Surgical outcome in PET‐positive, MRI‐negative patients with temporal lobe epilepsy

Abstract

SUMMARYPurpose: Fluorodeoxyglucose positron emission computed tomography (FDG-PET) hypometabolism is important for surgical planning in patients with temporal lobe epilepsy (TLE), but its significance remains unclear in patients who do not have evidence of mesial temporal sclerosis (MTS) on magnetic resonance imaging (MRI). We examined surgical outcomes in a group of PETpositive, MRI-negative patients and compared them with those of patients with MTS. Methods: We queried the Thomas Jefferson University Surgical Epilepsy Database for patients who underwent anterior temporal lobectomy (ATL) from 1991 to 2009 and who had unilateral temporal PET hypometabolism without an epileptogenic lesion on MRI (PET+/MRI)). We compared this group to the group of patients who underwent ATL and who had MTS on MRI. Patients with discordant ictal electroencephalography (EEG) were excluded. Surgical outcomes were compared using percentages of Engel class I outcomes at 2 and 5 years as well as KaplanMeier survival statistic, with time to seizure recurrence as survival time. A subgroup of PET+/MRI) patients who underwent surgical implantation prior to resection was compared to PET+/MRI) patients who went directly to resection without implantation. Key Findings: There were 46 PET+/MRI) patients (of whom 36 had 2-year surgical outcome available) and 147 MTS patients. There was no difference between the two groups with regard to history of febrile convulsions, generalized tonic-clonic seizures, interictal spikes, depression, or family history. Mean age at first seizure was higher in PET+/MRI) patients (19 ± 13 vs.14 ± 13 years, Mann-Whitney test, p = 0.008) and disease duration was shorter (14 ± 10 vs. 22 ± 13 years, student's t-test, p = 0.0006). Class I surgical outcomes did not differ significantly between the PET+/MRI) patients and the MTS group (2 and 5 year outcomes were 76% and 75% for the PET+/MRI) group, and 71% and 78% for the MTS group); neither did outcomes of the PET+/MRI) patients who were implanted prior to resection versus those who went directly to surgery (implanted patients had 71% and 67% class I outcomes at 2 and 5 years, whereas. nonimplanted patients had 77% and 78% class I outcomes, p = 0.66 and 0.28). Kaplan-Meier survival statistics for both comparisons were nonsignificant at 5 years. Dentate gyrus and hilar cell counts obtained from pathology for a sample of patients also did not differ between groups. Significance: PET-positive, MRI-negative TLE patients in our study had excellent surgical outcomes after ATL, very similar to those in patients with MTS, regardless of whether or not they undergo intracranial monitoring. These patients should be considered prime candidates for ATL, and intracranial monitoring is probably unnecessary in the absence of discordant data.

Surgical Treatment of MRI-Negative Temporal Lobe Epilepsy Based on PET: A Retrospective Cohort Study

“…However, even if the resolution of MRI keeps elevating, there are still many TLE cases in which no meaningful abnormality can be observed. Such cases are classified as MRI- TLE, accounting for approximately 20-30% of TLE [3,4,10,11]. Recently, many MRI- TLE are surgically treated and the prognoses are satisfactory.…”

“…After successful standard anterior temporal lobectomies (sATLs), most patients can achieve excellent outcome. However, epilepsy surgeons frequently run into TLE without meaningful abnormality on MRI, which is the so-called MRI-negative TLE (MRI- TLE), and this accounts for 20-30% of all TLE [3,4]. Multiple one-center retrospective studies reported that the rate of favorable surgical prognosis (Engel grade I + II) of MRI- TLE is approximately 45-90% [2,5].…”

“…According to one meta-analysis involving 46 independent studies, the predictive value of PET to good surgical outcome (Engel I + II) of MRI- TLE is 80% [6]. Although preoperative invasive electroencephalogram (EEG) is still applied by many centers for such types of TLE, more and more epilepsy centers operate on these patients directly without invasive intracranial electrode implantation [2,4,5]. This study retrospectively analyzes 60 cases of unilateral TLE which were surgically treated in our department, including 41 cases of HS + TLE and 19 cases of MRI- TLE.…”

Automatic Lateralization of Temporal Lobe Epilepsy Based on MEG Network Features Using Support Vector Machines

“…TLE is traditionally associated with mesial temporal sclerosis (MTS), cell loss, and gliosis in the hippocampus, entorhinal cortex, and amygdala [2]. Currently, surgical intervention is the main choice of treatment for medically intractable TLE [3]. However, surgery helps only 70% of patients become seizure free [4].…”

Nuclear Medicine Methods in Epilepsy

“…(10). MR negatif grupta yapılan çalışmalar bu hastalarda PET'in önemini açık olarak ortaya koymaktadır (11). Hatta farklı bir radyofarmasötik madde olan F-18 FCWAY isimli ajan ile yapılan PET çalışmaları bu ajanın MR negatif grupta FDG'den daha faydalı olabileceğini göstermektedir (12).…”