Stroboscopy

Stroboscopy unedited

1. STROBOSCOPY DR. SANJAY MAHARJAN PG, ENT-HNS, MANIPAL

2. Videostroboscopy has evolved as most practical and useful technique for clinical evaluation of visco -elastic properties of phonatory mucosa painless, office-based procedure essential evaluation of laryngeal mucosa, vocal fold motion biomechanics, and mucosal vibration key elements for detecting and assessing pathology as well as determining impact on voice and airway function

3. Stroboscopy : Method used to visualize vocal fold vibration Uses synchronized, flashing light passed via flexible or rigid telescope Flashes of light are synchronized to vocal fold vibration at slightly slower speed, allowing examiner to observe it during sound production in slow motion Information is essential for planning effective phonomicrosurgery Provides useful, real-time information concerning nature of vibration, image to detect vocal pathology, and permanent video record of examination Improves sensitivity of subtle laryngeal diagnoses

4. The Talbot law: Images on human retina linger for 0.2 seconds after exposure (persistence of vision) Concept of correspondence: Interpretation of a corresponding portion of sequential images representing an object in motion

5. Strobolaryngoscopy takes advantage of these principles: producing intermittent light flashes in close relation to frequency of vocal-fold vibration microphone picks up frequency of examinee's sustained voice, which triggers stroboscopic light source. With provision that vocal vibrations are periodic, a frequency of light flashes equal to vocal frequency produces a clear, still image of same portion of vibratory cycle.

6. Instrumentation: A videostroboscopic unit consists of stroboscopic light source and microphone video camera rigid or flexible endoscopes video recorder . .

7. Fundamental frequency Measured by using strobe unit and is used to set frequency of light flashes Amplitude : Lateral excursion of vocal folds during their displacement away from midline during oscillation Highly dependent on pitch frequency and loudness Generally graded as normal, less or greater than normal

8. Symmetry : Normal motion of arytenoid cartilages is assessed during flexible or rigid telescopic laryngoscopy and vibratory characteristics of phonatory mucosa are assessed during stroboscopy . Glottic closure: In a healthy person musculomembranous portion of vocal folds completely closes during vibratory cycle. Mucosal wave: reflects rheological properties of phonatory mucosa during a specific vocal task.

9. Periodicity: Regularity of successive vocal vibratory cycles Normal vibratory activity is regular and periodic.

10. Diagnostic Findings: Vocal fold cysts region of cyst demonstrates diminished pliability exact characteristics of mucosal-wave deficit depend on size and location of cyst . Vocal fold polyps vibratory patterns of 2 vocal folds are asymmetric, with diminution of vibration near lesion

11. Vocal fold nodules Glottic closure is compromised, esp . in high pitch frequencies Mucosal wave is usually preserved bilaterally, but pliability and amplitude of excursion are decreased in region of nodule Sulcus vocalis refers to a spectrum of phonatory mucosal vibratory deficits in which stroboscopic findings demonstrate zones of diminished mucosal pliability