lunedì 17 maggio 2010

Focal cortical dysplasia


Figure 1 and Figure 2: Axial FLAIR and T2W MR images demonstrate blurring of the grey-white junction with high signal intensity in the subcortical white matter of the right frontal lobe. Adjacent cortical ribbon thickening is also present. These findings are characteristic of focal cortical dysplasia.

Diagnosis: Focal cortical dysplasia

Focal cortical dysplasia (FCD) is a congenital disease in which the neurons arrange abnormally in focal areas of the cerebral cortex. It is a common cause of intractable and drug resistant epilepsy, and while seen mostly in the pediatric population, it is not uncommon to see the disease manifest itself in adulthood. Radiologic diagnosis is important for pre-surgical planning and can have prognostic implications.

FCD can be further sub-typed based on histopathology. In Type I FCD there is architectural distortion of the cerebral cortex alone without any abnormal cells. In Type II FCD, however, pathology will demonstrate both architectural distortion and dysmorphic neurons. This includes the characteristic elliptically shaped neuron with a displaced nucleus and lack of axons, known as the “balloon cell”. While the pathologic diagnosis is made retrospectively, clinically those with Type I FCD generally are responsive to medical therapy, while those with Type II FCD are resistant.

Regardless of the pathologic type of FCD, patients that demonstrate preoperative imaging findings tend to have a better outcome after surgery than those who do not demonstrate any findings. The characteristic MR abnormalities in FCD include blurring of the grey-white junction, abnormal high T2 signal in the subcortical white matter, and adjacent focal cortical thickening. Often these findings are very subtle and may not be detected on MR imaging alone. In such cases MR/FDG-PET fusion has been utilized for more sensitive detection. Surgery is the mainstay of treatment for these patients.

Extra: Balloon cells are large elliptical shaped cells with displaced nuclei and are characteristic of focal cortical dysplasia.

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