Severe destruction of the olfactory neuroepithelium has resulted from infection with the influenza virus7 and herpes simplex encephalitis.8 Naes- sen9 has observed alteration of the olfactory neuroepithelium in humans

olfactory neuroepithelium.5,6 Douek et aP have described the histopathologic changes in the olfactory neuroepithelium in several types of anosmia. Incorrect or incomplete contact of the olfactory receptor neurons with the CNS was detected in a patient with congenital anosmia. Severe destruction of the olfactory neuroepithelium has resulted from infection with the influenza virus7 and herpes simplex encephalitis.8 Naessen9 has observed alteration of the olfactory neuroepithelium in humans who did not have intranasal or intracranial diseases and has suggested that these changes occur with aging. Naessenl°,ll has also described invasion of the olfactory area by islets of respiratory epithelium. The present study was undertaken to compare the olfactory and respiratory epithelia in the human fetus and adult to deter.Human olfactory neuroepithelium and respiratory mucous membrane in fetal and adult whole-mount sections were studied. In the fetus, the olfactory neuroepithelium extends from the roof of the nasal cavity to the midportion of the nasal septum and onto the superior turbinate in a continuous fashion. In the adult, the zonal distribution of supporting, sensory receptor, and basal cells is frequently disrupted, and the supporting and sensory receptor cells are often depleted or degenerate. The degree of the degeneration of the adult olfactory neuroepithelium varies from case to case. The most striking feature In the adult is the replacement of large areas of olfactory neuroepithelium with respiratory epithelium. The extensive replacement of olfactory neuroepithelium with respiratory epithelium points out the sampling problem related to small, random biopsy specimens of the olfactory area. (Arch Otolaryngo/1984;110:641-646)