Transmission electron microscopy of cortical dendritic spines in the human oedematous cerebral cortex

The cortical biopsies of 31 patients with clinical diagnosis of congenital hydrocephalus, vascular anomalies, brain tumours and brain trauma were examined with the transmission electron microscope. A variety of swollen spine shapes were found: mushroom shaped, filopodic, lanceolated spines, and megaspines. The spines appeared axonless or making asymmetric synaptic contacts with swollen presynaptic axons. They exhibited a disrupted actin-like network, dilated endoplasmic reticulum profiles, oedematous clear or dense mitochondria, and clusters of free ribosomes. Some spines contained a hypertrophic cytoskeleton. The spine apparatus appeared generally swollen with clear and dilated cisterns. In severe brain trauma and tumours some spine apparatus appeared disorganised or atrophic. In complicated brain trauma with subdural haematoma or hygroma some degenerated spines displayed a high electron density. The ultrastructural findings suggest that alterations of the spines are responsible for the neurological symptoms exhibited by some patients, which imply a disturbance of cortical nerve circuits. The presence of axonless spines is symptomatic of a loss of nerve connectivity, and are expected to have a significant input on neurological and mental functions.