Incidental finding of a intrathecal, extramedullary mass.  The differential includes; schwannoma, neurofibroma or a metastasis. The former is in the most likely in this case, given the imaging characteristics.  Note the similarity in appearances, especially on the post contrast sequences to a schwannoma at the IAM - avidly enhancing with small cystic areas of degeneration within.

The appearances were static on a repeat scan 5 months later.