MRI IN LHERMITTE-DUCLOS-DISEASE

Lhermitte-Duclos disease (LDD) is a disorder sometimes referred to as a dysplastic gangliocytoma of the cerebellum. This is a focally indole nt growth of the cerebellar cortex in which the folia enlarge due to a profusion of dysplastic cortical neurons and a thickening of the mole cular layer. Loss of Purkinje cells and thinning of medullary white ma tter results. The enlarged folia lose their secondary foldings and asy mmetrically expand the cerebellar hemisphere. These morphologic featur es produce a characteristic pattern on some CTs and all MRIs, affordin g an opportunity for a preoperative diagnosis, MRI of a pathologic spe cimen suggested that the abnormal T-1 and T-2 signals corresponded to the atrophic folial white matter, thickened granule cell layer, and ou ter molecular layer. Because of inherent Hounsfield artifact in poster ior fossa with CT, MRI is the imaging modality of choice, with better visualized striated pattern. The uniqueness of these imaging features obviates the need for an obligatory biopsy for asymptomatic patients a nd either permits more definitive planning for surgical decompression or, in restricted lesions, guides more assuredly complete excision of the cerebellar mass.