Advantages

Rigid endoscopes used with LVES are usually 70- or 90-degree scopes. Rigid scopes have the advantage of high resolution with bright, clear pictures. Contrast is excellent, there is a large selection of viewing angles, and the image is more accurately magnified than with a flexible endoscope. The examination is simple and does not usually require topical anesthesia.^2–4

Disadvantages

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.

Technique

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

Troubleshooting

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

Advantages

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.

Disadvantages

The primary limitation of flexible endoscopy is that light transport and magnification of the image are inferior to those of rigid endoscopy. There is also a distortion of the periphery of the image and a trade-off between adequate focus and light fiber mismatch, so that when the image is in focus, there is a moiré or honeycomb effect that is enhanced by the edge-detection software of digital imaging systems. The honeycomb effect is not a concern with the newer-technology flexible endoscope with a charged-coupled device (CCD) camera in the tip. These “chip-tip” endoscopes eliminate the fiberoptic bundle and provide superior optics. Although the chip-tip endoscope represents a significant improvement, the new technology comes at a significant cost increase, and the quality of resultant examinations is not equal to that achieved with rigid endoscopy. In addition, many patients find the flexible examination to be more invasive than the rigid examination, and the flexible technique carries the risks of nosebleed, adverse reactions to the anesthetic, and vasovagal reaction.

Technique

The flexible endoscope is typically inserted after the application of a topical anesthetic and a vasoconstrictor. It can be passed through the inferior or middle meatus of the nose. The higher path is preferred for examination of the velopharyngeal port, but the paths are equivalent for visualizing the larynx. The examiner should raise the endoscope slightly as the patient swallows to avoid triggering a cough or laryngeal closure reflex, which can occur if the endoscope touches the rising larynx during a swallow.

Troubleshooting

As with the rigid endoscope, a good-quality flexible examination means that the image is in focus, large enough to show small lesions, bright enough to show details, and not so bright that details are obscured. Varying the field of view of the flexible endoscope is easy, but it is sometimes challenging to bring the endoscope close enough to the vocal folds for optimal light and vibratory detail. Patients generally allow a more complete examination when they are fully informed about the procedure, have some feeling of control (e.g., they know the examiner will respond if they say they have had enough), and have received adequate anesthetic.

Protocol

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.^11–14 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

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 typically described as mobile or immobile, symmetric or asymmetric, and upright or rotated. Immobility is further described by position: median, paramedian, intermediate, or lateral. Motion of the arytenoid should be described separately from movement of the posterior third of the vocal fold because sometimes the arytenoid is mobile when the vocal fold is fixed. Mobility is rated when patients phonate then breathe, and during laryngeal diadochokinesis, cough, whistling, and sniff. The etiology of the motion impairment, along with particular characteristics such as arytenoid position, gap size, shape, and vocal-fold plane difference, can influence management strategy as described in Chapters 66 through 68.

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 swallow. Thickened mucus adhering 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 gentle cough.

Vascularity

The vocal folds are generally pearly white. A blush throughout the tissue is considered erythema or hyperemia. If capillaries are visible, they are generally aligned parallel with the free edge; horizontal vascularity is cause for concern. Abnormally dilated and tortuous vessels, called capillary ectasias or microvarices, might represent areas of stiffness or risk for hemorrhage. Hemorrhage occurs when enough blood cells have escaped from a vessel to lend a diffuse coloring to the vocal fold. Post-hemorrhage vocal folds often appear yellow-brown, similar to healing bruises in other areas.

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

Figure 57-1. A, Vocal folds during respiration. B, Vocal folds with anteroposterior constriction during phonation.

Figure 57-2. A, Vocal folds during respiration. B, Vocal folds with lateromedial constriction during phonation.

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.^18–20 Stager and associates²⁰ found that supraglottic movements were present at the initiation of phonation in normal controls. Behrman and colleagues¹⁸

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