(Multnomah County, OR)  --  A teenager from Troutdale is being treated for serious injuries, after suffering a fall while hiking near the top of Angel's Rest trailhead.  Authorities say the 16-year-old Centennial High School student fell 50 to 100 feet yesterday while walking with a large group of hikers.  Coast Guard officials say an off-duty paramedic and emergency room doctor, who were hiking nearby, stabilized the teen.  He's reported to have suffered head trauma and possibly a spinal injury.