Metabolic patterns and seizure outcomes following anterior temporal lobectomy

Abstract

Objective: We investigated the relationship between the interictal metabolic patterns, the extent of resection of 18 Ffluorodeoxyglucose positron emission tomography ( 18 FDG-PET) hypometabolism, and seizure outcomes in patients with unilateral drug-resistant mesial temporal lobe epilepsy (MTLE) following anterior temporal lobe (TL) resection. Methods: Eighty-two patients with hippocampal sclerosis or normal magnetic resonance imaging (MRI) findings, concordant 18 FDG-PET hypometabolism, and at least 2 years of postoperative follow-up were included in this 2-center study. The hypometabolic regions in each patient were identified with reference to 20 healthy controls (p < 0.005). The resected TL volume and the volume of resected TL PET hypometabolism (TLH) were calculated from the pre-and postoperative MRI scans coregistered with interictal 18 FDG-PET. Results: Striking differences in metabolic patterns were observed depending on the lateralization of the epileptogenic TL. The extent of the ipsilateral TLH was significantly greater in left MTLE patients (p < 0.001), whereas right MTLE patients had significantly higher rates of contralateral (CTL) TLH (p = 0.016). In right MTLE patients, CTL hypometabolism was the strongest predictor of an unfavorable seizure outcome, associated with a 5-fold increase in the likelihood of seizure recurrence (odds ratio [OR] = 4.90, 95% confidence interval [CI] = 1.07-22.39, p = 0.04). In left MTLE patients, greater extent of resection of ipsilateral TLH was associated with lower rates of seizure recurrence (p = 0.004) in univariate analysis; however, its predictive value did not reach statistical significance (OR = 0.96, 95% CI = 0.90-1.02, p = 0.19). Interpretation: The difference in metabolic patterns depending on the lateralization of MTLE may represent distinct epileptic networks in patients with right versus left MTLE, and can guide preoperative counseling and surgical planning.

18F-FDG PET-guided diffusion tractography reveals white matter abnormalities around the epileptic focus in medically refractory epilepsy: implications for epilepsy surgical evaluation

“…AI mapping is thus a promising tool for guiding assessment of surgical candidacy in epilepsy, especially in MRI-negative cases. Furthermore, similar to our findings, past studies have reported FDG-PET hypometabolism in contralateral brain regions in some epilepsy patients (Aparicio et al 2016;Cahill et al 2019), presumably due to spread of epileptic activity across hemispheres. Despite these challenges with FDG-PET specificity, we were still able to show that FDG-PET can aid detection of the epileptogenic zone and assessment of surgical candidacy in epilepsy, especially when combined with DTI.…”

“…Numerous standalone PET and diffusion MRI studies have reported functional and structural alterations in MRE (Henry and Pennell 1998;Knowlton 2006;Focke et al 2008;Lin et al 2008;Thivard et al 2011;James et al 2015;Labate et al 2015;Burneo et al 2015;Sivakanthan et al 2016;Jiang et al 2017;Güvenç et al 2018;Cahill et al 2019), however, very few studies have assessed relationships between FDG-PET and diffusion MRI findings in epilepsy. Similar to our study, one previous report also found microstructural alterations (decreased FA and increased apparent diffusion coefficient) Note: EF localization concordance between AI mapping and the clinical hypothesis is reported in the second column Abbreviations: +, concordant with clinical hypothesis or improved confidence after PET/DTI; ++, PET/DTI improved confidence and indicated that the patient may benefit from an anterior temporal lobectomy; −, discordant with clinical hypothesis or unchanged confidence after PET/DTI in WM adjacent to the epileptic zone identified by FDG-PET hypometabolism (Lippé et al 2012), while another study revealed that metabolic and structural alterations seen using FDG-PET and DTI involve similar brain regions in mesial temporal lobe epilepsy (Aparicio et al 2016).…”

“…Medically refractory epilepsy (MRE) affects approximately 30% of epilepsy patients and is defined as a chronic neurological disorder where seizures persist despite administration of anti-epileptic drugs (AEDs) (Helmstaedter et al 2003;Richardson et al 2004;Jiang et al 2017). In some MRE patients, surgical resection of the epileptic focus (EF)the brain region responsible for seizures-can alleviate seizure occurrence and improve overall quality of life (Richardson et al 2004;Caciagli et al 2014;Cahill et al 2019). Positive surgical outcomes are highly dependent on accurate identification of the EF to ensure the epileptic region is safely removed without harming surrounding healthy brain tissue (Bettus et al 2009).…”

“…PET, on the other hand, is the most sensitive non-invasive clinical tool for identifying the EF especially in cases where MRI is negative or equivocal (Burneo et al 2015). 18 F-Fluorodeoxyglucose PET (FDG-PET) can be used to detect the EF as brain areas showing decreased glucose uptake (glucose hypometabolism) (Sarikaya 2015;Burneo et al 2015;Aparicio et al 2016;Cahill et al 2019). Glucose hypometabolic regions of interest (ROIs) are often identified by visual assessment of FDG-PET images, however, some abnormalities may be missed during this process.…”

Quantitative [18]FDG PET asymmetry features predict long-term seizure recurrence in refractory epilepsy

“…Several studies have identified important temporal and extratemporal regions on functional and structural imaging that predict prognosis [3][4][5][6][7]. A recent study suggests that lateralized hypometabolism and extent of resection are strong indicators of seizure recurrence with differential outcomes based on seizure lateralization [8]. Quantification has the advantage of precision and objectivity over qualitative visual [ 18 F]FDG-PET interpretation, potentially improving presurgical planning.…”