Please read this just to learn from our experience. The chances are minute that it will happen to your DC, but if we'd known....
DS had a sudden bad headache just before Christmas. It got worse, and Calpol wasn't making any difference. The pain was over one eye, and my GP diagnosed sinusitis. No response to antibiotics, pain getting worse by the day, vomiting, waking up in pain at night. Then his eye went droopy. Took him to A&E - they prescribed migraine medication. He still deteriorated and the eye looked very strange. After CT scans, MRI, lumber puncture, still no diagnosis. Then my poor DS spent his final night in our local hospital screaming in agony, rolling his eyes, incoherent, collapsing, vomiting. NO pain relief helped, until they gave him morphine. The next day he was blue lighted to Gt Ormond St, where they eventually found a ruptured aneurysm in his brain. He was critical for 48 hours.
Miraculously, 2 weeks later we are home, and he is doing really well, just very tired.
The deals I made with God in those 48 hours obviously worked.
We have a happy ending, and our son is still exactly the same as he was. But I wouldn't want anyone to go through what we have just been through, which is why I'm posting. Brain aneuryms in children are incredibly rare, so your DCs headache is very unlikely to be one. I just wanted to flag up what happened to our DS, so that similar symptoms might ring a bell.