I know about the separate board certification for AOA neurosurgery. However, once you get out in the real world, you will see there is a lot of prejudice against having "board certification" by a group that oversees so many different specialties, "general surgery, neurologic surgery, plastic and reconstructive surgery, cardiothoracic surgery, urological surgery, general vascular surgery, surgical critical care, or such other surgical specialty that may be assigned to this Board by the AOA Board of Trustees" and by their own admission, they are still in the process of refining what exams and certification is actually needed to pass and get "board certified".
Translated: most neurosurgeons who are ABNS board certified do not feel that this is rigorous enough to merit "real" board certification.
Regardless of what you or I may think, this is the feeling of many neurosurgeons out there. While I believe increasing the supply of neurosurgeons out there is a good thing to keep adequate neurosurgery coverage sustainable, others do not (and some feel that the very rapid growth of AOA neurosurgery residency spots, in comparison to the slow growth of ABNS neurosurgery spots is detrimental to the field of neurosurgery). Again, not my opinion, but this is what you're up against.
This was a topic of conversation and a presentation at the AANS meeting this year.