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NCT Number: NCT06020937

Olfactory and Trigeminal Functions in Patients With Multiple Sclerosis: Case-control Study

The sensation of smell is influenced by the somatosensory and chemesthetic sensati¬ons of the nose: for example, the cooling sensation of menthol or the prickle of carbon dioxide from carbonated drinks. These sensations are mediated in the nose by the trigeminal nerve and there is increasing evidence that trigeminal and olfactory functions are closely linked and potentially interdependent. In addition, trigeminal activation is crucial to the perception of nasal airflow. Some researchers speculate about the impact of trigeminal nerve on the entire olfactory sensation and about the presence of some specific "trigeminal cells" into the nose.Patients with Multiple sclerosis (MS) can suffer from quantitative olfactory disorders that generally are of light entity and do not interfere with daily life activities but it is important to underline that olfactory loss can be an onset sign of the MS. Considering the "trigeminal component" in the olfaction, because trigeminal nerve inflammation is quite common in MS patients due to central and peripheral inflammation, it could be possible that these patients suffer from changes in the quantitative, but more in the qualitative smell functions that are generally not identified because poorly investigated.

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Key information

Conditions

Multiple Sclerosis Autoimmune Diseases Autoimmune Diseases of the Nervous System Demyelinating Autoimmune Diseases, CNS Demyelinating Diseases Immune System Diseases Nervous System Diseases

Age range

18 year–55 year

Sex eligibility

Female

Study type

Observational

Primary location

Arianna Di Stadio

Catania, Sicily, 95121, Italy

Location contact

Arianna Di Stadio

CONTACT

About this study

From a theoretically point of view pain in the trigeminal nerve increases the surrounding perception, including the perception of the odors. It has been shown that by using sweet food it is possible to reduce the level of pain; on the other side, sweet food in contrast to the bitter one was able to reduce the sensation of odor unpleasantness present with pain increase.

To date no studies have investigated the relationship between trigeminal inflammation, odors and pain in a cohort of patients with MS. This study aims at investigating the possible correlation between alteration in trigeminal functions and perception of odors using Sniffin' Stick Threshold, Detection and Identification test and quality smell questionnaire in a sample of healthy patients compared to MS patients.

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

Adult women (age 18 to 55) diagnosed with multiple sclerosis using the 2017 McDonald Criteria under treatment with Disease Modifying Therapy (DMTs) with or without trigeminal concerns, or newly diagnosed with MS

Exclusion criteria

  • Chronic rhinosinusitis with and without nasal polyposis; current allergic rhinitis; other nasal issues that lead to olfactory dysfunction
  • anamnestic COVID with incomplete recovery
  • Neurodegenerative disorders (Parkinson, Alzheimer, Fronto-temporal Dementia, cognitive impairment and brain vascular diseases)
  • History of stroke in the last three years
  • Depression or any psychiatric condition
  • intake of drugs with sedating side effects
  • major health issues that might affect olfactory function (e.g., significant renal insufficiency, uncontrolled diabetes)
  • Chronic alcoholism / drug abuse
  • Severe head trauma
  • Severe facial injuries
  • Smoker over 20 cigarettes day or smoking from more than 15 years

Treatment and study plan

TDI

Diagnostic Test

Sniffin' Sticks Threshold and Identification Test

Trigeminal Test

Diagnostic Test

Test the trigeminal smell answer by a device that releases air and a substance that stimulates the trigeminal response

Cognitive Evaluation by Montreal Cognitive Assessment

Diagnostic Test

Montreal Cognitive assessment

Anxiety and Depression questionnaire

Diagnostic Test

Specific test to evaluate patient's mood

Visual Analogue Scale Ratings

Diagnostic Test
  • Smell ability (How is your sense of smell right now? 0 cannot smell, 1-3 severe impairment, 4-6 moderate impairment, 7-9 mild impairment, 10 normal)
  • Nasal breathing (How well can you breathe through your nose right now? 0 complete nasal obstruction, 1-3 severe impairment, 4-6 moderate impairment, 7-9 mild impairment, 10 normal)

Quality of smell Questionnaire

Diagnostic Test

Patients will answer to a validated questionnaire

Primary outcomes

  1. Trigeminal component

    Time frame: 12 months

    One bottle contains 10ml Eucalyptol (pure / 99%), the other bottle contains only air 15ml stimuli would be released from both bottles using the squeezer device A 3cm long, 4mm inner diameter silicon tubing is placed over the nozzle of each bottle to minimize irritation at the nostrils Silicon tubing should reach beyond the nasal valve area

    • Trigeminal intensity ratings (How intense is the tickling or cool sensation in the nose? 0 no feeling, 10 very strong feeling)
    • The trial can be done on the left nostril, then on the right nostril and this already corresponds to the first presentation for the actual test
    • Total of 20 presentations (10 on each side) with interstimulus interval of around 10 seconds between each presentation, and a longer pause of 30 seconds every 5 presentations
    • The score is the sum of correct lateralizations

Sponsors and collaborators

Lead sponsor

University of Catania

Other

Collaborators

  • Hospital General Universitario Santa Lucia
  • Klinik und Poliklinik fur Kinderheilkunde
  • University of Roma La Sapienza

Registry information

Official study title

Olfactory and Trigeminal Functions in Patients With Multiple Sclerosis

Important dates

Study start
2026
Primary completion
2026
Study completion
2028
First posted
Sep 1, 2023
Registry last updated
May 12, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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