Visual Documentation of the Larynx

Key Points

Laryngeal endoscopy, using flexible or rigid endoscopes, is used to examine vocal fold structure and gross function.
Videostroboscopy is used to examine vocal fold vibration patterns and the relationship between the body and the cover.
Laryngeal high-speed videoendoscopy complements endoscopy and stroboscopy by showing details of short and aperiodic vibration and quantifying vibration parameters.
Narrow-band imaging uses the tissue's light-absorption characteristics to show vascular detail.
Each vocal fold visualization tool makes a unique contribution to the assessment puzzle.
Several options are available for visualizing and documenting laryngeal structure and function, and each has unique advantages and limitations. This chapter discusses laryngeal videoendoscopy and stroboscopy (LVES), laryngeal high-speed videoendoscopy (LHSV), and narrow-band imaging (NBI).

The term endoscopy is used here to refer to an examination with a continuous light source and a rigid or flexible endoscope. Laryngeal videoendoscopy provides information about vocal fold structure and gross function. It is used to diagnose and document voice and laryngeal disorders, plan treatment, make longitudinal comparisons, educate patients, and provide biofeedback for voice and breathing therapy. Recording the examination and including still images in the medical record are important for routine follow-up and for medicolegal reasons.

Stroboscopy is a lighting technique used to examine vocal fold vibration patterns and the relationship between the vocal fold body and cover. It is valuable for describing mucosal disease and its effect on vocal fold vibration. Stroboscopy is necessary to determine glottal closure and mucosal pliability and, sometimes, to identify or differentiate lesions. Rigid and flexible endoscopes can be used for stroboscopic evaluations and have different advantages and limitations.

Laryngeal high-speed videoendoscopy (LHSV) complements endoscopy and stroboscopy. It allows short and aperiodic vibration to be observed, and analysis procedures provide quantification of vibratory details that is not otherwise possible.

Narrow-band imaging (NBI) is a technique that uses the absorption characteristics of light to enable a detailed analysis of vascular patterns within and outside a lesion. In the larynx, it has been used to improve identification of recurrent respiratory papillomatosis and to screen for malignancies by identifying high-yield areas to sample for biopsy.

Endoscopic imaging of the larynx and vocal tract is within the scope of practice of both otolaryngologists and qualified speech-language pathologists. Assessment of mucosal health and diagnosis of laryngeal pathology are solely within the purview of the otolaryngologist, and both professionals use endoscopy and stroboscopy to assess (1) vibratory patterns during various voicing conditions, (2) the behavior of the laryngeal and supralaryngeal structures during phonation, and (3) how treatment probes alter phonatory physiology. Speech-language pathologists also use endoscopy for visual feedback during therapy for voice, resonance, and laryngeal airway disorders. Because each professional brings a different perspective to the process, the most thorough examinations are typically conducted and analyzed in a team setting.

The first section of this chapter pertains to endoscopy and stroboscopy: assessment protocols, equipment, examination technique, and medical records. The second section describes LHSV, and the third section discusses NBI.

Videoendoscopy and Stroboscopy

Endoscopy: Assessment Using Continuous Light

Endoscopic examination with continuous light, as opposed to stroboscopy, provides information about structure and gross movement. Several aspects of laryngeal structure, arytenoid and vocal fold motion, mucus, vascularity, supraglottal activity, and vocal fold edge shape can be observed.

Laryngeal Structure

Abnormalities and asymmetries of the valleculae, piriform sinuses, epiglottis, aryepiglottic folds, ventricular folds, and posterior glottal rim are noted. Lowered pitch during sustained “ee” widens the angle, allowing better visualization of the valleculae. An omega-shaped epiglottis is a common variant in men, but it is rare in women. Signs of laryngeal irritation or possible laryngopharyngeal reflux are noted; these primarily include edema and erythema of the posterior larynx, cobblestoning of the posterior pharyngeal wall, interarytenoid bar, and pseudosulcus. The changes can occur for reasons other than reflux, such as infection, allergies, and mechanical trauma and also occur in well-screened “normal” volunteers. Intra-rater and inter-rater reliability of the findings is often poor, particularly when rated from flexible fiberoptic laryngoscopy.

Arytenoid and Vocal Fold Motion

Movement and position of the arytenoids inform the examiner about the integrity of the cricoarytenoid joint and the recurrent laryngeal nerve. Arytenoids are described with respect to their mobility and symmetry. Immobile arytenoids are further described by position (e.g., paramedian, intermediate, and lateral) and their axis (e.g., upright and anteromedial rotation). Mobility is most easily rated when patients phonate and then rapidly inhale, such as during “ee”-sniff or coughing. Rapid pitch glide from lowest to highest notes is helpful for observing symmetry of posterior and lateral pharyngeal wall bulging. Tilting of the petiole during the pitch glide might indicate superior laryngeal nerve weakness.

Mucus

Thickened mucus often adheres to the vocal fold edges or superior surface. The presence of thick mucus generally relates to a lack of hydration or to chronic irritation from sources such as mechanical trauma, smoking, or laryngopharyngeal reflux. Mucus pooling in the pyriform sinuses can indicate poor laryngeal sensation, weak lateral pharyngeal walls, or inefficient swallowing. Thickened mucus adherent to the vocal folds can masquerade as a lesion or mask an abnormality. To allow differentiation of mucus from underlying structures or lesions, patients should be instructed to try to clear the mucus by swallowing or with a gentle cough.

Vascularity

A blush throughout the vocal fold mucosa is considered erythema or hyperemia. Visible capillaries are typically aligned parallel with the free edge; horizontal vascularity is notable. Abnormally dilated and tortuous vessels, capillary ectasias or microvarices , might represent areas of stiffness or risk for hemorrhage, particularly when they are located along the vocal fold edge. Hemorrhage occurs when enough blood cells have escaped from a vessel to lend a diffuse coloring to the vocal fold. Posthemorrhage vocal folds often appear yellow brown, similar to healing bruises in other areas. Increased vascularity of the vocal folds, ventricular folds, arytenoids, and epiglottis is common in women during premenstrual days.

Supraglottal Activity

Supraglottal activity refers to motion above the level of the vocal folds. Some supraglottal activity is normal: lateral wall constriction is frequently observed with increasing pitch, anteroposterior narrowing of the epilaryngeal space might help create the singer's formant, and aryepiglottic narrowing or dilation occurs for different vowels during connected speech.

Other supraglottal movements are clear signs of disorder: tremor and myoclonic movement, for example, are evidence of neurologic impairment. Supraglottal constriction is sometimes considered a normal variant, and other times it is a sign of disordered voice. Constriction occurring with initiation of phonation and mild constriction throughout a production can be normal findings, whereas sustained supraglottal constriction, as seen in Figs. 54.1 and 54.2 , is generally indicative of muscle tension dysphonia. Muscle tension dysphonia can be the cause of the voice disorder (primary muscle tension dysphonia), or it may be compensation for an underlying abnormality (secondary muscle tension dysphonia). Changing the production target to “oo,” “m,” increasing pitch slightly, or phonation on inhalation might decrease the constriction enough to achieve vocal fold visualization sufficient for teasing apart the etiology. If not, then voice therapy is recommended, followed by repeat visualization.

Fig. 54.1, (A) Vocal folds during respiration. (B) Vocal folds with anteroposterior constriction during phonation.

Fig. 54.2, (A) Vocal folds during respiration. (B) Vocal folds with lateromedial constriction during phonation.

Vocal Fold Edges

The degree to which the folds are straight or irregular and smooth or rough should be described. In addition to describing irregularities related to lesions, indicating whether edges are convex or concave (“bowed”) is necessary. Note that bowing is a descriptive term, not a disorder itself, and bowed folds can be a symptom of a number of underlying disorders.

Protocol

Typical tasks for the endoscopic exam are listed in Box 54.1 and provide the clinician the opportunity to focus on structure and gross function during a variety of activities. Typical rapid repetition rate for “ee” and “hee” is four to six syllables per second, and difficulty with accurate and rhythmic voice onset/offset is common in neurologic impairment. Assessment of connected speech (e.g., phrases, sentences, and conversation) is necessary when voice quality during sustained vowels is inconsistent with symptoms or what was heard during the patient interview. If there is concern about laryngeal sensation, a rough estimate can be gained through observing the patient's response to gently touching the endoscope to the posterior aryepiglottic folds. A more precise exam is possible using sensory threshold testing (FEESST). Examination of velopharyngeal function is indicated if nasal emission or hypernasality is present.

Box 54.1

Protocol for Laryngeal Videoendoscopy (Continuous Light)

Rest breathing
Deep breathing
Easy cough or throat clear
Sustained “ee” at the most comfortable pitch and loudness
Rapid pitch glide from lowest to highest note
Quiet and loud phonation
Rapid repetitions of “ee”
Rapid repetitions of “hee”
The “ee” followed by a quick sniff (×3) ^a

a If using a flexible endoscope.
Whistling ^a
Sentences and/or conversation as needed ^a
Gentle touch of endoscope to aryepiglottic folds ^a
Observation of velopharyngeal function during sustained sounds such as “ee” and “s” ^a
Observation of velopharyngeal function during sentences loaded with nasal-oral contrasts ^a

Limitations

Although endoscopy is appealing because of its routine availability in otolaryngology clinics, the information it provides is insufficient to fully understand a voice disorder. Observation of structural detail is limited compared to the other techniques, and the vibratory patterns thought to determine voice quality cannot be observed. Because vocal fold vibration occurs at hundreds of cycles per second, specialized lighting or cameras are needed to adequately visualize vocal fold vibration.

Assessment With Stroboscopy

Videostroboscopy is used to assess vocal fold vibration patterns. Understanding normal vocal fold physiology for different modes of phonation is essential to interpreting stroboscopic examinations. A brief description of vocal fold vibration follows, and more detailed explanations can be found elsewhere. Healthy vocal folds are comprised of a pliable “cover” consisting of the epithelium and superficial lamina propria and a stiffer “body” consisting of the intermediate and deep lamina propria and thyroarytenoid muscle. Muscle contraction is responsible for positioning (adduction and abduction to and from midline) and shaping (lengthening, shortening, and bulging) the vocal folds. Adequate position, shape, and mechanical properties allow aerodynamic and elastic forces to initiate and sustain vibration.

Two basic movement patterns underlie most normal and disordered vocal fold vibration. The first is lateral displacement and return to midline, which cyclically opens and closes the airspace between the vocal folds, called the glottis . The second pattern is a timing difference between the superior and inferior portions of the vocal folds, so that the inferior portion of the fold leads the superior portion in its movement away from and back to midline. This second pattern is sometimes called a vertical phase difference, and along with the inertia of the air column just superior to the vocal folds, it plays an important role in initiating and sustaining vibration. Vibration occurs as long as respiratory pressure provides a power source, and intraglottal pressure, the air pressure between the vocal folds, is at least partially in phase with the velocity of vocal fold movement. In other words, intraglottal pressure must be high as the vocal folds are separating and low as the vocal folds are returning to midline. The driving pressure asymmetry is facilitated by the vertical phase difference, the inertance of the supraglottal air column, or both. Alterations to vocal fold structure, occurring with disorders or postoperatively, can significantly affect the vibratory patterns; in the extreme, such perturbations may prevent vibration from occurring at all.

The vibrating vocal folds cyclically change the glottal area over time, converting the steady exhaled airstream into a series of air pulses that interact with the subglottal and supraglottal pressures; this is called the glottal flow . The particular pattern of vocal fold vibration and the influence of the supraglottal air column determine the temporal characteristics of each glottal flow pulse and influence the resultant sound quality. Glottal flow and the resultant sound pressure wave are discussed further in Chapter 55 .

To assess vibration patterns during phonation, where the fundamental frequency (F _o ) of vocal fold vibration is typically more than 100 cycles per second (Hz), vibration must be observed in slow motion or in what appears to be slow motion. Videostroboscopy is used clinically to approximate slow motion for laryngeal and voice evaluation. A stroboscopic light source brightly illuminates the vocal folds across multiple vibratory cycles, and a series of images are captured that highlight the vocal folds at successive phases of the cycle. When the images are presented to the viewer at the proper rate, the vocal folds appear to be moving and create smooth cycles of the vocal folds separating and returning to midline. The timing of the light flash and image capture is determined by predicting the measurement of current F _o and, if the prediction is incorrect, the illusion of slow motion vibration will crumble, and the vocal folds will appear to “flutter” rather than vibrate. The strobe light can also be used in a stop or locked mode, where the light flashes at a rate matched with the frequency of the vocal fold vibration and creates the illusion that the vocal folds are not moving at all.

Stroboscopic assessment is particularly valuable for characterizing stiffness, scar, or submucosal injury; detecting small vocal fold lesions; identifying asymmetric mass or tension; and monitoring tissue healing after phonosurgery. It has been shown to change the diagnosis in 30% to 47% of patients diagnosed using flexible endoscopy, and it provides additional detail to the original diagnosis in an additional 32% (e.g., where hyperfunction was indeed present but it appeared as a result of an underlying pathology, such as atrophy or a lesion). Many rating forms are available in the published literature and they include a core set of parameters for describing vocal fold vibration patterns and mucosal pliability. Inter-rater and intra-rater reliability vary by parameter and study. The Voice-Vibratory Assessment with Laryngeal Imaging Form (VALI) appears to improve relatability of ratings by incorporating parameter definitions, rating notes, and graphical depictions of each parameter into the rating form. Regardless of the rating scale used, the following parameters should be assessed.

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