Semiologic and Electrophysiologic Correlations in Temporal Lobe Seizure Subtypes

Abstract

Summary:Purpose: The International League Against Epilepsy (ILAE) classification distinguishes medial and neocortical temporal lobe epilepsies. Among other criteria, this classification relies on the identification of two different electroclinical patterns, those of medial (limbic) and lateral (neocortical) temporal lobe seizures, depending on the structure initially involved in the seizure activity. Recent electrophysiologic studies have now identified seizures in which medial and neocortical structures are both involved at seizure onset. The purpose of the study was therefore to study the correlations of ictal semiology with the spatiotemporal pattern of discharge in temporal lobe seizures.Methods: The 187 stereoelectroencephalography-recorded seizures from 55 patients were analyzed. Patients were classified into three groups according to electrophysiologic findings: medial (M; seizure onset limited to medial structures, n = 24), lateral (L; seizure onset limited to lateral structures, n = 13), and medial-lateral (ML; seizure onset involving both medial and lateral structures, n = 18). Clinical findings were compared between groups.Results: Initial epigastric sensation, initial fear, delayed oroalimentary and elementary upper limb automatisms, delayed loss of contact, long seizure duration, and absent or rare secondary generalizations were associated with M seizures. Initial auditory illusion or hallucination, initial loss of contact, shorter duration of seizures, and more frequent generalizations were associated with L seizures. Initial epigastric sensation, initial loss of contact, early oroalimentary and verbal automatisms, and long duration of seizures were associated with ML seizures.Conclusions: Although the syndrome of mesial temporal epilepsy is now relatively well defined, our findings support the idea that the organization of temporal lobe seizures may be complex and that different patterns exist. We demonstrate three distinct patterns, characterized by both semiologic and electrophysiologic features. This distinction may help to define better the epileptogenic zone and the subsequent surgical procedure.

Initiation, Propagation, and Termination of Partial (Focal) Seizures

“…This EEG pattern is observed in the majority of intracranially explored partial epilepsies, such as TLEs, focal cortical dysplasias, and postanoxic lesions. Another common seizure-onset pattern, defined as hypersynchronous, is characterized by large-amplitude spike potentials (Engel et al 1990;Maillard et al 2004). The hypersynchronous pattern is most often seen in TLEs with hippocampal sclerosis Ogren et al 2009) and was never reported in neocortical focal epilepsies.…”

Correlation of the patterns of behavior in focal epileptic seizures and localization of the epileptic lesions

“…Naime, iako velika većima autora veruje da se bihejvioralni arest u suštini generiše u mezijalnim temporalnim epilepsijama, studija sa implantiranim elektrodama u svim bitnim temporalnim strukturama pokazala je da je tokom lokalizavanog praženja u mezijalnim strukturama ovaj znak nedostajući (160). Na osnovu ovoga se spekuliše da je ovaj znak zapravo vezan za disrupciju integracije medijalnih i lateralnih temporalnim struktura.…”

“…Učestalost oroalimentarnih automatizma u populaciji temporalne epilepsije je značajnije veća i zavisi od ishodišta u samoj grupi temporalnih epilepsija (mezijalna temporalna epilepsija 62%, lateralna temporalna epilepsija 15,4% i meziolateralna temporalna epilepsija 61% (definisana u slučajevima kada bi se tonička praženjenja snimljena stereoelekotroencefalografijom simultano dešavala iz mezijalnih i lateralnih temporalnih struktura)) (160). S obzirom da je naša populacija dominantno sačinjena od bolesnika sa temporalnom epilepsijom (70%), ali ne isključivo (25% nelezione epilepsije i 5% ostala lokalizacija), ukupni procenat učestalosti ovog semiološkog znaka odgovara ranijim literaturnim podacima.…”

“…Ovo je, shodno rezultatima, koji su zabeleženi na bolesnicima kod kojih je evaluacija urađena uz pomoć stereotaksično plasiranih elektroda, a gde je notirano da se oroalimentarni automatizmi javljaju u drugoj polovini napada, u slučajevima kada je iktalni početak zabeležen u mezijalnim temporalnim regionima. U istoj studiji je pokazano da se ovi automatizmi javljaju u prvoj polovini napada, samo ukoliko napad počinje iz mezijalnih i lateralnih struktura u isto vreme (160).…”

“…Pored toga, nedvosmisleno je pokazano i u seriji sa invazivno plasiranim dubokim stereotaksičnim elektrodama da je epigastrična aura, (i viscerosenzitivne senzacije bliske njoj), mnogo češća u grupi bolesnika sa mezijalnom temporalnom epilepsijom (79%) nego u grupi sa mezio-lateralnom (50%) i striktno lateralnom (28%) temporalnom epilepsijom. I u ovoj studiji se hipotetiše da je ključna aktivacija i insule za puno postizanje ove senzacije (160). Ipak, i u našoj seriji, a i prema drugim radovima, postoji mogućnost da epilepsije posterionog korteksa takođe imaju epigastričnu auru što se može smatrati propagacijom u temporalni režanj (105).…”