Medicalese for the condition of being somewhat crazy, mad non compos mentis. It derives from the phrase: playing without a full deck.
Cf. this comment about Nancy Pelosi at iowntheworld: "Final diagnosis: Hypodeckia complicated by intra-auricular pheumanosis (Medicalese for playing with less than a full deck complicated by air between the ears)."
by Hess123 February 25, 2014