The mental fog and memory and concentration disturbances that persist for months after the Covid-19 infection could in some cases be linked to alterations in the metabolism of the brain and the accumulation of molecules toxic to neurons: one study out of seven indicates this patients coordinated by the University of Milan and conducted in collaboration with the Aldo Ravelli Center of the State University, the Asst Santi Paolo e Carlo and the Irccs Auxologico.
The results, which open up new questions about post-Covid damage, are published in the Journal of Neurology.
The researchers, led by neurologist Alberto Priori, selected seven patients hospitalized for Covid who, one year after discharge, still had cognitive disorders detected by specific neuropsychological tests.
These volunteers were examined with the method of positron emission tomography (Pet) to evaluate the metabolic activity of specific areas of the brain.
The reports revealed that three patients had impaired functioning of the temporal areas (site of memory function), of the brainstem (site of some circuits that regulate attention and balance) and of the prefrontal areas (which regulate energy mentality, motivation and, in part, behaviour).
In one of these patients who had a more serious cognitive disorder, a special Pet was also performed that allows the deposition of amyloid in the brain to be visualized.
"Amyloid is a protein which, when it accumulates in neurons, determines their premature aging and degeneration and which is implicated in Alzheimer's disease", explains Luca Tagliabue, director of the Nuclear Medicine and Radiodiagnostics division of Asst Santi Paolo and Carlo.
"Well, in the patient examined, Pet revealed an abnormal accumulation of amyloid in the brain and particularly in the frontal lobes and in the cingulate cortex, linked to complex cognitive functions and emotions".
The researchers thus came to the conclusion that in just under half of the patients with memory and concentration disorders one year after Covid there may be functional alterations of the temporal, frontal and brain stem areas, while in the other cases the cognitive disorders "they do not have a functional impact on the brain, but can derive from exclusively psychological modifications similar to post-traumatic stress disorder", explains Roberta Ferrucci, professor of psychobiology at the University of Milan.
The observation of amyloid elevation in a patient, reported for the first time in this study, could be related to the infection or to the infection's triggering of the neurodegenerative cascade.
This data will have to be evaluated by future studies, to understand if SarsCoV-2 infection could determine an increased risk of neurodegenerative diseases in the future.
"This study offers a range of interpretative hypotheses of the post-Covid damage and lays the foundations for a diversified evaluation of the patient in the long term", comments Vincenzo Silani, former professor of Neurology at the State University and director of the Neuroscience Department of the Irccs Auxologico.
"Neurodegenerative processes could also be triggered post-infection in selected cases according to different pathogenic pathways and this, obviously, is the main question we ask ourselves: can we expect neurodegenerative pathologies in the future?".
