An expert has warned it “remains to be seen” whether the coronavirus causes similar brain damage as Spanish flu.
The 1918 pandemic left some sufferers battling viral encephalitis, brain swelling that can occur if a pathogen enters the central nervous system.
Some survivors went on to develop viral Parkinsonism, defined as symptoms similar to Parkinson’s disease like shaking and stiff movements.
It is increasingly coming to light that a relatively small group of coronavirus patients endure neurological complications, like strokes or delirium.
A small study by University College London (UCL) found a “higher than expected number of people” showed signs of brain damage, with such patients not necessarily having severe respiratory symptoms.
Early research suggests the coronavirus is mild in four out of five cases, however, it can trigger a disease of the airways called COVID-19.
Neurological complications ‘higher than expected’
The UCL scientists analysed 43 patients, aged 16 to 85, with confirmed or suspected coronavirus.
Ten of these individuals had transient encephalopathies, temporary brain dysfunction, alongside delirium or psychosis. Nine made a full recovery with just supportive care.
The scientists also picked up on a dozen cases of brain inflammation, of which nine were acute disseminated encephalomyelitis (ADEM).
ADEM is defined as a “brief but widespread attack of inflammation in the brain and spinal cord”. This damages the fatty protective covering that surrounds nerves and allows electrical impulses to be transmitted.
Viral or bacterial infections are a recognised cause.
The scientists noted they typically see one ADEM case per month. This rose to an incident a week from around early March, when the coronavirus outbreak really took hold in the UK.
Of the nine ADEM cases, five had internal bleeding and one suffered tissue death of one of their organs.
One of the patients made a full recovery, 10 had a partial recovery and one died.
Eight cases of stroke and eight other forms of nerve damage were also identified. The latter was mainly Guillain-Barré syndrome, a neurological condition that in severe cases leaves patients struggling to swallow, walk or even breathe.
Six of the eight patients with nerve damage made a “partial and ongoing recovery”.
“We identified a higher than expected number of people with neurological conditions such as brain inflammation, which did not always correlate with the severity of respiratory symptoms,” said study author Dr Michael Zandi.
“We should be vigilant and look out for these complications in people who have had COVID-19.
“Whether we will see an epidemic on a large scale of brain damage linked to the pandemic – perhaps similar to the encephalitis lethargica [sleeping sickness] outbreak in the 1920s and 1930s after the 1918 influenza pandemic – remains to be seen.”
Perhaps surprisingly, the coronavirus was not detected in the cerebrospinal fluid of any of the patients who were tested for the pathogen, suggesting it indirectly attacks the brain.
Although unclear, the scientists wondered whether the immune response triggered by the infection causes inflammation that damages the vital organ.
Previous coronavirus research by UCL also found a “higher than expected number of patients with stroke”, which was put down to it making blood “stickier”.
“Given the disease has only been around for a matter of months, we might not yet know what long-term damage COVID-19 can cause,” said study author Dr Ross Paterson.
“Doctors needs to be aware of possible neurological effects, as early diagnosis can improve patient outcomes.”
‘Time will tell’
Dr David Strain from the University of Exeter called the UCL scientists’ results “not surprising at all”.
Early research suggests between 20% and 30% of all coronavirus patients develop delirium or a change to their mental status while in hospital, rising to 60% to 70% in particularly severe cases.
Calls have also been made for greater research into so-called post-COVID syndrome, with some scientists questioning whether it is a condition in its own right.
Dr Strain added we do not know how frequently neurological complications arise, with further research being required.
Professor Anthony David from UCL said there was “rightly no attempt to estimate the incidence of the disorders described in the [UCL] paper since the cases were identified by interested clinicians willing to share their knowledge”.
He pointed out more than 11 million cases of the coronavirus have been diagnosed worldwide since the outbreak emerged at the end of 2019.
“This, plus the scrutiny the pandemic attracts, means it would be very unlikely there is a large parallel pandemic of unusual brain damage linked to COVID-19”, said Professor David.
Nevertheless, some degree of neurological symptoms is “very likely”.
“Post-infection neurological syndromes comprise a chapter found in all textbooks of neurology and this topic has been boosted by the recent description of novel autoimmune encephalitides [brain inflammation]”, he said.
“COVID-19 can now be added to the list of possible causes.
“Will that chapter remain a relatively slim esoteric one? In my opinion, probably yes, as I think these complex neuropsychiatric conditions associated with COVID-19 are likely to be rare.”
Professor David pointed out people who survived Spanish flu but went on to develop sleeping sickness were not found to have traces of the pathogen in their brain, suggesting the complication was “immune mediated”.
“Again, despite the scrutiny on the current pandemic and the near instantaneous speed of information sharing in the internet age we have yet to hear of the first case of post COVID-19 encephalitis lethargica and so it seems unlikely these neurological complications will be common symptoms but time will tell,” he added.
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