A bunch of symptoms, which may persist many months or even years after an acute COVID infection has cleared, have been described in the medical literature with increasing frequency since the onset of the pandemic. This constellation of findings has been dubbed “long COVID.” Long COVID’s effects on the brain, in particular, have certainly been in the news, and it’s also been popping up in the medical literature. So, what’s the relationship between coronavirus (and the vaccine) and neurological long COVID?

Neurological long COVID

In their excellent 2024 paper, Spanish researchers reported on their experience with patients suffering neuropsychological symptoms and signs which persisted long after the acute COVID-19 infection had cleared. The scientist evaluated more than a hundred patients who’d been diagnosed with coronavirus. Eighty of the volunteers continued to suffer from persistent problems and the other twenty had recovered completely.

The subjects underwent psychological and neurological examinations as well as MRI scans. About half of the patients diagnosed in the Spanish study with long COVID had significant memory problems. About a quarter of them had problems thinking, which included language issues (fluency of speech), attention disorder, and the ability to mentally process any kind of intellectual challenge at a normal speed (slow or labored cognition). In 2023, Croatian researchers elucidated the more common clinical aspects of neurological long COVID. Based on an analysis of more than 200 patients, the Croatian doctors determined that long COVID is more common in women than men. Affected patients often suffer from a constellation of symptoms, which might include headaches, problems thinking clearly, loss of smell, numbness, tiredness, dizziness, and insomnia.

Long COVID also altered brain anatomy in many affected patients. The Spanish researchers discovered that, compared to the twenty patients who’d completely recovered from COVID, the eighty who suffered persistent neurological symptoms demonstrated MRI abnormalities. The white matter (the cables that connect different parts of the central nervous system) of those who suffered long COVID was disrupted over wide swathes of the brain. What’s more, MRI disclosed that the gray matter (the thinking part of the brain) of a significant cohort of neurological long COVID patients had wasted away in the left-sided posterior superior temporal gyrus (a part of the brain crucial for language comprehension).

Are vaccines protective against neurological long COVID?

The largest study (by far) that examined the relationship between vaccination and the development of long COVID was performed by a multinational group of scientists (American, Japanese, and British) in 2023. These researchers evaluated the medical records of more than 600,000 people. Unfortunately, their efforts weren’t focused on neurological long COVID (most of their long COVID patients reported only tiredness and shortness of breath), but I believe the conclusions may be extrapolated. The scientists discovered two important facts. Firstly, those who were vaccinated enjoyed a significantly lower chance of developing long COVID. Secondly, for those who were already suffering from long COVID, additional vaccinations (boosters) didn’t cause symptom exacerbation.

Can vaccines cause neurological long COVID?

As of April 2023, a multinational team of Swiss and German scientists pointed out that, globally, there’d already been 760 million cases of confirmed COVID-19 and more than 13 billion doses of vaccine administered. These researchers acknowledged the existence of a significant number of people who’d been injected with an mRNA-based vaccine and later developed a syndrome similar to long COVID. The manuscript’s authors cautioned the medical establishment against poo-pooing this adversely affected portion of the population by lumping them with those derogatorily referred to as ‘anti-vaxxers.’

In 2022, Saudi Arabian doctors described complications related to COVID-19 vaccines, specifically those that were likely to result in long-term neurological problems. Their report centered on three major classes of issues. Firstly, the scientists described post-vaccination cerebral venous thrombosis (blood clots in the vessels of the brain), which was often accompanied by a significant incidence of stroke. Secondly, the doctors were confronted with post-vaccination Guillain-Barré Syndrome (a potentially progressive paralysis of the legs, arms, and diaphragm (breathing muscles). Lastly, the researchers observed several patients who suffered from post-vaccination Miller-Fisher Syndrome (a disorder where the immune system attacks nerves that control the movement of the face and eyes).

A 2023 publication described the MRI findings in patients who suffered neurological complications after receiving COVID-19 vaccines. The doctors who cared for patients throughout Iran reviewed almost 90 scientific studies and reported numerous deleterious imaging sequelae of vaccinations. The most commonly observed brain injury was related to minor or major strokes. The researchers also observed (sometimes severely destructive) inflammation in widespread areas of the brain and spine.

You can plainly see that our understanding of neurological long COVID is evolving. We are learning more and more about the causes and symptoms of the dreaded syndrome. The jury is still out as to the degree of benefit or culpability of vaccines in relation to neurological long COVID.

Marc Arginteanu is a neurosurgeon and author of Azazel’s Public House.