NCV revealed a conspicuous number of subclinical neurop- athies and moreover, in association with the evaluation of age at onset and clinical conditions, it directed towards specific bio- chemical tests.

256. PHOTOSENSITIVITY IN EPILEPSY: DO EN- VIRONMENTAL FACTORS FAVOR PHOTOSENSITIV- ITY PENETRANCE? Alberto Guerrero, MD and Marcelo Di Blasi, MD, Neuquen, Argentina

Twenty-eight patients residing in the Comahue region who presented with photosensitivity in response to intermittent photic stimulation (IPS), were studied between Oct. 1984-1991. Their average age was 10.7 years, with a female/male ratio of 3.5 to 1; there was a 25% positive family history for epilepsy and/or febrile seizures. All were symptomatic and the clinical features varied from: vagal syncope (2 of 28), head or eyelid myoclonies (11 of 28), generalized tonic-clonic convulsions (7 of 28), absences and atypical absences (15 of 28), and spon- taneously, related to environmental daily stimulus and to IPS. TV-induced seizures (3 of 28). No patients presented with auto- induced seizures. Photosensitivity is related to dominant auto- somic inheritance with low penetrance. Prevalence in epileptic patients is 5%, in nonepileptic ages 5-20 years: 5-7%. Since the plain-dwelling papio-papio baboon was described as having a lesser genetic susceptibility than those captured in the jungle, the interaction between environmental and constitutional factors has been considered. High levels of environmental sunlight may be associated with a low prevalence of photosensitivity. In our region with characteristic high level of sunshine, all the photo- sensitive patients have had crises. Therefore, other possible spe- cific regional factors have been considered to determine the dis- tinctive characteristics of the Comahue region: (1) generation and transport of 40% of the Argentinian electric energy supply; and (2) climatic factors like strong winds, absence of lightning storms, and low precipitation. Considering that these regional features induced electromagnetic fields which change according to them, that these fields are a thousand times higher than those belonging to the brain bioelectrogenesis, and knowing some of the biologic effects in the retina and nervous cell membranes, we believe that electromagnetic fields interacting with constitu- tional factors, should be taken into account.

257. WITHDRAWN

258. ASYMPTOMATIC EPILEPTIFORM ACTIVITY OF HEALTHY CHILDREN Wu Xian and Shen Xiang, Harbin, China

ELECTRIC

Fifteen cases with epileptiform electric activity, such as spike- wave and point-wave were found among 618 children's EEGs ages 5-8 years during physical examination. The incidence was 2.43%, lower than 6.36% reported by Kono et al. [1]. The epi- leptiform electric activity involved frontal, temporal, and occipi- tal areas of the lateral or bilateral cerebri hemisphere. All 15 cases had no clinical symptoms. Among the 128 children who ever had mumps, 8 children (6%) showed epileptiform electrical activity in their EEG. However, among the 490 children without history of mumps; there were only 7 cases who had epileptiform

electric activity. On statistics, the incidence of ep~leptifi~rm e lec , . 3

tric activity was significantly higher in the hrst glonp IX = 9.96. P < 0.01). Therefore. we should develop planned-immunity in children to prevent mumps and take active measmes t~ separate and treat the children when they are infected. I ifteen cases in this group have been followed up lor 6 years: most asympto- matic epileptiform electrical activities have favorable prognoses. All of them remain without clinical symptoms except one who had grand mal epilepsy. EEGs had become normal naturally in 10 cases. Reference: [1] Kono T. et al. The brain wave of chil- dren. Clin EEG 1981;23:488.

259. GM2 GANGLIOSIDOSIS B1 VARIANT: POSSIBLE PORTUGUESE ORIGIN OF A CAUSAL MUTATION M. Maia, D. Alves, R. Santos, G. Ribeiro, R. Pinto, A. Guimar~es, and M.C. S~i Miranda, Porto, Portugal

Since Li et al. published the first case of GM2 gangfiosidosis Bj variant [1], 6 more cases have been described. All but one of these cases had the late-infantile form leading to death around 3-6 years of age. In 1990, we reported 7 patients with a juvenile form [2], presenting with a clinical phenotype similar to the Spanish patient previously described. Ohno and Suzuki [3] iden- tified a point mutation (G --+ A at nucleotide 533; the so-called DN allele in the hexosaminidase A c~-gene. We report 18 Por- tuguese patients: 16 juvenile patients with the homozygous form of the DN-allele and 2 late-infantile patients with the hetero- zygous form. Considering that the Bt-variant is a rare disorder in the world, the exceptionally large number of cases found in Portugal and the Hispanic background of previously described patients has led to the postulation that the DN allele may have originated in Portugal [4]. References: [1 ] Li SC, Hirabayashi Y, Li Y. Biochem Biophys Res Commun 1981;101:479-85. [2] Maia M, Alves D, Ribeiro S, Pinto R, S~ Miranda MC. Neuro- pediatrics 1990;21:18-23. [3] Ohno K, Suzuki K. J Neurochem 1988;50:316-8. 14] Santos MR, Tanaka A, Sfi Miranda MC, Ribeiro MG, Maia H, Suzuki K. Am J Hum Genet 1991;49: 886-90.

260. CORRELATION BETWEEN THE SIMPLIFIED SARNAT'S CLASSIFICATION AND GRADES OF CT IN NEONATES WITH HYPOXIC-ISCHEMIC ENCEPH- ALOPATHY (HIE) Xing Feng, Meiqian Wu, Fuzhen He, et al., Suzhou, China

The clinical classification of HIE was first reported by Sarnat et al. [Arch Neurol 1976;33:696]. Because of the complex and special equipment, it is too difficult to be widely used in main- land China. Based on Samat's classification criteria, Dr. Yu chose the most important parts as the criteria, including the con- sciousness, hypotonia, original reflex, seizures, and duration of symptoms [J Neonatol 1989;4:33]. One hundred cases of HIE neonates were classified into 3 types (i.e., mild, moderate, and severe) by 3 doctors. All of them had the CT scan in the first week of life. The rate of positive CT was 91%. Four cases were complicated with intracranial hemorrhage. The grades of CT depended upon the criteria described by Adsett et al. [Dev Med Child Neurol 1985;27:155]. The result of rank test showed that Sarnat's simplified classification correlated well with the grades

408 PEDIATRIC NEUROLOGY Vol. 8 No. 5