Secondary bilateral synchrony due to fronto-mesial lesions: an invasive recording study

Abstract

-Frontal lobe epilepsies may present difficulties in focus localization in the pre-operative work-up for epilepsy surgery. This is specially true in patients with normal MRIs. We report on a 16 years-old girl that started with seizures by the age of 8 years. They were brief nocturnal episodes with automatisms such as bicycling and boxing. Seizure frequency ranged from 4-10 per night. Scalp EEG showed few right frontal convexity spiking and intense secondary bilateral syncrhony (SBS). High resolution MRI directed to the frontal lobes was normal. Ictal SPECT suggested a right fronto-lateral focus. Ictal video-EEG showed no focal onset. She was submitted to invasive recordings after subdural plates implantation. Electrodes covered all the frontal convexity and mesial surface bilaterally. Ictal recordings disclosed stereotyped seizures starting from the right mesial frontal. Using a high-resolution tool to measure intra and interhemispheric latencies, the timing and direction of seizure spread from the right fronto-mesial region were studied. Motor strip mapping was performed by means of electrical stimulation. She was submitted to a right frontal lobe resection, 1.5 cm ahead of the motor strip and has been seizure free since surgery (8 months). Pathological examination found a 4 mm area of cortical dysplasia. Invasive studies are needed to allow adequate localization in patients with non-localizatory non-invasive work-up and may lead to excellent results in relation to seizures after surgery.KEY WORDS: frontal lobe epilepsy, surgery, sub-dural electrodes. Sincronia bilateral secundária devido a lesões mesiais: estudo com registros invasivosRESUMO -Podem ocorrer dificuldades na localização de focos nas epilepsias frontais, principalmente nos pacientes que possuem ressonância magnética (RM) normal. Relatamos o caso de uma paciente de 16 anos de idade que começou a apresentar crises convulsivas aos 8 anos. As crises eram breves episódios noturnos que incluíam automatismos tais como pedalar e boxear. A frequência das crises era 4-10 por noite. O eletrencefálograma (EEG) mostrou raras descargas na convexidade frontal direita e intensa sincronia bilateral secundária não localizatória. A RM foi normal e o SPECT ictal sugeriu um foco frontal lateral direito. Realizou-se implante com eletrodos subdurais cobrindo a convexidade frontal e a superfície mesial bilateralmente. Registros ictais mostraram o início das crises na superfície fronto-mesial direita. As latências intra e inter-hemisféricas foram medidas com aparelhagem de alta resolução. O mapeamento da área motora foi realizado através de estimulação elétrica. A paciente foi submetida a ressecção frontal 1,5 cm anterior à área motora. Está sem crises desde a cirurgia há 8 meses. O estudo anátomo-patológico mostrou uma área de 4 mm de displasia cortical. Estudos invasivos são necessários para permitir a localização adequada para o tratamento cirúrgico das epilepsias em pacientes com focos frontais e RM normais. A despeito da maior complexidade, os resultados qua...

Eyelid myoclonia seizures in adults: An alternate look at the syndrome paradox

“…In accordance to the secondary synchronization seen in patients with focal-lateralized structural lesions [40,41], all of our cryptogenicsymptomatic cases with EM seizures had generalized discharges on EEG, potentially leading to confusion and misdiagnosis. MRI findings, neurological examinations, and asymmetrical beginning of polyspike- wave discharges on EEG may be additional clues in diagnosing symptomatic epilepsy patients with EMs and in preventing misdiagnosis as IGEs or EMA.…”

Objective Detection of Epileptic Foci by18F-FDG PET in Children Undergoing Epilepsy Surgery

“…Seizures arising from medial (parasagittal) cortical regions can give rise to secondary bilateral synchrony on the ictal scalp electroencephalography (33,34), and it may be challenging to identify such foci for surgical resection. SPM analysis appears to be a particularly useful approach for assessing medially located seizure foci and can contribute to optimal subdural grid coverage.…”

Lesion‐negative anterior cingulate epilepsy

“…It can pose significant lateralization/localization problems and often necessitates invasive evaluations (table 1). It is well described in frontal lobe epilepsies, especially in the mesial region and is a frequent lateralization conundrum (Marcus and Watson, 1968;Musgrave and Gloor, 1980;Cukiert et al, 1991;Cukiert et al, 1999;Lacruz et al, 2007;Umeoka et al, 2010;Iwasaki et al, 2011). Extensive connectivity between homotopic regions of both frontal lobes is a likely explanation (Lacruz et al, 2007;Iwasaki et al, 2011).…”

“…Extensive connectivity demonstrated between homotopic cingulate and mesial frontal regions across the corpus callosum in mammals (Marcus and Watson, 1968;Musgrave and Gloor, 1980;Umeoka et al, 2010;Iwasaki et al, 2011) may provide the basis for the lateralization difficulties encountered in humans. Localization and lateralization challenges are compounded in MRI-negative patients (Cukiert et al, 1999;McGonigal et al, 2008). Although semiological descriptions of ACE exist (Bancaud and Talairach, 1992;Alkawadri et al, 2013), recent reports suggest semiological Lesion-negative anterior cingulate epilepsy heterogeneity between different frontal regions and even within the subgroup of ACE (Alkawadri et al, 2013;Bonini et al, 2014).…”