WHAT ARE THE RED FLAGS IN HEADACHE whenever the headache is of sudden onset associated with vomiting and giddiness it may be an emergency situation, bleeding inside the brain has to be looked for.this can be a subarachnoid hemorrhage.most often this results from rupture of an aneurysm. aneurysm requires immediate treatment either by blood vessel coiling which is less invasive or by neurosurgical procceedure called clipping