Nose, Nerve - Atrophy

The olfactory nerves in the lamina propria are bundles of axons from the olfactory neurons whose cell bodies lie in the olfactory epithelium. These nerves are unmyelinated and traverse openings in the ethmoid bone and terminate at the olfactory bulbs. The lesion is characterized by decreased size and number, or complete loss in severe cases (Figure 3), of the olfactory nerves. Atrophy of the olfactory nerves (Figure 1, Figure 2, and Figure 3; compare with normal control in Figure 4) is secondary to loss of olfactory nerve cells from the olfactory epithelium or to damage to the olfactory bulb of the brain. It is most commonly the result of loss of olfactory neurons in the olfactory epithelium, so the lesion almost always accompanies changes in the olfactory epithelium, such as atrophy or respiratory metaplasia. Since these lesions are usually part of a larger spectrum of lesions in the nasal cavity, inflammation and changes to the respiratory epithelium are often present as well.