Semiological and Electroencephalographic Characteristics of Kainic Acid-Induced Status Epilepticus in Rats

ABSTRACT

BACKGROUND: Status epilepticus (SE) shows stereotyped progression of electroencephalogram (EEG) and behaviors in human and some SE models. We analysed semiologic features with the electroencephalographic characteristics of kainic acid (KA)-induced SE which showed different patterns from the previously reported patterns of SE. METHODS: Seventeen male Sprague-Dawley rats weighing 150~220 grams were used. SE was induced 5~7 days after the place-ment of epidural electrodes on the rats, using 13 mg/kg kainic acid I.p.. EEGs were recorded and behaviors were contin-uously observed until the end of SE. RESULTS: After the initial akinesia which was apparent within minutes of the KA injection, limbic motor seizure (LMS) composed of facial clonus, head nodding, and akinesia were repeated. Each LMS progressed into more vigorous patterns composed of facial clonus, head nodding, bilateral upper extremity clonus and rearing, without akinesia. Each cycle was repeated as the SE progressed. Severe LMS made up of facial clonus, head nodding, bilateral upper extremity clonus, rearing, falling, and jumping was followed and reiterated. After severe LMS, rats entered subtle SE. In the EEG, repeated discrete seizures mostly consisted of low voltage regular sharp waves and spikes with flat periods. After entering into the LMS, discrete seizure, merging seizure, continuous ictal discharges & periodic epileptiform discharges (PEDs) appeared sequentially in a single cycle and also reiterated. Even during subtle SE, rhythmic cycles were composed of alternating continuous ictal discharges and PEDs. PEDs were gradually replaced by sharp waves or spikes and rats recovered from SE. CONCLUSIONS: Semiologic features and the EEG sequence of KA-induced SE were composed of a series of rhythmic cycles, which have separate EEG patterns in a single cycle. Late EEG patterns of SE were more prominent as the SE progressed.