rs : conception of the work ; acquisition of data for the work ; revising it critically for important intellectual content ; final approval of the version to be published . l : conception of the work ; acquisition of data for the work ; revising it critically for important intellectual content ; final approval of the version to be published . fa : revising the work critically for important intellectual content ; final approval of the version to be published . ma : revising the work critically for important intellectual content ; final approval of the version to be published .
key clinical messageunwitnessed penetrating head injuries ( phis ) are often challenging . 
 the inability to locate a foreign body should not exclude this diagnosis nor should it delay treatment . 
 attempts must be made to clarify the mechanism of injury , as this may allow for a better understanding of the patient 's condition .