[Morphological findings on the brain of rats after local freezing (author's transl)].

In continuation of our investigations of the wound healing process after cryonecrosis in the liver, kidney, spleen and stomach, the wound healing in the brain was studied under the same condition. Through a trepanation of about 3 mm diameter, the cortex of the parietal region of the cerebrum was frozen by a cryoprobe applied directly through the intact dura mater (-196degreesC/30s). The animals were killed at definite time intervals between 12 h and 21 days after freezing. Twelve hours after freezing, the necrosis of the brain cortex is complete. It extends wedgeshaped into the subcortical white matter. The central parts of the necrosis become colliquative and are demarcted by leucocytes. Two days after freezing, the necrotic area is almost totally invaded by leucocytes. Three days p.op. the brain wound is infiltrated by microglial cells, later on the mesenchymal cell proliferation extends to the meninges. There is new capillary formation and partially a wall like proliferation of the perivascular connective tissue cells. Ten days and later, an uni- or multiloculated pseudocyst develops, which can be considered as the final stage of the reparative wound healing of the cryonecrosis. Similar as in the other investigated organs (liver, kidneys, spleen) these investigations underline the rapid wound healing of the cryonecrosis in the brain. The advantages of cryosurgical manipulations with the well known good wound healing process of other organs, justifies therefore the short term tissue freezing on the cerebrum.