As expected, the Marine Corps has expanded the rules for rating a Purple Heart for Marines who suffered mild traumatic brain injury. Bottom line up front:  it used to be a Marine had to lose consciousness to get a Purple Heart for mild TBI. Now, if a medical officer determines that a Marine is “not fit for full duty” after 48-hours from the time of the concussive event, the wound merits a Purple Heart. The new policy became effective April 15, and is retroactive to Sept. 11, 2001. This means thousands of Marines whose medical records show that they meet…