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Arachnoid Cyst (AC)

Last Updated: March 27, 2020

Figure 1: This left middle crania fossa extra-axial lesion follows CSF on all sequences and is in a very common location for arachnoid cyst. Note how the temporal lobe is displaced but is without edema (top left and right). No diffusion restriction is present that would suggest this lesion to be epidermoid cyst (bottom). Given the degree of mass effect, for most other lesions one would expect evidence of cerebral herniation, a finding not typically seen with arachnoid cysts.

Figure 2: This arachnoid cyst posterior to the right cerebellar hemisphere demonstrates T2...