Voice Science: Glottal Closure Analysis

Glottal Closure

• Closure pattern describes vocal fold contact during phonation.
• Key questions: Complete closure? If not, what's the gap shape?
• Closure is rated at most comfortable pitch and loudness (MCPL).
• Complete closure is common in men, sometimes in women at MCPL or with increased loudness.
• Posterior gap is most common in women, potentially a normal variant in men.
• Gap location varies; MCPL typically between cartilaginous folds, but can extend into membranous folds during quiet phonation.
• Anterior and spindle-shaped gaps are common normal variants in men and older women, and can be seen in voice disorders (scarring, surgery, etc.).
• Hourglass-shaped gaps are common with bilateral lesions (vocal nodules) or unilateral lesions with contralateral reactions; large unilateral lesions can also cause this.
• Incomplete closure, extending entire length of folds, is linked to vocal fold motion impairment, scar tissue, and a muscle tension dysphonia type.
• Closure can alternate, needing multiple patterns denoted.

Phase Closure

• Describes closure duration.
• Glottis is open (or in transition states) for about ⅔ of a vibratory cycle at MCPL.
• Closed time generally decreases with higher pitches.
• Closed time may increase or decrease in older adults, inconsistently across studies.
• Useful measurement for breathy voice with complete closure and hyperfunction.

Vertical Closure Level

• Vocal folds usually meet on the same vertical plane.
• Off-plane closure can be due to neuromuscular differences (paralysis/paresis), trauma, or surgery.
• Vertical level difference affects glottal flow and voice quality.

Mucosal Pliability and Stiffness

• Vibration amplitude (fold excursion from midline) is a pliability/stiffness indicator.

• Normal excursion is approximately ⅓ of fold width.

• Maximum vibration amplitude is generally symmetric, smaller in women, and varies with loudness and inversely with pitch.

• Decreased amplitude results from incompetence, tight closure, increased mass/stiffness in lesions (firm polyps, cysts, etc).

• Increased amplitude is a sign of decreased tonicity (paresis/atrophy).

• Mucosal wave: Vertical upheaval of vocal fold cover.

• Driven by vertical phase shift (upper/lower margins timing differences).

• Travels from inferior edge, up the medial edge, then across the superior surface.

• Velocity related to phonation pressure.

• Normal wave travels approx. half fold width at MCPL, farther for loud phonation, and is decreased/absent in stiff mucosa, different layers or with increasing pitch or aging.

Symmetry

• Phase symmetry: Assessing vocal fold mirroring during vibration.
• Folds should depart and return to midline at the same time.
• Asymmetric vibration suggests mechanical/neurologic fold differences (position, mass, tension, etc.).
• Mild asymmetry is common in normal voices (almost 80% of control subjects).

Protocol

• Stroboscopy parameters are traditionally assessed from sustained phonation at MCPL.
• A more comprehensive videostroboscopy protocol is described in Box 54.2.
• Vibratory parameters are rated from "ee" phonation at MCPL.
• Voice quality differences with stroboscopy- conversational quality requires additional productions.
• Inhalation phonation can reduce supraglottal constriction; used for ventricular fold visualization limitations, highlighting edema/lesions of the inferior compartment.
• Bilateral, symmetric fold lengthening during ascending pitch glides indicates functional cricothyroid function.
• High-pitch phonation highlights midmembranous edema/stiffness/scarring along the edge.
• Locked mode evaluates vibratory regularity.
• Connected speech assessment with flexible endoscope for non-sustained issues.
• Patient concerns (singing) should be included in examination.
• Trial therapy (probe therapy) can be used to alter muscle tension or vibratory patterns.

Explore the intricacies of glottal closure patterns during phonation. This quiz delves into the various types of vocal fold contact, their implications for voice quality, and the conditions under which different gap shapes occur. Ideal for students and professionals in voice science and phonetics.