Parkinsons Disease - a chronic disease of the central nervous system caused by lowered levels of the inhibitory neurotransmitter dopamine. Symptoms include muscular tremors and weakness. Once you get this definition it should be clear.
This man & woman have been married to each other for over sixty years. For the last few years the only sex they have, is she holds his penis in her hand.
Anyway, the husband comes home late one night and says "Honey I'm sorry,I still love you, but I'm leaving you for another woman."
The wife gets hysterical and starts screaming at him. "Well, is she younger than me?" He says "No." She screams "Well, is she prettier than me?" He says "Well, no." She asks "Is she rich?" He says "Hell no!" By then the woman has completely lost it, and screams at the top of her lungs, "Well then what does that BITCH have that I don't have?" Husband replies with a grin "P-P-PP-Parkinsons Disease."