Keith Richards believes he was "semiconscious" for two years of his life.
The 71-year-old rocker suffered two seizures and underwent emergency surgery to remove a blood clot from his brain in 2006 after he smashed his head on a tree trunk while holidaying in Fiji.
And he believes it took at least 24 months for his health to be fully restored after the horrific incident because he spent most of his recovery time in a haze.
He explained: "I think that bang on the head, that did quite a bit more damage than people thought.
"You take a blow like that, you kind of feel stunned for another year or two afterwards, really. You suddenly realise you've been semiconscious."
Meanwhile, the Rolling Stones guitarist also suffered another worrying fall earlier this year when he slammed headfirst to the ground at a show in Indianapolis but, at the time, he refused to divulge details about the painful injury because he worried about putting the group's gigs in jeopardy.
He explained to The Times magazine: "Somebody tossed a red straw boater hat, and it landed right in front of my feet. I kicked it aside ... and it f***ing bounced back in front of me and I hit the floor. Suddenly I'm on my hands and knees in front of 60,000 people.
"'I might have cracked a rib but there's nothing the doctors can do about it.' I thought, 'Sh*t, if I let them know how much I'm hurting, the doctors and the insurance companies will be like, "Cancel the next gigs." ' "
"F**k it, I'll live with it. After 50 years on stage, you're going to fall over occasionally and take a knock."