Well, that's not quite how I read it but maybe I'm not reading it right. It doesn't seem to make a determination of WHICH was THE cause, only that both were? Here's the quote:
"Cause of death of this six year old female is asphyxia by strangulation associated with craniocerebral trauma".
I see your point but the sentence doesn't seem definitive as to what THE cause was.
Parse the grammer then. Cause... is... asphyxia. Craniocerebral truama is a prepositional phrase. Also the lack of extensive bleeding indicates she was near death or dead when the blow occurred.