What is videostroboscopy (a diagnostic tool used in ear, nose, and throat - ENT)?

Videostroboscopy: Definition and Clinical Application

Videostroboscopy (also called video-strobo-laryngoscopy or VSL) is an advanced laryngeal examination technique that uses stroboscopic light synchronized with vocal fold vibration to create a slow-motion visualization of the vocal folds during phonation, allowing detailed assessment of vocal fold vibratory function, pliability, symmetry, and mucosal wave patterns that cannot be seen with standard laryngoscopy. 1

Technical Mechanism

Videostroboscopy works by using a strobe light that flashes at a frequency slightly different from the vocal fold vibration frequency, creating an optical illusion of slow-motion movement of the vocal folds. 1 This allows clinicians to assess:

• Vocal fold vibratory pliability and symmetry during active phonation 1
• Mucosal wave patterns that indicate the health and flexibility of the vocal fold tissue 2
• Amplitude of vibration from each vocal fold 3
• Glottic closure patterns during the vibratory cycle 2
• Periodicity and symmetry of vocal fold oscillation 2

Performance Methods

Videostroboscopy can be performed using two approaches 1:

• Rigid endoscopy through the mouth (transoral approach)
• Flexible laryngoscopy through the nose (transnasal approach)

Flexible stroboscopy is preferred when assessing vocal fold motion during normal running speech and directed tasks, as patients cannot speak naturally when their tongue is held during rigid laryngoscopy. 1

Diagnostic Superiority Over Standard Laryngoscopy

Detection of Subtle Pathology

Videostroboscopy changes the diagnosis in 14-38% of patients compared to standard laryngoscopy alone, making it particularly valuable when symptoms are out of proportion to standard laryngoscopic findings. 1, 4, 5

The technique is most useful for detecting:

• Vocal fold scar and fibrosis (100% addition in diagnosis) 4
• Early vocal nodules (66.66% addition in diagnosis, 54.54% of inconclusive standard laryngoscopy cases diagnosed) 4
• Presbylarynges, Reinke's edema, and muscle tension dysphonia (100% change in diagnosis) 4
• Subtle vocal fold motion abnormalities consistent with neuropathy 1

Diagnostic Accuracy

When compared to laryngeal electromyography as the gold standard, videostroboscopy demonstrates a sensitivity of 97.9%, specificity of 63.2%, positive predictive value of 95.9%, negative predictive value of 77.42%, and test efficiency of 94.41%. 1

Clinical Indications

Mandatory Use Scenarios

According to the American Academy of Otolaryngology-Head and Neck Surgery guidelines, videostroboscopy should be used:

• Before prescribing voice therapy to establish accurate diagnosis and plan optimal therapy regimens 1
• When hoarseness symptoms are out of proportion to standard laryngoscopic examination 1
• For patients with early glottic tumors being considered for surgical versus nonsurgical treatment to optimize voice preservation 1
• To document effectiveness of voice therapy in remediation of vocal lesions 1

Specific Patient Populations

Videostroboscopic examination is particularly valuable for:

• Singers, performers, and professionals with high vocal demands who require detailed functional assessment 1
• Patients with suspected vocal fold paralysis where standard laryngoscopy findings are equivocal 5
• Patients with functional dysphonia where subtle pathology may be missed on standard examination 5

Limitations and Availability

Videostroboscopy technology is not widely available compared to standard flexible laryngoscopy, which represents a practical limitation to its routine use. 1 However, the additional healthcare costs are justified when:

• The larynx cannot be examined adequately with mirror examination 1
• Vocal fold movement abnormality is unclear after standard examination 1
• Identified vocal fold abnormality requires more accurate definition for treatment planning 1

Common Pitfall

Do not confuse videostroboscopy with standard video laryngoscopy—while both use video recording, only stroboscopy provides the slow-motion assessment of vibratory function that reveals subtle mucosal and functional abnormalities. 4, 5 Standard video laryngoscopy shows only gross anatomy and movement, missing up to 38% of diagnoses that stroboscopy would detect. 4