Stroke-prone spontaneously hypertensive rats as an experimental model of malignant hypertension. I. A light- and electron-microscopic study of the brain.

A pathological study of the brain of the stroke-prone spontaneously hypertensive (SHRSP) rats revealed development of fibrinoid necrosis of the wall of the intracerebral arterioles. These arterioles were frequently accompanied by occlusion of the lumen, and occasionally intracerebral hemorrhages and mincroinfarcts. The predominant tissue alteration consisted of rarefaction and cyst formation in the white matter, and rarefaction of the neuropil and preserved neurons in the neocortex at the paramedian region of the cerebral hemispheres. Edema fluid was present in and around the lesions. The tissue degeneration can be interpreted to be the sequela of brain edema. Microinfarcts or hemorrhages are only focal lesions, and are assumed to have minor contribution to the brain swelling. Widespread expansion of the extracellular space is assumed to be responsible for the brain swelling. Overall vascular changes of the brain, kidney, and other organs were consistent with those found in malignant hypertension.