Photo Credit: James Mutter

The following is a summary of “Mannitol provocation enhances laryngoscopic diagnosis of suspected inducible laryngeal obstruction,” published in the February 2025 issue of Annals of Allergy, Asthma & Immunology by Stojanovic et al. 

Inducible laryngeal obstruction (ILO) is diagnosed by paradoxical vocal fold movement (PVFM), but its intermittent nature reduces test sensitivity. Isolated expiratory PVFM may be a normal response to lower airway obstruction. 

Researchers conducted a retrospective study to assess mannitol provocation for clarifying laryngoscopic diagnosis in suspected ILO.  

They assessed laryngoscopic PVFM in suspected ILO at baseline and after mannitol provocation, defined as any inspiratory adduction, ≥50% expiratory adduction, or both. They analyzed the accentuation of PVFM after mannitol, defined as new or increased PVFM. They examined isolated expiratory PVFM, lower airway obstruction on spirometry, and bronchial hyperresponsiveness to mannitol as well as studied healthy volunteers. 

The results showed PVFM in 42/80 (52.5%) patients at baseline and 58/80 (72.5%) after mannitol. Mannitol accentuated PVFM in 45/80 (56%), with new PVFM in 17/80 (21%) and increased PVFM in 28/80 (35%), including 28/42 (67%) with baseline PVFM. Among 30 patients with isolated expiratory PVFM, 21 had accentuation, with no link to airway obstruction or bronchial hyperresponsiveness. In 15 healthy volunteers, PVFM rates were 4/15 (27%) at baseline and after mannitol, all with isolated expiratory PVFM, and none (0/15) had accentuation. 

Investigators found that mannitol accentuation improved differentiation between suspected ILO and healthy volunteers. Isolated expiratory PVFM without accentuation was a normal finding, unrelated to bronchial obstruction or hyperresponsiveness. 

Source: annallergy.org/article/S1081-1206(25)00069-9/abstract