Carbon monoxide encephalopathy
Selective topography of CNS lesion
Springer Online Journal Archives 1860-2000
Summary Experimental studies were performed to elucidate the significance of various physiological factors contributing to the pathogenesis of carbon monoxide (CO) encephalopathy, such as systemic blood pressure (BP), common carotid artery blood flow (CF), local blood flow (LBF) of the brain and blood gas including pH, and to analyse the morphological character of the cerebral white matter lesions in the acute phases with light and electron microscopes; 14 adult cats were exposed to 0.3% CO/air gas under respiratory control for 1 h and 17 min to 2 h and 50 min and killed 1.5 h to 3 weeks later. During the 1st h the CF and LBF increased along with the concentration of CO haemoglobin and the BP showed slight decrease in all the CO-exposed cats. After the 1st h, the BP dropped progressively as well as the CF and LBF. The LBF of the cortex and white matter changed in parallel, but often that of the latter approximated or exceeded that of the former in the cerebrum. During CO exposure, acidosis occurred in all the cats and haemoconcentration resulted in almost all of the cats. In all the cats except one which showed the least BP drop, lesions occurred selectively in the cerebral white matter and in six or seven cats focal coagulation necrosis or ischaemic changes occurred in the nerve cells in the bilateral pallidum, substantia nigra, and hippocampus similar to human patients. The cerebral white matter lesions were suggestive of those caused by circulatory disturbance. The severity of the white matter damage showed a good positive correlation with the intensity of the BP drop, but not with other factors, such as the duration of CO-exposure, CO-haemoglobin level, acidosis, or haemoconcentration. On the basis of such physiological and morphological findings, we have found the following to be essential for the selective damage of the cerebral white matter rather than the cerebral cortex or white matter of other regions of the CNS: (1) the coexistence of the initial phase of increase in and the succeeding decrease in the cerebral blood flow and (2) the anatomical finding that the cerebral white matter is supplied by its own long nourishing arteries with small amounts of capillary beds and a thinner media compared with that of the subarach-noidal artery.
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