Original ArticleMagnetic Resonance Imaging Findings in Children With a First Recognized Seizure
Introduction
Few studies systematically examined structural brain abnormalities in children at seizure onset. Shinnar et al. [1] recruited 218 children in New York City, aged 1-19 years, who presented with their first unprovoked afebrile seizure from 1983-1992; imaging studies (73% computed tomography) were obtained over the course of the disorder (personal communication, P.S. Fastenau, February 15, 2006). Of these, 45 (21%) exhibited abnormalities on at least one scan; 39 (17.9%) were presumed to be etiologically related (i.e., “significant” abnormalities). However, computed tomography likely underestimates the extent of structural brain abnormalities. Also, many imaging studies were completed many years after onset, which can be a confounding factor because brain structure may change during chronic epilepsy [2], [3]. Finally, the sample might not have been representative, because the investigators excluded children with typical absence seizures, myoclonic seizures, infantile spasms, generalized tonic-clonic seizures if patients had manifested previous absence or partial seizures, and prior unrecognized seizures, which were reported in approximately one third of children referred to their study [4].
In a parallel study, Berg et al. [5] reported on 488 children in Connecticut, of whom 79.9% had completed an imaging study (only 63.3% of all patients had magnetic resonance imaging) after a second unprovoked seizure, i.e., newly diagnosed epilepsy. In that study, 62 (12.7% of children who underwent imaging studies) exhibited significant abnormalities on at least one scan.
Other studies of new-onset seizures focused on children presenting at emergency departments, but these studies were limited with regard to full assessment of first unprovoked seizure. They relied on computed tomography, included substantial proportions of febrile seizures (30-71%), used small sample sizes [6], [7], [8], [9], [10], and/or included relatively few children [11].
This study characterized structural abnormalities associated with onset of seizures in a large prospective cohort of children, using magnetic resonance imaging and a standardized classification system. The present study extends earlier work by other investigators in several ways. First, imaging was limited to magnetic resonance imaging, the current anatomic “gold standard” [12]. Second, imaging was performed nearer to the time of seizure onset, i.e., the first recognized seizure. Third, we applied a standardized classification system to magnetic resonance imaging findings, and present a more comprehensive and systematic description of imaging findings than did previous investigations. Fourth, data were coded directly from magnetic resonance images by a neuroradiologist who read the images firsthand. Finally, magnetic resonance imaging findings were examined in relation to various epileptic syndromes, to provide a basis for more informed clinical decision-making in new-onset seizures.
Section snippets
Subjects
This study was part of a larger National Institutes of Health-funded study examining cognitive and behavioral measures in children with a first recognized seizure. Children were recruited from clinics at 2 major medical centers (Indiana University Medical Center and Cincinnati Children's Hospital Medical Center), as well as from physicians in private practice and school nurses in metropolitan and outlying rural areas. Compared with 2 other large community-based prospective studies of new-onset
Results
Of 349 children enrolled in the study, 281 (81%) underwent a magnetic resonance imaging examination within 6 months after their first recognized seizure. Demographic and clinical characteristics of this sample are presented in Table 1. Age of onset was distributed across the entire age range, with roughly equal numbers of boys and girls. Estimated intelligence quotient covered a broad range, with the mean and median falling in the middle of the average range for healthy children, consistent
Discussion
Our major finding was that the use of a standardized scoring system with good-quality magnetic resonance imaging for new-onset seizures demonstrated a higher rate of total abnormal findings (31%) compared with previous studies. A number of general observations can be based on our data. Only a minority of children at their first recognized seizure displayed classic epileptogenic lesions involving the cortex or gray matter. White-matter lesions were more commonly associated with the first
Conclusions
The use of magnetic resonance imaging and a reliable, valid standardized scoring system in a large sample of children after their first recognized seizure identified a high rate of abnormalities (87/281, 31%), which may have important implications for practice guidelines in this population. First, some findings that might have been regarded as incidental in the past (e.g., volume loss/ventricular enlargement, and white-matter abnormalities) appear to be present at the onset of seizures and may
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