The team eventually suspects he suffers from TTP, but the splenectomy they perform does not improve his situation, ruling that condition out.
However, it is later revealed that a depression as a teenager due to his loneliness as a child prodigy led him to attempt suicide, and House realizes that the ribs he broke back then made his spleen split into several parts, which is why the procedure had no effect – it was TTP all along.
The remaining symptoms are explained after the discovery of his use of DXM (mixed with alcohol to prevent brain damage), which he used to reduce his intellect.
As Sidas regains his status of intellectual genius by not abusing the addictive medicine, he begins work in applied physics, drawing a schematic for a toroidal helicon plasma device, and is reassured that he cannot relate to his wife with his original intellect.
House, relating to his situation, essentially helps "lobotomize Einstein" by giving him back his meds, as the patient wishes to be dumb and happy rather than smart and miserable.