Local cerebral blood volume in head-injured patients. Determination by emission computed tomography of 99mTc-labeled red cells.

Local cerebral blood volume (CBV) was mapped in 10 normal subjects and in 30 patients after head injury. In normal subjects, the mean CBV was 4.34 ml/100 gm. The coefficient of variation was 12% for the group mean, and 3% for values obtained in duplicate studies of individuals. Patients with head injuries were divided into three groups according to the stage of their illness: acute illness, early recovery, and later recovery. Averages of mean CBV were within one standard deviation of normal. In contrast, consistent changes were found in serial studies of the mean CBV in the same patient. Compared to recovery values, levels of mean CBV measured soon after injury were reduced, largely at the expense of the gray-matter compartment. In five adults with predominantly unilateral lesions, there was an average early reduction in mean CBV and cerebral blood flow of 15% and 36%, respectively. In three children with diffuse brain swelling, there was an average early mean CBV reduction of 12%; a single child had early increased mean CBV at a time when intracranial pressure was high. Greater changes were seen in local CBV on individual sections. There were mixed zones of hypervolemia and hypovolemia in regions of infarction and intracerebral hematoma. Subdural hematomas had consistent medial margins of increased local CBV, representing dilated blood vessels of the underlying cortex. The presence and displacement of this hypervolemic zone were sensitive indicators of persistent subdural collection and mass effect, even when the collection was lucent to x-ray computed tomography.