We have briefly reviewed the literature pertaining to the movement of tracer molecules and infectious organisms within the olfactory nerve. There is a body of evidence indicating that tracers placed in the CSF will quickly move via the olfactory nerve to the nasal mucosa and then to the cervical lymph nodes. Organic and inorganic tracer materials and organisms as diverse as viruses, a bacillus, and an amoeba, when placed in the nasal cavity, have been shown to move from the nasal mucosa via the olfactory nerve to the olfactory bulb and the CSF. We think that a portion of the data on tracer movement is due to incorporation of tracer materials and organisms into the axoplasm of the olfactory neurons with subsequent anterograde or retrograde axoplasmic transport. However, some of the movement of tracers may occur within the olfactory perineural space. This space may be continuous with a subarachnoid extension that surrounds the olfactory nerve as it penetrates the cribriform plate. To our knowledge, no one has yet followed the perineural space to determine if it is continuous from olfactory receptor to olfactory bulb. The consideration of this space and its role is the main reason for this review.
Animals Axonal Transport