Hm. Unless there's a bad smell in here, I guess no one is sure.

Without the benefit of an informed opinion, my best shot is probably to look at words which have "calculare" as a root, and see what their adjectival endings are.

The adjective of "calculate" is "calculative"; so, shouldn't the adjective of "dyscalculia" be "dyscalculative" ?

What do you think?