Respostas auditivas evocadas em regime permanente para avaliar acoplamento anormal em modelos animais de crises convulsivas

Abstract

Two thirds of patients with temporal lobe epilepsy (TLE) do not respond adequately to anticonvulsants and in the past thirty years there has been little progress in pharmacological treatment, so a new approach is needed in the epilepsies study. Currently, epilepsy is understood as an imbalance between excitation and inhibition and recently the hyper synchronism between neural networks in the presence or not of this imbalance has been shown to be a new way of understanding the reasons that predispose the brain to epilepsy development. In this work, the auditory steady-state-evoked response (ASSR) was used to assess the hyper-synchronism between neural networks and the changes in brain processing that occur in an animal model of temporal lobe epilepsy with intrahypocampal kainic acid (KA) injection. It has been demonstrated that there is an increase in the synchronism between the studied areas (hippocampus, amygdala and inferior colliculus) progressively in the process of epileptogenesis, mainly ipsilateral to the injection of KA in right CA3, in addition to impairment of the brain auditory processing and of top-down modulation. These changes show that even more rostral lesions such as the one performed in the hippocampus are capable of changing the brain's primary sensory processing of more caudal structures such as the inferior colliculus. Thus, ASSR showed that animals in TLE have impaired brain processing of structures not directly involved in this type of epilepsy. The changes in brain processing shown in the present study are more profound than previously shown in the literature and could be responsible for the comorbidities found in epileptic patients, such as the psychiatric disorders that are more frequent in this population. The hyper synchronism between neural networks found in this work and in other works with different types of epilepsy allows us to infer that hyper synchronism may be a general property of epilepsies and so it may be used as a new therapeutic target, and ASSR as a possible diagnostic aid tool. In addition, this study showed that ASSR has the potential to help diagnose the laterality of the crisis by presenting different responses, depending on the hemisphere initially affected. Thus, further studies are needed to assess hyper-synchronism in other types of epilepsy in addition to the replication of results in patients with TLE.