Memory issues, brain fog and problems in concentration after recovering from Covid-19 infection could be linked to issues in a part of the brain, a new study published in the scientific journal PLOS ONE has found.
Research by Griffith University scientists have found that long Covid patients display swelling in the hippocampus, the area of the brain that helps with learning and memory.
Scientists noted that they also saw similar issues or enlargement in hippocampus, in patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS).
The researchers, based at the National Centre for Neuroimmunology and Emerging Diseases (NCNED), while looking at the high-resolution magnetic resonance imaging brain scans from 17 long Covid patients, 29 ME/CFS patients, and 15 people with neither condition, found this abnormality in the brains of patients with long Covid and ME/CFS compared to 15 healthy participants.
The scientists found a link between symptoms such as impaired concentration, nonrestorative sleep, pain and fatigue, and size of the hippocampus.
NCNED director and study co-author Sonya Marshall-Gradisnik stated that the study's findings underscored the connection between long Covid and ME/CFS, as revealed by brain imaging scans, particularly the enlargement of the hippocampus.
"Because there's such overlap between ME and long COVID, it allows us to fast-track, potentially, treatments that we've been exploring in ME patients, and how we can then apply them to long COVID," Professor Marshall-Gradisnik said.
The research also found that the hippocampal volume was associated with symptom severity in both patient groups.
“Therefore, hippocampal impairment in Long Covid and ME/CFS patients may play a significant role in cognitive difficulties such as memory problems, difficulty concentrating, and delayed responses to questions or conversations.”
The reason behind the brain swelling
The researchers feel that the larger hippocampal volume could be due to neurogenesis, the formation of new neurons, or a virus in the brain.
Long Covid and neurological issues
Long Covid can cause neurological symptoms both in the acute and post-infection phases, affecting cognition, sleep, and mental health. These symptoms are more common in women and young adults and may persist for months or even years. Some studies suggest improvement after a year, while others report long-term effects.
Cognitive impairment in long Covid affects attention, memory, executive function, and processing speed. It occurs in both mild and severe cases. Studies using brain scans and neuropsychological tests show that many patients experience ongoing cognitive difficulties, with some still affected after 24 months. The likely causes include inflammation, brain blood flow changes, and potential viral effects on the nervous system.
Sleep disturbances, particularly insomnia, are common in long Covid, affecting up to 26% of patients. Possible causes include inflammation, stress, anxiety, and changes in brainstem function. Poor sleep hygiene and social isolation may also contribute to sleep problems, including hypersomnia and worsened sleep apnea.
Long Covid has been linked to mood disorders, anxiety, PTSD, and even psychosis. The virus may disrupt neurotransmitter balance, oxygen supply to the brain, and immune responses, leading to mental health issues. Studies have found high rates of anxiety, depression, and PTSD months after infection. Symptoms such as fatigue and isolation further impact emotional well-being.
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