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Simonini L, Frijia F, Ait Ali L, Foffa I, Vecoli C, De Gori C, De Cori S, Baroni M, Aquaro GD, Maremmani C, Lombardo F. A Comprehensive Review of COVID-19-Related Olfactory Deficiency: Unraveling Associations with Neurocognitive Disorders and Magnetic Resonance Imaging Findings. Diagnostics (Basel) 2024; 14:359. [PMID: 38396398 PMCID: PMC10888385 DOI: 10.3390/diagnostics14040359] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2024] [Revised: 01/31/2024] [Accepted: 02/05/2024] [Indexed: 02/25/2024] Open
Abstract
Olfactory dysfunction (OD) is one of the most common symptoms in COVID-19 patients and can impact patients' lives significantly. The aim of this review was to investigate the multifaceted impact of COVID-19 on the olfactory system and to provide an overview of magnetic resonance (MRI) findings and neurocognitive disorders in patients with COVID-19-related OD. Extensive searches were conducted across PubMed, Scopus, and Google Scholar until 5 December 2023. The included articles were 12 observational studies and 1 case report that assess structural changes in olfactory structures, highlighted through MRI, and 10 studies correlating the loss of smell with neurocognitive disorders or mood disorders in COVID-19 patients. MRI findings consistently indicate volumetric abnormalities, altered signal intensity of olfactory bulbs (OBs), and anomalies in the olfactory cortex among COVID-19 patients with persistent OD. The correlation between OD and neurocognitive deficits reveals associations with cognitive impairment, memory deficits, and persistent depressive symptoms. Treatment approaches, including olfactory training and pharmacological interventions, are discussed, emphasizing the need for sustained therapeutic interventions. This review points out several limitations in the current literature while exploring the intricate effects of COVID-19 on OD and its connection to cognitive deficits and mood disorders. The lack of objective olfactory measurements in some studies and potential validity issues in self-reports emphasize the need for cautious interpretation. Our research highlights the critical need for extensive studies with larger samples, proper controls, and objective measurements to deepen our understanding of COVID-19's long-term effects on neurological and olfactory dysfunctions.
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Affiliation(s)
- Ludovica Simonini
- Institute of Clinical Physiology, National Research Council (CNR), 54100 Massa, Italy; (I.F.); (C.V.)
| | - Francesca Frijia
- Bioengineering Unit, Fondazione Toscana G. Monasterio, 56124 Pisa, Italy;
| | - Lamia Ait Ali
- Institute of Clinical Physiology, National Research Council (CNR), 54100 Massa, Italy; (I.F.); (C.V.)
- Pediatric Cardiology and GUCH Unit, Fondazione “G. Monasterio” CNR-Regione Toscana, 54100 Massa, Italy
| | - Ilenia Foffa
- Institute of Clinical Physiology, National Research Council (CNR), 54100 Massa, Italy; (I.F.); (C.V.)
| | - Cecilia Vecoli
- Institute of Clinical Physiology, National Research Council (CNR), 54100 Massa, Italy; (I.F.); (C.V.)
| | - Carmelo De Gori
- Department of Radiology, Fondazione Monasterio/CNR, 56124 Pisa, Italy; (C.D.G.); (S.D.C.); (F.L.)
| | - Sara De Cori
- Department of Radiology, Fondazione Monasterio/CNR, 56124 Pisa, Italy; (C.D.G.); (S.D.C.); (F.L.)
| | - Monica Baroni
- Fondazione “G. Monasterio” CNR-Regione Toscana, 54100 Massa, Italy;
| | - Giovanni Donato Aquaro
- Academic Radiology Unit, Department of Surgical, Medical and Molecular Pathology and Critical Area, University of Pisa, 56124 Pisa, Italy;
| | - Carlo Maremmani
- Unit of Neurology, Ospedale Apuane, Azienda USL Toscana Nord Ovest, 54100 Massa, Italy;
| | - Francesco Lombardo
- Department of Radiology, Fondazione Monasterio/CNR, 56124 Pisa, Italy; (C.D.G.); (S.D.C.); (F.L.)
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