BACKGROUND: Lack of an olfactory bulb (OB) is typically associated with anosmia. METHODS: We present a patient with subnormal olfactory function in whom the OB could not be detected with magnetic resonance imaging (MRI). RESULTS: Olfactory function was evaluated on two occasions. Orthonasal olfactory function was assessed with the "Sniffin' Sticks" test providing a score equivalent to hyposmia. Retronasal olfactory function was studied with "smell powders" indicating a decreased, but not absence of, olfactory function. Importantly, chemosensory event-related potentials were clearly present in response to olfactory and trigeminal stimuli. CONCLUSION: This indicates that olfactory function may be present in some subjects even when an OB can not be detected with MRI.
Rombaux, P., Mouraux, A., Bertrand, B., Duprez, T., & Hummel, T. (2007). Can we smell without an olfactory bulb? American Journal of Rhinology, 21(5), 548-550. https://doi.org/10.2500/ajr.2007.21.3067 (Original work published 2007)