Clinical trial NCT06817499: Treatment of Olfactory Dysfunction Using Vagus Nerve Stimulation
Official title: Treatment of Olfactory Dysfunction Using Vagus Nerve Stimulation
Study type: INTERVENTIONAL
Overall status: NOT_YET_RECRUITING
Phase: NA
Conditions: Hyposmia
Keywords: VNS
Hyposmia
Olfaction
Olfaction Disorders
Sensation Disorders
Vagus Nerve
Lead sponsor: Karolinska Institutet
Sponsor class: OTHER
First posted: 2025-02-10
Enrollment: 40
Sex: ALL
Minimum age (years): 18
Maximum age (years): 65
Standard ages: ADULT
OLDER_ADULT
Accepts healthy volunteers: no
Allocation: RANDOMIZED
Intervention model: PARALLEL
Primary purpose: TREATMENT

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.

Eligibility criteria: 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

Primary outcomes:
measure: Sniffin' Sticks TDI test (objective olfactory function)
timeFrame: From enrollment to the end of treatment at 8 weeks
measure: Self rated olfaction questionnaire (subjective olfactory function)
timeFrame: From enrollment to the end of treatment at 8 weeks
measure: General Wellbeing Questionnaire (general wellbeing)
timeFrame: From enrollment to the end of treatment at 8 weeks
measure: Adherence to training questionnaire (Compliance)
timeFrame: From enrollment to the end of treatment at 8 weeks
Secondary outcomes:
Other outcomes:
Locations:
city: Solna
country: Sweden
facility: Karolinska Institutet
state: Stockholm
Study officials:
References: