Medical technology assessment photic stimulation--standardization of screening methods

Electroclinical Features and Long-Term Photosensitivity Outcome in Patients With Photoparoxysmal Response With Epilepsy

BACKGROUND

To investigate electroclinical phenotypes and long-term photosensitivity outcome in a large pediatric cohort of patients with epilepsy with photosensitivity.

METHODS

Patients with epilepsy with photosensitivity with four or more years of follow-up were included. Sustained terminal remission (STR) of photosensitivity (≥3.5 years) and seizure control were investigated, as well as the prognostic factors of photosensitivity. Furthermore, a cluster analysis was used to study the different subgroups of photoparoxysmal responses (PPR).

RESULTS

We included 190 individuals with a median age at diagnosis of photosensitivity of 93.1 months (interquartile range [IQR] 62.8 to 120 months) and a median follow-up duration of 68.5 months (IQR 51.8 to 84 months). STR of photosensitivity was achieved in 97 (51.1%) patients, and the mean time from age at diagnosis of photosensitivity onset to STR was 16.5 months. Age at the last follow-up (9 to 18 years [P = 0.001]), a history of photoconvulsive response (PCR) (P = 0.009), and posterior epileptiform discharges (EDs) of PPRs (P = 0.05) were significantly associated with a lower chance of entering STR according to a Cox proportional hazards model. The subgroup of generalized epilepsy syndrome exhibited 46.2% of eye closure sensitivity and 47.7% of PCR. The rates of focal epilepsy syndrome (cluster 1), generalized epilepsy syndrome (cluster 2), and unclassified epilepsy (cluster 3) were similar and not statistically different in photosensitive outcome (P = 0.527).

CONCLUSIONS

Age nine to 18 years, a history of PCR, and posterior EDs of PPRs were the adverse factors affecting photosensitivity, suggesting the effect of age-related brain changes in STR. There was no difference in the prognosis of photosensitivity in different epileptic syndromes.

Efficacy of color lenses in abolishing photosensitivity: Beyond the one-type-fits-all approach?

OBJECTIVE

Red-light filtering lenses represent an additional option to medication in photosensitive epilepsy. Blue lenses (Clarlet Z1 F133) can dramatically reduce seizure frequency, with a substantial restriction in luminance that can limit their applicability in daily life. We investigated the efficacy of 4 blue lenses with higher transmittance and reduced chromatic distortion in abolishing the photoparoxysmal EEG response (PPR) compared to the gold-standard Z1 lenses.

METHODS

We reviewed EEG data during photic-and pattern stimulation in 19 consecutive patients (6-39 years) with photosensitivity (PS). Stimulation was performed at baseline and while wearing Z1 and the four new lenses. Lenses were tested in the same session by asking the patient to wear them in a sequentially randomized fashion while stimulating again with the most provocative photic/pattern stimuli. The primary outcome was the change in the initial PPR observed for each lens, categorized as no change, reduction, and abolition.

RESULTS

Photosensitivity was detected in 17 subjects (89.5%); pattern sensitivity (PtS) was identified in 14 patients (73.7%). The highest percentages of PPR abolition/reduction were observed with Z1, for both PS and PtS. Regarding the new lenses, B1 + G1 offered the best rates, followed by B1 + G2. B1 + G3 and B1 showed lower efficacy rates, particularly for PtS. In the comparative analysis, no significant differences in PPR suppression were detected between the five lenses for PS. For PtS, the capacity of Z1 for PPR abolition was significantly higher compared with B1 + G3 and B1.

CONCLUSIONS

This preliminary study suggests efficacy of the new group of blue lenses with potentially greater tolerability, particularly in regions with fewer sunlight hours during winter. In line with the current trend for personalized approach to treatment, this study suggests that in some patients there might be scope in extending the testing to offer the lens with the higher transmittance effective in abolishing the PPR.

Interrater agreement of classification of photoparoxysmal electroencephalographic response

Our goal was to assess the interrater agreement (IRA) of photoparoxysmal response (PPR) using the classification proposed by a task force of the International League Against Epilepsy (ILAE), and a simplified classification system proposed by our group. In addition, we evaluated IRA of epileptiform discharges (EDs) and the diagnostic significance of the electroencephalographic (EEG) abnormalities. We used EEG recordings from the European Reference Network (EpiCARE) and Standardized Computer-based Organized Reporting of EEG (SCORE). Six raters independently scored EEG recordings from 30 patients. We calculated the agreement coefficient (AC) for each feature. IRA of PPR using the classification proposed by the ILAE task force was only fair (AC = 0.38). This improved to a moderate agreement by using the simplified classification (AC = 0.56; P = .004). IRA of EDs was almost perfect (AC = 0.98), and IRA of scoring the diagnostic significance was moderate (AC = 0.51). Our results suggest that the simplified classification of the PPR is suitable for implementation in clinical practice.

Light-emitting-diode and Grass PS 33 xenon lamp photic stimulators are equivalent in the assessment of photosensitivity: Clinical and research implications

The assessment of the effect of photic stimulation is an integral component of an EEG exam and is especially important in patients referred for ascertained or suspected photosensitivity with or without a diagnosis of epilepsy. A positive test result relies on eliciting a specific abnormality defined as the "photoparoxysmal response". Reliability of this assessment is strongly influenced by technical and procedural variables, a critical one represented by the physical properties of the stimulators used. Established clinical norms are based on data acquired with the "gold-standard" Grass PS stimulators. These are no longer commercially available and have been replaced by stimulators using light emitting diode (LED) technology. To our knowledge no comparative study on their efficacy has been conducted. To address this gap, we recruited 39 patients aged 5-54 years, referred to two specialized centers with confirmed of suspected diagnosis of photosensitive epilepsy or generalized epilepsy with photosensitivity in a prospective randomized single-blind cross-over study to compare two commercially available LED-bases stimulation systems (FSA 10® and Lifeline® stimulators) against the Grass PS 33 xenon lamp device. Our findings indicate that the LED systems tested are equivalent to the Grass stimulator both in identifying the PPR in affected individuals.

Photosensitive epilepsy and photosensitivity of patients with possible epilepsy in Chinese Han race: A prospective multicenter study

Photosensitive is probably caused by multiple factors including gender, familiar, etc. We aim to study the clinical and EEG features of Chinese Han patients with photosensitivity. A total of 5482 consecutive patients with possible epilepsy from 3 center in China. Of the 73 patients with PPR to IPS, 48 were female. 69.9% patients were evoked by frequency ranged 8 Hz-25 Hz, with accompanying seizures in 13 patients. 6 of 9 patients with eyes closure sensitivity experienced epileptic seizures during IPS. We found some new features: 1) The patients with eyes closure sensitivity apt to experience electro-clinical seizures provoked by IPS; 2) Female epilepsy patients with PPR and ECS maybe difficult to be seizure free. Preventive measures for related seizures should be performed to the patients with generalized PPR, upper threshold evoking frequency, and eyes closure sensitivity when they received the IPS.

Safety Aspects, Tolerability and Modeling of Retinofugal Alternating Current Stimulation

BACKGROUND

While alternating current stimulation (ACS) is gaining relevance as a tool in research and approaching clinical applications, its mechanisms of action remain unclear. A review by Schutter and colleagues argues for a retinal origin of transcranial ACS' neuromodulatory effects. Interestingly, there is an alternative application form of ACS specifically targeting α-oscillations in the visual cortex via periorbital electrodes (retinofugal alternating current stimulation, rACS). To further compare these two methods and investigate retinal effects of ACS, we first aim to establish the safety and tolerability of rACS.

OBJECTIVE

The goal of our research was to evaluate the safety of rACS via finite-element modeling, theoretical safety limits and subjective report.

METHODS

20 healthy subjects were stimulated with rACS as well as photic stimulation and reported adverse events following stimulation. We analyzed stimulation parameters at electrode level as well as distributed metric estimates from an ultra-high spatial resolution magnetic resonance imaging (MRI)-derived finite element human head model and compared them to existing safety limits.

RESULTS

Topographical modeling revealed the highest current densities in the anterior visual pathway, particularly retina and optic nerve. Stimulation parameters and finite element modeling estimates of rACS were found to be well below existing safety limits. No serious adverse events occurred.

CONCLUSION

Our findings are in line with existing safety guidelines for retinal and neural damage and establish the tolerability and feasibility of rACS. In comparison to tACS, retinofugal stimulation of the visual cortex provides an anatomically circumscribed model to systematically study the mechanisms of action of ACS.

Efficacy and safety of a video-EEG protocol for genetic generalized epilepsies

INTRODUCTION

Video-EEG has been used to characterize genetic generalized epilepsies (GGE). For best performance, sleep recording, photic stimulation, hyperventilation, and neuropsychological protocols are added to the monitoring. However, risks and benefits of these video-EEG protocols are not well established. The aim of this study was to analyze the efficacy and safety of a video-EEG neuropsychological protocol (VNPP) tailored for GGE and compare its value with that of routine EEG (R-EEG).

METHODS

We reviewed the VNPP and R-EEG of patients with GGE. We considered confirmation of the clinical suspicion of a GGE syndrome and characterization of reflex traits as benefits; and falls, injuries, psychiatric and behavioral changes, generalized tonic-clonic (GTC) seizures, and status epilepticus (SE) as the main risks of the VNPP.

RESULTS

The VNPPs of 113 patients were analyzed. The most common epileptic syndrome was juvenile myoclonic epilepsy (85.8%). The protocol confirmed a GGE syndrome in 97 patients and 62 had seizures. Sleep recording had a provocative effect in 51.2% of patients. The second task that showed highest efficacy was praxis (39.3%) followed by hyperventilation (31.3%). Among the risks, 1.8% had GTC seizures and another 1.8%, SE. Eighteen percent of patients had persistently normal R-EEG, 72.2% of them had discharges during VNPP. Generalized tonic-clonic seizures, myoclonic status epilepticus, and repeated seizures were the main risks of VNPP present in 6 (5.31%) patients while there were no complications during R-EEG.

CONCLUSIONS

The VNPP in GGE is a useful tool in diagnosis and characterization of reflex traits, and is a safe procedure. Its use might preclude multiple R-EEG exams.

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.

"Selfie-epilepsy": A novel photosensitivity

PURPOSE

Photosensitivity is a well-described phenomenon; affecting a relatively small proportion of individuals with epilepsy. Typically people with photosensitive epilepsies are at risk of seizures induced by shimmering natural light, strobe lights and with particular patterns or flicker frequencies on television and video games.

METHODS & RESULTS

We present a novel case of photosensitivity captured during video EEG monitoring showing reproducible photosensitivity with the ever-popular social phenomenon; the "selfie." The patient had previously demonstrated photosensitive myoclonus with intermittent photic stimulation on routine EEG.

CONCLUSION

This case suggests that taking "selfies" may represent a new area of caution for those with photosensitive epilepsies.

Visual-Sensitive Epilepsies: Classification and Review

Photosensitivity, photosensitive seizures, and photosensitive epilepsy are discussed. The International League against Epilepsy has suggested the term “visual-sensitive” replace “photosensitive”. Visual-sensitive seizures may be more common than is realized. A classification for visual-sensitive epilepsies is presented. Chromosomal and DNA testing may help to refine the classification further. A standardized approach for neurophysiologic testing, such as that proposed by European experts, is recommended. These steps should promote evidenced-based management for this group of disorders.

Cortical Thickness Changes Associated with Photoparoxysmal Response

Photoparoxysmal response (PPR) is an EEG trait of spike and spike-wave discharges in response to photic stimulation that is closely linked to idiopathic generalized epilepsy (IGE). In our previous studies we showed that PPR is associated with functional alterations in the occipital and frontal cortices. The aim of the present study was to determine structural changes associated with PPR. For this purpose we analysed the cortical thickness as derived from T1 MRI images in PPR-positive-subjects (n = 12; 15.5 ± 8.6 years; 4 males), PPR-positive-IGE-patients (n = 12; 14.9 ± 2.7 years; 4 males) and compared these groups with a group of PPR-negative-healthy-controls (HC, n = 17; 15.3 ± 3.6 years; 6 males). Our results revealed an increase of cortical thickness in the occipital, frontal and parietal cortices bilaterally in PPR-positive-subjects in comparison to HC. Moreover PPR-positive-subjects presented a significant decrease of cortical thickness in the temporal cortex in the same group contrast. IGE patients exhibited lower cortical thickness in the temporal lobe bilaterally and in the right paracentral region in comparison to PPR-positive-subjects. Our study demonstrates structural changes in the occipital lobe, frontoparietal regions and temporal lobe, which also show functional changes associated with PPR. Patients with epilepsy present changes in the temporal lobe and supplementary motor area.

Diagnosing photosensitive epilepsy: fancy new versus old fashioned techniques in patients with different epileptic syndromes

PURPOSE

To demonstrate the clinical importance of using a high quality photic stimulator for recording EEGs to diagnose photosensitivity.

METHODS

We performed EEG examinations on 2 adult and 2 paediatric patients with a history of visually induced seizures; routinely we used a Grass PS 40 photic stimulator (rectangular Xenon lamp giving flashes of 10 μs duration, 0.7J, 1-30 Hz, width 7 cm, length 12 cm). We repeated the IPS with a Grass PS 33 plus stimulator (round Xenon lamp giving flashes of 10 μs duration, 1J, 1-60 Hz, diameter 14 cm).

RESULTS

Patients were affected by both benign and catastrophic epilepsies. They complained about episodes of dizziness (case 1), dizziness accompanied by a sensation in the arms and fear (case 2), absences (case 3), and myoclonic jerks (case 4). These symptoms occurred when working with neon lights, computers or ironing striped clothes (case 1), while driving (case 2), whenever there was sunlight (case 3 and 4). Only IPS performed with the Grass PS 33 plus stimulator evoked PPRs accompanied by their typical complaints. In all cases, the revised diagnosis led to changes in their treatment and the disappearance or diminishment of their complaints and PPR range.

CONCLUSION

A PPR can occur in various types of epilepsy, can have a different meaning, and requires a different therapeutic intervention. Only an appropriate photic stimulator with diffuse white light and a flash intensity level of 1J/flash, can reliably demonstrate whether a patient is photosensitive, or equally important exclude it.

Treatment of photosensitivity

Not all visually sensitive patients need antiepileptic drug treatment, and even those who do can benefit from additional preventive measures. Visually provoked seizures, in particular, can be prevented or treated by avoiding or altering the triggering stimulus. Apart from individual preventive measures (use of specific television or video screens, colored glasses, etc.), prevention and warning on a larger scale are helpful. The choice for drug treatment will depend on the type of stimulus, the environment in which the person has to live and work, the frequency and severity of seizures, and the type of epileptic syndrome. A review is given of all treatment options with focus on the specific nonpharmacologic and pharmacologic tools used in clinical practice.

Altered cortical visual processing in individuals with a spreading photoparoxysmal EEG response

Photosensitive individuals respond with epileptiform electroencephalography (EEG) discharges to intermittent photic stimulation. The pathogenetic mechanisms underlying this photoparoxysmal response (PPR) remain to be clarified. We investigated the involvement of magnocellular and parvocellular pathways in the processing of nonprovocative visual stimuli in healthy subjects with different phenotypic expressions of PPR (15 individuals with a local PPR, i.e. occipital discharges only, and 15 with a PPR propagating to anterior brain regions) and in 17 PPR-negative healthy controls using pattern-reversal visual evoked potentials (VEP). Checkerboard stimulation was performed at a low and a high spatial frequency to preferentially activate the magnocellular and parvocellular pathways. VEP habituation was also assessed over 15 blocks (each 100 trials) of recording. PPR-positive individuals with propagating PPR showed an increase in the N75-P100 and P100-N135 VEP components for both spatial frequencies, whereas individuals with a local PPR had normal VEP amplitudes. Individuals with propagating PPR also showed a stronger VEP habituation and reported more aversive sensations during continuous visual stimulation with the high spatial frequency checkerboard. The selective increase in VEP amplitudes in individuals with propagating PPR corroborates the notion that PPR with propagation is pathophysiologically distinct from local PPR. The increase in VEP amplitudes was independent of the spatial frequency of visual stimulation, indicating an increased neuronal excitability in both the parvocellular and magnocellular pathways. The stronger habituation in these individuals may reflect a compensatory mechanism to stabilize excitability in the visual system.

Photoparoxysmal responses in children with chromosomal aberrations

Electroencephalographic (EEG) anomalies and epilepsy are commonly observed in the clinical picture of patients with chromosomal aberrations. However, no investigations have been performed on the relationship between chromosomal disorders and photoparoxysmal response (PPR). In this study, we evaluate the characteristics of PPRs elicited with intermittent photic stimulation during a routine electroencephalogram in children affected by chromosomal anomalies and correlated this with the clinical profile of the child. A review of the literature has also been performed. PPRs occurred in 14% (4/28) of patients. PPRs were brief (<less 5s), self-limited, elicited by several series of flashes, with an onset latency between 2 and 9s, and scarcely controlled by anticonvulsants. Although further studies are needed to confirm the present data, our observations and the review of the literature suggest that patients carrying chromosomal anomalies might have a higher risk for photosensitivity when compared to the normal population. In these patients, PPR might occur early in life, persist into adulthood, and is commonly inscribed in more polymorphic electroclinical patterns.

Clinical analysis in familial cortical myoclonic tremor allows differential diagnosis with essential tremor

Familial cortical myoclonic tremor (FCMT) is a rare disorder often leading to a wrong clinical diagnosis of essential tremor. Electrophysiological data are usually considered to allow a correct diagnosis. We describe a FCMT French family with previously unreported clinical features such as sensitivity to glucose deprivation, vibration, repetitive visual patterns, and intense visual or auditory stimulation and contrasts. Electrophysiological studies of the propositus confirm the cortical reflex myoclonus elicited by photic stimulation and the absence of epileptic electroencephalographic discharges. We emphasize that a precise clinical analysis can lead to a correct diagnosis before electrophysiological confirmation. This is also the first-ever report of efficacy of levetiracetam in FCMT.

Photosensitivity in Idiopathic Generalized Epilepsies

Photosensitivity is an abnormal visual sensitivity of the brain in reaction to flickering light sources or patterns and is expressed in the electroencephalogram as generalized spike-and-wave discharge and in more susceptible individuals as clinical seizures. The most common types of seizures are generalized tonic-clonic, followed by myoclonic and absence. The photosensitive epilepsies are classified as pure photosensitive, where seizures occur only with the flickering light source/pattern or during intermittent photic stimulation (IPS) in the laboratory, and epilepsy with photosensitivity, where spontaneous seizures also occur. Positive response to IPS in idiopathic epilepsy syndromes, which are included in the International Classification or are in development, is reported to range from 7.5% in juvenile absence epilepsy to 100% in pure photosensitive epilepsy. The treatment of photosensitivity and pure photosensitive epilepsy with rare seizures includes general and specific protective measures. For most patients, however, combination treatment with antiepileptic drugs is necessary. Valproic acid monotherapy has a success rate of 73-86%. Levetiracetam appears to be a new alternative therapeutic option. Clobazam, lamotrigine, ethosuximide, and topiramate also have been recommended as second-choice therapies.

Human photosensitivity: from pathophysiology to treatment

Photosensitivity is a condition detected on the electroencephalography (EEG) as a paroxysmal reaction to Intermittent Photic Stimulation (IPS). This EEG response, elicited by IPS or by other visual stimuli of daily life, is called Photo Paroxysmal Response (PPR). PPRs are well documented in epileptic and non-epileptic subjects. Photosensitivity rarely in normal individuals evolves into epilepsy. Photosensitive epilepsy is a rare refex epilepsy characterized by seizures in photosensitive individuals. The development of modern technology has increased the exposition to potential seizure precipitants in people of all ages, but especially in children and adolescents. Actually, videogames, computers and televisions are the most common triggers in daily life of susceptible persons. The mechanisms of generation of PPR are poorly understood, but genetic factors play an important rule. The control of visually induced seizures has, generally a good prognosis. In patients known to be visually sensitive, avoidance of obvious source and stimulus modifications are very important and useful to seizure prevention, but in the large majority of patients with epilepsy and photosensitivity antiepileptic drugs are needed.

Photic- and pattern-induced seizures: a review for the Epilepsy Foundation of America Working Group

PURPOSE

This report summarizes background material presented to a consensus conference on visually provoked seizures, convened by the Epilepsy Foundation of America.

METHODS

A comprehensive review of literature was performed.

RESULTS

Photosensitivity, an abnormal EEG response to light or pattern stimulation, occurs in approximately 0.3-3% of the population. The estimated prevalence of seizures from light stimuli is approximately 1 per 10,000, or 1 per 4,000 individuals age 5-24 years. People with epilepsy have a 2-14% chance of having seizures precipitated by light or pattern. In the Pokemon cartoon incident in Japan, 685 children visited a hospital in reaction to red-blue flashes on broadcast television (TV). Only 24% who had a seizure during the cartoon had previously experienced a seizure. Photic or pattern stimulation can provoke seizures in predisposed individuals, but such stimulation is not known to increase the chance of subsequent epilepsy. Intensities of 0.2-1.5 million candlepower are in the range to trigger seizures. Frequencies of 15-25 Hz are most provocative, but the range is 1-65 Hz. Light-dark borders can induce pattern-sensitive seizures, and red color also is a factor. Seizures can be provoked by certain TV shows, movie screen images, video games, natural stimuli (e.g, sun on water), public displays, and many other sources.

CONCLUSIONS

Recommendations on reducing risk of seizures have been developed by agencies in the United Kingdom, Japan, and the International Telecommunications Union, affiliated with the United Nations. The Epilepsy Foundation of America has developed a consensus of medical experts and scientists on this subject, reported in an accompanying work.

Intermittent photic stimulation as an activation method for electroencephalographic screening of aircrew applicants

Disqualifying criteria for aircrew in Europe (JAR-FCL 3) are, besides a diagnosis of epilepsy after the age of 5 and a history of episode(s) of disturbance of consciousness, epileptiform paroxysmal electroencephalographic abnormalities and focal slow waves. Intermittent photic stimulation (IPS) provokes in about 0.5% of healthy subjects (range 0-2%) a photoparoxysmal response and is most often the only abnormality (70-90%). The literature is scarce and shows great diversity in methodology. Standardized IPS with simultaneous video will not only allow collection of sufficient data for proper epidemiological studies, but can also reveal clinical and often unnoticed or misinterpreted signs and symptoms like myoclonia, loss of consciousness, and occipital seizures with visual auras. The pilot (sleep deprivation, strong sunlight) and the traffic controller (stress, monitors) are more prone to visually induced seizures. Furthermore, the increasing exposure to potentially seizure-triggering visual stimuli might have its impact in a more indirect or cumulative way.

Genome-wide linkage scan of epilepsy-related photoparoxysmal electroencephalographic response: evidence for linkage on chromosomes 7q32 and 16p13

Photoparoxysmal response (PPR) is an abnormal visual sensitivity of the brain in reaction to intermittent photic stimulation. It is an epilepsy-related electroencephalographic trait with high prevalence in idiopathic epilepsies, especially in common idiopathic generalized epilepsies (IGEs), such as childhood absence epilepsy and juvenile myoclonic epilepsy. This degree of co-morbidity suggests that PPR may be involved in the predisposition to IGE. The identification of genes for PPR would, therefore, aid the dissection of the genetic basis of IGE. Sixteen PPR-multiplex families were collected to conduct a genome-wide linkage scan using broad (all PPR types) and narrow (exclusion of PPR types I and II and the occipital epilepsy cases) models of affectedness for PPR. We found an empirical genome-wide significance for parametric (HLOD) and non-parametric (NPL) linkage (Pgw(HLOD)=0.004 and Pgw(NPL)=0.01) for two respective chromosomal regions, 7q32 at D7S1804 (HLOD=3.47 with alpha=1, P(NPL)=3.39x10(-5)) and 16p13 at D16S3395 (HLOD=2.44 with alpha=1, P(NPL)=7.91x10(-5)). These two genomic regions contain genes that are important for the neuromodulation of cortical dynamics and may represent good targets for candidate-gene studies. Our study identified two susceptibility loci for PPR, which may be related to the underlying myoclonic epilepsy phenotype present in the families studied.

EEG Diagnostic Procedures and Special Investigations in the Assessment of Photosensitivity

Photosensitivity can be assessed in laboratory conditions with different methods. The most common procedure is intermittent photic stimulation (IPS), whose effectiveness in detecting photosensitivity depends largely on methodologic aspects. Although IPS is a widespread and routinely used procedure in EEG laboratories, only recently has a standardization of the IPS method been proposed. Furthermore, other modalities of visual stimulation, including pattern stimulation and low-luminance visual stimulation (LLVS), have proven their usefulness in detecting photosensitivity. We provide an overview of the methodologic aspects and clinical implications of these procedures, resulting from recent consensus meetings, and the diagnostic usefulness of the LLVS technique in photosensitive individuals whose seizures are triggered particularly by television images. Finally, we briefly illustrate the potential of advanced neurophysiological (magnetoencephalography and high-density EEG) and functional imaging techniques in the investigation of the pathophysiologic mechanisms underlying photosensitivity.

Genetics of Photosensitivity (Photoparoxysmal Response): A Review

We present a review of phenotype-genotype correlation and the genetics of photosensitivity. The photoparoxysmal response in EEG (PPR) is still one of the best paradigms for exogenously triggered brain responses based on a genetic predisposition. The definition of the PPR phenotype requires multiple, precise methodologic guidelines. Individual factors such as age and gender but also other, unknown factors influence the expression of the PPR. For example, PPRs occur during adolescence and can disappear at a later age. As a consequence, it is difficult to assign nonaffected disease status correctly. Autosomal dominant inheritance has been found in clinical studies of relatives of PPR-positive epilepsy and nonepilepsy subjects. Genetic heterogeneity of the PPR is obvious because the PPR also can be evoked in a number of autosomal recessive diseases. PPR is most commonly associated with idiopathic generalized epilepsies (IGEs) such as juvenile myoclonic epilepsy (JME). This comorbidity suggests that a genetic factor involved in photosensitivity also may influence the susceptibility for JME. Finding the gene for PPR also might represent a step forward in unraveling the genetic background of JME. The search for the genetic factors causing PPRs should focus on the genes affected in such epilepsies, such as genes (coding) for ion channels and neurotransmitters and their receptors. The expression of defined proteins with as-yet-undetermined functions, is changed in a few types of epilepsies with a mendelian mode of inheritance. These additional genes and the human equivalents of the genes found to be mutated in animal models also are candidates for molecular genetic studies of the PPR.

Visual Stimuli in Daily Life

People of all ages, but especially children and adolescents, are increasingly exposed to visual stimuli. Typical environmental stimuli that can trigger epileptic seizures in susceptible persons are televisions (TVs), computers, videogames (VGs), discothèque lights, venetian blinds, striped walls, rolling stairs (escalators), striped clothing, and sunlight reflected from snow or the sea or interrupted by trees during a ride in a car or train. Less common stimuli are rotating helicopter blades, disfunctioning fluorescent lighting, welding lights, etc. New potentially provocative devices turn up now and then unexpectedly. During the last decades especially, displays have become increasingly dominant in many of our daily-life activities. We therefore focus mainly on the characteristics of artificial light and on current and future developments in video displays and videogames. Because VG playing has been shown also to have positive effects, a rating system might be developed for provocativeness to inform consumers about the content. It is important that patients with epilepsy be informed adequately about their possible visual sensitivity.

Eyelid myoclonia with absences: an overlooked epileptic syndrome?

AIM

To identify, among patients referred to our Epilepsy Center, those fulfilling eyelid myoclonia with absences (EMA) criteria and to evaluate their semiological, electroclinical and evolutive features. In addition, to examine some possible causes of underdiagnosis and to stress the role of video-EEG (VEEG) recording.

MATERIALS AND METHODS

Retrospective analysis of 2780 epileptic patients.

INCLUSION CRITERIA

Eyelid myoclonia and brief absences, related to EEG generalized paroxysmal activity and triggered by eye closure and/or by intermittent photic stimulation.

RESULTS

7.46% of our patients with idiopathic generalized epilepsy (IGE) could be classified as EMA. Female/male ratio was 1.7:1. Familial history of epilepsy was present in about half of the patients, with two pairs of identical twins in the sample. Rare generalized tonic-clonic seizures occurred in most cases.

CONCLUSIONS

EMA is a not infrequent condition among IGEs. It is likely to be underdiagnosed due to the subtle clinical semiology and to masking of EEG changes by the effects of age and anti-epileptic drugs. VEEG analysis is often needed for diagnosis of EMA. Most likely, only genetic research will be able to clarify whether EMA is a distinct epileptic syndrome.

Guidelines for the use of EEG methodology in the diagnosis of epilepsy. International League Against Epilepsy: commission report. Commission on European Affairs: Subcommission on European Guidelines

The Commission of European Affairs of the International League Against Epilepsy published 'Appropriate Standards for Epilepsy Care Across Europe' which contained recommendations for the use of electroencephalography (EEG) in the diagnosis of epilepsy (Brodie et al. Epilepsia 1997; 38:1245). The need for a more specific basic document of EEG methodology was recognized and the Subcommission on European Affairs was asked to produce more detailed guidelines to be used across Europe recognizing the range of practices in EEG laboratories. There are many general guidelines published on EEG methodology but this document focuses on the diagnosis of epilepsy. Details from previously published guidelines are included in references and in an appendix. These guidelines are not meant to be used as minimal standards but recommendations that can be applied to all EEG laboratories despite variations in equipment.