What does it mean for Reuben Abati as Dr Okupe is appointed SSA on public affairs?

President Goodluck Jonathan yesterday appointed Dr. Doyin Okupe as his Senior Special Assistant on Public Affairs. The medical doctor was former spokesman to President Obasanjo.

Reuben Abati is Special Adviser on Media and Publicity to President Jonathan, now there's a Senior Special Assistant on Public Affairs...is there any difference in their respective duties?