The hybrid brain PET/MRI method with 18F-FDG in the diagnostics of focal cortical dysplasia in patients with focal drug-resistant epilepsy

BACKGROUND: Up to 30% of the patients with epilepsy are resistant to drug therapy. One of the leading causes of drug-resistant epilepsy in adults and children is the focal cortical dysplasia. The complete resection of the epileptogenic focus in 60–70% of the cases results in the complete resolving of epileptic seizures, however, its detection and determining its margins by using magnetic resonance imaging (MRI) could be a difficult task. Positron emission tomography combined with MRI (PET/MRI) is a new hybrid method of diagnostics, which can be used in case of negative and indefinite MRI results, as well as in case of non-compliance of the MRI findings to the data from videoelectroencephalography (video-EEG-monitoring). AIM: To evaluate the diagnostic possibilities of the hybrid brain PET/MRI method with the use of the radiopharmaceutical — Fluorodeoxyglucose (18F-FDG) in detecting the focal cortical dysplasia in patients with focal drug-resistant epilepsy and to analyze the metabolic patterns in cases of focal cortical dysplasia of various type and location. METHODS: The retrospective analysis of data from 23 patients included the comparison of data from the brain PET/MRI with 18F-FDG, from the MRI and from the video-EEG-monitoring, as well as the analysis of 18F-FDG hypometabolism patterns in cases of focal cortical dysplasia of various types and locations. RESULTS: Focal cortical dysplasia was found in 13 (56.5%) patients by means of MRI, in 22 (95.6%) — by means of PET/MRI with 18F-FDG; 6 (26.1%) were MRI-negative, while in 3 (13%) cases the signs of focal cortical dysplasia were found upon the retrospective targeted analysis of MRI images in the 18F-FDG hypometabolism zone. Small focal area of 18F-FDG hypometabolism in our research was found only when the epileptogenic focus was located in the frontal lobe, which was 75% of the cases of the frontal variant of FCD. In all the cases of the temporal location, the zone was spreading to two and more gyri. As of the moment of article publication, the absence of seizures acc. to the classification by J. Engel (Engel I) in the postoperative period was reported for 11 (84.6%) of 13 operated patients, the Engel II class outcome was registered in 1 (4.3%) patient. CONCLUSION: Brain PET/MRI with 18F-FDG in patients with focal drug-resistant epilepsy increases the detection rates of focal cortical dysplasia by 39% comparing to MRI, including the MRI-negative patients and the patients with minor structural changes. The analysis of PET/MRI images in patients with suspected presence of epileptogenic focus of frontal location requires special attention.