Geek and Head case

Geek noun - A person slavishly devoted to intellectual or academic pursuits.

Head case and geek are semantically related In some cases you can replace phrase "Head case" with "Geek", this terms are similar.

Head case noun - A person judged to be legally or medically insane.

Geek and head case are semantically related (North American) in screwball topic. Sometimes you can use "Geek" instead a noun phrase "Head case".