Smell dysfunction significantly impacts quality of life and safety, with limited effective treatments. This open-label study evaluates the preliminary efficacy of combining non-invasive trigeminal nerve stimulation (TNS) with standard smell training (ST) to improve olfactory function. Participants will complete 8 weeks of at-home treatment and attend three in-person visits for assessment. Improvements in smell, mood, sleep, and quality of life will be measured.
Age 18-80
Self-reported or medically documented smell loss
Treatment-seeking for their smell loss
Naïve to TNS
Medical Records not available to confirm eligibility
Documented/Suspected head injury (e.g. sport, accident, blast exposure)
Neurological disorder (e.g. epilepsy, neurodegenerative disorder)
Serious mental illness (e.g. schizophrenia, bipolar disorder)
Single group
Trigeminal Nerve Stimulation-enhanced Smell Training
Combination productTNS is a form of cranial nerve stimulation that uses a simple transcutaneous electrical nerve stimulation device, and adhesive electrodes that are attached to forehead to deliver low-level electrical current. Stimulating the trigeminal nerve activates the trigeminal afferent sensory pathway and central brain regions where the intranasal trigeminal and olfactory circuits converge. Smell Training requires 4 odors to be smelled individually for 10 sec each and record ratings.
Change in Psychophysical Olfactory Function from Baseline to 4 and 8 Weeks
Sniffin' Sticks (Bughardt Messtechnik, Wedel Germany) will be used to determine odor threshold (T), odor discrimination (D), and odor identification (I), each on 16-point scales, and summed for a total TDI score. Higher scores indicate better function.
Change in Perceived Intensity of Odorants from Baseline to 4 and 8 Weeks
Perceived intensity on 100-mm visual analog scales with anchor points: 0="imperceptible" to 100="extremely intense".
Change in Perceived Hedonics of Odorants from Baseline to 4 and 8 Weeks
Perceived hedonics on 100-mm visual analog scales with anchor points: 0="extremely unpleasant" to 100="extremely pleasant".
Change in Olfactory-related Quality of Life from Baseline to 4 and 8 Weeks
The Modified Questionnaire of Olfactory Disorders-Negative Statements (QOD-NS) consists of 17 negative statements (rated on a scale from 0 to 3; total score ranging from 0 to 51), with lower scores indicating better olfactory-related quality of life.
Change in Mood State from Baseline to 4 and 8 Weeks
The Profile of Mood States Short Form (POMS-SF) is a psychological rating scale used to assess transient, distinct mood states across six different dimensions including Tension or Anxiety, Anger or Hostility, Vigor or Activity, Fatigue or Inertia, Depression or Dejection, and Confusion or Bewilderment.
Change in Sleep Quality from Baseline to 4 and 8 Weeks
The Pittsburgh Sleep Quality Index (PSQI) is a self-report questionnaire that assesses sleep quality over a 1-month time interval. The measure consists of 19 individual items, creating 7 components that produce one global score. Scores greater than 5 are indicative of a sleep disturbance.
Change in Symptoms of Depression from Baseline to 4 and 8 Weeks
The Patient Health Questionnaire-9 (PHQ-9) is a self-administered 9-item questionnaire to screen for the presence and severity of depression. Items are rated on a 3pt scale ranging from 0="Not at all" to 3="Nearly every day". Total score ranges from 0-27 and is used to classify depression severity: 0-4=None/Minimal; 5-9=Mild; 10-14=Moderate; 15-19=Moderately Severe; 20-27=Severe.
Change in Symptoms of Anxiety from Baseline to 4 and 8 Weeks
The Generalized Anxiety Disorder-7 (GAD-7) is a 7-item questionnaire to screen for presence and severity of anxiety disorder. Items are rated on a 3pt scale ranging from 0="Not at all" to 3="Nearly every day". Total score ranges from 0 to 21 and is used to classify anxiety severity: 0-4 (minimal anxiety), 5-9 (mild anxiety), 10-14 (moderate anxiety), 15-21 (severe anxiety).
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