C. Pulmonary arteriovenous shunt
A pyogenic brain abscess can occur because of purulent spread from infections in the middle ear, meninges, paranasal sinuses, mastoids, lungs (in cases of empyema, bronchiactesis, and pulmonary abscess), heart (in cases of infective endocarditis or cyanotic congenital heart diseases), gastrointestinal tract, or mouth (in cases of dental infection). A brain abscess can also occur after head trauma and neurosurgical procedures.1 Among the pulmonary causes, digital clubbing and pyogenic brain abscess can be seen in empyema thoracis, lung abscess, bronchiactesis, interstitial lung disease, and pulmonary arteriovenous shunts.2 Symptoms of pulmonary arteriovenous shunt depend on the size of the shunt. A patient with a pulmonary arteriovenous shunt may remain asymptomatic, whereas patients with empyema thoracis and lung abscess present with acute fever, chest pain, cough, and dyspnea on exertion or at rest.3