More than half of the patients affected by the of Sars-CoV-2 infection report a sudden loss or alternation of the sense of smell and taste. Humanitas doctors have recently conducted and published in the Journal of Neurology a study on the effects of the virus on the central nervous system.

In “Neurological features in SARS-CoV-2 infected patients with smell and taste disorder”, the team of Humanitas medical researchers used online tests and questionnaires to evaluate the neuro-invasive potential of the virus on 105 patients between 23 and 90 years of age, who accessed the Humanitas emergency department with the Sars-CoV-2 infection and did not report previous pathologies of the central nervous system.

Among the patients that took part in the study, 74.3% reported reduced sense of taste or smell. Interestingly, this symptom was more frequent in women (88% of the women interviewed), than in men (65%). Patients with smell and taste disorders were on average 10 years younger than those without symptoms. No correlation was found between the symptoms and the setting of the disease management – home as opposed to the hospital- or the severity of the infection.

“51.3% of patients recovered their sense of smell and 60.3% of their taste within 20 days of the onset of symptoms – explains Professor Alberto Albanese, Head of Neurology at Humanitas and professor at Humanitas University. Patients with smell / taste disturbances presented mild neurological symptoms, such as headaches, impaired balance, dysphonia, dizziness, mild confusion, sensory and visual alternations. This may suggest a direct action of SARS-CoV-2 on nasal epithelial cells and its possible propagation beyond the olfactory bulb, with mild and transient involvement of the central nervous system “.

This hypothesis is supported by another study published in Jama Neurology by Humanitas neuroradiologists, who observed morphological alterations of the olfactory bulb in some patients with Covid-19. The collaboration among Humanitas neurologists, otolaryngologists and neuroradiologists aims to clarify whether the olfactory bulb acts as a possible gateway for the virus towards the nervous system.

Previous studies on other coronavirus strains reinforce this hypothesis, having already demonstrated the virus’ ability to attack the central nervous system through the olfactory neuroepithelium, the tissue in the back of the nasal cavity consisting of glands capable of transforming chemical signals into nervous signals.

“There is still much to learn on the pathophysiology of the neurological manifestations of SARS-CoV-2 – continues Pr. Albanese – SARS-CoV-2 infection is a systemic disease whose neurological signs, especially if mild, can be overlooked when severe respiratory symptoms prevail or when patients are isolated at home. The true incidence of neurological symptoms, therefore, could be higher than that identified by the study. We trust that what has been learned can be used to increase the level of knowledge around the disease and help other clinicians in their work with patients.”.