Thread by @thiagoarzua

It was about time.

COVID-19 and the brain 🧠: a thread 🧵

Bring snacks and a drink, it'll be a journey.
Full references at the end.

@OpenAcademics @AcademicChatter

First things first: I am not a neurologist, nor a physician.

None of this is medical advice.

Talk to your doctor if you are feeling sick.
Stay inside if possible.
Take care of yourself and the ones you care about.

Anyway, we had evidence back from the 2003 SARS pandemic that SARS-CoV was able to infect the brain.

The theory is that the pathologies were similar in the brain and lungs: an inflammatory response out of control.

Shown here, the lesions found in the brain of a SARS patient.

Fast forward to 2020, Mao et al report on patients from Wuhan.

Out of 214 patients, ~36% had some neurological manifestation. Most of those were older (~58 yo) and had a more severe form of the infection.

Below, the CTs of a patient with an ischemic stroke - more on that later.

Mao's paper, among others, started a series of studies on the neurological aspects and diseases associated with COVID-19. To the best of my knowledge, they can be summarized as:

1) Anosmia (Loss of smell)
2) Stroke
3) Possible encephalitis
4) Guillain–Barré Syndrome

Loss of smell might sound like a detail in the grand scheme of things, but from what we have seen so far, it might be one of the first symptoms to show up.

That means that we could prevent a whole lot of people from coming in contact with others by paying attention to this.

The anosmia could also be a link between the brain and respiratory symptoms.

Li et al hypothesized that the virus could infect neurons responsible for breathing, before any damage to the lungs. Some of the receptors affected in the lungs are also expressed in some brain regions

Despite some of the scary headlines, the relationship between COVID and strokes is still really unclear.

One theory relies on the out-of-control inflammation we talked about, also known as a cytokine storm. But it can also be associated with the increased cardiac issues we see

Another hypothesis is that the virus is affecting the lining of certain blood vessels.

Oxley et al reported on 5 patients in NY (< 50 yo) who had large vessel strokes. The fact that these were relatively young and healthy being a key factor here, but more research is needed.

Next, something that has been quite rare, but worth discussing to make it clear: links between COVID and encephalitis.

We've had, as far as I can tell, only very few described cases. On the more serious one, the patient was diagnosed with Acute Necrotizing Encephalopathy (ANE).

ANE is a rare condition, often resulting from a serious viral infection. It's associated with the cytokine storm we mentioned, but at this point, we really do not know what its relation to COVID might be.

Shown here the MRI from that patient, showing the diagnostic lesions.

On that same note, the cases of Guillain–Barré Syndrome (GBS) associated with this virus are still unclear, and very rare.

GBS is a rare form of paralysis, that has, indeed, been previously associated with different viral infections, e.g. cytomegalovirus, Epstein-Barr, and Zika.

We could talk about mental health, but that could be another thread altogether (noted). Instead, I'll leave it at this:

It's not surprising to see these neurological symptoms. COVID is now clearly a systemic disease, and the brain, being the diva it is, is also being affected.

Even with these neurological factors, people still die primarily from their pulmonary and other systemic symptoms. COVID affects the whole body, and there's still a lot we don't know.

That being said: stay inside as much as possible, support your essential workers, and be safe.

As promised, here is a full list of references.

docs.google.com/document/d/1o1…