A follow-up on quantitative and qualitative olfactory dysfunction and other symptoms in patients recovering from COVID-19 smell loss.

BACKGROUND: Sudden smell loss is a specific early symptom of COVID-19, which, prior to the emergence of Omicron, had estimated prevalence of ~40% to 75%. Chemosensory impairments affect physical and mental health, and dietary behavior. Thus, it is critical to understand the rate and time course of smell recovery. The aim of this cohort study was to characterize smell function and recovery up to 11 months post COVID-19 infection. METHODS: This longitudinal survey of individuals suffering COVID-19-related smell loss assessed disease symptoms and gustatory and olfactory function. Participants (n=12,313) who completed an initial survey (S1) about respiratory symptoms, chemosensory function and COVID-19 diagnosis between April and September 2020, were invited to complete a follow-up survey (S2). Between September 2020 and February 2021, 27.5% participants responded (n=3,386), with 1,468 being diagnosed with COVID-19 and suffering co-occurring smell and taste loss at the beginning of their illness. RESULTS: At follow-up (median time since COVID-19 onset ~200 days), ~60% of women and ~48% of men reported less than 80% of their pre-illness smell ability. Taste typically recovered faster than smell, and taste loss rarely persisted if smell recovered. Prevalence of parosmia and phantosmia was ~10% of participants in S1 and increased substantially in S2: ~47% for parosmia and ~25% for phantosmia. Persistent smell impairment was associated with more symptoms overall, suggesting it may be a key marker of long-COVID illness. The ability to smell during COVID-19 was rated slightly lower by those who did not eventually recover their pre-illness ability to smell at S2. CONCLUSIONS: While smell ability improves for many individuals who lost it during acute COVID-19, the prevalence of parosmia and phantosmia increases substantially over time. Olfactory dysfunction is associated with broader persistent symptoms of COVID-19, and may last for many months following acute COVID-19. Taste loss in the absence of smell loss is rare. Persistent qualitative smell symptoms are emerging as common long-term sequelae; more research into treatment options is strongly warranted given that even conservative estimates suggest millions of individuals may experience parosmia following COVID-19. Healthcare providers worldwide need to be prepared to treat post COVID-19 secondary effects on physical and mental health.

Effect of electrical stimulation of the baso-lateral amygdala nucleus on defensive burying shock probe test and elevated plus maze in rats.

In the present report, the putative effect of a single electrical stimulation (75, 150 or 300 microA) to the baso-lateral amygdala (BLA) nucleus was assessed in shock probe defensive burying behavior test (DB) and elevated plus maze (EPM). These models have been used for measuring anxiety levels and screening putative anxiolytic compounds. A group of 28 rats were randomly divided for the following experimental conditions: Control-control, sham-operated, BLA stimulated groups: 75, 150 and 300 microA tested for DB. The cumulative defensive burying in a 15 min-test, the latency of burying, the number of shock received and the height of the bedding material in the probe were recorded. Another group of 28 individuals was also randomly distributed for the following experimental conditions: Control-control, sham-operated, BLA stimulated animals: 75, 150, 300 microA and tested in the EPM. The time the subjects spent in the open arms, the crosses and the faeces number excreted during the test were recorded. Decreased levels of defensive burying were observed in 75, 150 and 300 microA stimulated groups. The 150 and 300 microA groups reached statistical significance. The fact that 300 microA stimulated group showed statistically significant increase in the latency of defensive burying, in the number of shock received and decreased amount in bedding material suggests a sedative action of electrical stimulation. Increased time in the open arms and augmented number of crossings in 150 microA group was observed. No changes in the number of faeces were observed in any group. The evidence supported the notion of an inhibitory amygdaline mechanism triggered by sub-threshold electrical stimulation.