Abstracts

Rationale:
Traumatic brain injury (TBI) is a significant cause of epileptogenesis, but the evolution, pathophysiology, and variability among patients remain incompletely understood. We have developed, and are currently validating, a swine model of post-traumatic epilepsy (PTE) after somatosensory neocortical impact that incorporates continuous video EEG to quantify the evolution of seizures over time. Here we describe the semiology of porcine posttraumatic seizures, analogous to the Racine scale in rodents. 
Method:
To date, eight Yucatan male swine have undergone bilateral somatosensory cortical impact at age 5.12 ± 0.15 months (mean ± std err) followed by placement of epidural screw electrodes for EEG monitoring using a 3-channel bipolar montage.  The snout somatosensory area was targeted on one side and the facial somatosensory area was targeted on the contralateral side.  Post-traumatic epileptogenesis including convulsions within 3-7 months has been confirmed by video EEG in 3 injured pigs while in 5 injured pigs and 2 sham-operated controls, we have not observed PTE. 2 of the injured pigs were observed to have over 30 episodes of convulsions between the first convulsion and euthanasia. Seizures and associated behaviors were identified and annotated from video recordings. Onset times of the peri-ictal manifestations are plotted using Python to describe an event sequence for porcine post-traumatic seizures. A box-and-whisker plot was created describing the event onsets within ± 30 seconds of the start of frank convulsions in one subject to visualize the sequence of pre and postictal behaviors.  
Results:
The working sequence of peri-ictal behaviors of post-traumatic epilepsy includes the following behaviors: staring spell, head nodding or shaking, forelimb clonus, lowering to the ground, and finally, the convulsion terminating with a period of post-ictal stillness.  We will present the mean and variance of the onset of each peri-ictal behavior.  This sequential ordering of peri-ictal behaviors can be expanded to additional subjects to test the generalizability of the described event onset timing. Other behaviors such as tonic-extension or licking may be added to this plot when generalizing to other subjects in this study.
Conclusion:
A working semiological definition of post-traumatic seizures in swine has been developed and is being used to objectively determine if these behaviors, either in isolation or in combination, are characteristic  of  epilepsy after bilateral somatosensory neocortical injury.  The variety of automatisms and other behaviors that emerge during the development of PTE in swine is hypothesized to have consistent sequence within and among subjects with peri-facial somatosensory neocortical injuries. Understanding the symptomatic patterns of clinical seizures in swine will allow us to better determine the timing of post-traumatic epileptogenesis and characterize the evolution of PTE in this model.
Funding:
:Supported by CURE / DOD