Imbalanced brain connectome: A possible link behind functional somatic disorders, multiple chemical sensitivity, and long COVID patients

Background: Functional Somatic Disorders (FSDs) are characterized by persistent physical symptoms that cannot be explained by other somatic or psychiatric conditions. Multiple Chemical Sensitivity (MCS) is a non-allergic FSD characterized by odour intolerance and various somatic symptoms being attributed to the influence of toxic environmental chemicals in low, usually harmless doses. The pathophysiology of FSDs are still not clear. Smell and taste complaints were also among the notable symptoms characterizing the covid epidemic and the latest evidence suggests overlaps between long COVID and FSDs. Method(s): The study includes advanced analysis of MRI-derived functional and structural connectomes acquired on a 3 T MR scanner. Furthermore, it includes questionnaires and paraclinical tests, e.g. the Sniffin' Stick olfactory test, Mini-Mental State Examination, and Sino-Nasal Outcome test 22. The pilot part of the project included 6 MCS patients who were compared with 6 matched healthy participants. Later follow-up included analysis of 8 multiorgan FSD and 4 post-COVID patients. Result(s): The MCS group showed important brain structural connectivity differences in 34 tracts. Notably, for MCS patients, the olfactory cortex (especially in the right hemisphere) showed decreased connectivity with regions in the emotional system. Conclusion(s): We plan to extend these findings with whole-brain modelling of the functional connectivity in the patient groups. Long-term this could be used as a 'fingerprint' which could help with diagnosis and treatment monitoring in FSDs as well as with new diagnoses such as long-COVID.Copyright © 2023

Olfactory training in long COVID-19 patients with lasting symptoms including olfactory dysfunction

INTRODUCTION. Two-thirds of patients with COVID-19 developed smell and taste dysfunction, of whom half experienced improvement within the first month. After six months, 5-15% still suffered from significant olfactory dysfunction (OD). Before COVID-19, olfactory training (OT) was proved to be effective in patients with post-infectious OD. Therefore, the present study aimed to investigate the progress of olfactory recovery with and without OT in patients with long COVID-19. METHODS. Consecutive patients with long COVID-19 referred to the Flavour Clinic at Godstrup Regional Hospital, Denmark, were enrolled. The diagnostic set-up at the first visit and follow-up included smell and taste tests, questionnaires, ENT examination and instructions in OT. RESULTS. From January 2021 to April 2022, 52 patients were included due to long COVID-19-related OD. The majority of patients complained of distorted sensory quality, in particular, parosmia. Two-thirds of the patients reported a subjective improvement of their sense of smell and taste along with a significant decline in the negative impact on quality of life (p = 0.0001). Retesting at follow-up demonstrated a significant increase in smell scores (p = 0.023) where a minimal clinically important difference (MCID) in smell scores was found in 23% of patients. Full training compliance was significantly associated with the probability of MCID improvement (OR = 8.13;p = 0.04). CONCLUSIONS. The average effect of OT is modest;however, full training compliance was significantly associated with an increased probability of a clinically relevant olfactory improvement. FUNDING. none. TRIAL REGISTRATION. not relevant.Copyright © 2023, Almindelige Danske Laegeforening. All rights reserved.

The nose can be the focus of treatment and prophylactic approaches against COVID-19

Infection with SARS-CoV-2 frequently commences in the nasal cavity, yet knowledge about this initial virus-host interaction is sparse. In this review, we update our current understanding of SARS-CoV-2 infection via the nasal epithelium and the associated local immune response. Furthermore, we present considerations to how this interaction may influence the clinical course of COVID-19 and the systemic immune response, and lastly touch upon the potential for intranasal vaccination, intranasal antiviral therapies and immunomodulatory approaches.

[Taste and smell loss in patients with COVID-19]

In the aftermath of COVID-19, the association between SARS-CoV-2 and chemosensory deficits have been well established. Taste and smell loss have been included in the official lists of symptoms worldwide, as it is a common symptom (and for some patients the only symptom) of COVID-19 as described in this review. Patients with COVID-19 often have combined taste and smell loss, have a milder clinical presentation, and are younger than previous patients with postviral olfactory loss. Patients should start olfactory training early and should be seen by an ear, nose and throat physician if they do not experience improvement of the senses within 12 weeks.