Litten's sign, also known as the diaphragm phenomenon, is a term used to describe a paralyzed hemidiaphragm, the portion of the diaphragm in contact with the parietal pleura during espiration in the base of the pleural cavity. This can be recognized by a slight change of sound when the percussion technique is used during expiration and inspiration in the last intercostal spaces. It is caused by a hyperinflation of the lungs associated with chronic obstructive pulmonary diseases, specially to emphysema. Related findings to emphysema Hoover's sign (lung). ..