Paradigms for subdural grids' implantation in patients with refractory epilepsy

Abstract

-Rationale: The need for invasive monitoring in patients with refractory epilepsy has been greatly reduced by the introduction of new technologies such as PET, SPECT and MRI in the clinical practice. On the other hand, 10 to 30% of the patients with refractory epilepsy have non-localizatory non-invasive preoperative work-up results. This paper reports on the paradigms for subdural electrodes implantation in patients with different refractory epileptic syndromes. Methods: Twenty-nine adult refractory epileptic patients were studied. Patients were divided into five different epileptic syndromes that represented the majority of the patients who needed invasive recordings: bitemporal (Group I; n=16 ), bi-frontal-mesial (Group II, n=5), hemispheric (Group III; n=2), anterior quadrant (Group IV; n=3) and posterior quadrant (Group V; n=3). All of them were submitted to extensive subdural electrodes' implantation (from 64 to 160 contacts) covering all the cortical surface potentially involved in epileptogenesis under general anesthesia. Results: All patients tolerated well the procedure. There was no sign or symptom of intracranial hypertension except for headache in 22 patients. In all except one Group II patient, prolonged electrocorticographic monitoring using the described subdural cortical coverage patterns was able to define a focal area amenable for resection. In all Groups II-V patients cortical stimulation was able to adequately map the rolandic and speach areas as necessary. Conclusion: Despite recent technological advances invasive neurophysiological studies are still necessary in some patients with refractory epilepsy. The standardization of the paradigms for subdural implantation coupled to the study of homogeneous patients' populations as defined by MRI will certainly lead to a better understanding of the pathophysiology involved in such cases and an improved surgical outcome.KEY WORDS: epilepsy, surgery, subdural electrodes, outcome, standards. Paradigmas para implante de placas subdurais em pacientes com epilepsia refratáriaRESUMO -Introdução: O advento de novas tecnologias de imagem tais como o PET, SPECT e RM diminuíram em muito a necessidade da utilização de eletrodos invasivos na investigação pré-operatória de pacientes epilépticos. No entanto, 10 a 30% dos pacientes com epilepsias refratárias ainda possuem investigação não-invasiva inconclusiva. Este estudo relata nossos paradigmas para o implante de eletrodos subdurais nesta população de epilépticos refratários. Métodos: Vinte e nove pacientes portadores de epilepsias refratárias foram estudados. Eles foram divididos em 5 grupos de síndromes epilépticas que incluíam a maioria dos pacientes submetidos a implantes: bitemporais (grupo I; n=16), bifrontomesiais (grupo II; n=5), hemisféricos (grupo III; n=2), quadrante anterior (grupo IV; n=3) e quadrante posterior (grupo V; n=3). Todos foram submetidos a extensos implantes subdurais (de 64 a 160 contatos) cobrindo todo o córtex potencialmente epileptogênico, sob anestesia geral. Resultados: To...

The diagnostic utility of intracranial EEG monitoring for epilepsy surgery in children

“…The diagnostic utility of IEM for epilepsy surgery in children is poorly defined and varies greatly from the adult epilepsy surgery experience in which mesial temporal sclerosis (MTS) and bilateral implantations are common . In Cukiert's adult study, 72% cases were bilaterally implanted versus only 9% in our study . Children with intractable seizures frequently have extratemporal foci linked to cortical dysplasia and developmental tumors as the primary substrates—only 17% of our series revealed other histopathologic abnormalities.…”

“…The diagnostic utility of IEM for epilepsy surgery in children is poorly defined and varies greatly from the adult epilepsy surgery experience in which mesial temporal sclerosis (MTS) and bilateral implantations are common . In Cukiert's adult study, 72% cases were bilaterally implanted versus only 9% in our study .…”

“…Several studies have confirmed the efficacy of IEM . Most were performed in adults where bilateral epileptogenicity and hippocampal sclerosis are common and often mandate bitemporal implantation.…”

Placement of subdural grids in pediatric patients: technique and results

“…The epileptogenic zone (EZ) is defined as the area of brain necessary and sufficient to generate seizures [9]. Accordingly, accurate localization of the EZ and its relationship to eloquent cortex is crucial for the success of epilepsy surgery [10][11][12][13][14][15][16][17][18]. In defined and specific clinical situations, invasive electrode recordings allow for accurate localization of the EZ and mapping of functional cortical regions.…”

Craniotomy Size for Subdural Grid Electrode Placement in Invasive Epilepsy Diagnostics

“…Among the operative procedures for diagnostic epilepsy surgery, the implantation of subdural grid and strip electrodes accounts for one of the most invasive Stereotact Funct Neurosurg 2019;97:160-168 DOI: 10.1159/000501235 diagnostic workups. Though highly invasive, the placement of subdural electrodes can help to identify the epileptogenic zone and delineate eloquent brain areas such as speech or motor function [5][6][7][8]. For the highest diagnostic yield, the optimal placement of the electrodes is of the utmost importance.…”