic difficulties. Further studies are therefore needed to clarify the phenotypic spectrum of this EEG trait.

Absence seizures: a review of recent reports with new concepts

Absence seizures with bilateral spike-wave (SW) complexes at 3Hz are divided into the childhood form, with onset at around 6 years of age, and the juvenile form, with onset usually at 12 years of age. These seizures typically last 9-12s and, at times, are activated by hyperventilation and occasionally by photic stimulation. Generalized tonic-clonic (GTC) seizures may also occur, especially in the juvenile form. There may be cognitive changes, in addition to linguistic and behavioral problems. Possible mechanisms for epileptogenesis may involve GABAergic systems, but especially T-calcium channels. The thalamus, especially the reticular nucleus, plays a major role, as does the frontal cortex, mainly the dorsolateral and orbital frontal areas, to the extent that some investigators have concluded that absence seizures are not truly generalized, but rather have selective cortical networks, mainly ventromesial frontal areas and the somatosensory cortex. The latter network is a departure from the more popular concept of a generalized epilepsy. Between the "centrencephalic" and "corticoreticular" theories, a "unified" theory is presented. Proposed genes include T-calcium channel gene CACNA1H, likely a susceptible gene in the Chinese Han population and a contributory gene in Caucasians. Electroencephalography has revealed an interictal increase in prefrontal activity, essential for the buildup of the ictal SW complexes maximal in that region. Infraslow activity can also be seen during ictal SW complexes. For treatment, counter to common belief, ethosuximide may not increase GTC seizures, as it reduces low-threshold T-calcium currents in thalamic neurons. Valproic acid and lamotrigine are also first-line medications. In addition, zonisamide and levetiracetam can be very helpful in absence epilepsy.

A comparative study of obsessive-compulsive disorder and other psychiatric comorbidities in patients with temporal lobe epilepsy and idiopathic generalized epilepsy

Our aim was to assess the associations of temporal lobe epilepsy (TLE) and idiopathic generalized epilepsy (IGE) with comorbid psychiatric conditions, especially obsessive-compulsive disorder (OCD), in a comparative design. We evaluated 29 patients with TLE, 27 patients with IGE, and 30 healthy controls. The Structured Clinical Interview for DSM-IV (SCID), Yale-Brown Obsessive Compulsive Scale (Y-BOCS) Symptom Checklist, and Beck Depression Inventory (BDI) were administered. Among patients with TLE, 75.9%, and among patients with IGE, 48.1% had at least one Axis I psychiatric disorder. Clinically meaningful obsessive-compulsive symptoms (CM-OCS) were noted in 10 patients with TLE and in 3 patients with IGE, and this difference was statistically significant (P<0.05). CM-OCS were present in 9 of 18 patients with left-sided TLE, but in only 1 of 11 patients with right-sided TLE. Higher comorbidity in TLE suggests that involvement of the temporal lobe may play a role in the development of specific psychopathological syndromes.

The evaluation of interictal focal EEG findings in adult patients with absence seizures

PURPOSE

To investigate the focal interictal EEG abnormalities in adult patients with absence seizures (ASs) and to identify their clinical, EEG and semiological correlates.

METHODS

Fifty patients older than 18 years, diagnosed as having IGE with AS documented with ictal recordings. Interictal focal sharp or spike-waves and strictly focal paroxysmal slow activity were considered as focal EEG features. The patients having focal EEG features were classified as "Group I", whereas the remaining of them was classified as "Group II".

RESULTS

We observed focal findings in 34% of the patients, mainly in frontotemporal (41%), and frontal (29%) regions. There were no significant differences with respect to the clinical parameters such as sex, epilepsy duration, positive family history and the age of the onset between the groups. Psychiatric co-morbidities were significantly higher in Group I when compared to Group II (P=0.00). Accompanying automatisms were higher in Group I, whereas eye deviation during absences was higher in Group II. In Group I, the asymmetry of the ictal discharges was more frequently observed. Focal EEG features were more frequently seen in juvenile absence epilepsy syndrome, without reaching a significance level.

CONCLUSION

The focal findings in adult absence epilepsy patients could have some unknown etio-pathogenetic and prognostic implications. We emphasize the cautious interpretation of isolated interictal focal EEG abnormalities to prevent a wrong diagnosis of focal epilepsy in patients who may indeed suffer from generalized epilepsy.

Self-induction behavior in patients with photosensitive and hot water epilepsy: a comparative study from a tertiary epilepsy center in Turkey

PURPOSE

The goal of this study was to compare self-induction (SI) patterns in photosensitive epilepsy (PSE) and hot water epilepsy (HWE).

METHODS

Among 7609 consecutive patients, 129 were diagnosed as having PSE, and 34, HWE.

RESULTS

Thirteen patients with PSE (10 females, 3 males, age at onset: 8.6; 3 with mental retardation) and 9 patients with HWE (all males, age at onset: 13.1) reported experiencing SI. During the seizures, a pleasurable feeling was described by all patients with HWE, but only by 3 patients with PSE. Patients with PSE induced their seizures by going very close to the TV screen or by waving their hands and blinking in front of the light sources. In the patients with HWE, seizures were precipitated by increasing the temperature of the water poured over the head or body.

CONCLUSIONS

Our results indicate that SI is more frequent in HWE, although this behavior was attributed mostly to PSE in previous studies.