Neuroradiologic evaluation of the subdural pathogenesis in infants with small heads.

A marginal low density area is often revealed by CT scan in infants with microcephalia. However, it is difficult to assess precisely the main pathologic state of the marginal low density area and also whether such a lesion exists in the subdural-epiarachnoid space or in the subarachnoid space. A carotid angiographic evaluation of cortical vessels in the marginal avascular area was made and suggestive results were obtained. When there is acute subdural effusion or subdural hematoma, cortical arteries in the marginal avascular area will have a straightened and attenuated figure. But when such a pathologic state persists for a long period, it induces secondary cortical atrophy and the subarachnoid space becomes enlarged. The cortical artery appears as if it is flying in the enlarged subarachnoid space because it is detached from the gyrus and the sulcus following the cortical atrophy. This is why we named it the 'flying artery.' Angiographic findings allow more precise interpretation of the marginal low density area in the CT scan.