Videostroboscopy 2

Video Stroboscopy Lecture Part Two - Overview of the Lecture

  • Focus on evaluating vocal folds during video stroboscopy assessment.

  • Introduction of various rating forms for evaluating parameters:

    • A standard form widely used in voice clinics derived from the Blaine Block Institute in Dayton, Ohio.

    • The Valli form (VA L I) is introduced, a new rating method that features illustrations to help clinicians.

    • Adoption of the Valli form at Cincinnati VA as it aligns with current trends in voice assessment.

  • Parameters for Evaluation

    • Vertical Level

    • Definition: Refers to the alignment of vocal folds relative to each other, specifically their vertical height and position.

    • Challenge in assessment due to the superior view provided by video stroboscopy, which limits direct observation of level alignment. Clinicians primarily infer level from overlapping or staggered appearance.

    • An ideal assessment would involve a coronal view for a cross-section of the larynx, which is not feasible with stroboscopy.

    • Vocal folds may show misalignment, particularly in conditions like vocal fold paralysis, where one fold may appear higher or lower than the other, leading to inefficient closure or overlapping folds.

    • Vibratory Characteristics

    • Assessment requires sustained phonation at the patient's habitual or modal pitch and average loudness.

    • Important to ensure accurate pitch tracking and assess parameters in modal pitch and average loudness because these represent the most natural and representative vibratory pattern.

    • High pitch or loud phonation can artificially inflate amplitude readings and alter mucosal wave appearance, potentially leading to misinterpretation.

    • Aperiodic voices (dysphonic voices) significantly complicate the assessment of vibratory characteristics due to irregular vibration patterns that challenge the stroboscope's ability to create a clear 'slow-motion' effect.

    • Parameters discussed include:

    • Amplitude

      • Definition: The maximum horizontal excursion of vocal folds during vibration, representing how far the vocal folds move laterally from the midline during each cycle.

      • Normal amplitude involves the medial edge displacing approximately 50%50\% of the vocal fold's width towards the ventricle during phonation, indicating flexible and pliable tissue.

      • Stiffness resulting from conditions like scarring, lesions, or edema can lead to significantly reduced amplitude, as the folds are unable to move freely.

    • Mucosal Wave

      • Definition: The traveling wave seen on the superior surface of the vocal folds during phonation, reflecting the undulation of the superficial layer (mucosa) over the deeper, stiffer layers.

      • Rated for both left and right folds, with varying degrees observed from a full, rolling wave (normal) to a diminished or absent wave.

      • Decreased mucosal wave is associated with stiffness, edema, or lesions on the vocal folds, as these impede the normal movement of the mucosal cover.

    • Non-vibratory Portion

      • Refers to segments of vocal folds that do not vibrate at all.

      • Can be assessed as a percentage coverage of the vocal fold affected and is rated for both folds on the Valli form.

      • Example given of a patient with laryngeal cancer showing significant non-vibratory tissue affecting functionality.

    • Phase Closure

      • Definition: Degree of openness vs. closure of vocal folds during the vibratory cycle. This refers to the proportion of time the vocal folds are open versus closed within one full vibratory cycle.

      • Normal cycles typically have a longer open phase (approximately 50%50\% to 60%60\% of the cycle duration) than the closed phase, which is relatively brief but complete for efficient phonation.

      • Abnormal scenarios include hypofunction, where the folds fail to close completely or remain open for too long, resulting in a larger open phase and breathy voice quality. Conversely, hyperfunction involves excessive muscular tension, leading to a smaller, shorter open phase or even hyperadduction, potentially causing a strained or pressed voice.

      • Assessment involves observing frame-by-frame during video playback to gauge the timing and completeness of glottal closure.

    • Phase Symmetry

      • Definition: Degree to which vocal folds mirror each other's movements during phonation, specifically regarding the timing and extent of their lateral excursions.

      • Described in terms of degrees, with normal movement being mirror images where both folds begin and end opening and closing roughly simultaneously (effectively 180180 degrees out of phase, meaning when one is opening, the other is mirroring that open movement).

      • Asymmetries, such as 9090 or 100100 degrees out of phase, result in non-mirroring movements where one vocal fold may open or close significantly later than the other, or one may have a different amplitude or mucosal wave. This can be caused by neurological conditions or structural changes on one side.

    • Periodicity

      • Definition: Regularity of successive cycles of vibration, determining how consistent the vibratory pattern is from one cycle to the next.

      • Non-periodic movements appear shaky, irregular, or erratic in recordings, meaning the vocal folds do not vibrate in a consistent, repetitive fashion. This directly relates to voice dysphonia severity, as greater aperiodicity typically corresponds to a more hoarse or rough voice quality.

    • Overall Laryngeal Function

      • Normal vs. hyperfunctional or hypofunctional states during phonation assessed during video stroboscopy.

  • Video Stroboscopy Method

    • Standard clinical procedure involving:

    • Initial observation during breathing for anatomical abnormalities.

    • Sustained phonation at different pitches to assess full length of vocal folds, starting with high pitch for clear visibility.

    • Moderate pitch phonation for main assessment of stroboscopic parameters (normal functional state).

    • Glides to test frequency change capability of the system.

    • Vocal fold adduction and abduction evaluated through tasks like saying "he" for visual movements.

    • For rigid strobe, limited to those tasks; flexible endoscopy allows for speech tasks like reading and conversational speech.

  • Indirect Laryngeal Imaging

    • Clarification that laryngeal imaging is an indirect assessment compared to direct laryngoscopy (operating room procedure).

  • Limitations of Video Stroboscopy

    • Constraints include frame rate limitations (often only 25−6025-60 frames per second), which means the system can only sample a limited number of points during a rapidly oscillating vocal fold cycle. This fundamentally misses the high-frequency vibrations (typically 100−300100-300 Hz for human voice) and consequently cannot capture every individual vibratory cycle in real-time. Instead, it creates an optical illusion of slow motion by synchronizing flashes with slightly different points in successive cycles.

  • High-Speed Laryngeal Imaging

    • Discusses advancements in imaging technology capable of capturing between 10001000 to 80008000 frames per second leading to:

    • Better diagnostic capabilities due to