A healthy woman had no typical coronavirus symptoms. Then she suffered paralysis, lost her ability to speak, and almost died of COVID-19.

• Rebecca Wrixon almost died of COVID-19 when the infection provoked an autoimmune response that caused severe swelling in her brain.
• The 44-year-old nanny lost her ability to speak and move half of her body, but she never experienced common coronavirus symptoms like cough and fever.
• Patient studies have shown mild and severe cases of COVID-19 can lead to neurological symptoms such as strokes, headaches, or loss of taste or smell.

When Rebecca Wrixon was admitted to the emergency department in mid-April with numbness in her right arm and foot, it didn't occur to her that she might have COVID-19. She thought she was having a stroke.

Her doctors at University Hospital Southampton, in England, thought the same, especially as she began to struggle with speech and vision shortly after her admission. But tests revealed no sign of stroke and Wrixon's condition continued to deteriorate.

The doctors ordered another test — a throat swab for COVID-19, which was becoming standard practice in hospitals since the pandemic was declared. Wrixon tested positive for the virus.

"I actually didn't think it was anything to do with COVID because in the UK we were being told to look out for persistent cough and temperatures, which I didn't have either of," Wrixon told Insider.

Before her arm went numb, Wrixon said she experienced some itchiness and headaches for about a week. During her 18-night stay in the hospital, she lost her ability to speak and see clearly, and experienced paralysis of the right side of her body.

A blood plasma exchange that wiped out Wrixon's overactive antibodies saved her life

Wrixon's symptoms were especially perplexing because a test of her spinal fluid showed that the virus was not directly attacking her nervous system, said Ashwin Pinto, the consultant neurologist on Wrixon's case.

But an MRI scan showed her brain was severely inflamed, and something had to be causing the swelling. Pinto guessed that Wrixon's immune system might be the culprit.

Antibodies tell your immune system how to respond to an intruder like the coronavirus. But sometimes, antibodies get the message wrong and lead your body in an attack against itself.

"The hypothesis is that this is an immune-mediated phenomenon," Pinto told Insider. "The white blood cells and the antibodies that are helping you recover from the infection are somehow getting access into the brain and causing damage and symptoms."

The treatment for such an autoimmune response is blood plasma exchange: replacing the patient's own plasma (which contains their antibodies) with that of a donor with different antibodies — unlike the similar procedure used in other coronavirus patients to give them coronavirus antibodies.

By "washing out" Wrixon's overactive antibodies and replacing them with healthy blood plasma, Pinto and his team were able to reverse the inflammation and stop her symptoms.

The day after the plasma exchange, Wrixon could move her index finger. Within five days of the procedure, she was able to walk, talk, and move around, she said.

Nearly half of hospitalized coronavirus patients experience neurological symptoms

Although severe neurological symptoms of COVID-19 are uncommon, Wrixon's case isn't unique.

A review of research published in the Annals of Neurology concluded that COVID-19 poses a "global threat to the entire nervous system," with about half of hospitalized coronavirus patients experiencing some neurological symptoms.

Symptoms of COVID-19 central nervous system disease include delirium, difficulty concentrating, dizziness, a loss of smell and taste, seizures, strokes, weakness, muscle pain, decreased alertness, and headaches.

These neurological symptoms may present before any respiratory problems occur, so it's important that people know to look out for them, the study authors said in a press release.

While Wrixon's illness turned out not to be a stroke, some coronavirus patients do experience strokes as a result of blood clots or due to decreased oxygen flow to the brain. As the virus wears down the heart and lungs, the lack of oxygen can cause problems throughout the body.

"It's an extraordinary illness that's causing a huge number of different manifestations, which seem to vary quite a lot from patient to patient," Pinto said.

Another study published in July found that even patients with "mild" cases of COVID-19, meaning they do not require supplemental oxygen or a ventilator, may develop neurological symptoms.