Purpose: To describe the natural history of chronic epilepsy after experimental self-sustaining status epilepticus (SSSE) and to correlate patterns of SSSE with ictal, interictal, and plastic changes that characterize chronic epilepsy.
Methods: SSSE was induced in adult Wistar rats by 30-min intermittent electrical stimulation of the perforant path. In some animals, SSSE was treated by short-term administration of antiepileptic drugs (AEDs). After SSSE, EEG and animal behavior were monitored for </=1 year. Some animals were killed to study mossy fiber sprouting in the dentate gyrus.
Results: Despite the high reproducibility of the electrographic and behavioral manifestations of SSSE, patterns of chronic epilepsy varied considerably among animals in terms of seizure frequency, initial seizure pattern at the onset of chronic epilepsy, and frequency of interictal spikes. Statistically significant correlations were found between spike frequency during SSSE and interictal spike frequency, as well as between the frequency of spontaneous seizures and degree of mossy fiber sprouting. Early treatment of SSSE prevented the occurrence of spontaneous seizures and significantly decreased frequency of interictal spikes. Late treatment of SSSE did not prevent spontaneous seizures, but significantly decreased their frequency, and eventually may lead to remission of epilepsy.
Conclusions: SSSE leads after a "silent" period to chronic epilepsy, which is maintained for > or =1 year in the rat. The silence is only behavioral, because EEG paroxysmal activity is seen in every animal. In this model of SSSE, the timing of treatment is a major determinant of outcome. Early treatment reduces the incidence of chronic epilepsy, whereas late treatment only reduces its severity. The possibility that this reduction of the severity of epilepsy may led to spontaneous remissions merits further study.