The symptoms of Long Covid, which has a lasting effect, continue to emerge. Now, a new study has shed light on apparent brain changes or neurological consequences of COVID-19, especially in those who lost their sense of smell post-diagnosis. Published in Scientific Reports, the study found that those with anosmia (the loss of smell) during Covid-19 showed alterations in “brain functionality and even physical structure during recovery.” According to reports, this study is among the first to link Covid-19-related loss of smell to significant brain changes.

The August 2024 study studied this subject, given the early reports of neurological symptoms in patients affected by Covid-19. “We wanted to contribute from our unique perspective to understanding the potential damage caused by SARS-CoV-2 infection in the central nervous system. This led us to initiate this study, in which we evaluated recovered Covid-19 patients using structural and functional magnetic resonance imaging. At the same time, they performed decision-making and cognitive control tasks, as well as tracking their evolution with electroencephalography,” the authors noted. Loss of smell in Covid-19 occurs due to the virus’ impact on the olfactory system in the nasal passages, said Dr Ravi Shekhar Jha, pulmonologist, director pulmonology, MD, MRCP, Fortis Hospital, Faridabad. “Specifically, the SARS-CoV-2 virus targets cells in the upper part of the nasal cavity, where the olfactory neurons are located. These neurons are responsible for detecting smells and sending signals to the brain,” explained Dr Jha.

According to him, the virus infects supporting cells around the olfactory neurons, causing inflammation and disruption of normal function. “This inflammation can lead to a blockage of the nasal passages or direct damage to the cells that help detect smells, resulting in temporary or prolonged loss of smell,” said Dr Jha. Unlike other respiratory infections, where congestion may block the sense of smell, Covid-19‘s direct impact on the olfactory system often leads to a more pronounced and sometimes longer-lasting loss of smell, even in the absence of nasal congestion, he told indianexpress.com. That’s not all. The research — done on 100 adults in Santiago, Chile who had recovered from respiratory infections between February 2020 and May 2023, with the final sample including 73 participants who had confirmed cases of Covid-19 (the remaining participants had respiratory diseases caused by other agents, as confirmed by multiple negative PCR tests) — also had researchers using a combination of tests and brain scans across two sessions to assess the participant’s brain function and structure. Notably, the participants ranged in age from 19 to 65 years with none having severe cases of Covid-19 that required ventilators or intensive care.

Patients with anosmia were found to be more impulsive and made rapid changes in their decisions during neuropsychological testing. “Anosmia also correlated with brain measures, including decreased functional activity during the decision-making task, thinning of cortical thickness in parietal regions, and loss of white matter integrity,” the study findings read. The study further mentioned that the results highlight the importance of a history of olfactory dysfunction in relation to the presence of brain alterations. “Given the substantial number of patients recovering from Covid-19 worldwide, it is crucial to identify risk factors associated with potential brain damage. In this context, a history of olfactory dysfunction can be a useful criterion for prioritising deeper follow-up of these patients,” it read.

However, consultant neurologist Dr Sudhir Kumar, Apollo Hospitals, Hyderabad pointed out that the study has limitations. “It does not prove the cause-effect relationship, as there is no data on their cognitive functions or brain structure prior to Covid-19 infection. Also, the mechanism of brain function and structure changes by the virus infection needs to be determined,” said Dr Kumar.

Further follow-up is needed to determine the significance of these observations. “We need to see how long these changes persist. In addition, it would be interesting to note if these people are at increased risk of developing neurodegenerative diseases such as Alzheimer’s or Parkinson’s disease in the future,” said Dr Kumar.

Source: The Indian Expresss