Abstract

Cerebral cortical biopsies of 10 patients with a clinical diagnosis of severe and complicated human brain trauma with subdural and extradural hematoma or hygroma were studied to establish mitochondrial morphological alterations and their relationship with nerve cell death. Cortical biopsies obtained in the surgical room were immediately processed by conventional techniques for transmission electron microscopy. Three injured mitochondrial morphological patterns: swollen clear, swollen dense and dark degenerated mitochondria were found in neurons, degenerated myelinated axons, swollen and varicose dendritic process, and degenerated synaptic contacts. Swollen reactive astrocytes and hydropic oligodendroglial cells displayed clear edematous mitochondria. Isolated edematous mitochondria were embedded in the electron-dense hematogenous edematous fluid localized in the enlarged extracellular space. At the level of open or collapsed cortical capillaries, edematous clear mitochondria were observed in endothelial cells and pericytes. Dark ischemic nerve cell, apoptotic neurons, and astrocyte, and ischemic hydropic oligodendrocytes were frequently found. Swollen clear, swollen dense and dark degenerated mitochondria were observed. The swollen clear mitochondria exhibited low electron-dense mitochondrial matrix and discontinuities of outer and inner mitochondrial membranes. Swollen dense mitochondria showed high electron-dense matrix and swollen intact or fragmented cristae. Dense degenerated mitochondria displayed an overall high electron density of matrix and mitochondrial membranes and cristólisis. The injured mitochondrial patterns are related to nerve cell death and postulated as markers of lethal nerve cell injury.