Decrease in pain perception during acute SARS-CoV-2 infection: a case series

SARS-CoV-2-induced sensory perturbations: A narrative review of clinical phenotypes, molecular pathologies, and possible interventions

Background

The acute and post-acute sequelae of SARS-CoV-2 infection have been of great clinical interest since the inception of the COVID-19 pandemic. Despite a high prevalence of individuals with persistent symptoms, a wholistic view of the effects of SARS-CoV-2 on special sensory systems is lacking. Considering the significant impact of normal sensory function on quality of life, the goal of this review is to highlight unresolved issues related to SARS-CoV-2-associated insults to the sensory nervous system.

Major findings

In this narrative review, we discuss the epidemiology of SARS-CoV-2-induced sensory perturbations, underlying pathological mechanisms, and possible therapeutic strategies across the olfactory, gustatory, somatosensory, visual, and auditory systems. Examined literature included studies with human biospecimens, human-derived cell lines, and naturally susceptible animal models, which highlighted evidence of persistent functional disruption in all sensory systems. SARS-CoV-2 infection was associated with persistent inflammation in the olfactory epithelium/bulb, somatosensory ganglia, and gustatory systems, long-term transcriptional perturbations in the sensory central nervous system and peripheral nervous system, and detectable degeneration/apoptosis in the gustatory and visual systems. Few studies have proposed evidence-based therapeutic strategies for attenuating specific sensory abnormalities after SARS-CoV-2 infection.

Conclusion

While the olfactory system, and to some extent the visual and somatosensory systems, have been more thoroughly investigated from symptomatology, behavioral and molecular perspectives, there is still an unmet need for the development of therapeutics to treat COVID-induced impairment of these systems. Further, additional attention must be placed on COVID-associated impairment of the gustatory, visual, and auditory systems, which lack detailed mechanistic investigations into their pathogenesis.

SARS-CoV-2 airway infection results in the development of somatosensory abnormalities in a hamster model

Although largely confined to the airways, SARS-CoV-2 infection has been associated with sensory abnormalities that manifest in both acute and chronic phenotypes. To gain insight on the molecular basis of these sensory abnormalities, we used the golden hamster model to characterize and compare the effects of infection with SARS-CoV-2 and influenza A virus (IAV) on the sensory nervous system. We detected SARS-CoV-2 transcripts but no infectious material in the cervical and thoracic spinal cord and dorsal root ganglia (DRGs) within the first 24 hours of intranasal virus infection. SARS-CoV-2-infected hamsters exhibited mechanical hypersensitivity that was milder but prolonged compared with that observed in IAV-infected hamsters. RNA sequencing analysis of thoracic DRGs 1 to 4 days after infection suggested perturbations in predominantly neuronal signaling in SARS-CoV-2-infected animals as opposed to type I interferon signaling in IAV-infected animals. Later, 31 days after infection, a neuropathic transcriptome emerged in thoracic DRGs from SARS-CoV-2-infected animals, which coincided with SARS-CoV-2-specific mechanical hypersensitivity. These data revealed potential targets for pain management, including the RNA binding protein ILF3, which was validated in murine pain models. This work elucidates transcriptomic signatures in the DRGs triggered by SARS-CoV-2 that may underlie both short- and long-term sensory abnormalities.

The Interactive Effects of Post-Traumatic Stress Symptoms and Breathlessness on Fatigue Severity in Post-COVID-19 Syndrome

Background: Post-traumatic stress symptoms (PTSS) and breathlessness have been well documented in the acute phase of COVID-19 as well as in Post-COVID-19 Syndrome (PCS), commonly known as Long-COVID. The present study aimed to explore whether PTSS and breathlessness interact to exacerbate fatigue among individuals recovering from PCS, similar to the effects evidenced in other health conditions that feature respiratory distress.. Methods: Outcome measures were collected from 154 participants reporting persistent fatigue following acute COVID-19 infection who were enrolled in a 7-week rehabilitation course provided by the Primary Care Wellbeing Service (PCWBS) in Bradford District Care NHS Foundation Trust (BDCFT). Results: Hierarchical multiple linear regression revealed that fatigue severity was associated with a significant interaction between PTSS and breathlessness, even when controlling for pre-COVID health related quality of life (HRQoL), age, symptom duration and hospital admittance during the acute phase. Furthermore, improvements in fatigue following rehabilitation were significantly associated with improvements in PTSS. Conclusions: PTSS may be an important therapeutic target in multidisciplinary rehabilitation for reducing fatigue in the recovery from PCS. It is therefore important that treatment for PCS takes a biopsychosocial approach to recovery, putting emphasis on direct and indirect psychological factors which may facilitate or disrupt physical recovery. This highlights the need for all PCS clinics to screen for PTSD and if present, target as a priority in treatment to maximise the potential for successful rehabilitation.

Longitudinal observations of sympathetic neural activity and hemodynamics during 6 months recovery from SARS-CoV-2 infection

Cross-sectional data indicate that acute SARS-CoV-2 infection increases resting muscle sympathetic nerve activity (MSNA) and alters hemodynamic responses to orthostasis in young adults. However, the longitudinal impact of contracting SARS-CoV-2 on autonomic function remains unclear. The aim of this study was to longitudinally track MSNA, sympathetic transduction to blood pressure (BP), and hemodynamics over 6 months following SARS-CoV-2 infection. Young adults positive with SARS-CoV-2 reported to the laboratory three times over 6 months (V1:41 ± 17, V2:108 ± 21, V3:173 ± 16 days post-infection). MSNA, systolic (SBP) and diastolic (DBP) blood pressure, and heart rate (HR) were measured at rest, during a cold pressor test (CPT), and at 30° head-up tilt (HUT). Basal SBP (p = 0.019) and DBP (p < 0.001) decreased throughout the 6 months, whereas basal MSNA and HR were not different. Basal sympathetic transduction to BP and estimates of baroreflex sensitivity did not change over time. SBP and DBP were lower during CPT (SBP: p = 0.016, DBP: p = 0.007) and HUT at V3 compared with V1 (SBP: p = 0.041, DBP: p = 0.017), with largely no changes in MSNA. There was a trend toward a visit-by-time interaction for burst incidence (p = 0.055) during HUT, wherein at baseline immediately prior to tilting, burst incidence was lower at V3 compared with V1 (p = 0.014), but there were no differences between visits in the 30 HUT position. These results support impairments to cardiovascular health, and potentially autonomic function, which may improve over time. However, the improvements in BP over 6 months recovery from mild SARS-CoV-2 infection are likely not a direct result of changes in sympathetic activity.