What Causes Oily Skin And Acne On Nose And Forehead?

Had Endo sinus surgery 02/24/10 that resulted in CSF leak and a 7 day hospital stay. Ever since surgery, My forehead and nose have been very oily resulting in acne on nose and forehead. I am 40 y/o male in very good shape. Never had problem until surgery. Very frustrating, ENT Surg had no idea why. Any reason for this sudden onset of extrmely oily skin and pimples?