Post-traumatic anosmia. Ultrastructural correlates.

Five patients suffering post-traumatic anosmia were studied at the University of Colorado Health Sciences Center, Denver. Each patient underwent psychophysical testing, clinical evaluation, and olfactory biopsy. The biopsy specimens were examined ultrastructurally and were found to vary from normal tissues. The overall appearance of the olfactory epithelium in the post-traumatic patient is disrupted and the receptor cells are distorted. Large numbers of axons are located near the basement membrane and can often be found in bundles throughout the epithelium, extending even to the mucosal surface. Olfactory cilia are rarely seen in epithelia obtained from post-traumatic patients. Bald olfactory vesicles, often containing basal bodies, are frequently observed. We postulate that in these cases, the olfactory epithelium regenerates following head trauma and the receptor cells attempt to send axons centrally. However, the cribriform plate has undergone fibrotic healing and the axons are unable to penetrate it and make contact with olfactory bulb neurons.