Entorhinal Cortex and Persistent Olfactory Loss in {COVID}-19 Patients: A Neuroanatomical Hypothesis. Comment on Fiorentino et al. Correlations between Persistent Olfactory and Semantic Memory Disorders after {SARS}-{CoV}-2 Infection. Brain Sci. 2022, 12, 714

Recently, Fiorentino et al. [1] published a paper in which they investigated the association between semantic memory impairment in long COVID-19 patients and persistent olfactory disturbances. Semantic memory was impaired in 20% of these patients, especially the youngest patients (19–39 age-group), and the olfactory threshold score had the only significant correlation with semantic memory scores. This recent study confirmed the data from Di Stadio et al. [2], who found a correlation between the presence of memory alteration and the highest severity of quantity and quality smell alterations. Both articles underlined the importance of memory functions in the smell process and clinically evidenced that the alteration of memory had an impact on odor recognition memory, which begs the question, what may be the link between memory and smell? We want to discuss an intriguing hypothesis to explain the clinical data observed by these two authors. Currently, it is well-known that COVID-19 causes systemic inflammation and brain neuro-inflammation [3]; this neuro-inflammation could be caused by direct inflammation of the brain tissue [3,4] or be related to systemic alterations caused by COVID-19, such as cytokines storm and micro-/thrombotic events [5]. The inflammation, starting from the olfactory bulbs, spreads to other areas of the brain and causes several symptoms [5], including forgetfulness, short-term memory, mental clouding, lack of concentration, and attention deficits