Resection of individually identified high-rate high-frequency oscillations region is associated with favorable outcome in neocortical epilepsy

Objectives: High-frequency oscillations (HFOs) represent a novel electrophysiologic marker of endogenous epileptogenicity. Clinically, this propensity can be utilized to more accurately delineate the resection margin before epilepsy surgery. Currently, prospective application of HFOs is limited because of a lack of an exact quantitative measure to reliably identify HFO-generating areas necessary to include in the resection. Here, we evaluated the potential of a patient-individualized approach of identifying high-rate HFO regions to plan the neocortical resection. Methods: Fifteen patients with neocortical seizure-onset zones (SOZs) underwent intracranial electroencephalographic monitoring. To identify interictal HFOs, we applied an automated, hypersensitive HFO-detection algorithm followed by post hoc processing steps to reject false detections. The spatial relationship between HFO distribution and the SOZ was evaluated. To address high interpatient variability in HFO properties, we evaluated the high-rate HFO region, an unbiased statistical parameter, in each patient. The relationship between resection of the high-rate HFO region and postoperative outcome was examined. Results: Grouped data demonstrated that the rate of ripple (60–200 Hz) and fast ripple (200–500 Hz) was increased in the SOZ (both p < 0.01). Intrapatient analysis of the HFO distribution localized the SOZ in 11 patients. High-rate HFO regions were determined in all patients by an individually adjusted threshold. Resection of high-rate HFO regions was significantly associated with a seizure-free outcome (p < 0.01). The extent/ratio of SOZ or spiking region resection did not differ between seizure-free and seizure-persistent groups. Significance: Intrapatient analysis of high-rate HFOs provides more detailed description of HFO-generating areas and can mark the areas of clinically significant epileptogenicity—a crucial component of the neocortical epileptic network that should be removed to achieve a good outcome. Validating and adopting an unbiased quantitative HFO parameter has the potential to propel wider and prospective utilization of HFOs in the surgical treatment of neocortical epilepsy and to improve its outcome

Prognostic Role of Functional Neuroimaging after Multilobar Resection in Patients with Localization-Related Epilepsy.

To investigate the usage of functional neuroimaging as a prognostic tool for seizure recurrence and long-term outcomes in patients with multilobar resection, we recruited 90 patients who received multilobar resections between 1995 and 2013 with at least 1-year follow-up (mean 8.0 years). All patients were monitored using intracranial electroencephalography (EEG) after pre-surgical evaluation. Clinical data (demographics, electrophysiology, and neuroimaging) were reviewed retrospectively. Surgical outcomes were evaluated at 1, 2, 5 years after surgery, and at the end of the study. After 1 year, 56 patients (62.2%) became Engel class I and at the last follow-up, 47 patients (52.2%) remained seizure-free. Furthermore, non-localized 18F-fluorodeoxyglucose positron emission tomography (PET), identifying hypometabolic areas not concordant with ictal onset zones, significantly correlated with seizure recurrence after 1 year. Non-lesional magnetic resonance imaging (MRI) and left-sided resection correlated with poor outcomes. In the last follow-up, non-localized PET and left-sided resection significantly correlated with seizure recurrence. Both localized PET and ictal-interictal SPECT subtraction co-registered to MR (SISCOM) predicted good surgical outcomes in the last follow-up (69.2%, Engel I). This study suggests that PET and SISCOM may predict postoperative outcomes for patients after multilobar epilepsy and shows comparable long-term surgical outcomes after multilobar resection

Prognostic factors determining poor postsurgical outcomes of mesial temporal lobe epilepsy.

OBJECTIVES:To investigate the long-term postoperative outcomes and predictive factors associated with poor surgical outcomes in mesial temporal lobe epilepsy (MTLE). MATERIALS AND METHODS:We enrolled patients with MTLE who underwent resective surgery at single university-affiliated hospital. Surgical outcomes were determined using a modified Engel classification at the 2nd and 5th years after surgery and the last time of follow-up. RESULTS:The mean duration of follow-up after surgery was 7.6 ± 3.7 years (range, 5.0-21.0 years). 334 of 400 patients (83.5%) were seizure-free at the 5th postoperative year. Significant predictive factors of a poor outcome at the 5th year were a history of generalized tonic clonic (GTC) seizures (odds ratio, OR; 2.318), bi-temporal interictal epileptiform discharge (IED) (OR; 3.107), bilateral hippocampal sclerosis (HS) (OR; 5.471), unilateral HS and combined extra-hippocampal lesion (OR; 5.029), and bi-temporal hypometabolism (BTH) (OR; 4.438). Bi-temporal IED (hazard ratio, HR; 2.186), BTH (HR; 2.043), bilateral HS (HR; 2.541) and unilateral HS and combined extra-hippocampal lesion (HR; 2.75) were independently associated with seizure recurrence. We performed a subgroup analysis of 208 patients with unilateral HS, and their independent predictors of a poor outcome at the 5th year were BTH (OR; 5.838) and tailored hippocampal resection (OR; 11.053). CONCLUSION:This study demonstrates that 16.5% of MTLE patients had poor long-term outcomes after surgery. Bilateral involvement in electrophysiological and imaging studies predicts poor surgical outcomes in MTLE patients

Preoperative evaluations according to seizure outcomes in the last year of follow-up.

<p>Continuous variables are presented as mean ± SD; categorical variables are presented as N (%). IED, interictal epileptiform discharges; IOZ, ictal onset zone; MRI, magnetic resonance imaging; PET, positron emission tomography; SISCOM, subtraction ictal SPECT co-registered with MRI.</p><p>^#PET/SISCOM, Localized/non-localized are determined by ictal onset zone during the intracranial EEG monitoring.</p><p>*p < 0.05, Chi-Square test</p><p>Preoperative evaluations according to seizure outcomes in the last year of follow-up.</p

A Kaplan-Meier survival plots for groups with and without each predictor (A-D) from surgery to seizure recurrence.

<p>In the last year of follow-up, left-sided resection, non-localized PET, and incomplete resection were associated with recurrent seizures. PET, positron emission tomography; EEG, electroencephalography</p

Prognostic factors of seizure outcomes 1 year after surgery.

<p>Continuous variables are presented as mean ± SD; categorical variables are presented as N (%). EDs = epileptiform discharges. Multiple logistic regression was performed using variables, such as age at surgery, the presence of aura, left-sided resection, MRI (lesional vs. non-lesional), hypometabolic areas on PET (localized vs. non-localized) and incomplete resection.</p><p>Prognostic factors of seizure outcomes 1 year after surgery.</p

Prognostic factors of seizure outcomes at the last follow-up.

<p>Categorical variables are presented as N (%). EDs = epileptiform discharges. Multiple logistic regression was performed using variables, such as Lt-sided resection, hypometabolic area on PET (localized vs. non-localized) and incomplete resection.</p><p>Prognostic factors of seizure outcomes at the last follow-up.</p

Patient characteristics.

<p>Continuous variables are presented as mean ± SD unless otherwise indicated. GTC, generalized tonic-clonic; AED, antiepileptic drugs; FT, frontotemporal; FP, frontoparietal; PT, parietotemporal; TO, temporooccipital; TPO, temporoparietooccipital; FTO, frontotemporoocipital; FO, frontooccipital; PO, parietooccipital; FTP, frontotemporooccipital.</p><p>*ictal onset zone (IOZ) identified during intracranial EEG monitoring</p><p>Patient characteristics.</p