[Abnormal absence of displacement of the cerebral median line]

The angiographic cerebral midline is described. It is pointed out that the midline may be abnormally undisplaced despite the presence of a unilateral or bilateral expansive lesion. The causes of such abnormal non-displacement of the midline are reviewed in the light of examples, and the importance is stressed of bilateral carotid angiograms, sometimes with oblique series, in the case of head injuries and certain tumors.