Vibratory Blur

Part of the Intense Laryngeal Examination of the Integrative Diagnostic Model: Prior To, Or Instead of Stroboscopy (Where Not Available)

When someone phonates (produces voice), the vocal cords vibrate extremely fast. As an analogy, take a “fat” rubber band, stretch it moderately and then “twang” it. The vibratory blur you see is very similar to that seen when vocal cords vibrate.

The rate of vibration for speech might vary between approximately 100 and 300 times per second.

And the average male singer’s singing range might be the same, with a high soprano’s upper singing voice extension to more than 1000 vibrations per second in the region of high C (C6)!

Under continuous light during a video laryngoscopy, the camera will only record a blur. The term we use within the integrative diagnostic model of Bastian is therefore, “vibratory blur.”

An Aside: What Stroboscopy Adds

Stroboscopy uses a synchronized flashing light to create a slow-motion illusion of vocal cord vibration. If the patient’s fundamental frequency (think “pitch”) is A3 (just below “middle C”) that would be 220 Hz (cycles, or vibrations per second). If the strobe flashes 218 times per second, the camera will pick up what appears to be 2 vibrations per second.

Stroboscopy allows clinicians to analyze:

• open vs. closed phase of vibration;
• amplitude of movement;
• mucosal wave;
• symmetry of vibration between cords;
• segmental vibration; etc.

But as an important exercise of acute observation where stroboscopy is available, or where a strobe generator is not available or “down,” the examiner can already gain clues from the vibratory blur seen under normal light.

In many cases, the pattern of blur previews and predicts what stroboscopy will later confirm.

Why Vibratory Blur May Be Overlooked or Unappreciated

If clinicians content themselves with a somewhat distant view, vibratory blur will not be noticed or easily “mined” for the information it can yield. The Integrative Model (Bastian) uses topical anesthesia for every examination, allowing very close approach to the cords and magnified view. The cords fill the screen rather than being in the center of a more panoramic view of the laryngopharynx.

What Clinicians Who Make Use of It Look For in Vibratory Blur:

1. Presence on Both Sides

   • Normal: grey blur appears along both vocal cord margins.
   • Abnormal: blur only on one side → possible stiffness.

2. Amplitude of Blur

   • A very wide blur band suggests a large amplitude of vibration due to flaccid cords such as seen with vocal cord bowing.
   • As pitch ascends, the vocal cord lengthens, and normal (physiologic) stiffening reduces amplitude of vibration, causing a narrower vibratory blur.
   • If the blur disappears on one cord before the other as pitch ascends, this reveals stiffness on that side.

3. Symmetry of Blur

   • Equal “width” of the grey blur band between the cords.
   • Equal “width” of the blur band along the full length of each cord. Loss of blur on part of one cord suggests a focal stiff area.

4. Full Contact of Blur to Blur

   • Grey blur of one side merging into grey blur of the other suggests full contact during the closed phase of vibration.
   • A persistent black “line” between the blurred vocal cord margins suggests that the closed phase of vibration is not complete.

Vibratory Blur Is Useful Because It Indirectly Reflects:

• The intensity of the examination (particularly the “close, clear” rather than “far fuzzy” approach to laryngeal examination required by the Integrative Diagnostic Model
• Vibratory amplitude
• Vibratory symmetry
• The closed phase of vibration
• Stiffness

Summary

Vibratory blur is the fuzzy edge seen on vibrating vocal cords under continuous light. By studying that blur, clinicians can predict abnormalities in vocal cord vibration even where stroboscopy is not available, or before performing stroboscopy, where it is at hand.