can a stunned hero use fatigue for movement points?

let us know as soon as possible thanks in advance 

Yes, he can.  The Stun effect forces you to only take one half action instead of a full action and explicitly forbids you from doing anything that requires you to declare one of the four standard actions (except you're allowed to use your half action to place an order if you want.)  This is the only restriction, and fortunately for the heroes, spending fatigue to gain MPs does not require the declaration of any particular action.

Steve-O said:

so the hero can declare an attack and then move spending fatigue? (this will mean like a little battle action to me)

Lord Loren Soth said:

He can make an attack and spend Fatigue for movement before or after making the attack, in the desired quantity. This is like a little Advance action (move + attack) that requires spending Fatigue. It's not for free, and forcing Heroes to spend Fatigue is good for the Overlord.

Generally speaking, there are no restrictions for Fatigue use for movement in Descent, barring exceptions like the Iron Boots Dark Relic found in Altar of Despair or the almost useless Hugo the Glorious bonus hero. A Hero with a Web token can't receive any movement points but I think he can spend Fatigue for no effect, if he so wishes .