Headache-Associated Phantosmia as a Harbinger of Lewy Body Dementia.

Olfactory hallucinations, or phantosmias, can occur in many neurological, psychiatric, and medical conditions, but no widely used standardized approach exists to comprehensively assess qualitative olfactory dysfunction in the clinical setting. Additionally, medical professionals, patients, and their family members may not recognize phantosmia as a potentially neurological problem. Given the many possible etiologies for symptomatic phantosmia, it is important to recognize this unusual presentation and elicit a meaningful history to explore the potential underlying cause. We describe a 77-year-old gentleman with a two-year history of headaches accompanied by smelling a foul odor and discuss the differential diagnosis for new onset and persistent phantosmia. This unusual case ultimately manifested features consistent with Lewy body dementia, highlighting the varied clinical presentations that are possible with this neurodegenerative disorder. We discuss the possible pathophysiology of phantosmia in Lewy body disorders, including a proposed mechanism for olfactory hallucinations arising prior to the typical well-formed hallucinations in Lewy body dementia.