Electrical stimulation of the brain. IV. Ultrastructural studies

The ultrastructural response of tissues of the cat's central nervous system to chronic electrical stimulation with various parameters has been evaluated at four and a half days post stimulation. Cellular alterations included widespread cytoplasmic vacuolations, architectural derangement and disruption of plasmalemma and other membranes. Lipid inclusions and dense crystalline bodies were prominent in astrocyte-like phagocytic cells in the more severe lesions. Despite endothelial damage in brain parenchymal capillaries, significant extravasation of horseradish peroxidase was not observed. The ultrastructural damage observed following electrical stimulation varied from mild to severe. Although none of the parameters tested was found to be "safe" for clinical applications, it should be emphasized that the stimulations delivered in the present study were essentially continuous.