Influence of Pathway of Infection on Pathology of Olfactory Bulbs in Experimental Poliomyelitis

The purpose of this communication is to describe the lesions produced by the virus of poliomyelitis when it invades the olfactory bulbs from the nose and to indicate their absence when the virus reaches the central nervous system of Macacus rhesus monkeys by other pathways. In monkeys succumbing to poliomyelitis after nasal instillation of virus, the olfactory bulbs show changes in the 5 outer layers, i. e., the layer of olfactory nerve fibers, the glomerular, the external granular, the gelatinous, and the mitral cell layers. The lesions in the first 4 layers mentioned appear to be chiefly inflammatory, consisting of perivascular cuffing and diffuse infiltration of polymorphonuclear leucocytes, mononuclears, and lymphocytes. The involved mitral cells undergo necrosis and frequently show neuronophagia by polymorphonuclear and microglial cells.

These changes with some individual variation in extent, were observed in the olfactory bulbs of each of 10 monkeys given the virus by way of the nose, and it should be stressed that although the virus was instilled in both nostrils, the lesions were present, in at least 3 of the 10 animals studied, in only one of the olfactory bulbs. In 12 monkeys which succumbed to poliomyelitis after intracerebral, subcutaneous, or intrasciatic inoculation, examination of both olfactory bulbs revealed no lesions. It is apparent that a study of the olfactory bulbs may be useful as an indicator of the portal of entry of the virus in experimental poliomyelitis.

Practically no attention has hitherto been paid to the pathology of the olfactory bulbs in human poliomyelitis, and it is believed that their examination in the future should yield data of value to a better understanding of the epidemiology and prophylaxis of this disease.