Abstracts

Focal cortical photothrombosis and brain infarction of adult rats can result in epileptic seizures originating ipsilateral to the lesion. In a recently completed study of animals[apos] electrobehavioral properties following photothrombosis, we questioned whether lesioned epileptic (LE), lesioned nonepileptic (LNE), and sham-operated control (C) cohorts could be distinguished by interictal properties as well. We hypothesized that the EEG spectral properties of power (square of amplitude) and coherence (signal similarity of homotopic areas) would differ significantly among the animal cohorts.
2 mo old male Sprague-Dawley rats underwent photothrombosis of the left sensorimotor cortex. Digital video-EEGs were obtained intermittently for each animal for 6 mo. Nine animals (4 LE, 3 LNE, 2 C) were included for quantitative analysis (SensA, Stellate Systems) of power and coherence based on the technical reliability of the overall EEG record. Files with excessive artifact were excluded. Quantitative data analysis of individual files was grouped and averaged for each animal. Data of animals within the same cohort were similarly grouped and averaged before comparison to the other cohorts. ANOVA with multiple comparisons post testing was performed for both power and coherence functions (p[lt]0.01, significant difference; p[lt]0.05, small significant difference).
LE animals demonstrated a significant increase in delta range (0-3.9 Hz) power ipsilateral to the lesion compared to LNE animals, but not in theta (4-7.9 Hz) or alpha (8-13 Hz) ranges. Compared to C animals, LE animals showed a significant increase ipsilaterally in delta, theta, and alpha ranges. LE animals showed no difference contralaterally compared to LNE and C animals. Compared to C animals, LNE animals showed a significant increase in power ipsilaterally in the theta and alpha ranges, and small increases contralaterally within the same ranges. Coherence profiles of LE animals were significantly increased compared to C animals in the delta, theta and alpha ranges, most prominently in delta and low theta (4-5.9 Hz) ranges. Two LNE animals showed no difference compared to C animals except for an increase in the high theta range (6-7.9 Hz), where they showed no or a small difference from LE animals. Coherence profiles of one LNE animal were abnormally high, significantly different from every other animal in the study.
Our results indicate that power and coherence functions can reliably distinguish LE animals from C animals. LE animals develop increased delta range power ipsilateral to the infarct compared to LNE animals. Coherence profiles of LE animals did not reliably distinguish them from LNE animals. Future serial analyses of these EEG spectral properties may provide significant insight to the evolution of epileptogenesis following photothrombotic brain infarction.
[Supported by: American Heart Association GIA 0151398U to KMK]