London, Sep 23 : A Covid-19 infection may prompt auto-immune disorder, the Guillain-Barre syndrome (GBS), finds a study.
In the disorder, a person's immune system attacks the nerves, causing muscle weakness and occasionally, paralysis.
The condition is triggered by an acute bacterial or viral infection and can last for weeks or several years.
Since the beginning of the pandemic, doctors have reported over 90 GBS cases following a possible Covid-19 infection.
However, whether Covid-19 is another potential infectious trigger or whether the reported cases are coincidental is unclear.
"Our study shows that Covid-19 may precede Guillain-Barre syndrome in rare cases," said Bart C Jacobs, from Erasmus MC, University Medical Center Rotterdam, the Netherlands.
"But the existence of a true association or causal relation still needs to be established," he added.
The findings are published in the journal Brain.
Using an international collection of GBS patients known as the International GBS Outcome Study (or IGOS), researchers studied patients from January 30 until May 30, 2020.
Some 49 Guillain-Barre syndrome patients were added to the study during this period from China, Denmark, France, Greece, Italy, the Netherlands, Spain, Switzerland, and the UK.
In this cohort study, 22 per cent of the GBS patients included during the first four months of the pandemic had a preceding Covid-19 infection.
These patients were all over 50 years of age and patients frequently (65 per cent) experienced facial palsy (64 per cent) and had a demyelination form of GBS.
Demyelination is a condition that results in damage to the protective covering (myelin sheath) that surrounds nerve fibers in the brain, optic nerves, and spinal cord.
At hospital admission, 73 per cent of the GBS patients with a Covid-19 infection had increased inflammatory markers.
All these patients fulfilled the diagnostic criteria for both the GBS and Covid-19.
Researchers here emphasised, however, that they did not find more patients diagnosed with the GBS during the first four months of the pandemic compared to previous years.
This suggests that while a strong association between a Covid-19 infection and the GBS is not likely, a Covid-19 infection may sometimes lead patients to develop the disorder.
Meanwhile, the GBS has also been linked with Covid vaccinations.
It has been listed by the European health regulatory body as a "very rare" side effect of the AstraZeneca Covid vaccine, known as Covishield in India.
The Johnson (and) Johnson vaccine against Covid, developed using the same technology as AstraZeneca, was also listed for the GBS recently.
A study, published in the peer-reviewed medical journal Annals of Neurology in June, described an unusual variant of Guillain-Barre syndrome characterised by prominent facial weakness in seven cases from a regional medical centre in Kerala, India.
The cases occurred within two weeks of the first dose of vaccination.
"Six out of the seven patients progressed to areflexic quadriplegia and required mechanical ventilatory support," said Boby Varkey Maramattom, from the Department of Neurology, Aster Medcity, Kochi, Kerala.
"The frequency of GBS was 1.4 to 10 fold higher than that expected in this period for a population of this magnitude.
In addition, the frequency of bilateral facial weakness, which typically occurs in less than 20 per cent of GBS cases, suggests a pattern associated with the vaccination," he added.