Olfactory rehabilitation and olfactory bulb volume changes in patients after total laryngectomy: a prospective randomized study

Does Olfactory Training Improve Brain Function and Cognition? A Systematic Review

“…Jiramongkolchai et al ( 2021 ) Association of Olfactory Training with Neural Connectivity in Adults with Postviral Olfactory Dysfunction Total Sample: N = 36 • Adults with Postviral Olfactory Dysfunction (PVOD): n = 16 ( M age = 60 yrs) • Normosmic Control Group: n = 20 ( M age = 55 yrs) Entry Criteria • PVOD of 3 months or more • ENT exam with anterior rhinoscopy (no nasal polyps) • Non-smokers • No neurological disorder • Not currently experiencing upper respiratory infection • No exposure to head/neck cancer treatment • OT involved exposure to 4 odorants (rose, eucalyptus, lemon, and clove) 20–30 s each 2x/day for 12 wks • OT was charted in diary • Olfaction was assessed by Sniffin’ Sticks test and University of Pennsylvania Smell Identification test (UPSIT) at baseline and posttest • Normosmic control group was assessed at baseline only • Budesonide nasal irrigation conducted 1 month prior, to control for nasal inflammation • Resting state fMRI was conducted at baseline and posttest for PVOD group • One-group pre-post experimental design (over 3 months) • Control group was not administered OT or the posttest assessment Primary Outcome • Measurement of change in neural connectivity following OT using fMRI • Baseline fMRI demonstrated PVOD group had increased connectivity of the visual cortex, cerebellum, and angular cortex compared to controls • Following OT, PVOD group showed increased connectivity in olfactory regions of the brain, and decreased connectivity in visual areas • 9 of 16 participants improved scores in UPSIT or Sniffin’ Sticks Strengths • fMRI was used to measure neural activity • Controlled for possible inflammation • OT adherence was following throughout study Limitations • No long-term follow-up • Small N • Control group did not complete OT • OT adherence not reported 15. Gürbüz et al ( 2022 ) Olfactory Rehabilitation and Olfactory Bulb Volume Changes in Patients after Total Laryngectomy:A Prospective Randomized Study Men with Laryngectomy due to Advanced Laryngeal Cancer: N = 11 (M age = 58.18; post-surgery > 5 yrs) Entry Criteria • No nasal surgery or nasal polyps • No neurological or psychiatric illness • No head trauma • OT was performed for 30 min/day for 6 months using 4 odorants • Olfactory rehabilitation consisted of providing air flow, and thus access to odorant particles, using a larynx bypass technique • Cranial MRI was conducted before and 6 months following laryngectomy and was used to compute OB volume • Olfaction was assessed using the Connecticut Chemosensory Clinical Research Center (CCCRC) orthonasal olfactory tests • One-group pre-post experimental design (over 6 months) Primary Outcome • The effect of OT on OB volume and smell performance...…”

“…Jiramong kolchai et al ( 2021 ) N = 36 (2 groups, but only 1 TX group) • Adults w/ PVOD ( n = 16) • Normosmic Control Group ( n = 20) • 4 odorants • 2x/day • 12 wks • Diary • Contacted routinely to assess adherence • Data not reported + + No Change + Not Measured • OT increased neural connectivity with left parietal occipital junction, decreased connectivity with visual cortex 15. Gürbüz et al ( 2022 ) N = 11 (1 TX group) • Adults with Olfactory Dysfunction after Total Laryngectomy • 4 odorants • 30 min/day • 6 months • Adherence not reported but OT may have been supervised Not Reported + Not Reported + Not Measured • OB volume was increased following OT as measured by structural MRI 16. Rezaeyan et al ( 2022 ) N = 25 (3 TX groups) • Classic OT (COT) Group ( n = 9) • Modified OT (MOT) Group ( n = 7) • Control Group ( n = 9) • 4 odorants • 2x/day @ 10 s each • MOT new odorants every 4 wks • 16 wks of OT • Diary • Data reported + No Change No Change + Not measured • Increases in cortical thickness in right orbital frontal cortex and right insular were observed for both OT groups • Increases in cerebellar volume were observed for COT group Cognitive & Neuroimaging Studies 17.…”

“…Study limitations included a small sample size, lack of long-term follow-up, and no experimental control group. Gürbüz et al ( 2022 ) – Neuroimaging Study (Olfactory Bulb) In a unique within group pre-post design study, Gürbüz et al ( 2022 ) examined the effect of OT training on olfactory performance and olfactory bulb volume in patients at least five years following total laryngectomy for cancer. Patients with total laryngectomy often experience olfactory dysfunction, possibly due to a lack of airflow to olfactory regions.…”

“…Study limitations included a small sample size, lack of long-term follow-up, and no experimental control group. Gürbüz et al ( 2022 ) – Neuroimaging Study (Olfactory Bulb) …”

Research Progress of Olfactory Nerve Regeneration Mechanism and Olfactory Training

“… 76 A recent study found that the OB volume could be increased significantly in patients undergoing total laryngectomy after 6 months of OT. 77 Negoias et al measured the OB volume before and after OT by magnetic resonance imaging of 97 healthy participants who undertook OT while closing the other nostril. They demonstrated that the OB volume increased also for untrained nostrils showing, for the first time, that OT could modulate the OB volume by a central mechanism.…”