Neural Dissimilarity: A Promising New fMRI-based Measure of Smell? Changes in the Olfactory System Following Treatment for Severe CRSwNP With Monoclonal Antibodies

The sense of smell is essential in social interactions, food intake and hazard detection. Olfactory dysfunction (OD) affects approximately 20% of the adults and likely increased following the COVID-19 pandemic. The pandemic highlighted the substantial burden of OD on daily life and well-being.

A common cause of acquired OD is Chronic Rhinosinusitis with Nasal Polyps (CRSwNP) affecting 2-4% of adult Scandinavian population. The vast majority of CRSwNP in this population is driven by type-2 inflammation. Decreased sense of smell is an almost obligatory complaint in severe CRSwNP with an OD prevalences of ~95% and ranked as one of the most important.

OD is the symptom in CRSwNP with greatest effect on health-related quality of life and at the same time remains difficult to treat.

New treatments for patients with severe CRSwNP have recently become available in form of monoclonal antibodies selectively blocking pro-inflammatory cytokines in the type-2-inflammation cascade. These biologics show substantial improvements in self-reported olfactory tests.

Knowledge of neuroanatomical functional and structural correlates to olfactory function has long existed. However, only few have used functional magnetic resonance imaging (fMRI) to investigate OD in CRS patients. Patients with CRS-related OD offer a unique neurobiological model for studying olfactory plasticity as olfaction potentially improves.