Ectopic cerebellar tissue of the posterior cranial fossa: diffusion tensor tractography and MR spectroscopy findings

Well-differentiated ectopic cerebellar tissue is extremely rare, with only 12 cases in the literature. Here, we describe a unique case of radiologically proven ectopic cerebellar tissue, using diffusion tensor tractography (DTT) and MR spectroscopy (MRS) findings, in a 6-day-old newborn.

A 6-day-old newborn who had previously a fetal MRI referred to our department with the suspicion of an arachnoid cyst of the posterior fossa. Including the central nervous system, all of his physical examination tests were normal. Postnatal transcranial ultrasound (US) imaging and brain MRI also revealed a large posterior fossa cyst and a solid mass nearby the cerebellar tissue. The tissue showed a small connection and isointense signal with the cerebellum. Upon DTT, both the cerebellum and nearby solid tissue represented the same FA values. Tractographic studies showed a connection with fibers extending along the left cerebellar hemisphere from this tissue. The single voxel MRS of this solid tissue also revealed high choline (Cho) and a smaller N-acetylaspartate (NAA) concentration similar to that of the normal newborn cerebellum.

Ectopic cerebellar tissue can be characterized by advanced neuroimaging tools, like DTT and MRS, which provide information about brain metabolite concentrations and the microstructural integrity. In this way, unnecessary surgery can be avoided in order to obtain a histopathological diagnosis.