A Phase 1/2 interventional study of Stellate Ganglion Block in Anosmia, Hyposmia and Parosmia, sponsored by Washington University School of Medicine. Completed at 1 site in United States. Open to participants aged 18 Years to 70 Years. Per ClinicalTrials.gov, last updated 2026-02-12.
Sponsored by Washington University School of Medicine · Phase 1/2, Interventional, and Treatment
Chronic olfactory dysfunction from the COVID-19 pandemic is a growing public health crisis with up to 1.2 million people in the Unites States affected. Olfactory dysfunction impacts one's quality of life significantly by decreasing the enjoyment of foods, creating environmental safety concerns, and affecting one's ability to perform certain jobs. Olfactory dysfunction is also an independent predictor of anxiety, depression, and even mortality. While the pandemic has increased the interest by the scientific community in combating the burgeoning health crisis, few effective treatments currently exist for olfactory dysfunction. Furthermore, patients impacted by "long COVID," or chronic symptoms after an acute COVID-19 infection, experience impairments other than olfactory and gustatory dysfunction, such as chronic dyspnea, impaired memory and concentration, and severe fatigue. These symptoms have been hypothesized to be a result of sympathetic positive feedback loops and dysautonomia. Stellate ganglion blocks have been proposed to treat this hyper-sympathetic activation by blocking the sympathetic neuronal firing and resetting the balance of the autonomic nervous system. Studies prior to the COVID-19 pandemic have supported a beneficial effect of stellate ganglion blocks on olfactory dysfunction, and recent news reports and a published case series have described a dramatic benefit in both olfactory function and other long COVID symptoms in patients receiving stellate ganglion blocks. Therefore, we propose a single cohort prospective study to generate pilot data on the efficacy and safety of sequential stellate ganglion blocks for the treatment of COVID-19-induced olfactory dysfunction and other long COVID symptoms.
One of the hallmark symptoms of infection with SARS-CoV-2 is olfactory dysfunction, and it is estimated that up to 1.2 million people in the United States will experience chronic olfactory dysfunction from the COVID-19 pandemic. While the majority of patients recover from COVID dysosmia, up to 15%-25% have long-term hyposmia. Olfactory impairment can take the form of hyposmia (diminished sense of smell), anosmia (absent sense of smell), or parosmia (distorted sense of smell). Etiologies of olfactory dysfunction include post-viral, traumatic, inflammatory (e.g., chronic rhinosinusitis), neurodegenerative (e.g., Parkinson's disease), and congenital, among others. Prior to the pandemic, post-viral anosmia was the most common cause of olfactory dysfunction, which has further increased as the dominant etiology as a result of COVID-19. The proposed pathophysiologic mechanisms of chronic COVID-19-induced olfactory dysfunction include inflammatory cytokine release, damage to the supporting environment of the olfactory epithelium, and retrograde propagation to higher order neurons. A unique feature of COVID-19-associated olfactory dysfunction is the high rate of persistent parosmia. In one study of 222 patients with COVID-19-associated olfactory dysfunction, 148 (67%) of these patients experienced parosmia at some point. Of the 148 patients with parosmia at any point, 84 (57%) had persistent parosmia after a mean of 6.5 months, distinguishing COVID-19-induced olfactory dysfunction from any other etiologies of olfactory dysfunction. Patients with olfactory dysfunction have decreased quality-of-life and describe their life as if "living in a box." These patients have concern for environmental safety, decreased enjoyment of their food, depression, anxiety, and even higher risk of mortality. The COVID-19 pandemic has highlighted the importance of the sense of olfaction, however, there is a scarcity of effective treatments for olfactory dysfunction. Furthermore, chronic olfactory dysfunction is just one of the constellation of symptoms included in "long COVID," or persistent symptoms after recovery from acute illness due to COVID-19. Other symptoms of long COVID include fatigue, dyspnea, cough, and impaired memory and concentration, among many others.These chronic symptoms are hypothesized to be, at least in part, a result of sympathetic hyperactivity resulting in positive feedback loops. Therefore, the stellate ganglion block, which inhibits the sympathetic nervous system, is hypothesized to reset the balance of the autonomic nervous system and provide relief for long COVID symptoms, including olfactory dysfunction.
Treatment No standard of care treatment for post-viral olfactory dysfunction exists. The most commonly used treatment for post-viral olfactory dysfunction is olfactory training; however, a large proportion of patients do not receive benefit and continue to have persistent symptoms. A multitude of other therapies have been tried with minimal success, including theophylline, vitamin A, sodium citrate, and intranasal insulin. As a result, there is a critical need for the development of a novel intervention to address the large volume of patients with olfactory dysfunction as a result of the COVID-19 pandemic.
The stellate ganglion block (SGB) involves an ultrasound-guided injection of a local anesthetic to inhibit the stellate ganglion. The SGB is proposed to inhibit the sympathetic neural connections within the head, neck, and upper extremity, improve regional blood flow, reduce adrenal hormone concentration, and even reestablish circadian rhythms through modulation of melatonin. The SGB has been used successfully in a multitude of disorders, including post-traumatic stress disorder, cluster headache, complex regional pain syndrome, and peripheral vascular disease.
The SGB was first proposed to treat olfactory dysfunction by Lee et al in 2003, where 38 post-viral olfactory dysfunction participants were treated with SGB and 13 participants remained untreated as controls. Subjective olfactory function improved in 27 (71%) of the treated participants compared to zero (0%) of the controls. Olfactory perception was improved significantly in the SGB group assessed both by the butanol threshold test and odor identification test. There were no complications of SGB in the 38 treated participants. Another study in 2007 by Moon et al found that in 13 participants with various etiologies of olfactory dysfunction, seven (54%) demonstrated improvement with repeated SGBs. The same group conducted a study published in 2013 looking at the long-term results of SGB in treating olfactory dysfunction from various etiologies. Of 37 participants with olfactory dysfunction unresponsive to oral or intranasal steroids who underwent SGB, 15 (41%) were determined to be responsive and 22 (59%) unresponsive to the treatment. Importantly, the responsive group had a mean duration of olfactory dysfunction of 1.6 years vs. a mean duration of olfactory dysfunction of 4 years in the unresponsive group. The study found that in those who respond to SGB, the beneficial effects on olfaction last at least 5 years. Of the 37 treated participants there was only 1 who experienced a complication, which was a temporary brachial plexus block.
Most recently, anecdotal news reports and a published case series point to a possible beneficial effect of SGB on both chronic COVID-19-induced olfactory dysfunction and various other long COVID symptoms. A published case series by Liu et al describes two patients who underwent SGB for long COVID symptoms, including olfactory dysfunction. SGB was performed on the right side then either one or two days later to the left side. Both patients reported significant and durable improvement in symptoms, including fatigue, "brain fog," and olfactory and gustatory dysfunction that persisted at 60-day follow-up. Nearly all other long COVID symptoms, including cough, chest pain, heart palpitations, and orthostatic dizziness, also improved at the one week and two-month follow-up time points. The authors concluded that although the sample size is limited, SGB may have a significant impact on the dysautonomia caused by COVID-19 and improve long COVID symptoms, giving rationale to conduct a larger study. Therefore, we propose a single cohort prospective study to generate pilot data on the effectiveness and safety of sequential stellate ganglion blocks for the treatment of COVID-19-induced olfactory dysfunction and other long COVID symptoms.
180 studies on the registry are indexed under Anosmia; 45 are open to participants now.
This study's enrollment of 20 is below the median of 60 across 114 interventional studies indexed under Anosmia.
Browse Anosmia studies →Washington University School of Medicine is the lead sponsor of 1,803 studies on the registry; 271 are open to participants now.
Of its 329 completed or terminated interventional studies of FDA-regulated products, 216 (66%) have results posted.
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Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
History of conditions known to impact olfactory function:
History of coexisting conditions that make SGB :
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Chronic obstructive pulmonary disease: long-term lung disease that makes it hard to breathe out, including emphysema and chronic bronchitis.
From a breathing test (spirometry): how much air you can blow out in the first second. Often given as a percentage of what is expected for your age, height and sex.
Contraindication
A reason a treatment, test or procedure should not be given to a particular person, such as an allergy, another illness or a medicine they take.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
COPD
Chronic obstructive pulmonary disease: long-term lung disease that makes it hard to breathe out, including emphysema and chronic bronchitis.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
FEV1
From a breathing test (spirometry): how much air you can blow out in the first second. Often given as a percentage of what is expected for your age, height and sex.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
The ultrasound guided stellate ganglion blocks will be performed by a pain management specialist with extensive experience performing these blocks. The first SGB at the initial visit will be performed on the right side, and the second SGB will be on the left side 5-10 days after the first SGB, given that the patient tolerated the first SGB.
Drug: Stellate Ganglion Block
The stellate ganglion will be identified using ultrasound guidance, and after a test does of 1% lidocaine, 1% mepivacaine will be injected near the stellate ganglion.
Also known as: mepivacaine
Clinical Global Impression - Improvement (CGI-I) Score
Participants will be asked about their change in olfactory dysfunction on a 7-point Likert scale from much better to much worse.
Time frame: 5-10 days post SGB #1 and 1 month
University of Pennsylvania Smell Identification Test (UPSIT)
Participants will complete the 40-item scratch and sniff UPSIT and mean change will be assessed. The UPSIT has a minimum score of 0 and maximum score of 40 with lower scores indicating a greater degree of impairment. An UPSIT score of \>33 for men and \>34 for women is considered normosmic, and the minimal clinically important difference is a change of 4 points.
Time frame: baseline, 5-10 days, and 1 month
Olfactory Dysfunction Outcomes Rating (ODOR)
Participants will be asked to complete the ODOR, which is a patient-reported outcome measure assessing physical problems, functional limitations, and emotional consequences of olfactory dysfunction. The ODOR has a minimum score of 0 and a maximum score of 112 with higher scores indicating a greater degree of impairment and limitation. The minimal clinically important difference is a change of 15 points.
Time frame: baseline, 5-10 days post SGB #1, and 1 month
Clinical Global Impression - Severity (CGI-S) Score
Participants will be asked about the severity of their olfactory dysfunction (and gustatory dysfunction) on a 5-point Likert scale from no smell loss to severe smell loss.
Time frame: baseline, 5-10 days, and 1 month
| Milestone | Stellate Ganglion Block |
|---|---|
| Started | 20 |
| Completed | 20 |
| Not completed | 0 |
Participants will be asked about their change in olfactory dysfunction on a 7-point Likert scale from much better to much worse.
| Participants | Stellate Ganglion Block |
|---|---|
| CGI-I for Smell Loss at 1 Week — About the Same | 12 |
| CGI-I for Smell Loss at 1 Week — Slightly Better | 8 |
| CGI-I for Smell Loss at 1 Week — Moderately Better | 0 |
| CGI-I for Smell Loss at 1 Week — Much Better | 0 |
| CGI-I for Smell Loss at 1 Month — About the Same | 10 |
| CGI-I for Smell Loss at 1 Month — Slightly Better | 6 |
| CGI-I for Smell Loss at 1 Month — Moderately Better | 3 |
| CGI-I for Smell Loss at 1 Month — Much Better | 1 |
| CGI-I for Smell Distortion at 1 Week — About the Same | 11 |
| CGI-I for Smell Distortion at 1 Week — Slightly Better | 9 |
| CGI-I for Smell Distortion at 1 Week — Moderately Better | 0 |
| CGI-I for Smell Distortion at 1 Week — Much Better | 0 |
| CGI-I for Smell Distortion at 1 Month — About the Same | 11 |
| CGI-I for Smell Distortion at 1 Month — Slightly Better | 6 |
| CGI-I for Smell Distortion at 1 Month — Moderately Better | 2 |
| CGI-I for Smell Distortion at 1 Month — Much Better | 1 |
| CGI-I for Taste Loss at 1 Week — About the Same | 15 |
| CGI-I for Taste Loss at 1 Week — Slightly Better | 4 |
| CGI-I for Taste Loss at 1 Week — Moderately Better | 1 |
| CGI-I for Taste Loss at 1 Week — Much Better | 0 |
| CGI-I for Taste Loss at 1 Month — About the Same | 14 |
| CGI-I for Taste Loss at 1 Month — Slightly Better | 3 |
| CGI-I for Taste Loss at 1 Month — Moderately Better | 2 |
| CGI-I for Taste Loss at 1 Month — Much Better | 1 |
| CGI-I for Taste Distortion at 1 Week — About the Same | 13 |
| CGI-I for Taste Distortion at 1 Week — Slightly Better | 6 |
| CGI-I for Taste Distortion at 1 Week — Moderately Better | 1 |
| CGI-I for Taste Distortion at 1 Week — Much Better | 0 |
| CGI-I for Taste Distortion at 1 Month — About the Same | 12 |
| CGI-I for Taste Distortion at 1 Month — Slightly Better | 5 |
| CGI-I for Taste Distortion at 1 Month — Moderately Better | 2 |
| CGI-I for Taste Distortion at 1 Month — Much Better | 1 |
Participants will complete the 40-item scratch and sniff UPSIT and mean change will be assessed. The UPSIT has a minimum score of 0 and maximum score of 40 with lower scores indicating a greater degree of impairment. An UPSIT score of \>33 for men and \>34 for women is considered normosmic, and the minimal clinically important difference is a change of 4 points.
| units on a scale | Stellate Ganglion Block |
|---|---|
| UPSIT at Baseline | 16.5 (4 to 32) |
| UPSIT at 1 Week | 21 (10 to 31) |
| UPSIT at 1 Month | 22.5 (10 to 35) |
Participants will be asked to complete the ODOR, which is a patient-reported outcome measure assessing physical problems, functional limitations, and emotional consequences of olfactory dysfunction. The ODOR has a minimum score of 0 and a maximum score of 112 with higher scores indicating a greater degree of impairment and limitation. The minimal clinically important difference is a change of 15 points.
| score on a scale | Stellate Ganglion Block |
|---|---|
| ODOR at Baseline | 62 (16 to 85) |
| ODOR at 1 Week | 57 (13 to 82) |
| ODOR at 1 Month | 50.5 (2 to 75) |
Participants will be asked about the severity of their olfactory dysfunction (and gustatory dysfunction) on a 5-point Likert scale from no smell loss to severe smell loss.
| Participants | Stellate Ganglion Block |
|---|---|
| CGI-S for Smell Loss at Baseline — No Problem | 0 |
| CGI-S for Smell Loss at Baseline — Very Mild Problem | 1 |
| CGI-S for Smell Loss at Baseline — Mild Problem | 2 |
| CGI-S for Smell Loss at Baseline — Moderate Problem | 5 |
| CGI-S for Smell Loss at Baseline — Severe Problem | 12 |
| CGI-S for Smell Loss at 1 Week — No Problem | 0 |
| CGI-S for Smell Loss at 1 Week — Very Mild Problem | 3 |
| CGI-S for Smell Loss at 1 Week — Mild Problem | 2 |
| CGI-S for Smell Loss at 1 Week — Moderate Problem | 8 |
| CGI-S for Smell Loss at 1 Week — Severe Problem | 7 |
| CGI-S for Smell Loss at 1 Month — No Problem | 0 |
| CGI-S for Smell Loss at 1 Month — Very Mild Problem | 5 |
| CGI-S for Smell Loss at 1 Month — Mild Problem | 1 |
| CGI-S for Smell Loss at 1 Month — Moderate Problem | 9 |
| CGI-S for Smell Loss at 1 Month — Severe Problem | 5 |
| CGI-S for Smell Distortion at Baseline — No Problem | 1 |
| CGI-S for Smell Distortion at Baseline — Very Mild Problem | 1 |
| CGI-S for Smell Distortion at Baseline — Mild Problem | 1 |
| CGI-S for Smell Distortion at Baseline — Moderate Problem | 5 |
| CGI-S for Smell Distortion at Baseline — Severe Problem | 12 |
| CGI-S for Smell Distortion at 1 Week — No Problem | 1 |
| CGI-S for Smell Distortion at 1 Week — Very Mild Problem | 1 |
| CGI-S for Smell Distortion at 1 Week — Mild Problem | 4 |
| CGI-S for Smell Distortion at 1 Week — Moderate Problem | 4 |
| CGI-S for Smell Distortion at 1 Week — Severe Problem | 10 |
| CGI-S for Smell Distortion at 1 Month — No Problem | 3 |
| CGI-S for Smell Distortion at 1 Month — Very Mild Problem | 1 |
| CGI-S for Smell Distortion at 1 Month — Mild Problem | 2 |
| CGI-S for Smell Distortion at 1 Month — Moderate Problem | 5 |
| CGI-S for Smell Distortion at 1 Month — Severe Problem | 9 |
| CGI-S for Taste Loss at Baseline — No Problem | 0 |
| CGI-S for Taste Loss at Baseline — Very Mild Problem | 3 |
| CGI-S for Taste Loss at Baseline — Mild Problem | 2 |
| CGI-S for Taste Loss at Baseline — Moderate Problem | 4 |
| CGI-S for Taste Loss at Baseline — Severe Problem | 11 |
| CGI-S for Taste Loss at 1 Week — No Problem | 0 |
| CGI-S for Taste Loss at 1 Week — Very Mild Problem | 4 |
| CGI-S for Taste Loss at 1 Week — Mild Problem | 2 |
| CGI-S for Taste Loss at 1 Week — Moderate Problem | 5 |
| CGI-S for Taste Loss at 1 Week — Severe Problem | 9 |
| CGI-S for Taste Loss at 1 Month — No Problem | 0 |
| CGI-S for Taste Loss at 1 Month — Very Mild Problem | 5 |
| CGI-S for Taste Loss at 1 Month — Mild Problem | 2 |
| CGI-S for Taste Loss at 1 Month — Moderate Problem | 7 |
| CGI-S for Taste Loss at 1 Month — Severe Problem | 6 |
| CGI-S for Taste Distortion at Baseline — No Problem | 2 |
| CGI-S for Taste Distortion at Baseline — Very Mild Problem | 2 |
| CGI-S for Taste Distortion at Baseline — Mild Problem | 1 |
| CGI-S for Taste Distortion at Baseline — Moderate Problem | 3 |
| CGI-S for Taste Distortion at Baseline — Severe Problem | 12 |
| CGI-S for Taste Distortion at 1 Week — No Problem | 2 |
| CGI-S for Taste Distortion at 1 Week — Very Mild Problem | 3 |
| CGI-S for Taste Distortion at 1 Week — Mild Problem | 1 |
| CGI-S for Taste Distortion at 1 Week — Moderate Problem | 5 |
| CGI-S for Taste Distortion at 1 Week — Severe Problem | 9 |
| CGI-S for Taste Distortion at 1 Month — No Problem | 3 |
| CGI-S for Taste Distortion at 1 Month — Very Mild Problem | 2 |
| CGI-S for Taste Distortion at 1 Month — Mild Problem | 2 |
| CGI-S for Taste Distortion at 1 Month — Moderate Problem | 6 |
| CGI-S for Taste Distortion at 1 Month — Severe Problem | 7 |
Collected over 5 weeks. Non-serious events are listed at a 0% frequency threshold.
| Group | Deaths | Serious | Other |
|---|---|---|---|
| Stellate Ganglion Block | 0/20 (0%) | 0/20 (0%) | 20/20 (100%) |
| Event | Stellate Ganglion Block |
|---|---|
| Horner syndromeNervous system disorders | 20/20 |
| HoarsenessNervous system disorders | 9/20 |
| GlobusNervous system disorders | 7/20 |
| Brief lightheadednessCardiac disorders | 5/20 |
| Numbness of the faceNervous system disorders | 4/20 |
| Mild shortness of breathRespiratory, thoracic and mediastinal disorders | 4/20 |
| Nasal congestionGeneral disorders | 3/20 |
| Pain at the injection siteGeneral disorders | 3/20 |
| FatigueGeneral disorders | 3/20 |
| CoughGeneral disorders | 1/20 |
| Age, Continuous(years) | Stellate Ganglion Block |
|---|---|
| Mean | 46 ± 11 |
| Sex: Female, Male(Participants) | Stellate Ganglion Block |
|---|---|
| Female | 16 |
| Male | 4 |
| Race (NIH/OMB)(Participants) | Stellate Ganglion Block |
|---|---|
| American Indian or Alaska Native | 0 |
| Asian | 0 |
| Native Hawaiian or Other Pacific Islander | 0 |
| Black or African American | 0 |
| White | 20 |
| More than one race | 0 |
| Unknown or Not Reported | 0 |
PDFs hosted by the registry, ClinicalTrials.gov.
Plan to share: No
Ran from Sep 2022 to primary completion in Dec 2022, 3 months.
Results were first posted in Nov 2023, 10 months after primary completion.
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Studies of the drug tested here: Mepivacaine
Washington University School of Medicine →