Quantitative kinetic analysis of blood vessels in the outer membranes of chronic subdural hematomas.

Dynamic biologic modeling was used to calculate the transfer rate constant for gadolinium-diethylenetriaminepenta-acetic acid (Gd-DTPA) and capillary permeability in the outer membrane of chronic subdural hematomas and effusions. Following intravenous Gd-DTPA injection, Gd concentrations in the subdural fluid and in timed arterial blood samples were measured by ion-coupled plasma emission spectrometry in 53 chronic subdural hematomas and 18 chronic subdural effusions. The capillary surface area in outer membrane was assessed morphometrically. Transfer rate constants for subdural hematomas and subdural effusions were 12.4 +/- 1.0 and 20.6 +/- 1.7 (x 10(-4)min-1, respectively. Capillary permeabilities for subdural hematomas and subdural effusions were 16 +/- 1.2 and 19 +/- 3.7 ml.min-1(mm2/mm3)-1, respectively. The capillary surface areas for subdural hematomas and subdural effusions were 48 +/- 3 and 77 +/- 10 mm2/mm3, respectively. The high degree of infiltration of Gd into subdural effusions reflects the high capillary surface area in the outer membrane rather than greater permeability of individual capillaries. The value of transfer rate constant was correlated inversely with the duration of the chronic subdural fluid collection. Immature outer membrane has a high transfer rate constant which allows extravasation of plasma components into the subdural space, resulting in increasing volume of the subdural effusion. Delayed magnetic resonance imaging following Gd administration may be clinically useful for estimating the age of chronic subdural fluid accumulations.