This is a descriptive term to specify that the vocal cords are not matching in a straight line, with only a thin dark line between them at the moment of pre-phonation. Instead, the cords become gently concave or bowed outwards. At the moment of pre-phonation, there is a wider, oval slit between the cords.
Bowing can be physiologic, asymptomatic, and a genetic “given.” In this physiologic type, the bowing will be subtle to mild and there will be good vibratory pattern. When moderate or severe, bowing may more likely be the result of aging, vocal disuse, Parkinson’s disease, or other conditions. Moderate and severe bowing correlate with a degree of vocal cord atrophy and the vibratory pattern can be more flaccid. The voice tends to have a soft-edged quality, a little higher in pitch than normal, and can fade with use. Voice building is the primary treatment, but very occasionally severe bowing is treated with bilateral vocal cord implants.
Vocal Cord Bowing
Vocal cord bowing (1 of 4)
Bowing of vocal cords as seen under continuous light, at prephonatory instant, just before vibratory blur.
Vocal cord bowing (2 of 4)
Under strobe illumination, at maximum open phase (greatest lateral excursion).
Vocal cord bowing (3 of 4)
Maximum "closed" phase of vibration, which is not fully closed; greatest medial vibratory excursion does not bring the cords into full contact.
Vocal cord bowing (1 of 4)
Prephonatory instant shows an oval gap between the cords, rather than a thin line.
Vocal cord bowing (3 of 4)
Strobe light, maximum closed phase, with poor closure especially anteriorly. The greater flaccidity anteriorly may cause an independent vibratory segment and chaotic vibration with rough, gravelly quality.
Vocal cord bowing (2 of 5)
As the cords begin to adduct, medial turning of vocal processes accentuates the bowing of the musculomembranous (anterior 2/3) of the vocal cords.
Vocal cord bowing (3 of 5)
The prephonatory instant under continuous illumination, showing bowed free margins and an elliptical gap rather than the straight-line match of more normal vocal cords.
Weak voice (1 of 8)
This patient has a weak, air-wasting, and gravelly voice. In this distant view, prephonatory instant at a low pitch, D3 (147 Hz), severe bowing can be seen.
Phonatory view (2 of 8)
Also at D3 (147 Hz), but while producing voice. Note that the vibratory blur occurs only in the posterior membranous vocal cord.
D3, open phase (3 of 8)
Under strobe light, open phase of vibration at D3 (147 Hz), note that the amplitude of vibration is enormous, as the air stream easily throws flaccid vocal cords very far laterally.
"Closed" phase (4 of 8)
At D3 again, now closed phase, which is not closed except posteriorly, explaining the lack of vibratory blur anteriorly in photo 2. Some vibratory cycles are chaotic, too, explaining the gravelly, rough quality of the voice.
B3, open phase (5 of 8)
At B3 (247 Hz), open phase of vibration, the anteroposterior stretch required to produce higher pitch, also somewhat reduces the tissue flaccidity. Vibratory amplitude (lateral excursion) is diminished as well.
B3, closed phase (6 of 8)
At B3 again, closed phase of vibration is not really closed, yet is more successful than at the lower pitch in photos 3 and 4. Reduced closure anteriorly is typical for flaccid vocal cords.
Bb4, open phase (7 of 8)
Open phase of vibration at B-flat 4 (466 Hz). Added antero-posterior stretch subtly reduces vibratory amplitude further, especially anteriorly.
Bowed vocal cords (1 of 8)
An older man has a foggy voice, worsening with use. At medium range in partial abduction, note the bowed vocal cord margins.
Prephonatory view (2 of 8)
At a greater distance but at the prephonatory instant, there is a large oval gap between the cords.
Open phase (3 of 8)
Now under strobe light, at C3 (131 Hz). The lateral excursions of the cords are huge due to the flaccidity of the cords. Compare with photos 5 and 7.
At the same pitch, the closed phase of vibration is not fully closed, and the anterior segment that remains open is often unstable and flutters or vibrates as an independent segment, causing ‘gravel.’
Reduced flaccidity (5 of 8)
The vocal cords must lengthen to produce this higher pitch of F#3 (185 Hz). Lengthening also reduces flaccidity, explaining reduced amplitude (lateral travel) of vibration. Compare with photo 3 and 7.
Closed phase (6 of 8)
The closed phase of vibration, also at F#3, is completely closed, and the voice is more stable at this pitch. Compare with photo 4 and 8.
Falsetto, open phase (7 of 8)
Now at B-flat 5 (932 Hz), the cords are stretched and thinned. Amplitude is quite large, because falsetto tends to de-activate tension within the thyroarytenoid muscles. Compare with photos 3 and 5.
Ectatic capillary (1 of 4)
This young performer has a sense of a weakened voice and loss of vocal stamina. Here, we see an ectatic capillary of the left vocal cord (right of photo). Is the problem intermittent vocal hemorrhage from this vulnerable capillary? Is there increased susceptibility to edema due to this margin capillary?
Ectatic capillary, narrow band light (2 of 4)
Under narrow band light, the capillary is even more evident. The additional network of prominent capillaries prompt the same questions as in caption 1.
Margin swelling (3 of 4)
Under strobe light at B-flat 4 (494 Hz), we see subtle margin swelling (arrows), here of only “indicator lesion” magnitude.
Bowing, atrophy, and flaccidity (4 of 4)
The large amplitude of the open phase of vibration at the same pitch, along with the lack of closure in photo 3, reveals the actual problem to be bowing, atrophy, and flaccidity. These findings fit with the “bowing” symptom complex: loss of edge to voice quality and the tendency of voice quality and strength to “fade” as the day progresses.
Bowing vocal cords with furrows (1 of 4)
This middle-aged man's voice has become increasingly husky and weak across many years. In retrospect, it was never a "strong" voice. The cords are bowed, and the furrows seen here (arrows) become more visible in subsequent photos.
"Closed" phase (2 of 4)
Under strobe light at B-flat 2 (117 Hz), this is the "closed" phase of vibration, perhaps better defined in this instance as the "most closed" phase.
Open phase (3 of 4)
The open phase at the same pitch, shows a linear groove just below the margin of each cord. Some might call these glottic sulci, but "furrow" would be the better definition, as seen in the next photo.
Voice Building (shorter version):