Low-luminance visual stimuli compared with stroboscopic IPS in eliciting PPR in photosensitive patients

Favorite colors of patients with drug-resistant epilepsy: pilot study

OBJECTIVE

To evaluate the favorite colors of patients with drug-resistant epilepsy.

METHODS

Following examination, 50 patients were diagnosed in accordance with the 2005 proposal of the International League Against Epilepsy and the definition of drugresistant epilepsy since 2010. The favorite color examination used a six-color tape and Trycolors, an online color mixing tool. The patients' color preferences were compared with those of 50 individuals without epilepsy.

RESULTS

Patients with drug-resistant epilepsy preferred the color blue the most (30%), significantly more yellow (p = 0.0001), and significantly less green (p < 0.0001) compared to individuals without epilepsy. By mixing these colors at a certain percentage, we obtained the Go Ben color.

SIGNIFICANCE

This information on preferred colors can help to improve compliance and can be utilized in designing medications and environments for patients with epilepsy.

Photoparoxysmal response and its characteristics in a large EEG database using the SCORE system

OBJECTIVE

To characterize photoparoxysmal EEG response (PPR) using a standardized protocol of intermittent photic stimulation (IPS) and standardized definitions for PPR, classified into six types.

METHODS

Using the SCORE system (Standardized Computer-Based Organized Reporting of EEG) we prospectively built a large database of standardized EEG annotations. In this study, we extracted the features related to PPR from the structured dataset consisting of 10,671 EEG recordings with IPS, from 7,188 patients.

RESULTS

The standardized IPS protocol elicited PPR in 375 recordings (3.5%), in 288 patients (4%), with a preponderance among young (11-20 years) and female patients (67%). PPR was persistent in patients with multiple recordings. The most frequent type of PPR was activation of preexisting epileptogenic area (58%), followed by generalized-PPR limited to the stimulus train (22%). We could not find any recording with self-sustained posterior response. Seizures were elicited in 27% of patients with PPR, most often myoclonic seizures and absences, in patients with self-sustained generalized PPR.

CONCLUSIONS

The most common type of PPR was accentuation of preexisting epileptogenic area. Self-sustained posterior response could not be documented. Self-sustained generalized-PPR had the highest association with seizures.

SIGNIFICANCE

Using standardized stimulation protocol and definitions for PPR types, IPS provides high diagnostic yield.

Dealing with the storm: An overview of seizure precipitants and spontaneous seizure worsening in drug-resistant epilepsy

In drug-resistant epilepsy, periods of seizure stability may alternate with abrupt worsening, with frequent seizures limiting the individual's independence and physical, social, and psychological well-being. Here, we review the literature focusing on different clinical scenarios related to seizure aggravation in people with drug-resistant epilepsy. The role of antiseizure medication (ASM) changes is examined, especially focusing on paradoxical seizure aggravation after increased treatment. The external provocative factors that unbalance the brittle equilibrium of seizure control are reviewed, distinguishing between unspecific triggering factors, specific precipitants, and 'reflex' mechanisms. The chance of intervening surgical or medical conditions, including somatic comorbidities and epilepsy surgery failure, causing increased seizures is discussed. Spontaneous exacerbation is also explored, emphasizing recent findings on subject-specific circadian and ultradian rhythms. Awareness of external precipitants and understanding the subject-specific spontaneous epilepsy course may allow individuals to modify their lifestyles. It also allows clinicians to counsel appropriately and to institute suitable medical treatment to avoid sudden loss of seizure control.

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.

The photoparoxysmal response: the probable cause of attacks during video games

Photic stimulation is part of a typical EEG in most countries, especially to check on the photoparoxysmal response (PPR). Interest in this response was enhanced in 1997 when hundreds of Japanese children had attacks while viewing a TV cartoon called "Pokemon." The overall prevalence of the PPR among patients requiring an EEG is approximately 0.8%, but 1.7% in children and 8.87% in patients with epilepsy, more often in Caucasians and females. Autosomal dominant inheritance is indicated, and this response is seen especially at the wavelength of 700 nm or at the flicker frequency of 15-18 Hz. The PPR extending beyond the stimulus carries no increased risk of seizures. Prognosis is generally good, especially after 20 years of age. Attention to PPR has been increased with the advent of video games, and the evoked seizures from these games are likely a manifestation of photosensitive epilepsy. Drug therapy has emphasized valproic acid, but Levetiracetam has also been successful in eliminating the PPR.

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.

Analysis of photo-pattern sensitivity in patients with Pokemon-related symptoms

This study was designed to analyze photo-pattern sensitivity in patients who developed acute neurologic symptoms associated with watching an animated television program, "Pokemon." The 18 patients (13 females and five males) underwent electroencephalograms and photo-pattern stimulation testing, including special stimulation test batteries (strobe-pattern test and cathode ray tube-pattern test). Photo-pattern sensitivity was confirmed in 16 patients with and without seizure episodes. The strobe-pattern test including a white flickering light test (with eyes open, closed, and open or closed), and the cathode ray tube-pattern test each induced a photo-paroxysmal response in more than 80% of patients. However, with the eyes closed only, as is common in Japan, the photo-paroxysmal response induction rate with a white flickering light stimulus was significantly lower (43%). In the cathode ray tube-pattern test, higher spatial frequencies produced higher rates of photo-paroxysmal response induction. It was demonstrated that underlying photo-pattern sensitivity is more accurately investigated by our method than by standard intermittent photic stimulation alone. By characterizing underlying photo-pattern sensitivity and identifying predisposing factors more precisely, we can develop better guidelines for prevention of a second "Pokemon" incident. According to the results of the present cathode ray tube-pattern test, pattern sensitivity (especially spatial resolution) appears to also be involved in Pokemon-related symptoms, in addition to chromatic sensitivity.

Suppressive efficacies by adaptive temporal filtering system on photoparoxysmal response elicited by flickering pattern stimulation

PURPOSE

Based on our previous study that validated efficacies of an adaptive temporal filtering system (ATFS) suppressing a photoparoxysmal response (PPR) elicited by a chromatic flicker stimulation, we further studied ATFS efficacies on PPRs elicited by pattern-flicker stimulation in 13 photosensitive epilepsy patients.

METHODS

Subjects were 13 photosensitive epilepsy patients (two male and 11 female patients; mean age +/- SD, 20.9 +/- 8.9 years) who were all sensitive to a flickering geometric-pattern scene. We used a scene consisting of 15-Hz flickering 4 c/deg stripe images lasting for 4 s. With a 14-inch television set 2 m before a subject, we displayed the following video scenes: nonfiltered and filtered flickering-stripe scenes; for the latter, two kinds of ATFSs with mild efficacy and strong efficacy were used. Three flickering-stripe scenes altogether, each of which lasted for 4 s, were given at random with a 10-s interval.

RESULTS

A nonfiltered flickering-stripe scene elicited generalized PPRs in all patients; a filtered scene by use of an ATFS with mild efficacy elicited generalized PPRs in six patients (46%), whereas that by an ATFS with strong efficacy exhibited no PPRs.

CONCLUSIONS

This study, using an ATFS, again shows suppressive efficacy on PPRs elicited by flickering-pattern stimulation. Therefore a series of our studies suggested that ATFS may be useful as a preventive measure for photosensitive seizures triggered by stimulative flickering images from televisions or other displays.

Study on photo-pattern sensitivity in patients with electronic screen game-induced seizures (ESGS): effects of spatial resolution, brightness, and pattern movement

PURPOSE

With the ever-increasing popularity of computers, electronic screen game-induced seizure (ESGS) is beginning to pose a serious social problem. To elucidate the pathophysiology of ESGS, with the ultimate goal of prevention, we have been studying photo-pattern sensitivity in detail with a pattern-stimulation test using a CRT (cathode ray tube) display. This method is referred to as the "CRT-pattern test."

METHODS

We studied 17 patients brought to our department for evaluation of ESGS. EEG responses were recorded during exposure to various patterns consisting of three elements: spatial resolution, brightness perception, and pattern-movement recognition displayed on a CRT monitor. Photo-paroxysmal response (PPR) frequencies were compiled for each stimulation.

RESULTS

PPR was induced by the CRT-pattern test in nine of the 17 cases. In four cases, PPR induction was obtained only after introducing CRT-pattern tests in addition to standard intermittent photic stimulation (IPS). The rate of PPR induction differed according to the type of pattern, spatial frequency, and pattern-reversal frequency. However, neither the clarity of the edges of a pattern nor changes in the brightness of a pattern element had any effect on the rate of PPR induction. With the exception of a few subjects, the stimulation caused by pattern movement was not effective in eliciting PPR. Six cases in whom spatial resolution was involved showed occipital dominance in PPR provocation, and three in whom brightness perception and pattern movement recognition was involved showed frontal dominance.

CONCLUSIONS

The CRT-pattern test is useful for identifying patients with photosensitivity among patients considered to have incidental or nonphotosensitive seizures unresponsive to standard IPS. Patients with ESGS caused by photosensitivity can be divided into two groups: those with occipital dominance for PPR provocation, in whom spatial resolution is involved; and another group with frontal dominance, in whom brightness perception and pattern-movement recognition (or possibly perception of colors) are involved.

A study of the effect of color photostimulation from a cathode-ray tube (CRT) display on photosensitive patients: the effect of alternating red-cyan flicker stimulation

PURPOSE

In an attempt to establish evidence for developing better guidelines for the production of animation programs that would not induce photosensitive seizures in Japan, we evaluated the effects of red flicker, alternating red/cyan (complementary color to red) flicker stimuli, and of contrast between the red and cyan frames from a cathode-ray tube (CRT) display in photosensitive patients.

METHODS

We studied 35 photosensitive patients. They were exposed to seven types of flicker. The first three types were alternating red/cyan flicker (R/C) with the luminance of cyan set at three different levels, high, equal, and low luminance (65, 20, and 16 cd/m2, respectively) relative to the red (20 cd/m2). The following four types were red, cyan, yellow, and magenta flicker stimuli. EEGs were recorded while the patients watched these stimuli on a CRT display.

RESULTS

Rates of photoparoxysmal response (PPR) provocation were 11.4, 13.7, and 14.0% with high-, no- and low-contrast R/C flicker, respectively, and 3.7% with red flicker. The differences between red and each of the other R/C flicker stimuli were all statistically significant (p<0.05, 0.01, 0.01). No significant differences were found between the effects by each of the three levels of contrast in alternating R/C flicker (p > 0.05).

CONCLUSIONS

These findings suggest that alternating R/C flicker is more provocative than simple red flicker, and that contrast between frames of different colors may play some role in the effects of alternating flicker stimuli from a CRT display in photosensitive patients. Therefore, caution against the use of the combination of red and cyan, in addition to the red flicker stimulus, should be included in any guidelines drawn up to prevent photosensitive seizures.

A new adaptive temporal filter: application to photosensitive seizure patients

A new adaptive temporal filtering (ATF) technique was developed to prevent heath hazards due to flicker stimuli from televisions, videos or other displays. This ATF method could reduce frame-to-frame or field-to-field flicker stimuli at around 10-30 Hz which are particularly risky for photosensitive individuals. The present ATF efficacy with a computer simulation was studied in 11 photosensitive epilepsy patients. In order to control visual stimuli and induce photoparoxysmal response (PPR), we employed a problematic scene of the Pocket Monster incident containing 12 Hz red/blue flicker images lasting for 4 s. This image, shown with a 14-inch, television set 2 m in front of subjects, promptly elicited generalized PPR in all cases, while the filtered image did not induce any PPR. These results suggest that the present ATF method may be useful as a preventive measure of photosensitive seizures triggered by stimulative images from televisions or other displays.

Photoparoxysmal response elicited by flickering dot pattern stimulation to the center and periphery

OBJECTIVE

We performed this study to elucidate the roles of stimulus spatial frequency and visual field in eliciting generalized photoparoxysmal response (PPR) by flickering dot pattern (FDP) stimulation.

METHODS

We studied 20 photosensitive epilepsy patients, aged 7-48 years (means +/- SD, 21.4+/-11.7 years), producing a 20 Hz FDP stimulation with a strobo-filter. Using dot patterns (0.5, 1, 2, 4 and 6 mm in diameter), we gave FDP stimulation to the center (11x11 degrees ) and periphery (11-30x11-30 degrees ) of subjects with eyes open, and analyzed each PPR appearance latency.

RESULTS

Significant results were: latency by 1 (2.1 c/deg) and 0.5 mm (4.9 c/deg) FDP stimulation to the center was shorter than that to the periphery; latency by 4 mm (0.8 c/deg) FDP stimulation to the periphery was shorter than that to the center. As for 2 (1.5 c/deg) and 6 mm (0.5 c/deg) FDP stimuli, no significant difference could be observed.

CONCLUSIONS

A higher spatial frequency FDP stimulation to the center elicits PPR more strongly than that to the periphery, whereas a lower spatial frequency FDP stimulation showed the opposite result, with peripheral stimulation being more effective than central stimulation.