A Sparta teenager received possible life-threatening head injuries after falling out of a moving truck Sunday afternoon. Monroe County Sheriff Scott Perkins said 18-year-old Gabriel C. Woodhouse of Sparta was westbound on Jancing Avenue. Two passengers, 18-year-old Austin J. Zwiefel and a juvenile male, both of Sparta, were standing in the bed of the truck. The vehicle operated by Woodhouse left the roadway and entered the ditch.  The vehicle then re-entered the roadway, causing Zwiefel to be ejected from the bed of the truck.  Zwiefel was transported to Sparta Mayo Hospital and subsequently, he was flown to Gundersen Health Systems in La Crosse.  The crash remains under investigation by the Monroe County Sheriff’s Office.