Flumazenil and Glucose PET Compared for Presurgical Delineation of Seizure Foci
Flumazenil and Glucose PET Compared for Presurgical Delineation of Seizure Foci
Abstract & Commentary
Source: Juhasz C, et al. Relationship of flumazenil and glucose PET abnormalities to neocortical epilepsy surgery outcome. Neurology. 2001;56:1650-1658.
The success of surgery for intractable epilepsy depends upon the accurate presurgical delineation of the regions responsible for generating seizures. Juhasz and associates analyzed whether the extent of cortex showing 2-deoxy-2 [18F] fluoro-D-glucose (FDG) or [11C] flumazenil (FMZ) abnormalities correlated with the outcome of epilepsy surgery. They studied 15 young patients (8 girls and 7 boys, mean age 12 ± 7 years) with medically intractable partial epilepsy of neocortical origin who underwent cortical resection. Preoperative testing included brain MRI (normal in 9, abnormal in 6), EEG monitoring, and FDG and FMZ PET examinations. The extent of preoperative PET abnormalities was correlated with outcomes: seizure free (n = 8) or not seizure free (n = 7).
Large preoperative FMZ PET abnormalities were associated with poor outcome (r = 0.57; P = 0.025). Larger areas of nonresected cortex with preoperative FMZ PET abnormalities in the lobe of seizure onset also were associated with worse outcomes in the whole group (r = 0.66; P = 0.007), in patients with extratemporal resection (r = 0.73; P = 0.007) and in those with no lesion on MRI (r = 0.06; P = 0.049). Patients who were seizure free had smaller nonresected cortex with FMZ PET abnormalities than those who continued to have seizures (P = 0.022). No significant correlations were found between nonresected FDG PET abnormalities and surgical outcome.
Commentary
This study showed first that better outcomes of neocortical epilepsy surgery can be achieved when preoperative cortical FMZ PET abnormalities are smaller and when the bulk of the cortex with FMZ PET abnormalities in the lobe of the epileptic focus is resected. This was true both for patients with nonlesional and extratemporal epilepsy.
The second finding was that the size of nonresected FDG PET abnormalities was not a predictor of outcome of neocortical epilepsy surgery. Other studies have shown that the degree of temporal lobe hypometabolism measured by FDG PET is a strong predictor of outcome after temporal lobectomy (Radthe RA, et al. Neurology. 1993;43:1088-1092; Manno EM, et al. Neurology. 1994;44:2331-2336; Theodore WH, et al. Epilepsia. 1997;38:81-86). In the present study, neocortical FDG PET abnormalities generally were larger and occasionally were localized to different cortical areas than the FMZ PET abnormalities. Although FDG PET successfully indicated some abnormality in the lobe of seizure onset, the size of the region of glucose hypometabolism did not reflect the exact anatomic location or size of the epileptogenic cortex.
FMZ PET seems to be particularly useful in defining the epileptogenic region in patients with nonfocal EEG results and large FDG PET abnormalities. —John J. Caronna
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