Other causes include spinal stenosis, cancer, trauma, epidural abscess, and epidural hematoma. Such wound infections mainly take the form of either incisional abscess or wound cellulitis. Other potential complications of a spreading pericoronal abscess include peritonsillar abscess formation or cellulitis. Skin infections such as abscess and ulcers can also complicate necrotizing fasciitis. Peptostreptococci can cause fatal endocarditis, paravalvular abscess, and pericarditis. A collection of pus is called an abscess, not a cyst. Surgery for abscess or fistula is indicated either urgently or electively. Ovarian endometriosis may complicate pregnancy by decidualization, abscess and/or rupture. Toothache caused by a periodontal abscess is generally deep and throbbing. Other pulmonary complications include lung abscess and empyema. They include dental infection, dental abscess, and Ludwig's angina. Sometimes there is an associated pericoronal abscess (an accumulation of pus). It also may show signs of pneumonia, a lung abscess, or a tumor. A periodontal abscess may be difficult to distinguish from a periapical abscess. He died of pneumonia and a pulmonary abscess in 1922.