Brain abscesses: the lung connection.

Pulmonary arteriovenous fistulas are uncommon abnormalities of capillary development which cause right to left shunting and, if not treated, may lead to severe neurological complications, including meningitis and brain abscess. Pulmonary arteriovenous fistulas are commonly a result of hereditary haemorrhagic telangiectasia (Rendu-Osler-Weber disease) and both conditions may be readily diagnosed by careful history taking and physical examination. Two cases of brain abscess associated with hereditary haemorrhagic telangiectasia, which remained unrecognized for many years, are reported. These cases emphasize the importance of early diagnosis and treatment of pulmonary arteriovenous fistula in preventing central nervous system infections.