Inducible Laryngeal Obstruction/Vocal Cord Dysfunction

Inducible Laryngeal Obstruction/Vocal Cord Dysfunction (ILO/VCD) is conceptualised as a functional laryngeal disorder where clinical manifestations arise from inappropriate, transient laryngeal obstruction (Leong et al, 2023). ILO/VCD has been referred to by many different names in the literature – it is commonly referred to as “paradoxical vocal fold movement” (PVFM), “inducible laryngeal obstruction (ILO)” or “vocal cord dysfunction (VCD)”. ILO/VCD is part of the spectrum of dysfunctional larynx which includes chronic cough, muscle tension dysphonia and globus pharyngeus (Vertigan et al. 2022).

ILO/VCD often occurs during inspiration, but may also occur during expiration  It may be accompanied by a sensation of choking and suffocating, throat or chest tightness. Symptoms can be triggered quickly and can also resolve quickly once the triggering stimulus is removed. There is a substantial burden of disease reported among patients with ILO/VCD (Majellano et al. 2024).

ILO/VCD should be considered when other respiratory causes for symptoms are excluded or are insufficient to explain the severity of the condition.

Differential diagnosis includes: asthma, anaphylaxis, laryngeal spasm and subglottic stenosis (Stojanovic et al. 2021, Stojanovic et al. 2022)

• In contrast with asthma, symptoms in ILO/VCD are often localised to the larynx, there is more difficulty with inspiration than expiration, and onset and resolution of dyspnoea episodes is rapid rather than sudden. ILO/VCD may co-exist with asthma or may be misdiagnosed as asthma. Symptoms of ILO/VCD can mimic asthma leading to an incorrect diagnosis of asthma and escalating treatment of asthma including inhaled and systemic corticosteroids (Lee et al. 2018)
• Subglottic stenosis usually results in increased symptoms during exercise
• Voice symptoms can occur in asthma in the absence of ILO/VCD
• ILO/VCD commonly co-occurs in chronic cough (Shembal et al. 2017)

The existence of different ILO/VCD phenotypes has previously been proposed (Leong et al. 2022)

This concept has subsequently been validated using latent class analysis, yielding the following observable phenotypes (Gardner et al. 2025 )

• Isolated ILO/VCD characterised by inhaled and airborne triggers without the presence of comorbidities
• Hyperventilation-associated ILO/VCD– characterised by hyperventilation, anxiety, sino-nasal disease, and also triggered by airborne and inhaled triggers
• Poly-morbid ILO/VCD– characterised by anxiety, sinonasal disease, lower airway obstruction, obesity and gastro-oesophageal reflux
• Pseudo-allergic ILO/VCD– characterised by patient-presumed exposure to allergen but in the absence of specific IgE sensitization.

Importantly, these phenotypes were also distinguished by differences in clinical course, laryngoscopic appearance and treatment responsiveness, providing support for distinct pathogenic pathways.

In addition to the above-mentioned ILO/VCD phenotypes, there is an additional form of ILO/VCD triggered by strenuous exercise termed Exercise-Induced Laryngeal obstruction (EILO), which often occurs in a younger more athletic population and involves a supraglottic component (Wong et al. 2005)

The prevalence of ILO/VCD is difficult to estimate. It varies between studies and depends on the study population and setting.

• ILO/VCD has been reported in:
  • Up to two thirds of people with chronic cough (Vertigan et al, 2018)
  • Up to 30% of patients with difficult asthma (Radhakrishna et al. 2016)
  • 5-22% of patients requiring emergency care for dyspnea (Jain 1997)
  • 15% of US recruits assessed for asthma (Morris et al. 2002)
  • 5% – 27% of elite level performers  (Rundell et al. 2003 & Irewall et al, 2021)
  • Up to 70% of ILO/VCD cases are in women (Lee et al. 2020)
• Some literature suggests female predominance (2:1), and is also recognised in people with high levels of irritant exposure, elite athletes, and some military personnel (Morris et al. 2013).

Based on an international Delphi consensus statement, the diagnosis of ILO/VCD requires verification of inappropriate, transient, reversible laryngeal narrowing in a compatible clinical context (Leong et al. 2023).

In the same Delphi, the proposed gold standard diagnostic tool was laryngoscopy with provocation.

Laryngoscopy allows visualisation of the vocal folds during quiet respiration, phonation, exercise and during odour challenge. Adduction of the vocal cords of > 50% during inspiration or expiration are both considered abnormal (Leong et al. 2023). Supraglottic structures such as the false vocal folds may also demonstrate medial and/or anterior/posterior constriction.  The larynx may appear normal at rest and provocation through irritant exposure or exercise may be needed to observe symptoms (Halvorsen et al. 2017). A recent study showed better discrimination between clinical and healthy populations using dynamic worsening of adduction in response to mannitol provocation in order to diagnose ILO/VCD, when compared to using adducted vocal cords at baseline laryngoscopy (Stojanovic et al. 2025).

Based on an international Delphi consensus statement, the diagnosis of ILO/VCD requires verification of inappropriate, transient, reversible laryngeal narrowing in a compatible clinical context (Leong et al. 2023).

In the same Delphi, the proposed gold standard diagnostic tool was laryngoscopy with provocation.

Laryngoscopy allows visualisation of the vocal folds during quiet respiration, phonation, exercise and during odour challenge. Adduction of the vocal cords of > 50% during inspiration or expiration are both considered abnormal (Leong et al. 2023).. Supraglottic structures such as the false vocal folds may also demonstrate medial and/or anterior/posterior constriction.  The larynx may appear normal at rest and provocation through irritant exposure or exercise may be needed to observe symptoms (Halvorsen et al. 2017). A recent study showed better discrimination between clinical and healthy populations using dynamic worsening of adduction in response to mannitol provocation in order to diagnose ILO/VCD, when compared to using adducted vocal cords at baseline laryngoscopy (Stojanovic et al. 2025).

The below video is a step-by-step demonstration of performing flexible transnasal laryngoscopy including a scent challenge, to inform a diagnosis of ILO/VCD. For more information click here

Questionaires are not diagnostic for ILO/VCD but assist in “generating a clinical impression” (Leong et al. 2023). These include;

• Pittsburgh Vocal Cord Dysfunction Index
• Dyspnoea Severity Index
• Newcastle Laryngeal Hypersensitivity Questionnaire (LHQ)
• Vocal Cord Dysfunction Questionnaire

(For more information see Resources – Comorbidity Components)

While some individuals with ILO/VCD have abnormal flow volume loops, the Delphi consensus statement concluded that spirometry could not confirm a diagnosis of ILO/VCD and served mainly to detect asthma and other pathologies (Leong et al. 2023).

Representative Flow Volume Loop

Representative flow volume loop with flattened inspiratory curve (black arrow) following methacholine challenge. Reproduced with permission from the ©ERS 2018  (Kenn et al. 2011).

320-slice computed tomography (CT) larynx

This allows dynamic images that can be reconstructed to visualise movement of the anatomical structure (Ruane et al. 2014). Reported specificity exceeds 90%, but sensitivity ranges from 50-75% (Koh et al. 2023)

There are limited high quality data on treatment for ILO/VCD (Mahoney et al. 2022; Haines et al. 2022). Some treatment options include:

• Continuous positive airway pressure (CPAP) lowers expiratory flow and increases lung volume, opening the glottis to relieve dyspnea. CPAP also reduces the effort required for inspiration by establishing a favourable pressure gradient for inhalation (Shin et al. 2016).
• Botox injections into the vocal folds prevents release of acetylcholine at nerve terminals, with use previously demonstrated for the management of dystonias. Effects of injections may last up to 14 weeks (Perez et al. 2012).
• Neuromodulating medication, such as pregabalin and gabapentin has been reported in the chronic cough literature (Ryan et al. 2012, Vertigan et al. 2016) and has been used to treat ILO/VCD where laryngeal hypersensitivity is suspected. More research is required to determine effectiveness in ILO/VCD.
• Speech pathology treatment is the mainstay of intervention. It contains several components including:
  • Education on what ILO/VCD is, how it coexists with asthma and why it needs a different approach to asthma treatment
  • Reducing laryngeal irritation by reducing exposure to laryngeal irritants, desensitisation, hydration and reducing phonotraumatic vocal behaviours (Boris et al. 2002)
  • Symptom control exercises such as PVFM release breathing. Exercises are timed with asthma medication.
  • Psychoeducational counselling
  • Inspiratory muscle training
  • Treatment of co-existing laryngeal issues such as cough, globus and dysphonia

A recent trial showed that speech pathology intervention improved symptom frequency or severity measured by validated questionnaires in 75% of participants (Mahoney et al. 2025). However, in routine clinical practice, engagement with speech pathology is often less than ideal and outcomes are correspondingly poorer (Stojanovic et al. 2022). Patient engagement is therefore an important area for further research and improvement (Mahoney et al. 2024).

The Centre of Excellence has developed the free Vocal Cord Dysfunction/Inducible Laryngeal Obstruction (ILO/VCD) Toolkit as a resource for clinicians to facilitate and improve the diagnosis, assessment and management of ILO/VCD.

The recognition of ILO/VCD is increasing. It is now evident that ILO/VCD plays an important role in numerous specialty areas including ENT surgery, respiratory medicine, pediatrics, sports medicine, allergy, emergency medicine, neurology, intensive care, and speech pathology. In the setting of suspected airways disease, ILO/VCD can mimic asthma and make it appear ‘severe’ or ‘difficult-to-treat’, resulting in potential iatrogenic harm from high dose inhaled and oral corticosteroid prescriptions. Diagnosis requires systematic assessment and confirmation of laryngeal narrowing usually with laryngoscopy. The toolkit will assist in raising awareness of ILO/VCD and provide resources for patients living with ILO/VCD.

• ILO/VCD is an important comorbidity in asthma. It can mimic asthma leading to inappropriate escalation in asthma treatment.
• ILO/VCD should be considered as a differential diagnosis or co-morbid in patients with severe asthma.
• Speech pathology treatment is effective in relieving symptoms.