| Background:Photosensitive epilepsy(PSE) is the most common form of reflex epilepsy,with seizures triggered by visual stimuli. The forms of photosensitivity present on the electroencephalogram(EEG) are localized or generalized spikes, spike-and-wave,(poly)spike-and-wave discharge and it was called as photoparoxysmal response(PPR).Researchers abroad reported that the annual incidence of photosensitive is 1.1/100000 in the general population, representing 2% of all new cases of epilepsy. When restricted to the age range 7–19 years, the annual incidence increased to 5.7/100000. This number was10% of all new cases of epilepsy in this age range. This response is more common among females at any age. PPR is probably caused by multiple factors, including gender, age,familial inheritance factors, etc. Some reports suggested that incidence of photosensitivity is associated with ethnicity. The incidence of photosensitivity is different because of different ethnic groups of patients with epilepsy: 0.4% of Blacks, 4% of Coloureds and5.2% of Whites. However, the clinical and EEG features of Chinese Han patients with PSE are hardly to see until now.IPS is a common procedure performed in the EEG laboratory in children and adults to detect abnormal epileptogenic sensitivity to flickering light(i.e., photosensitivity). This is also why IPS known as one of the three "activation process" of EEG, which can improve the positive diagnosis rate. Although it is widely used, in practice, substantial variability in outcome is anecdotally found due to themany different methods used per laboratory and country. The latest algorithm incorporates the consensus of repeated scientific meetings of European experts in this field over a period of 6 years with feedback from general neurologists and epileptologists to improve its validity and utility. It has substantially increased content, detailing technical and logistical aspects of IPS testing and the rationale for many of the steps in the IPS procedure. It can give patients suggestions to help them avoid inducing factors in daily life by using the updated IPS, meanwhile it provides help in estimating choice and curative effect for the antiepilepic drugs(AEDs).Consequently, it is necessary for EEG laboratories to adopt standardized IPS method to explore the clinical and electrophysiological characteristics of PSE better.Objective : Through analyzing and summarizing the characteristics of clinical and electrophysiology of patients with PPR and it can provide basis for the clinical and EEG features of Chinese Han patients with photosensitivity. To Analyze every adverse event that occured in all patients and investigate if updated European standard of IPS is applied to Chinese population; By summarizing characteristics of the patients with photosensitivity in aspects of gender, age, three eye conditions, the the most provocative frequency range, seizure types etc.so as to provide basis for increasing the diagnostic rate of IPS, and help the classification of epilepsy. Meanwhile, it can provide guidance for selecting medication and help assess the success rate of dosage of medicine.Methods: A total of 5482 unselected patients with possible epilepsy from three Departments of Clinical Neurology, Xi'an, China(Xijing Hospital, Fourth Military Medical University,First Affiliated Hospital, Xi'an Jiaotong University, Pediatric Hospital,Xi'an Jiaotong University) from November 2013 to October 2014. These patients underwent 24-hour video-EEG recording. IPS was performed using a standard procedure in accordance with updated European algorithm for visual stimulation. Basic demographic characteristics and detailed case data of all the people was recorded by an uniform questionnaire. At recruitment, patients' EEG, IPS and imaging data were collected for analyzing every adverse event that occured in all patients. Clinical and EEG features of the patients with PPR were studied for analyzing and summarizing sex ratio,age distribution, sensitive frequency range, seizure type and so on. Analyzing the characteristics of the patients with eyes closure sensitivity, with a follow-up of 1 year.Results:(1) There were 73(1.3%)patients with PPR. The gender ratio was M:F = 1:1.9, and The media age was 15 years.(2) There were 64(87.7%) patients identified as generalized epileptiform discharges and 9(12.3%) patients as localized epileptiform discharges. Four patients with normal EEG during the routine resting and sleep recording had PPR to IPS.(3) 72 patients were identified as epilepsy, photosensitive epilepsy and one patient was diagnosed as migraine. The migraine patient was a 9-year-old girl and the symptom started from two years ago. She was exclusively with performance of eye closure at 25 Hz during IPS.(4) Family history was found in three patients. Two patients have a history of visually induced seizures, one was looking straight into the sun and one was watching TV.(5) Epileptic seizures were precipitated by IPS in 21 of 73 patients(28.8%), consisting of myoclonia in 9 patients, eyelid myoclonia in 2 patients, absence in 1 patient, generalized tonic-clonic seizure in 3 patients, focal seizure in 5 patients, and focal secondary GTC seizure in 1 patient.(6) The range(8 to 25Hz) was the most effective flash stimulation frequency, seen in 51patients(70.0%). Of the 51 patients, 14 patients(27.0%) had electro-clinical seizures elicited by IPS. The flash frequencies(upper threshold?40Hz in any eye condition) were seen in 18(24.7%) patients. However, seven of them(38.9%) experienced electro-clinical seizures during IPS.(7) Of nine female patients with eyes closure sensitivity, five patients(55.6%) experienced epileptic seizures during IPS, three were on antiepileptic medications at the time of EEG testing: one on levetiracetam(LEV), one on oxcarbazepine(OXC), one on lamotrigine(LTG) and carbamazepine(CBZ). But seizures were still out of control. The rest of the 6patients were given valproic acid(VAP) monotherapy. By following up for 1 year, there were just 4 patients meet seizure-free, three patients still had frequent seizures, twice a month, and others were 2 to 3 times in one year. There were four patients older than 24 years old; There were three patients that PPR was seen only in eyes closure condition.(8) Twenty-seven of 73 patients(37%) with PPR were on antiepileptic medications(mono-therapy or poly-therapy) at the time of EEG testing: ten on VPA, five on LTG,three on topiramate(TPM), three on LEV, seven on CBZ, three on OXC and one on phenobarbital(PB).(9) Of the 5482 patients, no symptomatic cardiovascular, respiratory or cerebrovascular adverse events, psychogenic non-epileptic seizures and non-epileptic attacks were observed during and after IPS. Eye discomfort and tearing were reported in 3 patients, but the symptoms were self-limiting and relieved on cessation of photic stimulation. Slight headache in two patients and dizziness in one patient were reported.Conclusion:(1) Photosensitivity was age-dependent. Children and adolescents with epilepsy are the largest population of PPR to IPS.(2) Updated IPS can help in increasing the diagnostic rate of IPS and determining the lower and upper thresholds of sensitivity so as to advise lifestyle restraints. Moreover, the adverse events incidence rate was very low and minor symptoms that were self-limiting and relieved soon.(3) The higher electro-clinical seizures induced by IPS during EEG were highly correlated with generalized PPR and upper threshold evoking frequency, therefore, when giving higher stimulus frequency(?40Hz) to patients, medical workers should be careful to prevent electro-clinical seizures and prepare for the corresponding rescue protection.(4) PPR are mostly found in a photosensitive epilepsy population, but it also can be found unexpectedly in a few patients with migraine.(5) The patients with eyes closure sensitivity may apt to experience electro-clinical seizures provoked by IPS. So emergency measures should be prepared in advance.(6) Eyes closure sensitivity might be difficult to remit spontaneously in female patients with the increase of age, also implied poor prognosis. |
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