Electron microscopy of olfactory epithelia in two patients with anosmia.

Ultrastructural alterations were present in biopsy specimens of olfactory epithelia taken from two patients with anosmia. In both cases, the olfactory epithelia presented a disorganized appearance when viewed by transmission electron microscopy. The number of ciliated olfactory receptors was reduced; few olfactory vesicles were present at the epithelial surface. Where present, the olfactory vesicles usually lacked cilia. Since both patients had a history of head trauma, we speculate that the fila olfactoria may have been severed at the level of the cribriform plate. The histopathologic changes in the olfactory receptors that were revealed by electron microscopy may have resulted from the inability of regenerating axons to reach their normal site of synaptic contact--the second-order neurons (mitral cells) in the olfactory bulb of the brain.