The more we learn about COVID-19, the more concerning its effects become.
The global death toll has surpassed five million. Survivors can also experience long-term health problems.
COVID-19 can affect the lungs, heart, and brain. Researchers now find that it can also affect the ears.
The virus may cause hearing loss, tinnitus, and dizziness.
Viral infections can cause hearing loss and other ear-related problems. Before the pandemic, Dr. Konstantina Stankovic of Massachusetts Eye and Ear and Dr. Lee Gehrke of MIT studied these effects.
They examined how measles, mumps, hepatitis, and other infections affected hearing.
After the pandemic began, they heard reports of sudden hearing loss and other ear problems. They decided to investigate further.
The researchers collected cells from 10 patients who developed hearing or ear problems after testing positive for COVID-19.
Using induced pluripotent stem cell technology, or iPSC, they transformed the cells into inner-ear cells.
These included hair cells, supporting cells, nerve fibers, and Schwann cells.
The researchers compared these cells with cells from patients who had similar symptoms but had not contracted COVID-19.
They found that hair cells and Schwann cells contained proteins that the virus can use to infect cells.
This finding matters because hair cells help control balance. Schwann cells protect neuronal axons, which help nerve cells communicate.
By contrast, other inner-ear cells lacked those proteins and appeared less vulnerable to COVID-19.
In a news release, Dr. Stankovic said researchers still do not know how many people with COVID-19 developed hearing problems.
“Initially, routine testing was not readily available for patients diagnosed with COVID-19,” she said.
“When patients developed life-threatening complications, they also paid less attention to reduced hearing or tinnitus.
“We still don’t know the incidence. However, our findings call for increased attention to auditory and vestibular symptoms after COVID-19 exposure.”
The researchers do not know how the virus reaches the inner ear.
They speculate that it may travel through the Eustachian tube, a passage connecting the throat and middle ear.
The Eustachian tubes open when people sneeze, swallow, or yawn. This process prevents pressure and fluid from building up inside the ear.
The researchers think the tubes may allow particles from the nose to reach the ear.
The study appeared in the journal Communications Medicine.
CIRM has funded 17 different projects targeting COVID-19, several of which are still active.
Clinical investigation showed that patients with Covid-19 infection had high infection rate in hair and Schwinn cells which located in inner part of ears but not to others. Hair cells are sensory receptors of both the auditory system and the vestibular system in the ears of all vertebrates. Through mechanotranduction, hair cells detect movement in their environment. In mammals, the auditory hair cells are located within the spiral organ of corti on the thin basilar membrane in the cochlear of the inner ear. The hair bundles or stereocilia protrude from the apical surface of the cell into the fluid-filled cochlear duct. The hair bundles are arranged as stiff columns that move at their base in response to stimuli applied to the tips. Mammalian cochlear hair cells are of two anatomically and functionally distinct types, known as outer and inner hair cells. Damage to these hair cells results in decreased hearing sensitivity and because the innear ear hair cells cannot regenerate, the damage is permanant. The function of inner hair cells transforms the sound vibrations in the fluids of cochlear into electrical signals that are then relayed via the auditory nerve to the auditory brain stem and auditory cortex. The outer hair cells mechanically amplify low-level sound that enter the cochlear. The amplification may be powered by the movement of their hair bundles, or by electrically driven motility of their cell bodies. This is so-called somatic electromotility amplifies sound in all land vertebrates. It is affected by the closing mechanism of mechanical sensory ion channels at the tips of the hair bundles. On the other hand, Schwinn cells have important roles to serve the myelination cell of the peripheral nerves system (PNS) and support cells of peripheral neurons. They are concentrically around the inner axon and function by insulating and provide nutrients to axon. Myelination increases conduction velocity along the axon, allowing for the saltatory conduction of impulses.
Clinical investigation showed that, a number of viral infections can cause hearing loss. Hearing loss induced by these viruses can be congenital or acquired, unilateral or bilateral. Certain viral infection can directly damage inner ear structure, other can induce inflammatory responses which then cause this damage and still others can increase susceptibility for bacterial and fungal infection, leading to hearing loss. Typically, virus-induced hearing loss is sensorineural , although conductivity and mixed hearing loss can be seen following infection with certain virus.
Current study showed that, most of patients infected with Covid-19 experience hearing loss. As Covid-19 virus has ability to develop high viral loads and release high levels of inflammatory cytokines. Therefore , high expression of viral entry proteins, such as ACE2 receptors on hair and Schwann cells of inner ear, may attract high load of viruses to attack them and high volume of inflammatory cytokines released by those viruses may damage and dysfunction the inner part of ear leading to hearing loss. Organoids develop from iPSCs provide good model to determine the mechanism of virus infection and cause hearing loss of ear.
Does anyone know if hearing loss is permanent and what is treatment for the hearing lost
Hi Maryann, like a lot of things releated to COVID, we really don’t know. Hopefully it is temporary but just how temporary is not clear.
But where is the explanation as to why? Is it the S1 spike protein?
Are there any remedies at this point to try?
Hi Rick,happily there are several therapies, as well as the vaccines, that have been approved to treat people with COVID.