What is the diagnosis?
Fatty filum terminale (aka lipoma of the filum terminale or filar lipoma).
What is the most important feature to try and assess in predicting whether or not this patient is symptomatic?
Level of the conus (below the mid point of L2 suggest a tethered cord).
At what level do you think the conus is in this patient? Why?
No lower than the upper aspect of L2, as the fatty tissue extends that high (an thus so does the filum).
Non contrast CT of the lumbar spine demonstrates a strip of fat density located within the dura and extending from the superior aspect of L2 to L3/4. Degenerative disc change at L3/4 is present with marked disc height loss and end plate sclerosis.
On these images the location of the conus cannot be identified, but can be assumed to be at or above the level of L1/2.