How COVID-19 can damage all five senses

The virus that causes the disease disrupts not just smell and taste, but all the ways humans perceive the world. For some, the loss may be permanent.

Published 29 Sept 2021, 09:44 BST
A woman wearing a protective mask smells a rose as she wanders through the Paris streets. ...

A woman wearing a protective mask smells a rose as she wanders through the Paris streets. One of the reported hallmarks of COVID-19 infection is a loss of taste and smell – but there may be other sensory effects, too. 

Photograph by Myriam Tirler, Hans Lucas via Redux

Considering how sick he was, Michael Goldsmith seemed like one of the lucky ones, because he survived. After becoming severely ill with COVID-19 in March 2020, he spent 22 days on a ventilator in the ICU. Fortunately, Goldsmith’s condition improved, and he was moved to an intermediate level of care in the hospital as he recovered. That’s when he began to realise he had lost most of his hearing in his left ear.

“Anything I did hear had to be loud, and then it sounded like Charlie Brown’s teacher,” says Goldsmith, now 35, referencing the nonsensical noises the teacher made in the popular cartoon show.

He also had a static sound in that ear that turned out to be tinnitus. After he fully recovered from the infection and went back to his home in Bergenfield, New Jersey, the IT security analyst and father of two saw one doctor after another, seeking relief for his hearing problems. He tried several different prescription medicines, and still he was no better off.

It’s easy to take our senses for granted—until there’s a problem with one of them. This is something many people who suffered from COVID-19 discovered when they unexpectedly lost their senses of smell and taste. More recently, though, it has become apparent that a COVID-19 infection can also affect sight, hearing, and touch.

In the short term and the long run, this virus can affect all the ways we perceive and interact with the world.

Though not life-threatening, “it’s disarming to lose any of these senses, especially as suddenly as happens in the context of this infection,” says Jennifer Frontera, a professor of neurology at the NYU Grossman School of Medicine. 

Diminished hearing 

Like Goldsmith, many people who recovered from COVID-19 continued to experience some auditory loss. In the March issue of the International Journal of Audiology, researchers reviewed published case studies and other reports of COVID-19 symptoms, and they estimate that hearing loss has occurred in about 8 percent of patients who had COVID, while about 15 percent developed tinnitus.

The mechanisms aren’t completely understood, but experts suspect the disease may affect the eustachian tube, which connects the middle ear with the throat. “With any viral infection, you can have eustachian tube dysfunction, which can lead to fluid build-up in the middle ear—this acts as a mechanical dampener on the ear drum,” explains Elias Michaelides, an associate professor of otolaryngology at Rush University Medical Centre in Chicago.

Once someone recovers from the illness, the eustachian tube drains and hearing returns to normal in most cases, though it can take a couple of weeks, he says. In the meantime, taking an oral decongestant and using a nasal steroid spray may help hasten drainage, says Michaelides.

But if the virus damages the sensory neurones in the inner ear or cochlea, sudden hearing loss may occur, and it may be permanent. Exactly how this nerve damage happens isn’t clear, though it may have to do with COVID-19’s ability to trigger a cascade of inflammatory effects and small blood vessel damage.

Because Goldsmith’s hearing didn’t improve in his left ear after he fully recovered and tried various prescription medications, he went to see J. Thomas Roland, Jr., chair of the department of otolaryngology-head and neck surgery at NYU Langone Health. Roland told him he was a good candidate for a cochlear implant, a small electronic device that can directly stimulate the auditory nerve and generate signals that the brain registers as sound.

“The inner ear is a very delicate organ and very susceptible to microvascular problems and inflammation, so I’m not surprised people have experienced hearing loss or tinnitus related to COVID,” says Roland.

In September 2020, Goldsmith had a cochlear implant surgically placed in his left ear. It has made a world of difference, he says. “I now have 80 percent recognition of single words, and it’s even higher with full sentences in my left ear.” And when the device is on, his tinnitus disappears completely. “I wish I didn’t need this,” Goldsmith says, “but I’m glad I had it.”

Blurred sight

Other people who’ve had COVID-19 have reported problems with their vision. A study published last year in BMJ Open Ophthalmology found that light sensitivity, sore eyes, and blurred vision are among the more common eye disorders experienced by patients. And in a study involving 400 COVID-19 patients who were hospitalised, researchers found that 10 percent had eye disorders, including conjunctivitis, vision changes, and eye irritation.

“There is definitely a viral load in the eye that causes symptoms, but that doesn’t mean it necessarily causes long-term diseases in the eye,” says study co-author Shahzad I. Mian, a professor of ophthalmology and visual sciences at the University of Michigan Medical School.

Still, some doctors are finding that the SARS-CoV-2 virus can increase the risk of blood clots throughout the body, including in blood vessels in the retina, which can cause blurry vision or some degree of vision loss, explains Julia A. Haller, ophthalmologist-in-chief at the Wills Eye Hospital in Philadelphia.

If someone experiences any vision changes possibly related to COVID-19, it’s important for them to see an ophthalmologist as soon as possible, the experts say. “Some forms of vision loss are treatable with medications, depending on how much damage has occurred,” Haller says.

Tingling and numbness

A person’s sense of touch also can be affected by a COVID-19 infection, since the disease has been shown to cause persistent neurologic symptoms.

In a study published in May 2021, researchers evaluated 100 people who weren’t hospitalised for COVID-19 but had ongoing symptoms. They found that 60 percent had numbness and tingling six to nine months after the onset of their illness. Sometimes these symptoms were widespread throughout the body; in other instances, they were localised to the hands and feet.

The exact mechanisms behind these stubborn symptoms aren’t well understood, but they most likely relate to local inflammation and local infection with COVID-19 virus in the nerves, explains Igor Koralnik, a professor of neurology at the Northwestern Feinberg School of Medicine and chief of the division of neuroinfectious diseases and global neurology at Northwestern Memorial Hospital in Chicago.

“In most cases, [the numbness and tingling] improves over time,” he says. “Everybody goes at their own pace.” And in some cases, tingling and other symptoms of neuropathy can be treated with medications like gabapentin, a drug that is used to prevent seizures and relieve nerve pain.

Loss of smell and taste

Perhaps the most recognisable effect COVID-19 has on the senses is the one-two punch of lost smell and taste. Elizabeth DeFranco, a medical sales rep in Cleveland, Ohio, experienced both sensory changes shortly after developing a mild COVID-19 infection in June 2020.

“I was eating salt and vinegar potato chips, and I couldn’t taste anything,” recalls DeFranco, 58. Then she realised she couldn’t smell anything, either. These losses remain with her to this day, though once in a while she gets a brief whiff of an odour like freshly cut grass.

“Doctors may prescribe systemic or topical steroids and sometimes smell conditioning, which involves repeated exposure to essential oils that have different scents. It’s like the olfactory equivalent of physical therapy.”

Viral-induced smell loss existed before anyone had ever heard of COVID-19, but the percentage of people who experience smell dysfunction or loss is much higher with this virus than with other types of infections, experts say. A review of studies published in 2020 found that of 8,000 subjects with confirmed COVID-19, 41 percent experienced problems with smell and 38 percent reported problems with taste. When people who contract COVID-19 lose their sense of smell, a condition called anosmia, they lose it across the board, not just with one type of scent.

Generally speaking, there are two major types of smell loss. Conductive smell loss can occur when nasal congestion or obstruction prevents odour molecules from passing into the nasal cavity. Sensorineural smell loss involves damage or dysfunction to the olfactory neurones, which seems to be what’s happening with COVID-19.

“With COVID-19, most people don’t have a lot of nasal symptoms, and yet smell loss can be fairly severe,” says Justin Turner, an associate professor of otolaryngology-head and neck surgery at Vanderbilt University Medical Centre and director of the Vanderbilt Smell and Taste Centre. “We believe this stems from damage to sustentacular cells that live way up in the nose and are particularly susceptible to infection by the virus.”

As people recover from COVID-19, regenerating cells can spring into action and make new functional neurones, Turner explains. This allows most people to regain their sense of smell six to eight weeks after infection—but not everyone does. At that point, doctors may prescribe systemic or topical steroids and sometimes smell conditioning, which involves repeated exposure to essential oils that have different scents. It’s like the olfactory equivalent of physical therapy.

“What you’re doing is exposing the olfactory system to these odourants and helping the brain form new connections,” Turner explains. “Once the damage [to neurones] has been done, we’re relying on regenerative capacity in the olfactory system to help people regain their sense of smell.”

Losing the sense of taste usually goes hand in hand with the loss of smell, says Michael Benninger, professor and chair of the department of otolaryngology-head and neck surgery at the Cleveland Clinic Lerner College of Medicine.

“We are not seeing people who have truly lost their sense of taste [with COVID-19 infection]. When people lose their sense of smell, their taste is diminished”—meaning, their ability to discriminate between different flavours is lost. “If the sense of smell comes back, taste comes back, too,” Benninger says.

Since she recovered from COVID-19, DeFranco has tried numerous interventions—including steroid medications, antibiotics, cryotherapy, craniosacral therapy, supplements, homeopathic remedies, and smell retraining. Nothing has helped. So she has found ways to work around these limitations to protect her safety. She installed additional smoke detectors in her home because she wouldn’t be able to smell smoke. She throws all her food out by the “best by” date and often has a neighbour smell food from her fridge to make sure it hasn’t spoiled.

The worst part: “It is very depressing to think that this anosmia could be forever. I have no enjoyment of food,” she says. “I may never be able to appreciate the taste of wine or chocolate or the smell of a barbecue or cookies baking in the oven or the salt in the air when I go to the ocean. No one can really empathise unless it happens to them.”

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