Allelic association of juvenile absence epilepsy with a GluR5 kainate receptor gene (GRIK1) polymorphism

Juvenile absence epilepsy (JAE) is a common subtype of idiopathic generalized epilepsy (IGE). Hereditary factors play a major role in its etiology. The important function of glutamate receptors (GluRs) in excitatory neurotransmission, synaptic plasticity, and neurodevelopment suggests their involvement in epileptogenesis. A tetranucleotide repeat polymorphism in the non-coding region of the kainate-selective GluR5 receptor gene (GRIK1) on chromosome 21q22.1 provides the tool to investigate this candidate gene. The present association and linkage study tested the hypothesis that allelic variants of GRIK1 confer genetic susceptibility to the pathogenesis of JAE. Our family-based association analysis using the haplotype-based haplotype relative risk statistic revealed an association of JAE with the nine-repeat containing allele of the GRIK1 tetranucleotide polymorphism (chi2 = 8.31, df = 1, P = 0.004). Supportive evidence for linkage to a JAE related IGE spectrum (Zmax = 1.67 at GRIK1) under an autosomal dominant mode of inheritance and significant allele sharing (P < 0.05) among the affected family members suggest that allelic variants of GRIK1 contribute a major genetic determinant to the pathogenesis of JAE-related phenotypes.

Incidence of epilepsy in childhood and adolescence: a population-based study in Nova Scotia from 1977 to 1985

Data from a regional EEG laboratory allowed us to identify almost all children in Nova Scotia (population 85,000) with one or more unprovoked, afebrile seizures from 1977 through 1985. We then reviewed hospital and pediatric neurology physician charts to limit cases to those with two or more definite afebrile seizures between the ages of 1 month and 16 years. In all, 693 children developed epilepsy: typical childhood absence seizures (AS) (97), either generalized tonic-clonic (GTCs) or partial seizures either secondarily generalized or not (511), and other generalized seizure types, including infantile spasms (IS) as well as myoclonic, akinetic, tonic, and atypical AS (85). The incidence of epilepsy was 118 in 100,000 for children aged less than 1 year, 48 in 100,000 for those aged 1-5 years, 43 in 100,000 for those aged 6-10 years, and 21 in 100,000 for those aged 11-15 years. The incidence for each year of age between 1 and 10 years was remarkably constant (mean 46 in 100,000 +/- 7 SD). Comparison of the incidence rates showed significant differences for those aged less than one year as compared with all others, and for those aged greater than 10 years as compared with those aged 1-10 years. We conclude that the incidence of epilepsy is highest in the first year of life, plateaus in early childhood, and decreases markedly after age 10 years. The overall incidence of epilepsy in childhood is lower than that reported in previous studies.

Juvenile myoclonic epilepsy: a 5-year prospective study

We made a long term prospective study of 66 patients with juvenile myoclonic epilepsy (JME). Prevalence was 10.2% among 672 patients with epilepsies. Sex distribution was equal. Sixty-three were not diagnosed on referral; JME was not initially recognized in the epilepsy clinic in 22. Clinical typical absence seizures were reported in 33.3%, myoclonic jerks in 97% and generalized tonic-clonic seizures (GTC) in 78.8% of the patients. Mean age (+/- SD) at onset was 10.5 +/- 3.4 years (range 5-16 years) for absence seizures, 15 +/- 3.5 years (range 8-26 years) for myoclonic jerks, and 16 +/- 3.5 years (9-28) years (range 1-9 years) and GTC by 4.4 +/- 2.7 years (range 1-8 years) in 14 (21.2%) patients who manifested all three types of seizure. Absence were never antedated by myoclonic jerks or GTC. Myoclonic jerks occurred on awakening in 87.5% of the patients. GTC occurred mainly on awakening, but other patients had nocturnal or diurnal GTC with no circadian distribution. Neurologic examination was normal for all patients except for tremor of the hands similar to essential tremor, noted in 35% of patients. Computed tomography (CT) brain scans were normal: 93% of patients had precipitating factors: sleep deprivation (89.5%), fatigue (73.7%), photosensitivity (36.8%; television and video games 8.8%), menstruation (24.1% of women), mental concentration (22.8%), and stress (12.3%). Incidence of JME among siblings (13 of 41 examined families) implies an autosomal recessive mode of inheritance for this Arab population. EEGs were frequently normal in treated patients. At least one abnormal EEG was recorded in 56 (84.9%) patients. Abnormalities consisted mainly of generalized discharges of spike/double spike and/or polyspike and slow wave. Frequent multiple spikes and discharge fragmentations varied from 0.5- to 20-s duration (mean 6.8 s). Twenty (30.3%) had focal abnormalities, and 18 (27.3%) had photoconvulsive discharges. Eighty-eight percent of patients remained seizure-free for > or = 3 years of follow-up. Effective treatment was achieved with valproate (VPA); control of myoclonic jerks was improved with clonazepam (CZP). CZP monotherapy did not consistently prevent GTC. Adding small doses of CZP with simultaneous reduction of VPA was the most effective and better tolerated form of medication, particularly in patients demonstrating an adverse reaction or requiring a large VPA dosage. VPA dosage was successfully reduced in 15 patients who were seizure-free for > 2 years and had infrequent seizures before treatment, but 9 of 11 patients relapsed after VPA discontinuation.(ABSTRACT TRUNCATED AT 400 WORDS)

Epidemiology of epilepsy in Singapore

Though epilepsy is recognised as a major medical and social problem in Singapore, there is no epidemiological survey to realise the size of the problem. We studied this problem from data collected from hospitals, school health clinics and from military statistics. The prevalence varied in the three sample populations studied. The most accurate data for prevalence study were obtained in army recruits. A life-time prevalence of 3.8 per 1000 was noted. The prevalence variation with age, sex and races is discussed. The mortality from epilepsy was 0.5 per 100,000. The types of epilepsies and the treatment patterns are discussed.

Nonconvulsive status epilepticus in adults: thirty-two consecutive patients from a general hospital population

We studied all adult patients who between 1984 and 1989 were initially diagnosed at our hospital as having nonconvulsive status epilepticus. Thirty-two patients fulfilled the criteria, which included ictal EEG recordings. The annual incidence was 1.5 in 100,000 inhabitants. The median age at onset of status was 51 years. Ten patients had status as their first epileptic manifestation, but most patients had a previous history of epilepsy. Median duration of epilepsy at onset of status was 4 years. Fourteen patients had focal ictal seizure activity on EEG and thus met the criteria for complex partial status. Eighteen patients had generalized seizure activity on EEG, but only 6 of these had a history of absence epilepsy or juvenile myoclonic epilepsy. None had Lennox-Gastaut syndrome. The clinical features of status in the remaining 12 patients were in some respects similar to those of the patients with complex partial status. We hypothesize that the EEG seizure activity in these patients may have been generalized from an initial focus.

Epidemiology of absence epilepsy. III. Clinical aspects

Absence epilepsy was studied in a Swedish population, aged 0-15 years, in 1978-1982. Cases were selected by electroencephalographic criteria. In the 134 children with 3 Hz spike-and-wave discharges, 97 (72.4%) had absences alone or in combination with generalized tonic-clonic seizures (grand mal): 56 had absences alone, 31 absences followed by grand mal, and 10 started with initial grand mal. Two distinct groups could be discerned: 1) childhood absence epilepsy: onset before the age of 12, with a quick response to therapy, little or no risk of grand mal, and a high remission rate; 2) juvenile absence epilepsy: onset at the age of 12 or later, a very high risk of grand mal, and usually a good response to therapy, but a high risk of relapses at withdrawal. This classification of absence epilepsy into subgroups may be useful for prognostic guidelines.

Epidemiology of absence epilepsy: EEG findings and their predictive value

This population-based study of absence epilepsy comprised 97 children, ranging in age from newborns to 15 years. All had regular bilaterally synchronous and symmetric 2-4 Hz spike-and-slow wave discharges and absences with or without generalized tonic-clonic seizures (GTCS). Patients without GTCS tended to have long episodes of 2-4 Hz spike-and-slow wave discharges (greater than or equal to 10 sec), and simultaneous clinical correlates more frequently than those with GTCS. Posterior delta rhythm was found only in patients without GTCS. Focal abnormalities, albeit transient, were more frequent among patients with GTCS. The initial electroencephalogram was of some early predictive value in patients with only absences at the time of the initial registration. Brief episodes of 2-4 Hz spike-and-slow wave (less than 10 sec) without clinical correlates were associated with a slightly increased risk of future GTCS.

Epidemiology of absence epilepsy. II. Typical absences in children with encephalopathies

A population-based study of absence epilepsy in Swedish children, aged 0-15 years, comprised cases selected on the basis of EEG criteria. Absence epilepsy was found in 119 of the 134 children with 3 Hz spike-and-wave discharges, and 12 of these 119 (10.1%) had typical absences in addition to other generalized seizures and slow irregular spike-and-wave activity on the EEG. The mean annual incidence of this type of absence epilepsy was 0.7/100,000. The median age at onset of absences was 6 years. Eight of the 12 patients had neurological abnormalities and/or severe mental retardation. The patients constitute a heterogeneous group of encephalopathies. They may have a genetic predisposition for absence epilepsy, causing it to appear during the course of a more severe, encephalopathy related, type of epilepsy.

Epidemiology of absence epilepsy. I. Concept and incidence

An epidemiological study of absence epilepsy is presented. The study comprised a series of cases from a Swedish population, aged 0-15 years, selected on the basis of EEG criteria. All children with regular and symmetrical 3 (2-4) Hz spike-and-slow-wave complexes, recorded for the first time during the period 1978-1982, were included. A total of 134 children fulfilled the inclusion criteria, and of these, 108 (80.6%) had absences alone or in combination with general tonic-clonic seizures (GTCS); 11 (8.2%) had absences combined with other seizures; 15 (11.2%) had other types of seizures only. The mean annual incidence of absence epilepsy was 7/100,000 for children aged 0-15 years. Of these, 6.3/100,000 had absences alone or in combination with GTCS. The cumulative incidence of absence epilepsy was 98/100,000. The mean age of onset was 7 years.

Distribution of seizure types in an epileptic population

The distribution of seizure types was investigated in an epidemiological survey of 1,220 patients over 15 years of age. Classification of clinically dominant seizure type according to the International Classification of Epileptic Seizures (ICES) was possible in 1,005 cases (82.5%). Fifty-six percent of patients had partial seizures and 26.5% had generalized seizures. Subclassification of partial seizures revealed simple partial seizures (SPS) in 7.5% of the cases, complex partial seizures (CPS) in 23%, and partial secondarily generalized seizures (PSGS) in 25.5% of the cases. Simple partial onset was seen in 56% of the patients with CPS, and impairment of consciousness at the onset occurred in the remaining 44%. PSGS started with simple partial onset in 92% of the cases and the remaining 8% started with a complex partial phase. Tonic-clonic seizures were the most common type of generalized seizures, accounting for 23% of all and 88% of generalized seizures. Absence seizures were seen in 1% of the cases. A single seizure type was observed in 737 patients (60%) and the remaining 40% had multiple seizure types. SPS, CPS, and absence seizures were most commonly combined with other seizure types. The study revealed that distribution of seizure type varies as a function of age. Although the present study finds ICES relevant, difficulties in its utilization in epidemiological context are demonstrated.

The hospital experience and seizure control

We studied 30 patients who were admitted to the hospital because of intractable seizures. Twenty-three had fewer seizures during one or both of the first 2 hospital weeks than before admission, although medication was not changed. The role of environment in seizure control is difficult to measure, but hospital admission itself is a form of environmental manipulation. When seizure control is achieved in the hospital, the hospital experience itself must be considered in addition to other therapeutic interventions.

Epidemiology of different types of epilepsy in school age children of Modena, Italy

An epidemiologic study of epilepsy in school age children has been carried out in Modena, Italy, during the period 1968 to 1973. The prevalence of epileptics aged 5 to 14 years varied between 3.98% and 4.91%. The accession rate varied between 60 and 98 cases /100,000. The primary generalized epilepsies represent 30.8%, the epilepsies with rolandic spike foci 23.9%, the other types of partial epilepsy 42.1%, and the Lennox-Gastaut syndrome 3.2%. Of the 178 epileptics diagnosed during school age, 159 have been followed for at least 4 years, with recovery in 55% of the cases and tendency to improve in 24%.