Status spongiosus of nervous tissue

The diverse nature of status spongiosus of nervous tissue is revealed by electron microscopy in a variety of experimental models. Intracellular, extracellular and intramyelinic accumulation of fluid as well as artefactitious dissolution of myelin may account for spongiform changes. In cerebral edema following trauma the perivascular and perineuronal vacuoles in the cortex correspond to swollen astrocytic processes whereas in the white matter the sponginess mainly reflects enlarged extracellular spaces. Vacuolation of swollen dendrites, termnal axons and perikaryal cytoplasm of nerve cells characterizes the transmissible spongiform encephalopathies. Axonal swelling produced by anoxia accounts for the spongy changes seen in the optic nerve in acute glaucoma. Selective accumulation of fluid within myelin sheaths occurs in isonicotinic acid hydrazide poisoning. Aggregates of irregularly curved, lamellar structures, derived from the artifactitious disintegration of myelin, form grape-like deposits or Buscaino bodies which, when dissolved, appear as vacuoles that may be confused with other spongiform states.