Abstracts

Epilepsy is a common disease disproportionately affecting children. Often, seizures develop months or years [ndash] the [apos]latent period[apos] [ndash] following an initial brain injury, such as an episode of SE in early childhood. Not all individuals with comparable early life SE, however, develop epilepsy. Indeed, only a minority of children at risk subsequently develops epilepsy. To prospectively select children most likely to benefit from antiepileptogenic therapy it is necessary to identify surrogate markers. The recent advances in magnetic resonance spectroscopic imaging (MRSI) suggest that it may be possible to this tool to identify a surrogate marker of epileptogenesis., Lithium-pilocarpine status epilepticus (SE) was induced in 19-day old rat pups. Pups received intramuscular diazepam two hours after onset of SE to reduce mortality. The severity of seizures during SE were scored using the Racine scale. Pups displaying stage 5 seizures were selected for prospective repeated evaluation with MRSI 24h, 1wk, 2wk, 4wk, 6wk after SE. MRSI data were acquired with 2ul resolution. Three voxels within each hippocampus (6 voxels per rat) were selected for analysis. Continuous video recordings are analyzed to detect spontaneous seizures in the weeks after SE. In this model, it is expected that approximately 1/3 of rats will have seizures, while the remainder do not., At 24 h after SE, pups showed a 10-20% drop in N-acetyl-aspartate (NAA) to creatine (Cr) ratio in the hippocampus. Repeat scans at intermediate intervals show progressive decline in NAA/Cr in most rats undergoing SE, while control levels remain stable or rise. Preliminary evidence in some rats shows that after 6 weeks NAA/Cr may rise. Correlation of MRSI measurements with seizures detected by video recording is ongoing to determine whether the changes observed predict subsequent epileptogenesis., In immature rats, hippocampal NAA/Cr appears to decline for several weeks following SE. Preliminary results suggest there is partial recovery of NAA/Cr in some rats. Whether the degree of NAA/Cr decline, or possibly the extent of recovery, predict subsequent epileptogenesis will be determined as the rats are followed prospectively., (Supported by NINDS NS048149.)