It’s a subtle sense, the sense of smell. We tend not to give it much thought, or we think of its role as circumscribed, reserved for savoring the little luxuries of life—the perfume of violets, the aroma of hot chocolate, the milkiness of a newborn. Yet the olfactory sense protects and serves us—allowing us to detect the whiff of leaking gas, for example, or the notes in the concert of flavors on the tongue.
So it’s not surprising that patients with olfactory disorders that reduce their ability to smell report a slump in life’s quality. Such is the case in the absence of the sense of smell that describes anosmia, the dimming of it that is hyposmia, the altering of it that is parosmia, or the conjuring of it that characterizes phantosmia.
Therapies to correct wayward scents lag, however, a fact that led Eric Holbrook, an HMS assistant professor of otology and laryngology at the Massachusetts Eye and Ear Infirmary, to review what was known about the causes and treatments of smell disorders. In his look at the literature, Holbrook found that the vast majority of olfactory dysfunction cases result from head trauma, upper-respiratory infections, or chronic rhinosinusitis and polyp formation.
Underscoring the importance of isolating cause, Holbrook cites links between neurodegenerative diseases and olfactory dysfunction as well. The literature he reviewed indicates that olfactory biopsies may aid in diagnosing early-stage Alzheimer’s disease. And although a range of studies show Parkinson’s close association with olfactory loss, Holbrook’s analysis of those findings indicates that smell loss can predict development of the disease if the loss manifests within a seven-year window before motor issues arise.
Therapies for olfactory loss from non-neurological causes focus on the surgical removal of blockages and on steroid use, with improvements from oral steroids outstripping those from topical sprays used alone or in combination with oral forms.
With continued research on how smell loss happens, Holbrook notes that better interventions can be developed, returning the delights and the warnings of odors back into more lives.