Similarities and Differences of Acute Nonconvulsive Seizures and Other Epileptic Activities following Penetrating and Ischemic Brain Injuries in Rats

Abstract

The similarities and differences between acute nonconvulsive seizures (NCS) and other epileptic events, for example, periodic epileptiform discharges (PED) and intermittent rhythmic delta activities (IRDA), were characterized in rat models of penetrating and ischemic brain injuries. The NCS were spontaneously induced by either unilateral frontal penetrating ballistic-like brain injury (PBBI) or permanent middle cerebral artery occlusion (pMCAO), and were detected by continuous electroencephalogram (EEG) monitoring begun immediately after the injury and continued for 72 h or 24 h, respectively. Analysis of NCS profiles (incidence, frequency, duration, and time distribution) revealed a high NCS incidence in both injury models. The EEG waveform expressions of NCS and PED exhibited intrinsic variations that resembled human electrographic manifestations of post-traumatic and post-ischemic ictal and inter-ictal events, but these waveform variations were not distinguishable between the two types of brain injury. However, the NCS after pMCAO occurred more acutely and intensely (latency=0.6 h, frequency=25 episodes/rat) compared with the PBBI-induced NCS (latency=24 h, frequency=10 episodes/rat), such that the most salient features differentiating post-traumatic and post-ischemic NCS were the intensity and time distribution of the NCS profiles. After pMCAO, nearly 50% of the seizures occurred within the first 2 h of injury, whereas after PBBI, NCS occurred sporadically (0-5%/h) throughout the 72 h recording period. The PED were episodically associated with NCS. By contrast, the IRDA appeared to be independent of other epileptic events. This study provided comprehensive comparisons of post-traumatic and post-ischemic epileptic profiles. The identification of the similarities and differences across a broad spectrum of epileptic events may lead to differential strategies for post-traumatic and post-stroke seizure interventions.

Long-Term Consequences of Traumatic Brain Injury: Current Status of Potential Mechanisms of Injury and Neurological Outcomes

“…144 In studies being conducted in pre-clinical models, evidence for subclinical seizures has also been documented. 143,145 Using noninvasive longterm monitoring in awake rats after TBI, for example, evidence for patterns of abnormal EEG activity is observed at various posttraumatic periods.…”

Comprehensive Evaluation of Neuroprotection Achieved by Extended Selective Brain Cooling Therapy in a Rat Model of Penetrating Ballistic-Like Brain Injury

“…A reference electrode (R) was placed posterior to the lambda. The free end of each electrode wire was then soldered to a multi-pin connector (March Electronics, West Hempstead, NY) in the sequence of a (left frontal), b (left parietal), c (right frontal), and d (right parietal), which was individually referenced to the electrode R to create a fourchannel mono-referential EEG recording montage (Lu et al, 2013). The screw electrodes were secured on the rat skull with dental acrylic.…”

“…By contrast, our CCA cooling method significantly shortened cooling duration to achieve antiseizure effects without the complications of medications. More importantly, since the majority (*90%) of NCS occurred during 18-48 hours post-PBBI (Lu et al, , 2013, many hours beyond the cessation of SBC treatment, the shortterm SBC therapy has in fact achieved seizure prophylaxis.…”

Epilepsy Related to Traumatic Brain Injury

“…Chronic spontaneous seizures were reported after FP-and CCIinduced TBI, both in rats and mice. Acute epileptiform activity/seizures (up to 3 days after injury) has been reported in a rat model of penetrating ballistic injury [28][29][30][31] and blast injury [32], but whether late spontaneous seizures develop after these injury mechanisms remains to be studied. So far, studies have not found acute/late seizures after repeated mild concussive TBI [33].…”