Male, 24 years old, with left cerebellar lesion, follow up exam. Redemonstrated is a T1 iso-intense, mildly T2 hyper-intense lesion within the left upper cerebellum just off midline. The lesion measures up to 20 mm in maximal diameter, and has not significantly changed from the prior exam in size. The inferior margin of the lesion is sharply defined and very distinct from the normal cerebellar parenchyma. The superior margin is less well defined and seems to blend with the cerebellar folia which are slightly distorted as a result. No restricted diffusion or significant susceptibility is evident within the lesion. A 6 mm focus of enhancement internal to the lesion is similar in size to that seen previously. Elevated rCBV and rCBF are seen correlating with the enhancing nodule, but not with the remainder of the lesion. Single and multi-voxel spectroscopy of the lesion demonstrate a marked elevation of choline and marked reduction of NAA within the lesion with an abrupt return to a normal pattern beyond the lesion margins.The lesion induces no edema in the surrounding parenchyma, and only minimal mass effect is evident in the form of a slight indentation of the 4th ventricular margin. The brain parenchyma is otherwise normal. No additional areas of signal abnormality are seen. No other pathologic parenchymal or extra-axial enhancement is seen. Incidental developmental venous anomalies are present in the right parietal and left frontal lobes. No abnormal collections are seen and there is no evidence of acute intracranial hemorrhage. The ventricular system is otherwise normal in size and morphology. Bone marrow signal characteristics are normal. Mucosal thickening is seen in the right maxillary sinus.
Since the prior exam, there has been no significant change in the size or morphology of a lesion in the left upper cerebellum. A focus of enhancement internal to the lesion is also unchanged. This enhancing nodule corresponds to elevated rCBV and rCBF, but the remainder of the lesion does not. Spectroscopic assessment of the lesion reveals a marked elevation of choline and reduction of NAA. While some morphologic features of this lesion are suggestive of a dysplastic gangliocytoma (Lhermitte-Duclos), the marked reversal of choline and NAA argues against this diagnosis (most references, in fact, quote a reduction of choline in Lhermitte-Duclos). Perfusion data are also somewhat at odds with this diagnosis as the entire lesion would most typically show elevations of rCBF and rCBV.Given these findings, the possibility of a neoplastic process is considered more likely. Assuming that metastasis has been excluded, the statistically most likely primary tumor to be found in the cerebellum in this age group would be a hemangioblastoma. Other lower grade neoplasms can also be considered. However, the spectroscopic result suggests the possibility of a higher grade neoplasm. In particular, the desmoplastic variant of medulloblastoma can have a similar appearance. Higher grade astrocytoma is also a reasonable consideration. 