Inducible Laryngeal Obstruction Can Occur Without an Identifiable Trigger
While Inducible Laryngeal Obstruction (ILO) by definition implies an underlying cause, there are cases where a specific trigger cannot be readily identified, though an underlying mechanism must still exist. 1 The term "inducible" was specifically chosen to emphasize that an underlying cause does exist, even when the specific inducer of an attack cannot be immediately determined.
Understanding ILO and Its Triggers
ILO is defined as an inappropriate, temporary narrowing of the larynx causing breathing problems 2. The condition is characterized by:
- Temporary airway closure
- Episodes that are typically trigger-induced
- Reversibility of symptoms
- Breathing difficulties including shortness of breath, noisy breathing, and throat tightness
Trigger Identification:
The 2013 international consensus conference on ILO nomenclature specifically addressed this issue:
- Most cases have identifiable triggers (exercise, irritants, stress)
- Some cases present without readily identifiable triggers 1
- The term "inducible" was deliberately chosen over terms like "episodic," "recurrent," or "intermittent" which suggest randomness
- Even when triggers aren't obvious, the consensus states that "something, either known or unknown and intrinsic or extrinsic, has to cause the change in the larynx between asymptomatic and symptomatic periods" 1
Diagnostic Implications
When no obvious trigger is identified:
- Comprehensive laryngoscopic evaluation is still essential
- Provocation testing may be needed to visualize the laryngeal obstruction
- In some patients, ILO is only visible following provocation testing 3
- Documentation should clearly state when triggers cannot be identified
Clinical Significance
The absence of an identifiable trigger has important implications:
- May complicate diagnosis and lead to misdiagnosis (often as asthma)
- 38.3% of patients diagnosed with asthma may actually have ILO 4
- Can delay appropriate treatment
- May require more extensive investigation to rule out mimics
Management Approach
Even when triggers aren't identified:
- Focus on teaching specialized breathing techniques
- Coordinate care between pulmonology, otolaryngology, and speech pathology
- Provide psychological support if anxiety or stress are suspected contributors 2
- Consider reducing inappropriate medications (like high-dose inhaled corticosteroids) that may have been prescribed based on misdiagnosis 5
Important Caveats
- ILO must be distinguished from constant laryngeal obstructions that only cause symptoms when ventilatory requirements reach a critical point (these are not considered ILO) 1
- Laryngeal spasm, which is a physiological response to visceral sensory stimulation, is considered a mimic of ILO rather than true ILO 1
- Accurate classification is critical to determine whether symptoms are directly related to ILO or caused by comorbid conditions like asthma 4
When documenting cases where triggers cannot be identified, clinicians should follow the nomenclature structure but clearly state that the inducer is unknown, while still providing the complete laryngoscopic description of the obstruction pattern.