Similarly, bullets and other foreign bodies may become sources of infection if left in place. The location of the primary lesion may be suggested by the location of the abscess: infections of the middle ear result in lesions in the middle and posterior cranial fossae; congenital heart disease with right-to-left shunts often result in abscesses in the distribution of the middle cerebral artery; and infection of the frontal and ethmoid sinuses usually results in collection in the subdural sinuses.
Similarly, foreign objects like bullets can become sources of infection if left in place. The location of the primary lesion may be indicated by the abscess's position: infections of the middle ear result in lesions in the middle and posterior cranial fossae; congenital heart disease with right-to-left shunts often lead to abscesses in the distribution of the middle cerebral artery; and infection of the frontal and ethmoid sinuses usually results in collections in the subdural sinuses.