Optimisation des techniques avancées en IRM cérébrale dans la détection des lésions développementales épileptogènes

Abstract : Focal cortical dysplasia type 2 (FCD2) is a common cause of intractable partial epilepsy surgically treatable. Their detection by MRI is an independent factor of good prognosis. The MR imaging diagnosis remains difficult with up to 40% negative MRI. Our main objective is to improve the detection of FCD2from conventional sequences, to assess the relevance of increased magnetic field and validate new tools for detection, in particular by identifying sulcal abnormalities associated with FCD2 automatically and visually. This study was carried out from one of the largest cohort of patients (> 80 patients) with histologically proven FCD2. The evaluation of the frequency of each MR signs showed that, although no abnormality is seen in 41% of cases, the different signs in patients with a positive MRI were never isolated and the combination of the 3 most suggestive signs of FCD2 (cortical thickening, bluring of the gray-white matter interface and "transmantle sign") was found in 27 patients (64%), indicating that MRI can be very suggestive. By increasing the magnetic field from 1.5 to 3T MRI detection rate is only slightly changed but characterization of FCD2 is improved thanks to a better visualization of the " transmantle sign " considered as a MR signature of FCD2. The automated sulcus analysis based on the calculation of a new parameter called "sulcal energy" identifies abnormal sulcal patterns in patients with FCD2 in the central region in comparison to healthy subjects. This result underlines the importance of the identification of sulci and could provide an additional criterion for detecting and locating the lesion in patients with negative MRI. Finally, the visual analysis of sulci by 3D reformatting of the cortex allowed us to describe a new MR sign of FCD2 in the central region: a sulcal pattern called the "Power Button Sign". Given its excellent reproducibility and specificity, it could be used as a new major diagnostic criterion of FCD2 in the central region. All these results contribute to the better understanding of the developmental processes involved in the pathophysiology of FCD2 and offers many opportunities for improving their MR detection.
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Charles Mellerio. Optimisation des techniques avancées en IRM cérébrale dans la détection des lésions développementales épileptogènes. Médecine humaine et pathologie. Université René Descartes - Paris V, 2014. Français. ⟨NNT : 2014PA05T025⟩. ⟨tel-01073770⟩

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