Most neurologists treat headache but few specialize in it. The pain care center staff varies and usually includes a number of different specialties. Often you see an anesthesiologist, a neurologist or internist, a psychologist etc. The MRA will not rule in or out basilar migraine. I think they are doing it because of the prolonged spell that you had they wish to make sure your basilar artery does not show and abnormality that may be causing your problem.
Basilar migraine involves a specific symptom complex that can be very frightening.
Some patients may even experience weakness and cognitive changes. The symptoms usually last 10 to 30 minutes. I'm not sure what to make of your single event that lasted for a week. The other events do not sound that way. Occipital nerve blocks are common and done by many doctors.