And hopefully give me some hope? I'm 2 months in and while my smell has seemingly mostly come back my taste is still severely diminished. I thought I was making progress as I could taste things for the first few bites before the tast faded away. The past couple days it seems to have regressed. I'm really starting to get nervous that I won't get my taste back.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7885920/?fbclid=IwAR1N07d7IxnqR1_ENXB6VggIMOKJADkgySi3Ur4xNzEXPZ_qhkS-xKOEO2s

They're saying 3 things, generally. They do not see viral replication happening in neurons. They do see changes in gene expression in the neurons involved in smell. They think it's because the genome in the neurons is becoming disorganized, and probably because of signals coming from the non-neural cells that are infected.

It's an interesting paper, though I'm not sure they have sufficient sample size for claiming nuclear architecture disruption using the assay they did, but that assay gets you published.

I have no idea if it is transferable to taste. Need a different doctor, but if taste and smell signals generally work through similar cell signaling and neural architecture structure, then maybe?

I guess I'm wondering if these are positive indications that there isn't permanent damage and smell/taste will eventually come back or if it points to long lasting problems that aren't correctable.

REALLY painful article and a nice read by Cis. I don't think it says too much about the potential recovery. My GUESS is that it's more favorable for the non-neuronal, olfactory support cells to be affected than a direct effect upon the sensory neurons, but the whole system needs to be working in order for any of it to work. Much of taste is only smell, and there probably isn't a significant direct effect on taste epithelium, so it's generally expected that return of normal smell function will cause a return of taste function.

I'm more of a molecular person and all my neuro days was developmental, so forgive if I misunderstand. I think the key suggested by this paper is that they aren't showing evidence of neuroinvasive infection. The nasal epithelium is supposed to be highly regenerative though, right? So the delay in return has more to do with epithelial shedding and regeneration. This isn't unlike smoke burning out your sense of smell for a few days.

No idea if taste works the same way.

cisgenderedAggie said:

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I'm more of a molecular person and all my neuro days was developmental, so forgive if I misunderstand. I think the key suggested by this paper is that they aren't showing evidence of neuroinvasive infection. The nasal epithelium is supposed to be highly regenerative though, right? So the delay in return has more to do with epithelial shedding and regeneration. This isn't unlike smoke burning out your sense of smell for a few days.

No idea if taste works the same way.

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Correct. As the olfactory sensory neurons do not have ACE-2 and tmprss 2 receptors, the authors hypothesize that the mechanism of anosmia and hyposmia or dysosmia is not via direct viral infection of these neurons. Rather, they propose that the virus directly infects other nearby nasal epithelial cells and then this probably initiates a local cytokine-mediated neuropathy which causes disruption of the sensory neuron's neural architecture.

Obviously, this cytokine mediated inflammatory pathway is quite localized - hence the lack of mechanical obstruction seen in many of these patients who contract COVID. This is not consistent with how most viral-induced URIs are causing anosmia/hyposmia/dysosmia. This is why we normally treat sudden loss of sense of smell with steroids, without a whole lot of great evidence as to efficacy.

As far as recovery goes, I'm not sure I would categorize the nasal OLFACTORY epithelium as highly regenerative. The rest of the epithelium is definitely more easily regenerated than the olfactory epithelium. This is probably why it has been seen that recovery can take a year or more after a viral induced anosmia.

HTH. Don't ask me for more - that article was painful, and it's Friday.