Is 11C-flumazenil PET superior to 18FDG PET and 123I-iomazenil SPECT in presurgical evaluation of temporal lobe epilepsy?

Abstract

Objective-To determine the contribution of 58FDG PET, "IC-flumazenil PET, and 123I-iomazenil SPECT to the presurgical evaluation of patients with medically intractable complex partial seizures. Methods-Presurgical evaluation was performed in 23 patients, who were considered candidates for temporal lobe resective surgery (14 females and nine males with a median age of 34 (range 13 to 50) years).The presurgical diagnosis was based on seizure semiology as demonstrated with ictal video recording, ictal and interictal scalp EEG recordings, and MRI. Results-Eighteen patients had convergent findings in clinical semiology, interictal and ictal EEG with scalp and sphenoidal electrodes, and MRI that warranted surgery without depth EEG (DEEG). In five patients with insufficient precision of localisation, DEEG with intracerebral and subdural electrodes was performed. MRI showed abnormalities in 22 out of 23 patients. Of these 22, 18 had mesial temporal sclerosis. This was limited to the mesial temporal lobe in four and more widespread in the temporal lobe in 14 patients. In one patient only enlargement of the temporal horn was found and in three others only white matter lesions were detected. 18FDG PET showed a large area of glucose hypometabolism in the epileptogenic temporal lobe, with an extension outside the temporal lobe in 10 of 23 patients. Only in one of these patients DEEG showed extratemporal abnormalities that were concordant with a significant extratemporal extension of hypometabolism in 18FDG PET. 55FDGPET was compared with the results of scalp EEG: in none of the patients was an anterior temporal ictal onset in scalp EEG related to a maximum hypometabolism in the mesial temporal area. By contrast, the region of abnormality indicated by 55C-flumazenil PET was much more restricted, also when compared with DEEG findings. Extension of abnormality outside the lobe of surgery was seen in only two patients with "IC-flumazenil and was less pronounced compared with the intratemporal abnormality. Both 18FDGPET and "IC-flumazenil PET reliably indicated the epileptogenic temporal lobe.

A systematic review of the effectiveness and cost-effectiveness of neuroimaging assessments used to visualise the seizure focus in people with refractory epilepsy being considered for surgery

“…47 One study reported results for all patients included in the study and also allowed results to be extracted separately for patients in whom EEG localised the seizure focus. 40 This study reported very similar results for both sets of data. A second study reported data for two different tracers: IDEX and HMPAO.…”

“…40 Another study also reported results separately for two different tracers [␣-methyl-L-tryptophan (AMT) and FDG]. 58 A further study reported results for two methods of interpretation of the PET scans: visual and statistical parameter mapping (SPM) analysis.…”

“…PET localised a seizure focus in all patients in two studies, although some were partially or incorrectly localised. 40,63 The proportion of patients in whom PET partially localised the seizure focus ranged from 0 to 62%, with all but two studies having <25% partially localised. 40,58 Eight studies did not report any patients with partially localised scans; however, one of these did not report data in a format that would allow extraction of data on partially localised scans.…”

“…40,63 The proportion of patients in whom PET partially localised the seizure focus ranged from 0 to 62%, with all but two studies having <25% partially localised. 40,58 Eight studies did not report any patients with partially localised scans; however, one of these did not report data in a format that would allow extraction of data on partially localised scans. 81 Nine studies reported incorrectly localised scans, 36,43,52,53,58,63,65,81,102 with the proportion ranging from 3 to 25%.…”

“…30-32,40,41,46, 30,31,46,77 One study allowed results for all patients and for those in whom EEG had localised the seizure focus to be extracted separately. 40 The results for all patients were included in the main analysis below. One study provided results separately for two tracers, HMPAO and [ 123 I]iododexetimide (IDEX).…”