Blood as tracer for CSF circulation after subarachnoidal hemorrhage.

The amount and distribution of blood in the cerebrospinal fluid following subarachnoid hemorrhage can be monitored with CT. An investigation of 110 patients was performed retrospectively in 100 patients with a total of 132 CT examinations, and prospectively in 10 patients with 40 CT examinations. During the days following the hemorrhage, the blood was redistributed within the subarachnoid space and eventually reabsorbed. The blood in the basal cisterns was cleared first, whereas the amount of blood in the cortical sulci appeared to increase after a few days, later to be cleared. It is concluded that the redistribution of the blood reflects the circulation of the cerebrospinal fluid, and that the erythrocytes thus act as tracers of this circulation. The amount of blood within the ventricular system was correlated to the size of the ventricles; patients with large amounts of blood within the subarachnoid space had hydrocephalus more often than other patients.