Visualization of the Larynx

CHAPTER 57 Visualization of the Larynx

In this chapter, we describe several tools for laryngeal visualization and how to analyze and interpret the images. Laryngeal videoendoscopy and stroboscopy (LVES), high-speed digital imaging (HSDI), and narrow-band imaging (NBI) are discussed.

Laryngeal videoendoscopy is a clinical tool that is used to examine vocal fold structure and gross function. It is used to diagnose and document voice and laryngeal disorders, plan treatment, make longitudinal comparisons, educate patients, provide biofeedback for voice and breathing therapy, and provide a record for medicolegal proceedings. Both rigid and flexible endoscopes can be used for endoscopy.

Stroboscopy is a lighting technique that helps clinicians examine 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 glottic closure and mucosal pliability, to make inferences about tension, and, sometimes, to identify or differentiate lesions. The decisions to use continuous or strobe light and rigid or flexible endoscope are largely based on whether the examiner is more interested in gross structure and function or mucosal health and vibration patterns. Often, both rigid and flexible examinations are used as part of a dynamic assessment to thoroughly evaluate laryngeal function during a variety of voicing conditions and therapy probes.

Examination with high-speed digital imaging systems complements endoscopy and stroboscopy; details of short and aperiodic vibration can be observed, and the image analysis allows quantification of vibratory details that is not otherwise possible.

Narrow-band imaging is a new endoscopic imaging technique that uses the absorption characteristics of light to enable a detailed analysis of mucosal and vascular structures. The technique holds promise for becoming a powerful tool to screen for malignancies by identifying high-yield areas to sample for biopsy.

In most states, LVES, HSDI, and NBI can be performed by either an otolaryngologist or a qualified speech-language pathologist.1 Each professional brings a different perspective and training to the process, and the most thorough examinations are typically conducted in a team setting. The otolaryngologist is responsible for assessing mucosal health and diagnosing laryngeal pathology; the speech-language pathologist is interested in the vibratory patterns during various voicing conditions, the behavior of the laryngeal and supralaryngeal structures during phonation, and how treatment probes alter phonatory physiology. As team members work together over time, they often learn from each other and develop common skill sets.2

The advantages and disadvantages of rigid and flexible endoscopes are described in the first section of this chapter, with recommendations for technique and troubleshooting. The second section details the assessment process for endoscopy and stroboscopy. The third section discusses HSDI, its advantages and limitations, and how images are processed and analyzed. The final section is an introduction to the emerging technology of NBI.


Rigid Endoscopes


The primary limitation of the rigid endoscope is that phonation is limited to sustained vowels, most commonly “ee.” Because visualization with a 70-degree rigid endoscope usually requires an extended neck and protruded tongue, the size of a glottic gap might appear exaggerated with the rigid endoscope.5 To counteract this problem, Rammage and colleagues2 suggest a lateral approach to the larynx to decrease neck extension during the examination. Alternatively, a 90-degree endoscope does not require the same amount of neck extension as the 70-degree endoscope does. A second limitation is that the mobility of the arytenoids might not be accurately assessed via rigid endoscopy; often, it appears as if there is a vocal fold paresis when the perceived lack of motion is, in actuality, an artifact of the tongue protrusion and neck extension. Lastly, disorders more evident in connected speech than in sustained vowels (e.g., muscle tension dysphonia and spasmodic dysphonia) are not as well documented with rigid endoscopy as they are with flexible endoscopy.


The laryngeal examination with a 70-degree rigid endoscope is conducted with the patient bending slightly forward from the hips while maintaining a straight back. The neck and chin are extended, and the tongue is protruded. The examiner wraps the tongue in gauze and holds it gently during the examination. The endoscope is advanced just under the uvula or between the uvula and faucial pillars until the epiglottis is visualized. Turning the endoscope tip to face the cheek during insertion, to prevent tongue residue from coating the lens, might keep the lens cleaner. Having the patient vocalize a sustained “hey” lowers the tongue base, facilitating placement. The patient is then instructed to sustain “ee,” which moves the epiglottis anteriorly for a better view of the vocal folds. The examiner might need to flex the wrist to tilt the endoscope tip inferiorly. The angle can be varied for differing levels of magnification and differing fields of view. The patient is then guided through the examination tasks listed in the following “Assessment” section. Examination with the 90-degree endoscope is similar, but the patient does not need to bend forward or extend the neck. Another difference is the angle; the tip of the 90-degree scope is positioned with minimal tilt so that the light is parallel to the surface of the vocal folds. This type of endoscope is often preferable for viewing the larynx when a wider viewing angle is desired. A longer lens or a zoom lens might be necessary for adequate visualization of vocal fold details.

Defogging the endoscopes can be a challenge, because sterilizing beads can cause damage to both the lens and the patient. Alternatives include liquid defogger, hot (not boiling) water, soap film, surgical wax, and holding the endoscope lens briefly against the patient’s cheek or the side of the tongue. The examination is generally tolerated without topical anesthesia, but a small amount of benzocaine topical spray or a similar product is sometimes useful and does not appear to affect examination results.6


A good-quality examination means that the image is in focus, that it is large enough to show small mucosal irregularities, and that it is bright enough to show details (but not so bright as to obscure them). Contrasting color is important for differentiating subtle lesions and vascular changes. Ideally, an examination includes both a wide-angle view of the larynx and a close-up view of the vocal folds. The stroboscopic portion of the examination should include several complete stroboscopic cycles at the patient’s most comfortable pitch and loudness (MCPL) in addition to the rest of the protocol (see “Assessment”). Common imaging problems and solutions are listed in Table 57-1.

Table 57-1 Common Problems and Solutions for Laryngeal Endoscopy and Stroboscopy

Problem Solution(s)
Foggy image

Fuzzy image

Dark image

Grainy image

Image is tilted or the vocal folds appear to have different widths

Image is mostly of the valleculae and epiglottis or anterior commissure cannot be seen

Mostly arytenoids and posterior vocal folds are seen

The base of tongue is high

Uvula is “in the way”

Abnormal color

Omega-shaped epiglottis

Strobe is “not tracking”

“Plica ventricularis”: ventricular folds closed so the true vocal folds cannot be seen


Flexible Endoscopes


The primary advantage of the flexible endoscope is the ability to view the larynx dynamically—that is, during natural functions such as speech and singing. Arytenoid mobility and the glottic gap can be more accurately described with flexible than with rigid endoscopy because of the neutral tongue and neck positions.5 Flexible endoscopy also allows the clinician to assess the nasal cavity and velopharyngeal port during the same examination. Flexible endoscopy is preferred when the question is one of movement rather than structure or mucosal health. It is particularly useful for disorders such as spasmodic dysphonia and muscle tension dysphonia, in which the voice problem is more obvious during speech than in sustained vowels, and vocal fold motion impairment, where having the patient sniff through the nose allows the examiner to assess subtle motion.

Videoendoscopy and Stroboscopy

Endoscopy: Assessment Using Continuous Light


Endoscopic parameters that require only continuous light (as opposed to the xenon light of stroboscopy) include laryngeal structure, arytenoid and vocal-fold motion, color and quantity of mucus, vascularity, supraglottic activity or compression, and deformation of vocal fold edges. The tasks during this portion of the examination include rest breathing, deep breathing, easy cough or throat clear, and laryngeal diadochokinesis, which consists of rapid repetitions of “ee” with glottal stops between productions. Laryngeal diadochokinesis is a useful measure, and production rates of four to six syllables per second are considered normal.7 Difficulty with accurately and rhythmically producing the voice onset/offset gesture has been found in patients with neurologic impairment.8,9 If a flexible endoscope is used, several other parameters can be assessed, including repetitions of a short “ee” followed by a quick sniff through the nose, a standard set of phrases or sentences, and conversational speech if voice quality during the endoscopic examination is not consistent with what was heard before it. Examination of velopharyngeal function is indicated if nasal emission or hypernasality is heard. At a minimum, soft palate and lateral pharyngeal wall motion should be assessed during a sustained vowel and a voiceless fricative, as well as during words or phrases with nasal-oral consonant transitions. A sample protocol is outlined in Box 57-1.

Laryngeal Structure

The valleculae, pyriform sinuses, epiglottis, aryepiglottic folds, ventricular folds, and posterior glottic rim should be examined. Lowered pitch during sustained “ee” widens the angle, allowing better visualization of the valleculae. Abnormalities and asymmetries of laryngeal structure are noted. An omega-shaped epiglottis is a common variant in men, but it is rare in women.7,10 Signs of laryngeal irritation or possible laryngopharyngeal reflux are noted; these primarily include edema, erythema, surface irregularities, and lesions of the posterior larynx.1114 The specificity of signs for reflux is still being evaluated. In particular, interarytenoid bar, arytenoid medial wall erythema, and posterior pharyngeal wall cobblestoning have been found in a substantial number of “normal” volunteers.13

Supraglottic Activity

Supraglottic activity refers to any abnormal motion above the true vocal folds. Examples are tremor of the larynx or pharynx, other involuntary contractions (e.g., myoclonic movements), and compression of the supraglottic structures. Supraglottic movements help tease apart neurologic voice disorders from disorders caused by abnormal muscle tension; tremor and myoclonic movement are evidence of a neurologic disorder, whereas sustained constriction is more typically found in muscle tension disorders. Constriction is often categorized by direction (anteroposterior or lateromedial) and frequency (constant or intermittent). Anteroposterior constriction during phonation is shown in Figure 57-1, and lateromedial constriction in Figure 57-2. The Stroboscopy Evaluation Rating Form proposed by Poburka15 displays a superior view diagram of the vocal folds with superimposed concentric circles on which raters estimate the extent of constriction. Aryepiglottic narrowing or dilation and pharyngeal shape for different vowels can alter vocal-fold vibratory characteristics.2,16,17

The frequency and severity of supraglottic constriction in subjects without voice disorders is still somewhat uncertain, although it is clear that both anteroposterior and lateromedial constrictions are sometimes normal variants.1820 Stager and associates20 found that supraglottic movements were present at the initiation of phonation in normal controls. Behrman and colleagues18

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Jun 5, 2016 | Posted by in OTOLARYNGOLOGY | Comments Off on Visualization of the Larynx

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