Looking for complexity in quantitative semiology of frontal and temporal lobe seizures using neuroethology and graph theory.

Epileptic syndromes and seizures are the expression of complex brain systems. Because no analysis of complexity has been applied to epileptic seizure semiology, our goal was to apply neuroethology and graph analysis to the study of the complexity of behavioral manifestations of epileptic seizures in human frontal lobe epilepsy (FLE) and temporal lobe epilepsy (TLE). We analyzed the video recordings of 120 seizures of 18 patients with FLE and 28 seizures of 28 patients with TLE. All patients were seizure-free >1 year after surgery (Engel Class I). All patients' behavioral sequences were analyzed by means of a glossary containing all behaviors and analyzed for neuroethology (Ethomatic software). The same series were used for graph analysis (CYTOSCAPE). Behaviors, displayed as nodes, were connected by edges to other nodes according to their temporal sequence of appearance. Using neuroethology analysis, we confirmed data in the literature such as in FLE: brief/frequent seizures, complex motor behaviors, head and eye version, unilateral/bilateral tonic posturing, speech arrest, vocalization, and rapid postictal recovery and in the case of TLE: presence of epigastric aura, lateralized dystonias, impairment of consciousness/speech during ictal and postictal periods, and development of secondary generalization. Using graph analysis metrics of FLE and TLE confirmed data from flowcharts. However, because of the algorithms we used, they highlighted more powerfully the connectivity and complex associations among behaviors in a quite selective manner, depending on the origin of the seizures. The algorithms we used are commonly employed to track brain connectivity from EEG and MRI sources, which makes our study very promising for future studies of complexity in this field.

The epilepsies: complex challenges needing complex solutions.

It is widely accepted that epilepsies are complex syndromes due to their multi-factorial origins and manifestations. Different mathematical and computational descriptions use appropriate methods to address nonlinear relationships, chaotic behaviors and emergent properties. These theoretical approaches can be divided into two major categories: descriptive, such as flowcharts, graphs and other statistical analyses, and explicative, which include both realistic and abstract models. Although these modeling tools have brought great advances, a common framework to guide their design, implementation and evaluation, with the goal of future integration, is still needed. In the current review, we discuss two examples of complexity analysis that can be performed with epilepsy data: behavioral sequences of temporal lobe seizures and alterations in an experimental cellular model. We also highlight the importance of the creation of model repositories for the epileptology field and encourage the development of mathematical descriptions of complex systems, together with more accurate simulation techniques.

The neurobiological substrates of behavioral manifestations during temporal lobe seizures: a neuroethological and ictal SPECT correlation study.

Ictal behavior coupled with SPECT findings during 28 seizures in patients with temporal lobe epilepsy (TLE) with unilateral hippocampal sclerosis (13 left; 15 right) was displayed as flowcharts from right-sided (RTLE) plus left-sided (LTLE) seizures. Ictal SPECT was classified blind to neuroethology. Behaviors were categorized as ipsilateral to the epileptogenic zone (IL), contralateral to the epileptogenic zone (CL), or bilateral. SPECT intensity and region were categorized as IL or CL to the epileptogenic zone. All patients developed automatisms and had hyperperfusion in their temporal lobes. Patients' verbal responses to questions had statistical interactions in RTLE but not in LTLE sum. Most CL dystonic posturing was correlated to IL basal ganglia hyperperfusion. Basal ganglia activation occurred in seizures without dystonic posturing and CL manual automatisms, and lack of IL dystonic posturing and the presence of CL cerebellar hemispheric hyperperfusion were also observed. Coupling of neuroethology and SPECT findings reliably evaluates ictal behavior and functionality of associated brain areas.

Is dystonic posturing during temporal lobe epileptic seizures the expression of an endogenous anticonvulsant system?

In temporal lobe epilepsy (TLE) seizures, tonic or clonic motor behaviors (TCB) are commonly associated with automatisms, versions, and vocalizations, and frequently occur during secondary generalization. Dystonias are a common finding and appear to be associated with automatisms and head deviation, but have never been directly linked to generalized tonic or clonic behaviors. The objective of the present study was to assess whether dystonias and TCB are coupled in the same seizure or are associated in an antagonistic and exclusive pattern. Ninety-one seizures in 55 patients with TLE due to mesial temporal sclerosis were analyzed. Only patients with postsurgical seizure outcome of Engel class I or II were included. Presence or absence of dystonia and secondary generalization was recorded. Occurrence of dystonia and occurrence of bilateral tonic or clonic behaviors were negatively correlated. Dystonia and TCB may be implicated in exclusive, non-coincidental, or even antagonistic effects or phenomena in TLE seizures. A neural network related to the expression of one behavioral response (e.g., basal ganglia activation and dystonia) might theoretically "displace" brain activation or disrupt the synchronism of another network implicated in pathological circuit reverberation and seizure expression. The involvement of basal ganglia in the blockade of convulsive seizures has long been observed in animal models. The question is: Do dystonia and underlying basal ganglia activation represent an attempt of the brain to block imminent secondary generalization?

Correlation between shaking behaviors and seizure severity in five animal models of convulsive seizures.

Wet dog shakes (WDS) and head shakes (HS) are associated with experimentally induced convulsive seizures. We sought to determine whether these behaviors are correlated or not with major (status epilepticus (SE) or fully kindled animals) or minor (non-SE or partially kindled animals) seizure severity. WDS are directly correlated with SE induced by intracerebral star fruit extract (Averrhoa carambola) injection and with kindled animals in the amygdala fast kindling model. On the other hand, WDS are inversely correlated with SE induced by intracerebral bicuculline and pilocarpine injections. Systemic pilocarpine in animals pretreated with methyl-scopolamine barely induced WDS or HS. The role of shaking behaviors may vary from ictal to anticonvulsant depending on the experimental seizure model, circuitries involved, and stimulus intensity. The physical presence of acrylic helmets may per se inhibit the HS response. Also, methyl-scopolamine, a drug incapable of crossing the blood-brain barrier, can induce HS in animals without acrylic helmets.