Abstracts

Rationale: Traumatic brain injury (TBI) is a serious health problem and often associated with acute and chronic neurological sequela, including seizures. A previous experimental TBI study recorded ripples (R, 80-200Hz) and fast ripples (FR, 200-500Hz) immediately after injury and the rates of these events remained stable for up to 8 weeks (Li et al. 2021). In the current preclinical TBI study, we focused on the first two weeks after injury, a time when many animals have acute and to lesser extent late seizures, which could explain the appearance of ripples and fast ripples after injury.

Methods: For TBI group (n=5), LFPI was induced in adult male Sprague-Dawley rats (300–350 g at the time of the injury). Sham-treated rats (n=5) underwent the same procedures except animals didn’t receive the impact. EEG was recorded continuously for 14 days from bilateral frontal, central and occipital screws and two paired microelectrodes in perilesional cortical and ipsilateral hippocampus. EEG was reviewed for early (< =7 d post-LFPI) and late ( >7-14 d) seizures. RippleLab was used to detect R and FR in 3 h EEG epochs during the light period for each day post-LFPI.

Results: In TBI animals, seizures occurred during the first 7 days after injury and in the Sham group, seizures resolved within 3 days after surgery. No animals had seizures during second week after injury. Mean seizure duration was longer in TBI than Sham animals (86.95 s versus 60.89 s; p< 0.05). There was no difference in the incidence of early or late seizures between the groups (p >0.05). Overall, the rate of FR in TBI animals was higher than in Sham group (p< 0.001). Rates of FR in the TBI group increased immediately after injury (D0) and remained elevated for 14 days after injury in all sampled brain areas, including ipsilateral hippocampus and cortex as well as the contralateral cortex (p< 0.01). By contrast, the rate of R overall and in each brain area was similar between TBI and Sham animals.