Original
First important step is to have an MRI of your sacral region. I had one general, and an additional with contrast to ensure there were no other ailments in my spine other than the cyst. Unfortunately many people have multiple problems in their spine which can exasperate the symptoms of the Tarlov cyst. Diagnosing these are essential for proper treatment.
Additional tests which help narrow down if the cyst is the cause or other pre-existing conditions is to have a nerve block done on the sacrum to see how symptoms improve. Finally, I had basic tests done on my SI joints, and leg nerves to make sure that symptoms were related to nerves and not joints. This is pretty standard for the process of eliminating other diseases first.