Each part of the brain controls a different functionality therefore the symptoms would point your to the correct area of the brain that was injured.
Examples:
Frontal Lobe = motor control, speech, smell and concentration.
Temporal Lobe = Hearing
Occipital Lobe = Vision
(Just to name a few)
So a patient that has lost there vision would point to an occipital lobe injury, where as a person that was having trouble controlling body movements and speech would most likely have a Frontal Lobe injury.
Hope this helps