From traumatic brain injury to posttraumatic epilepsy: what animal models tell us about the process and treatment options

A large number of animal models of traumatic brain injury (TBI) are already available for studies on mechanisms and experimental treatments of TBI. Immediate and early seizures have been described in many of these models with focal or mixed type (both gray and white matter damage) injury. Recent long-term video-electroencephalography (EEG) monitoring studies have demonstrated that TBI produced by lateral fluid-percussion injury in rats results in the development of late seizures, that is, epilepsy. These animals develop hippocampal alterations that are well described in status epilepticus-induced spontaneous seizure models and human posttraumatic epilepsy (PTE). In addition, these rats have damage ipsilaterally in the cortical injury site and thalamus. Although studies in the trauma field provide a large amount of information about the molecular and cellular alterations corresponding to the immediate and early phases of PTE, chronic studies relevant to the epileptogenesis phase are sparse. Moreover, despite the multiple preclinical pharmacologic and cell therapy trials, there is no information available describing whether these therapeutic approaches aimed at improving posttraumatic recovery would also affect the development of lowered seizure threshold and epilepsy. To make progress, there is an obvious need for information exchange between the trauma and epilepsy fields. In addition, the inclusion of epilepsy as an outcome measure in preclinical trials aiming at improving somatomotor and cognitive recovery after TBI would provide valuable information about possible new avenues for antiepileptogenic interventions and disease modification after TBI.