Considered cardinal symptoms of COVID-19 infection,¹ loss of taste (ageusia) and smell (anosmia) has been reported to affect 36.6% and 38.2% of COVID-19 patients, respectively.² While these symptoms are generally self-limiting, and in most cases resolve spontaneously in a matter of weeks to months, multiple studies confirm up to 7% of patients continue to experience taste and smell impairments, even beyond 12 months.³ Certainly, this can be a frustrating, even depressing, syndrome to live with!

Many theories have been proposed to explain the link between COVID-19 infection and anosmia, and likely, multiple factors are at play. A focal point of discussion surrounds the angiotensin-converting enzyme 2 (ACE2) receptor. This receptor is known to bind the spike portion of the COVID-19 virus and facilitate its entry into cells, including the olfactory nerve cells (responsible for smell). While the ACE2 receptor is occupied with the virus, there is disinhibition, even perpetuation, of a downstream inflammatory response.³ In response to this inflammation, the autonomic nervous system activates a sympathetic (i.e., ‘flight or fight’) response. Ongoing viral replication within the nerve cell, disruption of multiple genomic components – even affecting the production and maintenance of the olfactory receptors themselves,⁴ and other tissue injury can result in a chronic sympathetic hyperresponsiveness. Also known as dysautonomia, chronic sympathetic hyperresponsiveness is commonly associated with impaired cerebral blood flow.³ This lack of blood flow may affect areas of the brain associated with the sense of smell and may also explain in part other symptoms of “long-COVID”, including chronic fatigue, brain fog, insomnia, anxiety, and depression.

The stellate ganglion is a group of sympathetic nerves primarily located anterior to the transverse process of C7 (lower neck) and provides most of the sympathetic innervation to the head, neck, and arms. Pain specialists have long been performing stellate ganglion blocks to treat sympathetically mediated pain, such has complex regional pain syndrome (CRPS), Raynaud disease, postherpetic neuralgia, and phantom limb pain, among others. This procedure has also been used to successfully treat nonpainful conditions, such as hyperhidrosis, refractory cardiac arrhythmias, and even post-traumatic stress disorder. Now, the stellate ganglion block is being used to recover loss of taste and smell due to COVID-19, and early results are promising.^3,5

A stellate ganglion block is performed in a surgery center. The patient lies supine and can be mildly sedated to reduce discomfort and anxiety, and to maximize procedural safety. Under X-ray (fluoroscopic) guidance, a fine needle is placed near the stellate ganglion and a mixture of local anesthetic and steroid is injected. This will result in a sudden reduction of norepinephrine being released from the stellate ganglion, effectively serving to ‘hit the reset button’ on what was a sympathetic hyperresponsiveness. The expectation is for normal cerebral blood flow to be restored, especially in the areas of the brain associated with the sense of smell. While there is no guarantee of outcome, if successful, recovery of taste and smell may be immediate.⁵ It is normal to experience a droopy or red eye, vocal hoarseness, or warmth in the face for a few hours after the procedure. This will go away once the local anesthetic wears off.

If you or a loved one are suffering from chronic altered or loss of taste or smell, give our office a call to schedule a consultation and see if a stellate ganglion block is right for you.

Dustin Leek, MD

Updated 11/17/2022

References:

1. de Melo GD, Lazarini F, Levallois S, Hautefort C, Michel V, Larrous F, Verillaud B, Aparicio C, Wagner S, Gheusi G, Kergoat L, Kornobis E, Donati F, Cokelaer T, Hervochon R, Madec Y, Roze E, Salmon D, Bourhy H, Lecuit M, Lledo PM. COVID-19-related anosmia is associated with viral persistence and inflammation in human olfactory epithelium and brain infection in hamsters. Sci Transl Med. 2021 Jun 2;13(596):eabf8396. doi: 10.1126/scitranslmed.abf8396. Epub 2021 May 3. PMID: 33941622; PMCID: PMC8158965.
2. Mutiawati E, Fahriani M, Mamada SS, Fajar JK, Frediansyah A, Maliga HA, Ilmawan M, Emran TB, Ophinni Y, Ichsan I, Musadir N, Rabaan AA, Dhama K, Syahrul S, Nainu F, Harapan H. Anosmia and dysgeusia in SARS-CoV-2 infection: incidence and effects on COVID-19 severity and mortality, and the possible pathobiology mechanisms – a systematic review and meta-analysis. F1000Res. 2021 Jan 21;10:40. doi: 10.12688/f1000research.28393.1. PMID: 33824716; PMCID: PMC7993408.
3. Chauhan G, Upadhyay A, Khanduja S, Emerick T. Stellate Ganglion Block for Anosmia and Dysgeusia Due to Long COVID. Cureus. 2022 Aug 8;14(8):e27779. doi: 10.7759/cureus.27779. PMID: 36106285; PMCID: PMC9450932.
4. Zazhytska M, Kodra A, Hoagland DA, Frere J, Fullard JF, Shayya H, McArthur NG, Moeller R, Uhl S, Omer AD, Gottesman ME, Firestein S, Gong Q, Canoll PD, Goldman JE, Roussos P, tenOever BR, Jonathan B Overdevest, Lomvardas S. Non-cell-autonomous disruption of nuclear architecture as a potential cause of COVID-19-induced anosmia. Cell. 2022 Mar 17;185(6):1052-1064.e12. doi: 10.1016/j.cell.2022.01.024. Epub 2022 Feb 2. PMID: 35180380; PMCID: PMC8808699.
5. Liu LD, Duricka DL. Stellate ganglion block reduces symptoms of Long COVID: A case series. J Neuroimmunol. 2022 Jan 15;362:577784. doi: 10.1016/j.jneuroim.2021.577784. Epub 2021 Dec 8. PMID: 34922127; PMCID: PMC8653406.