Focal cortical dysplasias: neuroradiological findings and differential diagnosis

Purpose: To describe MRI findings of four types of focal cortical dysplasia (FCD) and compare them with diagnostic criteria reported in the literature. Material and Methods: This study includes eight patients with seizures in whom cranial MRI diagnosed an FCD, with histologic confirmation in two patients. Results: In all patients, the dysplastic cortex was thickened. Its signal was hyperintense on T2-weighted and FLAIR images, but variable on T1-weighted images. Blurring of the corticomedullary junction was present in 5 patients. In one patient, MRI demonstrated vascular proliferation within the FCD. Type I or II FCD was diagnosed in six patients, and transmantle FCD and type IV FCD with capillary proliferation in one patient each. Discussion: Thickening and hyperintensity of the cortex on T2-weighted and FLAIR images are more reliable signs of FCD than blurring of the gray matter-white matter junction and signal changes on T1-weighted images. Typical vascular proliferation may be detectable with MRI and suggests the diagnosis of FCD with glial proliferation. Edema, calcification, or pathologic contrast enhancement has not been observed in FCD to date. (orig.)