I dont know your age or co-morbids , any how thunderclap headache
is not a good thing , as underlying cause of it could be subarachnoid hemmorrhage or aneurysm
rupture , but as your mra is normal aneurysm is ruled out , and even the tumor
is ruled out , the thing which is left is SAH with mass effect , as extra blood causes mass effect.
I think you need topiramate
, prothiadin , with lipid lowering drugs
Hope this helps.