Functional surgery in pediatric drug-resistant posterior cortex epilepsy: Electro-clinical findings, cognitive and seizure outcome

Surgical outcomes following resection in patients with language dominant posterior quadrant epilepsy

Posterior quadrant epilepsy surgery, involving the occipital lobe, parietal lobe, or the posterior border of the temporal lobe, accounts for a small percentage of focal resections for medically refractory epilepsy. Prior studies investigating seizure control from posterior quadrant epilepsy surgery are limited. In this study, a retrospective database of patients undergoing surgery for left sided posterior cortex epilepsy at a single large level 4 epilepsy center was analyzed between August 2008 to April 2021 in order to characterize seizure control outcomes. Nine patients presented with epileptogenic foci in the left posterior cortex with a malformation of cortical development deemed as the etiology of seizures for all but one patient. Absolute seizure freedom (Engel I) was achieved in 4 of 9 patients, with the remaining 5 patients achieving an improvement in the frequency of seizures (Engel II/III). Complete resection of the anatomic and physiologic abnormalities was performed in 3 of 4 patients with Engel 1 outcomes and 1 of 5 patients with Class II/III outcomes. Five patients developed new right sided visual field defects, all of which were expected based on the sub-lobar, occipital localization and were viewed as acceptable by the patients and did not interfere with activities of daily living. Overall, our study demonstrates the potential for surgical resection to yield excellent seizure-control outcomes with anticipated, tolerable neurological deficits. This information is important for patients with disabling seizures who may not benefit sufficiently from palliative procedures.

Outcome Predictors of Lesional Posterior Cortex Epilepsy Surgery

BACKGROUND

Lesional posterior cortex epilepsy (PCE) is often drug resistant and may benefit from surgical intervention. In this study, we aimed to identify potential predictive factors associated with seizure recurrence after epilepsy surgery in lesional PCE.

METHODS

We retrospectively reviewed patients with PCE who underwent surgery between 1998 and 2021. They were divided into 2 groups according to seizure outcome; the seizure-free group (group 1) and the non-seizure-free group (group 2). The relationship among clinical factors, electroencephalography (EEG) or cranial magnetic resonance imaging findings, disease, and seizure outcome was investigated.

RESULTS

A total of 60 patients, with a mean age of 27.26 ± 12.35 years (range, 9-61 years), were included in the study. There were 31 patients (51.66%) in group 1 (Engel class I) and 29 patients (48.33%) in group 2 (13 [21.66%], 10 [16.66%], and 6 [10%] patients in Engel class II, III, and IV, respectively), with a mean follow-up of 8.95 ± 6.96 years (range, 1-24 years). No difference was observed regarding age, gender, age at seizure onset, operation type, treatment gap, and presence of bilateral lesions between the groups (P > 0.05). However, bilateral findings on interictal EEG and gliosis as the underlying disease were predictors of seizure recurrence (P < 0.05).

CONCLUSIONS

More than half of the patients (including 2 with bilateral magnetic resonance imaging lesions) were seizure free at long-term follow-up. However, patients with bilateral findings on interictal EEG and gliosis were more likely to have recurrent seizures after surgery. Because lesional PCE is almost always drug resistant and has a potential for favorable outcomes, epilepsy surgery should be considered early.

The intellectual profile of pediatric patients with posterior cortex epilepsy

BACKGROUND

Cognitive functioning in epileptic syndromes has been widely explored in patients with temporal lobe epilepsy (TLE), but few studies have investigated the neuropsychological profile in posterior cortex epilepsy (PCE). In this study, we investigated the presurgical intellectual profile of children and adolescents with drug-resistant PCE.

METHODS

Children and adolescents diagnosed with PCE (n = 25) participated in this study. The data were obtained from medical records, with assessments carried out between the years 2003 and 2019. To compare the intellectual profile, we also included patients diagnosed with frontal (n = 26) and temporal lobe epilepsy (n = 40). The Wechsler Intelligence Scales were used for the assessment of general intelligence.

RESULTS

There was an effect of the brain region on the Working Memory Index (p < 0.01), in which patients with TLE had significantly higher scores than groups with FLE (p < 0.01) and PCE (p < 0.05). We also demonstrated that patients with PCE tended to perform worse in the Processing Speed Index than patients with TLE (p = 0.055). The Full-Scale Intelligence Quotient, Verbal Comprehension, and Perceptual Reasoning indexes did not differ among the brain regions.

CONCLUSIONS

Children and adolescents with PCE demonstrated significant impairment in working memory and processing speed. The pattern of cognitive dysfunction in PCE was similar to that observed in FLE, which expands the evidence of the involvement of frontoparietal networks on cognitive proficiency.

POSTERIOR CORTEX SEIZURES - PEDIATRIC CHALLENGES

Posterior cortex seizures have a complex semiologic presentation that is especially challenging in the pediatric population. Therefore, using clinical presentation in localizing ictal involvement is not sufficient in children, thus making this type of epilepsy quite under-recognized. As most of the ictal symptoms are subjective and could well be overshadowed by symptoms arising from adjacent cortices, primarily temporal and central ones, it is necessary not to overlook this large source of pharmacoresistant epilepsies. The parietal lobe as part of an extensive synaptic network is a great imitator, thus quite often producing inaccurate localization readings on scalp electroencephalography (EEG) due to very scattered interictal discharges and uninformative ictal recordings. Using direct cortical recordings in delineating the epileptogenic zone is helpful in some cases but even highly experienced epileptologists may erroneously interpret some features as arising from other localizations, especially the frontal lobe. Epilepsy surgery from the posterior quadrant is still quite rare and relatively unsuccessful, especially in non-lesional epilepsies due to elaborate mechanisms of connectivity, misleading semiology, and non-localizing EEG recordings, possibly due to insufficiency of parietal cortex synchronicity. Applying the aforementioned to the pediatric age makes it perhaps the most difficult challenge for a pediatric epileptologist.

Cognitive and behavioral profiles of pediatric surgical candidates with frontal and temporal lobe epilepsy

BACKGROUND

We aimed to prospectively analyze memory and executive and social cognitive functioning in patients with drug-resistant frontal lobe epilepsy (FLE) and temporal lobe epilepsy (TLE) with focal lesions and isolate the impact of intellectual ability on specific deficits.

METHODS

A neuropsychological evaluation was performed in 23 children with FLE, 22 children with TLE, and 36 healthy pediatric controls (HCs). Patients in the epilepsy groups had a range of lesions, including low-grade epilepsy-associated tumors (LEAT), focal cortical dysplasia (FCD) type II, and mesial temporal sclerosis (MS).

RESULTS

There were no significant differences between children with FLE and TLE regarding memory, executive, or social cognitive functioning. General Ability Index (GAI) was a predictor of memory, executive function, and social cognition scores and was influenced by age at onset, duration of epilepsy, and number of antiepileptic drugs (AEDs) prescribed at the time of assessment. Working Memory Index scores of patients with TLE, which measure verbal mnesic processing, were significantly lower than those of HCs and patients with TLE. The greatest differences in both clinical groups compared to HCs were recorded in cognitive executive functions, and patients with FLE had lower scores in this domain. Regarding behavioral executive functions, patients with TLE presented impaired emotional control and impulse inhibition and patients with FLE exhibited decreased flexibility.

CONCLUSION

Consistent with previous research, our findings provide further detailed evidence of small differences in cognitive performance among children with FLE and TLE. These differences emerge on analysis of the factors with which deficits are associated.

Networks in Posterior Cortex Epilepsies

Posterior cortex epilepsies comprise all epilepsies with seizures generated from the occipital, parietal, and posterior temporal areas. Seizures usually occur early in life. Visual phenomena during seizures are the hallmark for occipital lobe seizures. Most patients show objective semiology mimicking seizures from other brain regions. Separation of symptomatogenic and epileptogenic zones complicates diagnosis. Understanding networks of propagation is crucial for planning surgery. An overview about typical clinical findings and prognostic value is presented. It explains ways to investigate the epileptogenic zone and propagation pathways to identify seizures from the posterior cortex and better categorize epilepsies for precise surgical treatment.