Can we smell without an olfactory bulb?

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.