Patient B has the opposite problem. By using neuroimaging (or neuropathology post-mortem) to identify the overlap and dissociation between lesioned areas of the brain, one can infer something about the localization of visual and auditory function in the normal brain.
Using neuroimaging (or neuropathology post-mortem) to identify areas of the brain affected by lesions allows us to infer the location of visual and auditory function in a healthy brain.