I believe blightcp from this forum had one done at Brigham and Women's in MA. You can look up his posts on here to read about it. There seem to be several different kinds of neurostimulators and differences among doctors for how to get the best coverage of the PN.
PN started 2004 from fall. Surgery with Filler Nov. 2006, Dr. Campbell April 2007. Pain decreased by 85% in 2008 (rectal and sitting pain resolved completely), pain returned in 12/13.