[Histological study of vascular structure between the dura mater and the outer membrane in chronic subdural hematoma in an adult].

The authors reported the results of histological study of the vascular structure between the dura mater and the outer membrane of chronic subdural hematoma (CSH) in an adult. Many vascular connections were detected at particular part in CSH. According to the microscopical findings and location, these connective vessels were classified into 3 types. 1) Capillary-like vessels had thin walls and narrow diameters. They originated in the middle layer of the dura mater and were connected to macrocapillaries (MC) in the outer membrane. We could not perceive the flow direction in these vessels. 2) Small veins had thin walls and wide diameters. They gathered blood flow of many MC in the outer membrane and entered into the dura mater. Some of them penetrated through the total layer of the dura mater, then flowed into the paraarterial venous sinus of the middle meningeal artery (mmA). 3) Small artery had a thick wall and was about 50 mu in diameter. Though histological continuity was not proved, it was ascertained that the artery originated from a branch of the mmA, and entered the outer membrane. After entering, the small artery separated into many small branches which spread throughout the whole of the outer membrane. The vascular structure of the outer membrane consisted mainly of MC and small arteries with many branches. In this study. We were not able to find the location where both vessels of the outer membrane connected.