BBC Science Focus
DR RACHEL BROWN
A study carried out on a small number of confirmed or suspected COVID-19 patients at the National Hospital for Neurology and Neurosurgery has linked the coronavirus to a number of neurological conditions
A recent study has linked COVID-19 to a number of neurological conditions. We speak to researcher Rachel to explain these syndromes.
CAN YOU TELL US ABOUT YOUR RESEARCH?
COVID-19 is still predominantly a respiratory illness, but in a small subset of patients we’ve been seeing neurological symptoms and syndromes. Some of the early studies from Wuhan showed that around a third of patients were having neurological symptoms. In those early descriptions a lot of the symptoms that people were describing included things like headache and dizziness, loss of smell and things that could just really be attributed to viral illness. As we gained more experience, we noticed other cases appearing that looked a little bit different. We have information from other viral illnesses, SARS and MERS and things like that, so it wasn’t unexpected that neurological symptoms or syndromes might come out of COVID-19 as well.
At our centre, which is a specialist neuroscience centre linked with lots of different hospitals and centres across London and the UK, we already had a multidisciplinary platform for discussing inƃammator[ and infectious diseases. When COVID-19 came, we set up a weekly meeting open to colleagues across London. By doing that we were able to pool experiences as it [the disease] was coming through. That was really important, that collaborative effort, because these complications are on the rare end of the spectrum. It allowed us to spot patterns in what we were seeing. The sorts of things we were seeing were encephalopathy, which is a transient brain dysfunction; a delirium-type condition, which can be very common in infections and with hospital admission generally; and we were also seeing patients with postinfectious problems with the brain or the nerves – this ADEM-like [acute disseminated encephalomyelitis] illness and also some patients who had Guillain-Barre syndrome as well. We were also seeing some unusual strokes.
We now know that COVID-19 can make your blood sticky. In some patients, that can lead to development of stroke, even in those where there aren’t traditional risk factors.
WHAT ARE THE EFFECTS OF ADEM AND GUILLAIN-BARRE SYNDROME?
They’re both what we call para- or post
infectious inƃammator[ s[ndromes affecting the nervous system. ADEM affects the brain and the spinal cord, usually after an infection, and is usually most common in children and adolescents. Patients can get headaches, they can be drowsy, they can have weakness, sometimes seizures. But it tends to be a one-off illness with recovery afterwards.
Guillain-Barre is similar in that it’s
aNso a post infectious inƃammator[
“When these complications happen, they can be very severe, so it is important that we know about them”
syndrome, but it affects the peripheral nerves supplying movement and sensation to the arms and legs. It’s thought to be an immune cross-reaction, where the immune system mistakes certain proteins or cells in our body for viruses and can Nead to inƃammation.
HOW COMMON ARE THESE NEUROLOGICAL COMPLICATIONS LIKELY TO BE?
On the whole, I think the neurological complications are likely to be rare, and that the complications we are describing are on the more severe end of the spectrum. When these complications do happen, they can be very severe and can be life-changing, so it is important that we know about them, but on the whole they are likely to be rare.
ARE THERE ANY TREATMENTS THAT COULD LOWER THE RISK OF THESE NEUROLOGICAL COMPLICATIONS IN PATIENTS WHO ARE HOSPITALISED WITH COVID-19?
What we don’t know at the moment is exactly what is driving each of these conditions. We know that ADEM and Guillain-Barre are usually post- or parainfectious auto inƃammator[ iNNnesses but some of the cases were a little bit more unusual. We described some of the ADEM cases as ‘ADEM-like’ and saw small areas of microhaemorrhage [bleeding] more than we would expect. The delirium cases could have a range of underlying causes. For the stroke cases, the prothrombotic [abnormal blood clotting] effect that COVID-19 can trigger may be having an impact.
There are probably a number of different mechanisms underlying the different neurological syndromes that we’re seeing. One thought is whether the virus itself is doing some of this, but we don’t actually have a lot of good evidence, and few reports have actually found the virus in the brain or in the spinaN ƃuid. 5o thatos either reNated to the way we were looking for the virus or testing for it. Maybe our tests aren’t sensitive enough, or maybe it’s actually that there are other things that are underlying these conditions. The immune system is probably going to be a major factor for a number of these complications, but there also might be other factors. For example, some patients can become very hypoxic – that’s low oxygen levels – we know that that can affect the brain and the nerves. For others there may be a contributory effect of a prolonged or severe illness, including admission to the ICU.
WHAT ARE THE NEXT STEPS?
What’s been really exciting is just how much the medical community has mobilised and come together. My colleagues across the UK and the world will be trying to understand each of these conditions better to find out exactly what is driving each one. We need to look at each category. We need to see how frequently this is actually occurring and how many people it’s affecting. Is it the virus itself or the illness that is triggering it? What are the underlying mechanisms? We need to identify which patients are most at risk so that we can try and reduce the risk of these neurological complications happening, and then we need to look at how we’re going to treat each one.