Assessing the effects of smell training on the brains of patients with an impaired sense of smell after surgery
| ISRCTN | ISRCTN62670142 |
|---|---|
| DOI | https://doi.org/10.1186/ISRCTN62670142 |
| ClinicalTrials.gov (NCT) | Nil known |
| Clinical Trials Information System (CTIS) | Nil known |
| Protocol serial number | 170728010 |
| Sponsor | Pontifical Catholic University of Chile |
| Funder | Fondo Nacional de Desarrollo Científico y Tecnológico |
- Submission date
- 30/05/2020
- Registration date
- 02/06/2020
- Last edited
- 02/06/2020
- Recruitment status
- No longer recruiting
- Overall study status
- Completed
- Condition category
- Ear, Nose and Throat
Plain English summary of protocol
Background and study aims
Olfactory dysfunction is the inability to perceive smells. Its treatment is challenging due to limited therapeutic options. Olfactory training has been shown to improve smell identification, discrimination, and the threshold for odour detection of patients with olfactory dysfunction with postinfectious etiology (i.e. after an infection). The aim of this study is to assess the effect of olfactory training in patients with olfactory dysfunction after pituitary surgery (post-surgical etiology) using functional magnetic resonance imaging (fMRI scan) to see if it induces neural (brain) reorganization processes.
Who can participate?
Patients with post-surgical olfactory dysfunction lasting for at least 1 year after endoscopic transsphenoidal pituitary surgery
What does the study involve?
Participants undergo an examination that includes a nasal endoscopic evaluation. They are also tested using an olfactory measurement test (Sniffing Stick test) and undergo an fMRI scan. Participants are randomly allocated to undergo olfactory training for 12 weeks or no treatment. Olfactory training is performed using four essential oils. Participants are instructed to expose themselves twice a day to each odour taking deep sniffs for 30 seconds and resting 10 seconds between each oil. Additionally, they are instructed to evoke a memory or feeling during the odour exposure that is associated with the smell of the essential oil. Participants are contacted monthly to maintain compliance and motivation during the training period. At the end of the 12-week training period, both groups are assessed using the olfactory performance test and fMRI, and the control group receive olfactory training.
What are the possible benefits and risks of participating?
The possible benefits are the partial or complete recovery of olfactory function after olfactory training. This study does not have any risks for the participants.
Where is the study run from?
Pontificia Universidad Catolica de Chile (Chile)
When is the study starting and how long is it expected to run for?
May 2017 to May 2021
Who is funding the study?
Fondo Nacional de Desarrollo Científico y Tecnológico (Chile)
Who is the main contact?
Dr Francisco García-Huidobro
fggarciahuidobro@uc.cl
Contact information
Scientific
Marcoleta 352
Santiago
8330033
Chile
 ORCID ID |
0000-0002-5607-0740 |
|---|---|
| Phone | +56 (0)997459771 |
| fggarciahuidobro@uc.cl |
Study information
| Primary study design | Interventional |
|---|---|
| Study design | Single-center interventional randomized controlled trial |
| Secondary study design | Randomised controlled trial |
| Study type | Participant information sheet |
| Scientific title | Neuroplasticity assessment using fMRI after olfactory training in post-surgical olfactory impaired patients |
| Study acronym | NOTFMRI |
| Study objectives | Olfactory training will induce neuroplasticity processes on associated olfactory areas in patients with post-surgical olfactory dysfunction. |
| Ethics approval(s) | Approved 05/09/2017, the scientific ethics committee of Pontificia Universidad Catolica medical faculty (Marcoleta 381 – fourth floor, Office 42, Santiago, Chile; +562 (0)23548173; Cecmeduc@med.puc.cl), ref: 170728010 |
| Health condition(s) or problem(s) studied | Post-surgical olfactory dysfunction |
| Intervention | All participants undergo an olfactory measurement test to diagnose olfactory dysfunction and assess severity. Also, they are examined by an ENT specialist's including a complete physical exam and nasofibroscopy, to exclude other conditions that could be causing smell impairment. For the scanning sessions, an odour infusion system is attached to a single air-line, to perform the sniffing paradigm, which is characterized by an odour intake of eucalyptus essential oil through a nasal cannula. Also, a trigeminal activation paradigm is performed to assess the indemnity of the trigeminal system, characterized by the intake of odourless CO₂ through a nasal cannula. After the first fMRI and olfactory performance assessment, the smell-impaired cohort is randomized into two groups. Participants are randomized by simple randomization using computer-generated random numbers. The allocation is concealed from the research team. No masking is used. Intervention: Olfactory training for 12 weeks Control: No treatment Olfactory training is performed using four essential oils: lemon (limonene 67.08% and b-pinen 12.52%), eucalyptus glovus (1-8-cineole 60%), clove (eugenol 75.49% and eugenol acetate 13.59%) and lavender (linalool 36.53% and linalyl acetate 32.80%). Patients are instructed to expose themselves twice a day to each odour taking deep sniffs for 30 seconds and resting 10 seconds between each oil. Additionally, they are instructed to evoke a memory or feeling during the odour exposure that is associated with the smell of the essential oil. Patients are contacted monthly to maintain compliance and motivation during the training period. At the end of the 12-week training period, both groups are assessed using olfactory performance test and fMRI, and the control group receive olfactory training. |
| Intervention type | Other |
| Primary outcome measure(s) |
Activation areas and functional connectivity during olfactory stimulation measured using functional MRI images before olfactory training and 12 weeks after the intervention |
| Key secondary outcome measure(s) |
Olfactory function assessed using olfactometric measurements before olfactory training and 12 weeks after the intervention |
| Completion date | 01/05/2021 |
Eligibility
| Participant type(s) | Patient |
|---|---|
| Age group | Adult |
| Sex | All |
| Target sample size at registration | 25 |
| Key inclusion criteria | 1. Referred post-surgical olfactory dysfunction lasting for at least 1 year 2. Only patients with a definite diagnosis of olfactory dysfunction were finally included 3. No history of psychiatric or neurodegenerative diseases |
| Key exclusion criteria | 1. Olfactory dysfunction not related to surgical procedures 2. Associated psychiatric or neurodegenerative diseases 3. Pediatric age |
| Date of first enrolment | 01/10/2017 |
| Date of final enrolment | 31/12/2020 |
Locations
Countries of recruitment
- Chile
Study participating centre
Santiago
8330033
Chile
Results and Publications
| Individual participant data (IPD) Intention to share | Yes |
|---|---|
| IPD sharing plan summary | Stored in repository |
| IPD sharing plan | The data that is stored are the demographic data of each patient, the olfactometric results and the fMRI images of each of the patients. This data is private and the ethics committee only authorizes its use by the authors for scientific publication protecting the anonymity of the participants. There are no web links available, and data is stored in the Bioimaging center of the University. |
Study outputs
| Output type | Details | Date created | Date added | Peer reviewed? | Patient-facing? |
|---|---|---|---|---|---|
| Participant information sheet | Participant information sheet | 11/11/2025 | 11/11/2025 | No | Yes |
Editorial Notes
02/06/2020: Trial's existence confirmed by the scientific ethics committee of Pontificia Universidad Catolica medical faculty.
