A few of these case studies have been used to argue the extraordinary claim that brain volume has little or nothing to do with intelligence; authors have argued

A few of these case studies have been used to argue the extraordinary claim that brain volume has little or nothing to do with intelligence; authors have argued that hydrocephalus suggests enormous untapped cognitive potential which are tapped into rarely for repairs and can boost intelligence on net, or that intelligence/ consciousness are non-material or tapping into ESP. The thing about this "counter-argument" is it's conflating a basic point - some people, maybe only a few, are able to exhibit normal human intelligence with a much reduced brain size - with a host of apparently idiotic position people have taken in response to this situation. But of course dismissing the basic on this basis is fallacious.