Case 44 Answer: Spina Bifida (see below)

Yes, this was a bit tricky, but I tried to clue you in with the history. Windowing/leveling may have been helpful but I think the wide posterior fusion defect at L5 (and below) is readily obvious.

A vast majority of the times this is ignored on interpretation (often because the posterior lamina approximate but aren’t completely fused) but I bring this case to you because you need to be careful. Look how large this defect it. And the defect extends down much or all of the sacrum. This could be a simple bony fusion defect but due to the size of each defect as well as the extensive lower spine involvement, it would be wise to suggest an MRI to see is there is neural involvement.

This patient did not have confirmatory imaging because of her known history of spina bifida with meningocoele.

Remember: Spina bifida occulta by itself should NOT be associated with back pain.

Reference: http://radiopaedia.org/articles/spina-bifida