Histology of the middle meningeal artery and the dura mater, and their neurosurgical significance

Abstract Background There are rare articles dealing with middle meningeal artery (MMA) histology, which could be important in epidural hematoma (EDH) development, and in the skull base injury or surgery. Methods Fifty MMA specimens were collected, prepared for histologic examination in a standard way, following hematoxylin and eosin staining. In total, 627 slices were analyzed microscopically. Also, 13 patients were examined. Results A histologic MMA examination showed a typical intima coat with endothelial lining, and with the internal elastic lamina, but with a larger subendothelial space (mean, 27.93 µm). The media coat, with smooth muscle cells, was usually typical but reduced (70.67 µm), and the adventitial coat, mainly made of fibroblasts and collagen fascicles, was commonly thinner (70.90 µm). The entire MMA wall averaged 167.77 µm in diameter. The adventitia was continuous with the two dural parts, i.e. the periosteal and meningeal layer. The latter layer was in contact with the arachnoid membrane. The former layer covered the inner table of the vault bones, and thus formed the epidural space. Blood from a damaged MMA collects in this space. EDH averaged 2.6 cm in diameter. The mortality was 15.4%. The possible neurosurgical significance of these data was discussed. Conclusions The MMA, according to its structure, is a weaker vessel than typical muscular arteries, but it is well protected by the dura and cranial bones. In spite of this, a strong head impact, especially associated with an osseous fracture, can lead to MMA rupture and a dural laceration resulting in EDH.