A brain blood-vessel tangle—doctors call it an arteriovenous malformation, or AVM—is a knot of arteries and veins that formed the wrong way before you were even born. Most people never feel it, but if the tangle starts to act up it can shout at you in five clear ways.
- Sudden “thunderclap” headache
The pain hits like a switch flipped inside your head—zero to worst in seconds. It can feel like you’ve been hit with a bat, and it usually keeps you from finishing whatever you were doing. - Seizure out of the blue
You might jerk, stiffen, or blank out for a minute. If you’ve never had seizures before, a first one in adult life is a red flag. - Stroke-like clues
One side of the face may droop, an arm may drift down, or words can come out scrambled. These signs can fade fast, but they still mean “go to the ER now.” - Vision flickers or loss
Double vision, a gray curtain across one eye, or brief flashes can show up if the tangle sits near the visual circuits. - Slow-build pressure problems
Trouble walking, throwing up for no reason, or a constant dull headache that worsens over weeks can mean the tangle is leaking a little blood or pushing on brain tissue.
| Symptom | What it feels like | Action |
|---|---|---|
| Explosive headache | Worst pain of your life, starts in a snap | Call 911 |
| New seizure | Shaking, staring, or collapse with no history | ER visit |
| Weak/numb face, arm, or speech | One-sided, lasts minutes to hours | Stroke protocol—dial emergency |
| Vision change | Sudden blur, double, or patch of darkness | Eye check + brain scan |
| Steady headache + balance trouble | Builds over days, plus nausea or wobble | See a neurologist soon |