REMOTE_USER empty when protecting some URIs

If I protect the whole website with <Location “/”> the REMOTE_USER var is correctly received, but If I protect only some URIs like <Location “/sat”> the REMOTE_USER var is empty, the authentication is OK as it asks for user password when I access http://xxx.yyy.zzz/sat but the remote_user is empty, it’s a wordpress problem because if a put a single php file with no wordpress things just echo($_SERVER[‘REMOTE_USER’]) and protect it <Location /myphp.php> it’s ok and I see the right remote_user. So it seems like the REMOTE_USER var is missed in any step od the wordpress procesing of the page (includings, filters… I don’t know).
Any clue to resolve this ?

Thanks