The crux of any neurological assessment is the history, so expect to spend a lot of time answering questions. In the diagnosis of migraine the examination plays minimal part and there is unlikely to be an indication for a brain scan of any sort.
Migraine is a vascular phenomenon which may or may not be associated with headache. There are very clear symptoms associated with it and it is very often grossly misdiagnosed. In particular, amongst the general public 'migraine' is taken to be synonymous with 'severe headache'. It is nothing of the sort and I see many people every week who come in and say 'My migraines are terrible, doctor'. Almost invariably, they are suffering from tension headache and they do not appreciate the implications of a migraine diagnosis. In particular, for women such a diagnosis means that the combined contraceptive pill is pretty much contra-indicated. For people who want a class 1 medical it is the kiss of death.
Of the many types of migraine, the commonest is classical migraine. In this variant, a severe one-sided headache with nausea, vomiting and photophobia is preceded by 30-60 minutes by a migrainous aura. This is usually a visual aura, often consisting of zig zag lines in the visual field. The headache can last 24-36 hours, is excruciating and requires the sufferer to lie in a darkened room. Taking a drug of the sumatriptan class during the aura and before the headache can abort the headache. It is rare for migraines to occur more than once a month.
If this sounds like what you get, you might have classical migraine. As I say, there are a number of other migrainous syndromes too and, if you do suffer from migraine, I personally think it is probably correct that you don't get a class 1 for a variety of reasons.
Good luck!
QDM