A population-based survey of childhood epilepsy in Okayama Prefecture, Japan: reclassification by a newly proposed diagnostic scheme of epilepsies in 2001

Seizures, syndromes, and etiologies in childhood epilepsy: The International League Against Epilepsy 1981, 1989, and 2017 classifications used in a population-based cohort

OBJECTIVE

The study provides updated information about the distribution of seizures, epilepsies, and etiologies of epilepsy in the general child population, and compares the old and new classification systems from the International League Against Epilepsy (ILAE).

METHODS

The study platform was the Norwegian Mother and Child Cohort Study. Cases of epilepsy were identified through registry linkages and sequential parental questionnaires. Epilepsy diagnoses were validated using a standardized protocol, and seizures, epilepsies, and etiologies were classified according to the old (ILAE 1981/1989) and new (ILAE 2017) classifications. Information was collected through medical record reviews and/or parental telephone interviews.

RESULTS

The study population included 112,744 children aged 3-13 years at the end of follow-up on December 31, 2012. Of these, there were 606 children with epilepsy (CWE). Distribution of seizure types varied by age of onset. Multiple seizure types were common with early onset. Focal epilepsies were the most common, occurring in 317 per 100,000 children in the study population and in 59% of CWE. Generalized epilepsies were found in 190 per 100,000 (35% of CWE). CWE with onset during the first 2 years of life had an even distribution of focal and generalized epilepsies, whereas focal epilepsies became dominant at later ages of onset. A definite cause of epilepsy had been demonstrated in 33% of CWE. The ILAE 1989 classification allowed for a broad syndrome category in 93% of CWE and a defined epileptic syndrome in 37%. With the ILAE 2017 classification, 41% of CWE had a defined epileptic syndrome and 63% had either a defined syndrome or structural-metabolic etiology.

SIGNIFICANCE

The distribution of seizures and epilepsies is strongly dependent on age of onset. Despite diagnostic advances, the causes of epilepsy are still unknown in two-thirds of CWE. The ILAE 2017 classifications allow for a higher precision of diagnoses, but at the expense of leaving more epilepsies classifiable only at the mode of onset level.

Applicability of the new ILAE classification for epilepsies (2010) in persons with epilepsy at a tertiary care center in India

PURPOSE

To test the applicability of the new International League Against Epilepsy (ILAE) 2010 classification for epilepsies and to compare it with the ILAE 1989 classification and the ILAE 2001 diagnostic scheme in developing countries with limited resources such as India.

METHODS

Prospective data of 500 consecutive patients with epilepsy, presenting in neurology department of All India Institute of Medical Sciences, was collected from January 2011 to June 2012 and analyzed according to the three systems proposed by ILAE in 1989, 2001, and 2010.

KEY FINDINGS

All 500 patients could be classified in the ILAE 1989 classification system, but only 413 in the ILAE 2001 diagnostic scheme (in axes 3 and 4) and 420 in the ILAE 2010 classification system. Leading categories were localization-related epilepsies, symptomatic focal epilepsies, perinatal insult, and epilepsies attributed to structural and metabolic cause in ILAE 1989, 2001 axis 3, 2001 axis 4, and 2010 systems, respectively. The ILAE 1989 classification system could categorize significantly greater numbers of patients compared to the 2001 and 2010 systems, whereas the latter two remained similar.

SIGNIFICANCE

A large group of patients remained unclassified in the new classification system despite our tremendous gain in knowledge through improved imaging, genomics, and molecular biology, and so on, which could be attributed to lack of availability of facilities in developing countries. Dichotomy of localization-related and generalized epilepsy still makes for a fundamental and pragmatic working diagnosis and guides the physician about the extent of investigations and treatment especially in "epilepsies of unknown cause."

Incidence and classification of new-onset epilepsy and epilepsy syndromes in children in Olmsted County, Minnesota from 1980 to 2004: a population-based study

PURPOSE

To determine the incidence and classification of new-onset epilepsy, as well as the distribution of epilepsy syndromes in a population-based group of children, using the newly proposed Report of the ILAE Commission on Classification and Terminology 2005-2009.

METHODS

We identified all children residing in Olmsted County, MN, 1 month through 17 years with newly diagnosed epilepsy from 1980 to 2004. For each patient, epilepsy was classified into mode of onset, etiology, and syndrome or constellation (if present). Incidence rates were calculated overall and also separately for categories of mode of onset and etiology.

RESULTS

The adjusted incidence rate of new-onset epilepsy in children was 44.5 cases per 100,000 persons per year. Incidence rates were highest in the first year of life and diminished with age. Mode of onset was focal in 68%, generalized/bilateral in 23%, spasms in 3% and unknown in 5%. Approximately half of children had an unknown etiology for their epilepsy, and of the remainder, 78 (22%) were genetic and 101 (28%) were structural/metabolic. A specific epilepsy syndrome could be defined at initial diagnosis in 99/359 (28%) children, but only 9/359 (3%) had a defined constellation.

CONCLUSION

Nearly half of childhood epilepsy is of "unknown" etiology. While a small proportion of this group met criteria for a known epilepsy syndrome, 41% of all childhood epilepsy is of "unknown" cause with no clear syndrome identified. Further work is needed to define more specific etiologies for this group.

A population-based study of long-term outcomes of cryptogenic focal epilepsy in childhood: cryptogenic epilepsy is probably not symptomatic epilepsy

PURPOSE

To compare long-term outcome in a population-based group of children with cryptogenic versus symptomatic focal epilepsy diagnosed from 1980 to 2004 and to define the course of epilepsy in the cryptogenic group.

METHODS

We identified all children residing in Olmsted County, MN, 1 month through 17 years, with newly diagnosed, nonidiopathic focal epilepsy from 1980 to 2004. Children with idiopathic partial epilepsy syndromes were excluded. Medical records were reviewed to determine etiology, results of imaging and EEG studies, treatments used, and long-term outcome. Children were defined as having symptomatic epilepsy if they had a known genetic or structural/metabolic etiology, and as cryptogenic if they did not.

KEY FINDINGS

Of 359 children with newly diagnosed epilepsy, 215 (60%) had nonidiopathic focal epilepsy. Of these, 206 (96%) were followed for > 12 months. Ninety-five children (46%) were classified as symptomatic. Median follow-up from diagnosis was similar in both groups, being 157 months (25%, 75%: 89, 233) in the cryptogenic group versus 134 months (25%, 75%: 78, 220) in the symptomatic group (p = 0.26). Of 111 cryptogenic cases, 66% had normal cognition. Long-term outcome was significantly better in those with cryptogenic versus symptomatic etiology (intractable epilepsy at last follow-up, 7% vs. 40%, p < 0.001; seizure freedom at last follow-up, 81% vs. 55%, p < 0.001). Of those who achieved seizure freedom at final follow-up, 68% of the cryptogenic group versus only 46% of the symptomatic group were off antiepileptic medications (p = 0.01). One-third of the cryptogenic group had a remarkably benign disorder, with no seizures seen after initiation of medication, or in those who were untreated, after the second afebrile seizure. A further 5% had seizures within the first year but remained seizure-free thereafter. With the exception of perinatal complications, which predicted against seizure remission, no other factors were found to significantly predict outcome in the cryptogenic group.

SIGNIFICANCE

More than half of childhood nonidiopathic localization-related epilepsy is cryptogenic. This group has a significantly better long-term outcome than those with a symptomatic etiology, and should be distinguished from it.

Electroclinical characterization and classification of symptomatic epilepsies with very early onset by multiple correspondence analysis

PURPOSE

To characterize very early onset symptomatic epilepsies electroclinically, to identify meaningful factors to delineate epilepsy syndromes under this category, and to test validity of the current syndromic organization of these epilepsies by the International League Against Epilepsy (ILAE).

METHODS

Subjects were 38 epileptic patients with seizure onset before 3 months of age. We investigated the age of seizure onset, seizure types, myoclonus, EEG features, neuroimaging studies, outcome of seizures and development. We performed multiple correspondence analysis (MCA) to reveal associations among these characteristics and to find important characteristics to divide this epilepsy group into subgroups.

RESULTS

Very early onset epilepsies were characterized by partial seizures and epileptic spasms, especially occurring in combination as a single ictal event (combined seizures), and poor outcome. Suppression-burst (SB), hypsarrhythmia, EEG asymmetry and structural brain abnormalities were common. MCA demonstrated that presence or absence of SB was the most meaningful factor to separate this group into subgroups. MCA on the subgroup with SB revealed a subset with early-onset spasms, partial seizures with single focus, no myoclonus, SB during wakefulness and sleep, no EEG asynchrony, hypsarrhythmia and combined seizures, and another subset with late-onset spasms, partial seizures with multiple foci, myoclonus, EEG asynchrony, no combined seizures, SB during sleep only, no EEG asymmetry, no structural abnormality and no hypsarrhythmia. These corresponded to Ohtahara syndrome and early myoclonic encephalopathy, respectively.

CONCLUSIONS

Very early onset symptomatic epilepsies have the electroclinical characteristics distinct from those with later onset. This study supported the current ILAE organization on this epilepsy group from statistic approach.