amishmustafakhan

This really is the million dollar question. It is also the reason we wrote this paper, to highlight the need for more research that focuses on treatments for COVID-19 olfactory dysfunction. There is no strong evidence supporting the efficacy for most proposed interventions including intranasal corticosteroids. Smell training may benefit a subset of people. Our lab led by Dr. Jay F. Piccirillo is studying a number of interventions including modified smell training and intranasal theophylline.

Diagnostically, chronic olfactory dysfunction is that which lasts 6 months or greater. To my knowledge no one has studied continued rate of recovery beyond six months in COVID-19 olfactory dysfunction. However, it is reasonable to assume that there will be continued low-level rate of recovery beyond the 6 month time point.

The study estimates include those with anosmia (complete loss) and hyposmia (diminished smell).

The degree of smell loss is quantified in the clinical setting using the validated "Smell Identification Test" developed at University of Pennsylvania. It is literally a scratch-and-sniff test comprised of 40 multiple choice questions! A score of less than 34 out of 40 is considered abnormal. A score less than 19 implies complete loss of smell.

This is a great question!

You may still be able to "smell" whiskey. This is because injury to the olfactory nerve does not preclude the detection of irritants such as ethanol, acetic acid, and menthol which are detected by the trigeminal nerve. We use this to our advantage in the clinical and research settings by using menthol as a positive control!

Even prior to the COVID-19 pandemic, viral upper respiratory infections were the most common cause of chronic olfactory dysfunction, accounting for 20-40% of all cases. Viruses reported to be associated with olfactory dysfunction include adenovirus, rhinovirus (common cold), and influenza (flu).

What makes SARS-CoV-2 unique is the frequency and severity of the associated olfactory dysfunction. This may be due in part because SARS-CoV-2 has tropism (affinity) for receptors expressed in the olfactory region (ACE-2 and TMPRSS2).

https://jamanetwork.com/journals/jamaotolaryngology/fullarticle/2786433

Olfactory dysfunction includes a wide breadth of pathology including:

1. Hyposmia: Diminished smell
2. Anosmia: Absent smell
3. Parosmia: Distortion of odors in the presence of an odor stimulus
4. Phantosmia: Detection of odors in the absence of an odor stimulus

To meet the criterion for "chronic", symptoms must persist for 6 months or greater.