Interesting question, both in its own right, and in terms of what Wikipedia should do about it (something I've had an interest in [1] for a while). Looking at the university databases I have access to, I don't really find anything substantive beyond what you've found on Google Scholar. All the stories allege that he suffered a brain injury in 1915 that left him unable to sleep, but the stories themselves are never earlier than the 1930s, and are relatively short newspaper articles (at least, those surviving reports that are digitized and searchable). Is it a real case? A hoax? Something in between, misreporting a real case? Something well documented in an undigitized archive somewhere, waiting to be discovered? No idea.

[1] http://www.kmjn.org/notes/wikipedia_notability_verifiability...