Ultrastructural alterations of human cortical capillary basement membrane in perifocal brain edema.

The fine structural alterations of cortical capillary basement membrane have been studied in 16 patients with perifocal edema associated to brain tumors, traumatic injuries complicated with subdural or epidural hematoma or hygroma and congenital malformations, such as hydrocephalus, Arnold-Chiari and Alport's syndromes and vascular anomalies. The basement membrane displayed homogeneous and nodular thickening, vacuolization, rarefaction and reduplication. Its average thickness varied according to the etiology and severity of brain edema. In nine patients with moderate brain edema the thickness ranged from 71.97 to 191.90 nm and in the remaining seven patients with severe brain edema it varied from 206.66 to 404.22 nm. The basement membrane complex appeared apparently intact in moderate edema and showed glio-basal dissociation in severe edema. In areas of highly increased cerebro-vascular permeability, the basement membrane showed matrix disorganization and bifurcations acting as abluminal transcapillary channels. In regions of total brain necrosis, its structural stability was lost showing loosening, dissolution and rupture. Proliferation of collagen fibers was also found in three cases. Basement membrane swelling was interpreted as an overhydration of its matrix. The thickening, rarefaction and vacuolization seem to be induced by the increased vacuolar and vesicular transendothelial transport. The degenerated areas feature a finely granular precipitate interpreted as a protein or glycoprotein degraded matrix.