Itching a Sign of Saline Leakage?

Usually, a leak doesn't cause itchiness. You could be allergic to something else. If you do have a rupture, then you'd notice the deflation since it generally occurs quickly. I suggest you see your doctor for a physical exam.

It is probably more important to assess the breast size as a sign of leakage. I am not aware of leakage causing itching and threfore I think they are unrelated.

You would know if you had leakage of your implants as one would be getting smaller than the other.  Itching is not a symptom for leaking, there really is no sign or symptom other can the breast getting smaller.

Hope that helps.