Basement membrane surfaces and perivascular compartments in normal human brain and glial tumours. A scanning electron microscope study.

The relationship of perivascular tissues to arteries and veins in normal brain and glial tumors were investigated by light microscopy and by scanning and transmission electron microscopy. Vessels and perivascular tissues were separated through various planes by careful tearing of fixed tissue blocks of brain and tumour. Mirror surfaces of torn blocks were examined by scanning electron microscopy and the identity of the vessels and other structure confirmed by transmission electron microscopy. Perivascular glial basement membranes remained adherent to arterial adventitia in both normal brain and in tumour so that the torn surface around the vessel exposed perivascular glial processes attached to the vessel walls. A clear plane of separation of perivascular glial basement membrane from the adventitia of veins was achieved in glial tumours. Mirror surfaces showed the smooth undulating sheet of basement membrane separated from the fine fibrillary connective tissue of the vessel wall. Tears in the basement membrane revealed the perivascular glial processes. The structure of the perivascular basement membrane is discussed in relation to its role as an attachment site for perivascular glial and as an impedence to inflammatory cell migration into brain parenchyma.