 MRI: An area of T2 hyperintense, disorganized appearing tissue is redemonstrated within the cerebellar vermis measuring 22 x 25 mm. This lesion contains several foci of internal susceptibility corresponding to calcification on prior head CT, along with small foci of noncontiguous nodular enhancement. On some slices, there is the suggestion of a striated or "tigroid" appearance within the lesion best appreciated on thin slice T2 axial images. Mild bulging of the posterior wall of the fourth ventricle is seen without significant mass effect or hydrocephalus. The ventricles and sulci are unchanged.There are findings consistent with patient's known Chiari I malformation with inferior cerebellar tonsillar herniation and flattening. There is no acute infarct or midline shift. There are no separate areas of suspicious intracranial enhancement.MRS: Single voxel short and long TE spectroscopy of the cerebellar vermian lesion shows uniformly decreased myoinositol, choline, creatine and NAA peaks. Interrogation of normal-appearing cerebellar tissue demonstrates a normal spectroscopic pattern.
Midline cerebellar vermian lesion with internal foci of calcification and scattered small foci of enhancement. There has been no significant interval change since prior imaging. Spectroscopic assessment of this lesion shows uniform reduction of all major detectable metabolites. This pattern is non specific but argues against an aggressive, highly proliferative process. The differential diagnosis would include non neoplastic or equivocally neoplastic processes such as dysplastic cerebellar gangliocytoma (Lhermitte-Duclos disease) or simply a developmental dysplasia of the cerebellum. Uniform reduction of MRS peaks has been reported in Lhermitte-Duclos. Low grade tumors such as ganglioglioma or pilocytic astrocytoma among others may also be considered, but the MRS features are not typical. 