TOKYO, Oct 12 (Reuters) - I blamed the curry. A knot at the top of my chest and profuse sweating - if only I had taken sushi for lunch.

I got up from my desk and crossed the newsroom for some fresh air. In early September in Tokyo the oppressive summer heat lingers, so I was unfazed when the sweating did not abate.

My goal was to get to the men's room to let this thing run its course. I crossed the newsroom, weaving between desks. "Are you OK?" a colleague asked, shock on his face. "Must be the curry I had for lunch," I replied, not really believing myself. I became more nauseous and the spinning did not cease. I called a colleague to ask for an ambulance. "But no flashing lights, please," I said, hoping the episode would pass unnoticed.

That was optimistic. Doctors later confirmed I had suffered a stroke. I spent 17 days in hospital, began a humbling rehabilitation and learnt there were warning signs I should not have ignored.

FLAT ON MY BACK
By the time the ambulance I arrived my right arm was numb, I could barely talk and the left side of my face was partly frozen.

Just the week before I had felt very strange one afternoon, with my right arm and leg going numb, but that passed quickly and the hospital gave me a clean bill of health.

This time doctors shone lights into my eyes and tested my movement, asking me to try to stand and to squeeze their fingers with my hands. They did a CAT scan and a magnetic resonance imaging (MRI) to see inside my brain.

The MRI results gave the doctors a diagnosis. "You've had a stroke," said neurologist Dr Tanaka, showing an area of the scan with a lighter colour than the rest of my brain. "No doubt due to your atrial fibrillation. We suspect a cerebral embolism."

A stroke is caused by an interruption of blood supply to the brain, often by a blood clot. Atrial fibrillation, an irregular heart beat, can lead to clots forming in the heart's chambers. I had known about AF since February when I had a routine physical exam before moving from Italy to Japan. The doctor in Milan said it was not life threatening, but increased the risk of stroke.

My international move delayed treatment. But by Sept 4 when I was taken to hospital in Tokyo, I had been on medication for three weeks to treat the arrhythmia.

Between February and September I had learned a lot about AF. That some 2.2 million Americans and 4.5 million Europeans have it. That AF costs societies in the European Union some 13.5 billion euros ($19 billion) a year. That the risk of stroke is six times greater for someone with AF than for someone without.

Still, AF had not thwarted an active life, which included competitive squash. I considered myself a very fit 53-year-old.

DON'T WAIT 10 YEARS
At first I could not sit up or stand without vomiting. I could not go to the bathroom and I couldn't swallow.

To survive 17 days in hospital in Japan a few phrases help. "Atama ga itai desu" (My head aches), for starters.

Rehabilitation after a stroke is tough. Standing up is hard and walking in a straight line is next to impossible.

The Juntendo University Hospital rehabilitation room has a mini oval track. I called an elderly woman there "densha" (train) because she puffed "ichi, ni" (one, two) as she motored
around.

My treatment was straightforward: anticoagulants to prevent a new stroke (the main anticoagulant, warfarin, was first used as rat poison), and antiarrythmia drugs to fix the AF.

My blood INR (international normalised ratio) rose to above 2.0 - the target threshhold for avoiding clotting - allowing me to leave hospital on Sept. 21.

This month we will see if any blood clots are lurking in my heart. If not, doctors may do cardioversion - electroshocking the heart back to normal rhythm or, as one colleague put it, "rebooting" the heart.

The lessons? Don't wait 10 years between checkups, no matter how well you feel. If you feel dizzy or numb or suddenly nauseous, don't assume it will go away - it could be a stroke.

And if you have AF - as millions do - act on it. Quickly.