British-Swedish pharma firm AstraZeneca said on Tuesday that it had halted late-stage clinical trials of its coronavirus vaccine after a study participant developed an adverse reaction.

The inoculation called AZD1222, which is undergoing phase 2/3 trials, is being tested on thousands of people around the world, including over 17,000 volunteers in the UK.

Although the reaction was a routine hiccup that usually occurs during clinical trials, the company did not divulge any further details on the nature of the illness in the study participant, or when the (last stage) trial is expected to resume.

Meanwhile, New York Times reported a person familiar with trials said that one UK participant had 'transverse myelitis', an inflammatory syndrome in the spinal cord which is normally caused by viral infections. It's not clear yet if this was in direct response to AstraZeneca's vaccine candidate or coincidental.

Let's take a look at what exactly us 'transverse myelitis', what are its symptoms.

What is transverse myelitis?

Transverse myelitis is a neurological condition that occurs when both sides of the same section of a person's spinal cord get inflamed damaging myelin, which is a fatty substance that covers and protects one's nerve fibres. In simple words, Transverse myelitis is an inflammation of spinal cord resulting from damage to nerve cells in a certain area. When myelin gets damaged, the nerves underneath get hurt too and once they are scarred, it becomes harder for them (nerves) to send signals to other parts of a human body the way they should. This can cause weakness in muscles, pain, sensory problems, paralysis, or bowel and bladder dysfunction.

What causes transverse myelitis?

More than often, doctors are not sure what causes this inflammation but they know it occurs when a person's body tries to fight off a disease or is recovering from an infection, (COVID-19 in the current case), or when a human body's immune system attacks healthy cells for some reason.

What are the symptoms of transverse myelitis?

The initial symptoms of this inflammation include pain in the lower back or sharp, shooting sensations that radiate down the arms, legs, or around the torso.

How does it impact the human body and is it painful?

Transverse myelitis can cause paresthesias which means anomalous sensations in the body such as coldness, tingling, tickling, burning sensation, pricking, or numbness coupled with sensory loss. One of the most common issues patients are faced with is pain which comes in many forms as mentioned above, however the most common is burning or stabbing pain in arms, legs, or around the trunk.

How soon can a person recover from transverse myelitis?

Majority of patients with this condition have at least a partial recovery, with most of them recovering within the first three months following the attack, while some people may continue to recuperate for up to two years, and in certain cases even longer.

How bad does it get?

Once it is triggered, manifestations of this condition can get worse within hours of contracting it. In the majority of cases, symptoms hit their peak within 10 days, at which point around half the patients lose control of their legs. How much of one's body is affected hinges on which part of a person's spinal cord has the problem.

What is the treatment for transverse myelitis?

This condition is treatable with steroids, insertion of intravenous steroids in a patient's arms over the course of several days, plasma exchange therapy, antiviral medication, pain medication, etc.