Objective: The purpose of this study was to evaluate patients with reduced or no sense of smell since birth for sites of abnormality by MR imaging.
Materials and methods: Twenty-five patients who reported no olfactory function since birth were evaluated by olfactory testing, sinonasal endoscopy, and MR imaging. Surface coil and head coil images of the olfactory bulbs, olfactory tracts, subfrontal cortex, and temporal lobes in contiguous 3-mm sections were obtained. Two reviewers determined unilateral olfactory bulb and tract volumes and temporal lobe volumes in two separate sessions. Qualitative grading for olfactory bulb, olfactory tract, olfactory sulcus, subfrontal region, hippocampus, and temporal lobe damage also was performed.
Results: The absence of olfactory bulbs and tracts (68-84%) or the presence of hypoplasia (16-32%) was noted in all cases. Eight individuals had Kallmann's syndrome (hypogonadotropic hypogonadism with anosmia). Temporal and/or frontal lobe volume loss was noted in five individuals and was mild in all but one individual.
Conclusion: Congenital anosmia or hyposmia appears to be an olfactory bulb-olfactory tract phenomenon rather than a cerebral process.