Stellate Ganglion Block With Lidocaine for the Treatment of COVID-19-Induced Parosmia

Stellate Ganglion Block With Lidocaine for the Treatment of COVID-19-Induced Parosmia: Double-Blinded, Placebo-Controlled Randomized Clinical Trial

Chronic olfactory dysfunction, both hyposmia and parosmia, from the COVID-19 pandemic is a growing public health crisis, affecting up to 1.2 million people in the United States. Olfactory dysfunction significantly impacts one's quality of life by decreasing the enjoyment of foods, creating environmental safety concerns, and affecting one's ability to perform specific jobs. Olfactory loss is also an independent predictor of anxiety, depression, and mortality.

Recent research suggests that parosmia, more so than hyposmia, can increase anxiety, depression, and even suicidal ideation. While the pandemic has advanced the scientific community's interest in combating the burgeoning health crisis, few effective treatments currently exist for olfactory dysfunction. Persistent symptoms after an acute COVID-19 infection, or "Long COVID" symptoms, have been hypothesized to result from sympathetic nervous system dysfunction. 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 before 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. A previous pilot study using stellate ganglion blocks of 20 participants with persistent COVID-19 olfactory dysfunction resulted in modest improvements in subjective olfactory function, smell identification, and olfactory-specific quality of life, but it lacked a control group.

Therefore, we propose a double-blinded, placebo-controlled, randomized clinical trial assessing the efficacy of a stellate ganglion block with Lidocaine versus saline injection in up to 50 participants with persistent COVID-19-associated olfactory dysfunction.

This will be a double-blinded, placebo-controlled, randomized clinical to assess the efficacy of Stellate Ganglion Block with Lidocaine 1% (8mL). Participants with parosmia will be randomly assigned to SGB with Lidocaine 1% (8mL) or Placebo (saline solution). Baseline assessment will happen in person and will consist on demographic information, Parosmia Olfactory Dysfunction Outcomes Rating (DisODOR), Clinical Global Impression: Severity Scale (CGI-S), University of Pennsylvania Smell Identification Test (UPSIT), Long-COVID Questionnaire (LCQ), Olfaction Catastrophizing Scale (OCS), Hospital Anxiety and Depression Scale (HADS), Pre-Intervention Expectations. Then, after the assigned interventional procedures are performed three remote visits will be performed as follow-ups (1, 3, and 12 months), in which the variables above will be reassessed.

Inclusion Criteria:

1. Adults age 18 to 70
2. Diagnosis of COVID-19 at least 6 months prior to study enrollment with self-reported parosmia
3. Ability to read, write, and understand English
4. Score of at least 15 on DiSODOR

Exclusion Criteria:

1. History of smell loss or change prior to COVID-19 infection

2. History of conditions known to impact olfactory function:

   1. Chronic rhinosinusitis
   2. History of prior sinonasal or skull base surgery
   3. Neurodegenerative disorders (Parkinson's disease, Huntington's disease, Amyotrophic lateral sclerosis, Lewy body dementia, frontotemporal dementia)

3. Currently using concomitant therapies specifically for the treatment of olfactory dysfunction

4. Inability to tolerate a needle injection into the neck

5. History of coexisting conditions that make SGB contraindicated:

   1. Unilateral vocal cord paralysis
   2. Severe chronic obstructive pulmonary disease (FEV1 between 30-50% of predicted)
   3. Recent myocardial infarction within the last year
   4. Glaucoma
   5. Cardiac conduction block of any degree

6. Currently taking blood thinners or antiplatelet agents

7. Allergy to local anesthetic

8. Inability to extend the neck for any reason (e.g., severe arthritis)