Stroboscopy
- 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