Hyposmia
Conditions
Keywords
VNS, Hyposmia, Olfaction, Olfaction Disorders, Sensation Disorders, Vagus Nerve
Brief summary
Hyposmia, a reduced sense of smell, is commonly linked to viral infections like COVID-19. Currently, the sole recommended treatment is olfactory training, a method that is both time-intensive and limited in its effectiveness. Our team has previously evaluated a new type of olfactory training using nasal inserts that show increased adherence to training (compared to standard olfactory training using common household odors) but with similar treatment effect. The investigators recently demonstrated that brief transcutaneous vagus nerve stimulation (VNS) in the cymba conchae region affected participants olfactory abilities but only when a stimulation frequency relevant to olfactory bulb processing frequencies was used. The notion that VNS might modulate olfactory functions stems from findings in rats where VNS of the cervical nerve inhibited neurons within the periglomerular layers of the olfactory bulb. Although there is no known monosynaptic connection between the vagus nerve and the olfactory system in humans, VNS activates areas with mono-synaptic connections to the olfactory bulb, such as amygdala, hippocampus, and the hypothalamus. Given that VNS modulates the olfactory bulb in rats and our treatment protocol modulate olfactory functions in humans, the investigators hypothesize that VNS, when paired with olfactory training, will enhance olfactory functions in patients with hyposmia.
Detailed description
Participants with hyposmia will be recruited and randomly assigned to one of two treatment groups. One group will engage in olfactory training using nasal inserts while the other will use olfactory training with nasal inserts along with VNS. Both interventions will take place at home, Monday through Friday, over a two-month period. To evaluate the outcomes, subjective and objective measures of olfactory function will be collected before, during, and after the treatment, along with assessments of quality of life and overall well-being. Treatment adherence will also be evaluated at the end of treatment.
Interventions
OTHERNasal Insert + VNS
Participants will complete olfactory training with scented nose plugs along with VNS
OTHERNasal Insert
Participants will complete olfactory training with scented nose plugs
Sponsors
Karolinska Institutet
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
TREATMENT
Masking
NONE
Eligibility
Sex/Gender
ALL
Age
18 Years to 65 Years
Healthy volunteers
No
Inclusion criteria
* Correct age (18-65) * Physically and cognitively capable of participating in the study * Having appropriate olfactory screening test scores (hyposmic)
Exclusion criteria
* History of heart conditions * Individuals with other diagnoses that could affect the study results
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Sniffin' Sticks TDI test (objective olfactory function) | From enrollment to the end of treatment at 8 weeks | Objective olfactory function will be measured using the Sniffin' Sticks TDI extended test (Burghart Messtechnik) which gives separate scores for odor threshold, odor discrimination, and odor identification; as well as a summated score (TDI) of objective olfactory function. |
| Self rated olfaction questionnaire (subjective olfactory function) | From enrollment to the end of treatment at 8 weeks | Does the use of VNS increase the effect of olfactory training on subjective qualitative (parosmia) and quantitative (hyposmia) symptoms compared to only olfactory training? For this outcome, we will use self-ratings of qualitative and quantitative olfactory function, for example Do you experience smell distortion (parosmia)? (if yes, rate your problem from 0 to 10) and rate your sense of smell from 0 to 10 |
| General Wellbeing Questionnaire (general wellbeing) | From enrollment to the end of treatment at 8 weeks | Does the use of VNS increase the effect of olfactory training on subjective general wellbeing compared to only olfactory training? For this outcome, we will use the General Wellbeing Questionnaire (GWB). |
| Adherence to training questionnaire (Compliance) | From enrollment to the end of treatment at 8 weeks | Does the use of VNS affect the compliance of olfactory training compared to olfactory training only? For this outcome, we will use a questionnaire that participants answer during their final visit. The questionnaire separately assesses consistency, perceived tediousness, forgetfulness, and cause for potential discontinuation of the training, for example by asking how many times did you forget your training? |
Countries
Sweden
Outcome results
None listed