Efficacy of Stellate Ganglion Block in Treating Long-Term COVID-19-Related Olfactory and Gustatory Dysfunction: A Case Series

Parosmia: Pathophysiology and Management

PURPOSE OF REVIEW

Parosmia is a qualitative olfactory disorder in which there is a mismatch between the memory of an odor and the actual experience triggered by an odor. There has been a surge in parosmia-related publications since the COVID-19 pandemic. This review summarizes the latest clinical findings, theories on pathophysiology and potential treatment options.

RECENT ADVANCES

Potential models of parosmia include peripheral or central hypotheses, which refer to aberrancies in olfactory neuron regeneration or information processing in central olfactory centers respectively. This leads to an incomplete or disorganized pattern of olfactory information relay. Studies using gas chromatography and functional magnetic resonance imaging have identified molecular triggers and intracranial functional connectivity patterns in parosmia respectively. Parosmia tends to occur in a delayed fashion after virus-induced anosmia. It may run a protracted course, but typically improves over time. Currently there are no generally approved, objective ways to ascertain the presence and measure the extent of parosmia. Evidence-based treatment for parosmia remains elusive. In some people, this can lead to health and quality of life issues.

The Effectiveness and Safety of Stellate Ganglion Block in the Treatment of Symptoms from Long COVID-19: A Pilot Study

Purpose

Pilot study to evaluate the safety and effectiveness of stellate ganglion blocks in the treatment of symptoms related to long COVID infection.

Materials and Methods

A total of 17 patients who underwent stellate ganglion block for the treatment of their long COVID symptoms were included. COMPASS-31, GAD-7, PCL-5, and Fatigue Severity Score (FSS) pre and post intervention surveys and data on baseline heartrate and post- block heart rate recorded in the EMR.

Results

A total of 94% of patients reported moderate-to-severe autonomic dysfunction pre-procedure as measured by COMPASS-31. All patients reported some degree of symptomatic improvement from the block. Specifically, patients had significantly lower FSS scores (P = 0.002) and heart rate post-procedure (P = 0.008). Although the decrease in PCL-5 scores after the procedure was clinically meaningful, this change was not statistically significant (P = 0.159). No significant difference was found in pre and post procedure GAD-7 scores (P = 0.101).

Conclusions

Stellate ganglion block is a safe, low-risk, minimally invasive, and effective procedure in the treatment of symptoms for long COVID. It should be evaluated as an adjunctive treatment of select patients in this population.

Stellate ganglion block for treating post-COVID-19 parosmia

BACKGROUND

Post-COVID parosmia may be due to dysautonomia and sympathetic hyperresponsiveness, which can be attenuated by stellate ganglion block (SGB). This study evaluates SGB as a treatment for post-COVID olfactory dysfunction (OD).

METHODS

Retrospective case series with prospective data of patients with post-COVID OD undergoing unilateral (UL) or bilateral (BL) SGB. Patients completed Brief Smell Identification Tests (BSIT) (12 points maximum) and post-procedure surveys including parosmia severity scores on a scale of 1 (absent) to 10 (severe). Scores were compared from before treatment (pre-SGB) to after first (SGB1) or second (SGB2) treatments in overall, UL, and BL cohorts.

RESULTS

Forty-seven patients with post-COVID OD underwent SGB, including 23 UL and 24 BL. Twenty patients completed pre- and post-SGB BSITs (eight UL and 12 BL). Twenty-eight patients completed postprocedure surveys (11 UL and 17 BL). There were no differences in BSIT scores from pre-SGB to post-SGB1 or post-SGB2 for the overall (p = 0.098), UL (p = 0.168), or BL (p = 0.230) cohorts. Parosmia severity for the overall cohort improved from pre-SGB (8.82 ± 1.28) to post-SGB1 (6.79 ± 2.38) and post-SGB2 (5.41 ± 2.35), with significant differences from pre-SGB to post-SGB1 (p < 0.001) and pre-SGB to post-SGB2 (p < 0.001), but not post-SGB1 to post-SGB2 (p = 0.130). Number of parosmia triggers decreased for overall (p = 0.002), UL (p = 0.030) and BL (p = 0.024) cohorts. Quality of life (QOL) improved for all cohorts regarding food enjoyment, meal preparation, and socialization (p < 0.05).

CONCLUSION

SGB may improve subjective parosmia and QOL for patients with post-COVID OD, however it may not affect odor identification. Further placebo-controlled studies are warranted.