[Dissociation phenomenon occurring between olfactory detection threshold and recognition threshold and its clinical significance].

When the results of the standard olfactory acuity test assigned to about 8,000 patients with dysosmia, who visited our olfactory outpatient clinic of the Department of Otorhinolaryngology of Showa University Hospital, were analyzed, it was found that a difference in olfactory acuity loss between recognition threshold and detection threshold was over 1.0 in many of them. Since normal Subjects show the difference of below 1.0, we regard the difference of over 2.0 as "dissociation". The dissociation caused by either olfactory mucosal dysosmia or mixed dysosmia, involving in the olfactory mucosa, etc., seemed to result no only from a decrease in the number of olfactory cells with normal functions, but from the disorder of olfactory nerves (i.e. peripheral olfactory nerves) as well. The dissociation seemed to be related to the sensory mechanism and to the transmission in the olfactory pathway. In other words, the dissociation might occur when the amount of information being transmitted to the olfactory center is in insufficient supply. A complete dissociation clearly differed from those cases above mentioned. This type of dissociation was thought to be caused by a central olfactory disorder, which possibly occurred either in the cortex or an adjacent region. Form these results, it was confirmed that the dissociation found in the standard olfactory acuity test could be caused by any disorder occurring in the olfactory system, but that the modes of dissociation differ according to the sites of lesions. Our report contributed to the explanation for the mechanism of olfactory dissociation, and also suggested the result obtained by the standard olfactory acuity test indicates the site of lesions.