The work you're inquiring about goes by several titles these days, including endovascular surgical neuroradiology, interventional neurology, interventional neuroradiology, endovascular neurosurgery, and neurointerventional.
It is a competitive fellowship for neurologists to apply for, but attainable with proper work ethic, inclination, and contacts within the field. It has traditionally been performed by neurosurgeons and radiologists, but is becoming more open for qualified neurologists.
If you type in any of the job titles I mention on this forum, and the SDN radiology or neurosurgery fora, and/or check out www.uncleharvey.com
you will find a veritable avalanche of information. I mean pages, and pages, and pages, and pages of information answering everything you could ever feasibly ask about this topic.
You may also try looking into the Society of Vascular and Interventional Neurology website for more details.
Weren't you also querying about pain medicine fellowships not so long ago? What turned you off about the specialty?