Posttraumatic epilepsy: the challenge of translating discoveries in the laboratory to pathways to a cure.
ABSTRACT Translating laboratory discoveries into successful therapies for preventing epilepsy is a difficult task, but preventing epilepsy in those who are known to be at high risk needs to be one of our highest priorities. At present, we need to approach this task as a parallel set of research endeavors-one concentrating on laboratory experiments designed to learn how to prevent epilepsy after brain trauma and the other focusing on how to perform the appropriate clinical research in humans to demonstrate that whatever is discovered in the laboratory can be appropriately tested. It is too important to let the second process await conclusion of the first. Initially, we need to create a consortium of groups in trauma centers that are dedicated to antiepileptogenic studies and develop funding sources for long-term studies. We need to experiment with clinical protocols, making the studies as cost-effective as possible, while performing continuous data mining of outcomes and surrogate markers. The limitations of current technology to assist in antiepileptogenesis trials must be acknowledged: There is no currently available method for continuously monitoring electroencephalography (EEG) over prolonged periods, and there are no validated biomarkers for the process of epileptogenesis. As we learn more about the process of epileptogenesis and its underlying mechanisms, it is hoped that we will be able to prevent the development of epilepsy after traumatic brain injury (TBI) and after many other known epileptogenic lesions.
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ABSTRACT: Antiepileptic drugs are commonly used to prevent seizures that may follow head trauma. However, previous controlled studies of this practice have been inconclusive. To study further the effectiveness of phenytoin (Dilantin) in preventing post-traumatic seizures, we randomly assigned 404 eligible patients with serious head trauma to treatment with phenytoin (n = 208) or placebo (n = 196) for one year in a double-blind fashion. An intravenous loading dose was given within 24 hours of injury. Serum levels of phenytoin were maintained in the high therapeutic range (3 to 6 mumol of free phenytoin per liter). Follow-up was continued for two years. The primary data analysis was performed according to the intention to treat. Between drug loading and day 7, 3.6 percent of the patients assigned to phenytoin had seizures, as compared with 14.2 percent of patients assigned to placebo (P less than 0.001; risk ratio, 0.27; 95 percent confidence interval, 0.12 to 0.62). Between day 8 and the end of year 1, 21.5 percent of the phenytoin group and 15.7 percent of the placebo group had seizures; at the end of year 2, the rates were 27.5 percent and 21.1 percent, respectively (P greater than 0.2 for each comparison; risk ratio, 1.20; 95 percent confidence interval, 0.71 to 2.02). This lack of a late effect could not be attributed to differential mortality, low phenytoin levels, or treatment of some early seizures in patients assigned to the placebo group. Phenytoin exerts a beneficial effect by reducing seizures only during the first week after severe head injury.New England Journal of Medicine 09/1990; 323(8):497-502. · 51.66 Impact Factor
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ABSTRACT: Small animal magnetic resonance imaging (MRI) has opened a window through which brain abnormalities can be observed over time in rodents noninvasively. We review MRI studies done during epileptogenesis triggered by status epilepticus in rat. Most of these studies have used quantitative T2, diffusion, and/or volumetric MRI. The goal has been to identify the distribution and severity of structural lesions during the epileptogenic process, that is, soon after status epilepticus, during epileptogenesis, and after the appearance of spontaneous seizures. Data obtained demonstrate that MRI can be used to associate the development of brain pathology with the evolution of clinical phenotype. MRI can also be used to select animals to preclinical studies based on the severity and/or distribution of brain damage, thus making the study population more homogeneous, for example, for assessment of novel antiepileptogenic or neuroprotective treatments. Importantly, follow-up data collected emphasize interindividual differences in the dynamics of development of abnormalities that could have remained undetected in a typical histologic analysis providing a snapshot to brain pathology. A great future challenge is to take advantage of interanimal variability in MRI in the development of surrogate markers for epilepsy or its comorbidities such as memory impairment. Understanding of molecular and cellular mechanisms underlying changes in various MRI techniques will help to better understand complex progressive pathological processes associated with epileptogenesis and epilepsy.Epilepsia 02/2007; 48 Suppl 4:3-10. · 3.91 Impact Factor
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ABSTRACT: To investigate the temporal relation between high-frequency oscillations (HFOs) in the dentate gyrus and recurrent spontaneous seizures after intrahippocampal kainite-induced status epilepticus. Recording microelectrodes were implanted bilaterally in different regions of hippocampus and entorhinal cortex. A guide cannula for microinjection of kainic acid (KA) was implanted above the right posterior CA3 area of hippocampus. After recording baseline electrical activity, KA (0.4 microg/0.2 microl) was injected. Beginning on the next day, electrographic activity was recorded with video monitoring for seizures every day for 8 h/day for > or = 30 days. Of the 26 rats studied, 19 revealed the appearance of sharp-wave activity and HFOs in the frequency range of 80 to 500 Hz in the dentate gyrus ipsilateral to the KA injection. In the remaining seven rats, no appreciable activity was noted in this frequency range. In some rats with recurrent seizures, HFOs were in the ripple frequency range (100-200 Hz); in others, HFOs were in the fast ripple frequency range (200-500 Hz), or a mixture of both oscillation frequencies was found. The time of detection of the first HFOs after status epilepticus varied between 1 and 30 days, with a mean of 6.3 +/- 2.0 (SEM). Of the 19 rats in which HFO activity appeared, all later developed recurrent spontaneous seizures, whereas none of the rats without HFOs developed seizures. The sooner HFO activity was detected after status epilepticus, the sooner the first spontaneous seizure occurred. A significant inverse relation was found between the time to the first HFO detection and the subsequent rate of spontaneous seizures. A strong correlation was found between a decreased time to detection of HFOs and an increased rate of spontaneous seizures, as well as with a decrease in the duration of the latent period between KA injection and the detection of spontaneous seizures. Two types of HFOs were found after KA injection, one in the frequency range of 100 to 200 Hz, and the other, in the frequency range of 200 to 500 Hz, and both should be considered pathological, suggesting that both are epileptogenic.Epilepsia 09/2004; 45(9):1017-23. · 3.91 Impact Factor