Stellate Ganglion Block for the Treatment of COVID-19-Induced Olfactory Dysfunction: A Prospective Pilot Study

Objective: The objective of this study was to explore the safety and feasibility of stellate ganglion blocks (SGBs) to treat persistent COVID-19-induced olfactory dysfunction (OD). Secondarily, the goal was to determine effect sizes to plan a future randomized clinical trial. Study Design: Prospective case series. Setting: Quaternary Care Academic Medical Center. Methods: In this single-arm pilot trial, adult participants with a COVID-19 diagnosis ≥ 12 months prior to enrollment with OD underwent bilateral SGBs. Subjects were followed for 1 month after completion of SGB. The primary outcome measure was the change in the Clinical Global Impression-Improvement Scale for smell loss. Secondary outcome measures included changes in the University of Pennsylvania Smell Identification Test (UPSIT) and Olfactory Dysfunction Outcomes Rating (ODOR). Results: Twenty participants were enrolled with a mean (SD) age of 46 (11) years and a mean (SD) duration of OD of 21 (5) months. At 1 month, 10 (50%) participants experienced at least slight subjective improvement in their OD, 11 (55%) attained a clinically meaningful improvement in smell identification using the UPSIT, and 7 (35%) achieved a clinically meaningful improvement in olfactory-specific quality of life (QoL) measured by the ODOR. The median difference between UPSIT scores at baseline and 1 month was 6 (95% confidence interval: 3-11), exceeding the minimal clinically important difference of 4. There were no serious adverse events. Conclusion: Sequential SGBs for COVID-19-associated OD were safe and associated with modest improvements in subjective olfaction, odor identification, and olfactory-specific QoL. A placebo-controlled trial is warranted to determine the efficacy of SGBs for COVID-19-associated OD.