Treatment of Olfactory Dysfunction Using Vagus Nerve Stimulation

Karolinska Institute

Status: Active, not recruiting

Conditions: Hyposmia

Treatments: Other: Nasal Insert + VNS; Other: Nasal Insert

Study type: Interventional

Funder types: Other

Identifiers

NCT06817499

2021-06527 (Other Grant/Funding Number)

2023-03779-01_s3

Details and patient eligibility

About

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.

Full 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.

Enrollment: 40 estimated patients

Sex: All

Ages: 18 to 65 years old

Volunteers: No Healthy Volunteers

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

Trial design

Primary purpose: Treatment

Allocation: Randomized

Interventional model: Parallel Assignment

Masking: None (Open label)

---

40 participants in 2 patient groups

Olfactory training with nasal inserts + VNS

Experimental group

Description:

Participants will complete olfactory training with scented nose plugs along with VNS

Treatment:

Other: Nasal Insert + VNS

Olfactory training with nasal inserts only

Active Comparator group

Description:

Participants will complete olfactory training with scented nose plugs

Treatment:

Other: Nasal Insert