Magnetic Resonance Imaging Diagnosis of Focal Cerebellar Cortical Dysplasia

Focal cerebellar cortical dysplasia is an extremely rare disease. The diagnosis could be easily missed on routine computed tomography (CT) and magnetic resonance imaging (MRI) images because the lesion is isodensity on CT images, and isointense to normal gray and white matter on MRI images. Focal distortion of the cerebellar gray-white matter can be found if MRI images are surveyed carefully. Here we report an adult case of focal cerebellar cortical dysplasia and review the literatures. Correspondence Author to: Tsung-Hsien Chou Department of Radiology, Pingtung Hospital, Department of Health, Executive Yuan, Pingtung, Taiwan No. 270, Zih-You Road, Pingtung 900, Taiwan J Radiol Sci 2011; 36: 187-190 Focal cerebellar cortical dysplasia 188 J Radiol Sci September 2011 Vol.36 No.3 or other abnormal density in the brain. Bilateral temporal horns are slightly dilated. Bilateral cerebral hemispheres are unremarkable. Because of cerebellar tumor was suspected by CT images, MRI study was recommended by radiologist for further evaluation and was performed few days later. MRI study was performed on Philips Achieva 1.5T SE with axial T1W_SE, T2W_TSE, T2W_FLAIR, DWI, T2W_FFE, sagittal T2W_TSE, coronal T2W_FLAIR, and post-contrast (Dotarem, 0.2 ml/kg i.v. Guerbet S.A.) enhanced T1W_FFE pulse sequences with reconstructed images in three orthogonal planes. Folia malformation with deformed gray-white matter at posterior lobe of right cerebellar hemisphere was noted (Fig. 2). The lesion appeared isointense to white matter on T2W, FLAIR and DWI images without abnormal hyperintensity nor contrast enhancement. Focal cerebellar cortical dysplasia was diagnosed. Tumor was excluded because the lesion showed findings of folial thickening, deformed gray-white matter junction, absent contrast enhancement. She received medical treatment for her symptoms. Her symptom/sign did not change during 4 months follow-up period. DISCUSSION Focal cerebellar cortical dysplasia is an extremely rare disease with etiology still not clearly understood. In the retrospective review study by Sandeep Patel and A James Barkovich [1], 70 patients with diagnosis of some form of cerebellar malformation were summated during 15 years. Among the cases, only two were focal cerebellar cortical dysplasia. They also proposed an imaging-based classification system of cerebellar malformations by MRI finding because limited understanding of cerebellar embryology, limited histologic studies of these disorders, and lack of a practical classification of cerebellar malformations [1]. The cerebellar malformations were initially divided into those with hypoplasia or dysplasia, then into focal or diffuse malformations. And finally, the cerebellar lesions were separated by other features, such as brain stem and cerebral involvement. In the category of cerebellar focal dysplasia, two subdivisions were defined: 1. Isolated vermian dysplasia; which includes rhombencephalosynapsis and molar tooth malformations (associated with brain stem dysplasia); 2. Figure 1. Non-contrast brain CT reveals suspicious isodense ill-defined mass lesion (white arrow) at tonsil of right cerebellar hemisphere with compression of 4th ventricle. Figure 1 Focal cerebellar cortical dysplasia 189 J Radiol Sci September 2011 Vol.36 No.3 2a