Clinical Features

ILO/VCD is a condition that involves troublesome symptoms caused by abnormal movement of the vocal folds during breathing, and it is thought that this can lead to obstructed airflow. People with the disorder typically experience closure of the vocal folds (previously termed vocal cords) during inspiration, which is the opposite of normal respiration, and which has given rise to the term paradoxical vocal cord movement.

A recent Delphi consensus (Leong JACI 2023) surveyed experts and found four categories of clinical features encompassing symptoms, signs, history-related features and diagnostic clues associated with ILO/VCD, as shown in the Table.

First, clinical features classically occur in acute bouts sometimes termed “attacks”, though it should be noted that in some individuals with longstanding ILO/VCD clinical features can be chronic, with acute peaks. Attacks can be triggered by stimuli including perfumes or strong smells, exercise, stress, or respiratory tract infections. In some individuals, no trigger can be identified. The pattern typically involves a rapid onset of breathlesness (typically seconds) that is worse on inspiration. Episodes are frequently brief and dramatic. However they can linger for days in some individuals or an initial episode can lead to a sequence of recurrences.

Second, clinical features point to laryngeal involvement with features such as a ‘tight throat’, inspiratory difficulties or stridor, and voice changes.

Third, symptoms do not respond to usual ‘asthma’ directed treatment. Features of ILO/VCD and asthma (as well as other airways diseases) can overlap – for example, both manifest episodic breathlessness, ‘exacerbations’ or ‘flares’ and noisy breathing. However, well-intentioned asthma-directed treatment including beta-agonists, inhaled and oral corticosteroids rarely yields satisfying clinical relief.

Fourth, pulmonary function testing can demonstrate inspiratory loop flattening. This is a non-specific clue because it can also occur due to poor spirometric technique, or other medical and surgical conditions, and should not be used to establish the diagnosis.

A careful history and examination, can be highly informative in directing the clinician’s index of suspicion and there are some clues that can hint at ILO/VCD or asthma, though none of the features below are specific enough to confirm a diagnosis. It is important to recognize that individuals may have both ILO/VCD and asthma (or another airways disease), so identifying one does not rule out the other.

• First, triggers in asthma and ILO/VCD may differ with mechanical triggers more common in ILO/VCD and environmental triggers more common in asthma (Haines et al., 2020). Stress and psychological triggering have been variably reported as being helpful in ILO/VCD.
• Second, ILO/VCD differs from asthma in that the symptoms and obstruction are localised at the larynx, and not the lower airway as in asthma. Auscultation (listening with a stethoscope) can reflect this. An upper airway inspiratory monophonic sound (stridor) may be heard in people with ILO/VCD. This is distinct to the expiratory lower airway polyphonic wheeze heard in airways diseases such as asthma. Individuals with asthma often report chest tightness as distinct to laryngeal localizing features (tight throat).
• Third, as discussed above, in ILO/VCD does not improve with asthma-directed treatments such as rapid acting beta2-agonist inhalers nor other treatments such as inhaled or oral corticosteroids.

Features relating to acute presentations are discussed separately (link to acute presentations section), but in brief, if intubated, an individual intubated with ILO/VCD will be surprisingly easily to ventilate in comparison to someone who has asthma, the main differential diagnosis.

It is likely that phenotypes of ILO/VCD present and are described by people with ILO/VCD differently.

Once clinical features have been established, the 2023 Delphi consensus and the 2017 European Respiratory Society and European Laryngological Society statement both emphasize laryngoscopy to confirm laryngeal narrowing and thus confirm the diagnosis of VCD/ILO. This confirmation is necessary in most individuals.