Current DateSeptember 24, 2021

The effects of Covid-19 on the nervous system

The fact that Covid-19 also affects organs other than the lungs is not new: more and more, the infection with the coronavirus proves to be a body-wide disease, which also does not spare the nerves and the brain. Several research teams have now compiled the neurological consequences and side effects that Covid-19 can cause. According to reports, brain inflammation, damage to the myelin envelopes of the nerve pathways and also brain strokes occur not only in patients with severe cases, but also in mild cases. Although the percentage of such complications is low, this could affect thousands because of the high number of infections.

The coronavirus Sars-CoV-2 affects a whole range of tissues and organs of the body. In addition to the nose, airways and lungs, virus-sensitive cells are also found in the intestines, blood vessels or kidneys. The fact that up to two-thirds of all infected people develop olfactory disorders also demonstrates that the coronavirus also attacks the nerves. The olfactory nerve can also allow the virus to reach the brain relatively unhindered.

Indeed, as early as April 2020, Chinese physicians reported a conspicuous increase in neurological symptoms in Covid-19 patients in Wuhan. Just over a third of the 214 patients they examined showed neurological symptoms of various types, from headaches to dizziness, delirium to seizures and brain inflammation. Because Sars-CoV-2 also alters blood clotting, strokes are more common than normal.

Inflammation of the brain, nerve damage and paralysis

Until now, however, it remained unclear how often such neurological side effects of coronavirus infection occur. To provide more clarity, Mark Ellul of the University of Liverpool and his colleagues evaluated case reports and studies from around the world by mid-May 2020. In total, they encountered 901 cases of Covid-19 patients with neurological complications. 93 of these patients suffered from encephalopathy and thus large-scale changes in the brain, in eight cases brain inflammation (encephalitis) occurred and 19 patients developed Guillain-Barré syndrome – a temporary paralysis caused by inflammatory nerve changes. In addition, there were also cases of inflammation and signs of failure of peripheral nerves or the spinal cord, as well as seizures and other symptoms of impaired nerve function. However, whether these neurological diseases are caused by the coronavirus itself or indirectly by the compromised immune system remains to be seen, the researchers explain.

As the case analyses showed, such neurological abnormalities occur not only in patients with severe histories, but also in mild cases. For example, Ellul and his team describe the case of a 24-year-old man in Japan who initially suffered only from sore throats, fever and exhaustion. After nine days, however, confusion and periodic unconsciousness developed, in addition to more and more frequent seizures. Investigations revealed severe brain inflammation caused by Covid-19. The man’s condition deteriorated so badly that he had to be intubated and ventilated – not because of shortness of breath or lung damage, but because of the seizures. “It is important that physicians around the world are aware that Covid-19 can also cause encephalitis and other brain changes, as they can have severe, sometimes life-changing, consequences,” ellul’s colleague Ava Easton said. Similar to meningitis, encephalitis can also lead to permanent failures and late effects.

Even in mild cases without respiratory symptoms

Encephalomyelitis is also very common among neurological covid-19 manifestations. In this acute disseminated encephalomyelitis, the immune system attacks the myelin sheaths of the nerve pathways and thus disturbs the nerve conduction. Typically, this autoimmune reaction occurs a few weeks after infection, but is well treatable with cortisone preparations and then subsides. Typical symptoms include headaches, visual disturbances, gait disorders and paralysis, but also seizures. As Ellul and his team noted, Covid-19 can also cause this encephalomyelitis in adults – even with almost total absence of other typical infection symptoms. They describe the case of a middle-aged American woman who complained of head and muscle pain, then developed increasing speech disorders and left-side paralysis. Only a PCR test revealed her Sars-CoV-2 infection.

Michael Zandi of University College London and his colleagues also report on such an accumulation of brain inflammation and encephalomyelitis. They had examined 43 Covid-19 patients who had been treated at their university hospital for neurological complications. Among the patients were 12 cases of encephalitis, ten with acute disseminated encephalomyelitis, eight with strokes and eight with Guillain-Barré syndrome and similar failure symptoms. “Overall, we identified more such neurological cases than we expected – and not always these patients had pronounced respiratory symptoms,” Zandi says. Given the high number of cases in the Corona pandemic, he also believes it is very likely that there could be many such neurological complications overall – even if their proportion is not high compared to other symptoms and complications. In his view, it is also important to keep an eye on patients after apparently surviving infection, because some of these complications can only manifest themselves a few weeks later. “We should be vigilant and be prepared for such complications during the recovery period,” Zandi said.