Gaps

All types of gaps between the vocal cords create husky hoarseness by leaking air. There are five characteristic gap patterns — each with a distinct location, cause, and visual signature on endoscopy.

A laryngologist would do well to keep “Mind the gap” as a constant reminder. The gap between the vocal cords deserves primary attention during endoscopy and is easily overlooked while examining surrounding structures. Under idealized conditions, the vocal cords lie parallel during voice production and close completely with each vibratory cycle. All of these types of gaps leak air and create husky hoarseness.

Basic Laryngology: Mind the Gap — Part I. The gap between the vocal cords is the primary source of husky hoarseness.

Posterior Gap

If the vocal cords are moving from the breathing V-shape toward a parallel position but stop short of complete closure, a posterior gap remains. One example is muscle tension, where the opening muscles (PCA) partially tighten during phonation, competing with the closing muscles (LCA) and holding the cords slightly apart, allowing air to escape between the posterior portion of the vocal cords.

Posterior gap — incomplete closure at vocal processes
Arrows point to the gap remaining between the vocal processes when there is incomplete closure.

Anterior Gap

Vocal cord trauma may disrupt the vocal cords where they attach at the front of the larynx. If the vocal cords heal slightly apart at the anterior commissure, air escapes through the front of the vocal cords. It really becomes impossible for a person to close this gap without the help of surgery.

Anterior gap after removal of squamous cell carcinoma
Arrow points to an anterior opening created after removing a squamous cell carcinoma from the left anterior vocal cord. The vocal processes meet. The right membranous vocal cord reaches the midline, but air leaks out anteriorly.

Central Gap

If the vocal cord muscles are not exercised regularly, they atrophy and can no longer tense to a straight line. They remain concave even when the vocal processes are completely closed, creating a central gap. Aging contributes as well — the vocal cords sag with aging as they lose elasticity, producing a nearly oval-shaped gap with pointed ends. An asymmetric central gap is created when tension within one vocal cord is reduced, allowing it to oscillate further laterally than the other side, suggesting a thyroarytenoid muscle paresis.

Symmetric central gap with overclosure of vocal processes
Symmetric central gap: At the beginning of sound production, the vocal processes have touched. The arrows point to a large central gap. He is phonating at pitch E4 which is about an octave higher than the typical male – he is tensioning the cricothyroid muscle to stretch the vocal cords as a means of compensation to reduce the width of the central gap.
Asymmetric central gap — left recurrent laryngeal nerve paresis
Asymmetric central gap: The left vocal cord is not as tense as the right and oscillates further laterally (here at pitch F3#) allowing air leak from the left. She also cannot quite close the vocal processes at this pitch allowing some posterior air leak as well. This likely represents a left anterior branch of the recurrent laryngeal nerve paresis.

Split Gap

Vocal overdoers typically develop a callus or swelling in the very center of the membranous vocal cord. This protuberant swelling will touch first as the vocal cords are tensed, leaving an opening both anterior and posterior to it — a split gap. It is best visualized at higher pitches. As the vocal cords tighten, any marginal swelling is pushed further medially and made more visible to the examiner.

Split gap — bilateral vocal swellings prevent complete closure
Bilateral vocal swellings, likely polyps, touch before the vocal cords can completely close (pitch C4), allowing air to leak from in front of and behind them (arrows point to air leak).

Timing Gap

Anything that makes the vocal cords uneven — in mass, length, or tension — can put them out of sync. With a mild asymmetry, they may oscillate out of phase. Under a strobe light it looks like they are chasing each other. They may never touch, so air continuously leaks out even while crossing each other’s path. This is a gap created by timing. If they become slightly more asymmetric, they may begin to oscillate at different frequencies — diplophonia — and both huskiness and roughness are heard simultaneously.

Timing gap — asynchronous vocal cord movement
The same vocal cords viewed at two moments in time. In the left photo, the right vocal cord is near the midline and the left vocal cord is at its apogee laterally. In the right photo, the left cord has now come to the midline, but the right cord is now out in a lateral position so there is always an opening allowing continuous air leak.

What You Learned

  • Five gap patterns, one mechanism — posterior, anterior, central, split, and timing gaps all produce husky hoarseness by leaking air.
  • The gap’s location reveals its cause — posterior gaps suggest muscle tension; central gaps suggest atrophy; anterior gaps suggest trauma; split gaps suggest overdoer swellings.
  • A timing gap bridges huskiness and roughness — asynchronous cords that never touch create continuous air leak; if they become more asymmetric, two simultaneous pitches emerge.
  • Higher pitch makes gaps more visible — tensioning the cords with CT elongates them and exaggerates any central or split gap, improving diagnostic yield.