INTRODUCTION
The ability to visualize the vocal folds is an instrumental part of the evaluation of a patient with voice disorders. The precision and safety of in-office visualization and procedures have dramatically improved over time, with the advent of more advanced flexible distal chip laryngoscopes, finer instruments, and working channels. It is a highly cost-effective tool that provides immediate information that can hasten the diagnostic and therapeutic timeline and avoid the need for operative examinations and general anesthesia. , Another great advantage of being able to evaluate patients awake in the office is the ability to view phonating vocal folds and assess, in real time, response to interventions.
LARYNGOSCOPY AND VIDEOSTROBOSCOPY
Laryngoscopy and videostroboscopy play an integral role in the assessment of the vocal folds and vocal complaints.
Laryngoscopy in the office setting refers to the examination of the larynx with either a flexible or rigid endoscope with a continuous light source. Flexible laryngoscopy typically uses a continuous halogen or xenon light source and involves the placement of a flexible endoscope into the nose, passed through the nasopharynx to evaluate the appearance and motion of the larynx and pharynx. Having a recorded exam is beneficial as it can be reviewed immediately at reduced speed to assess subtle abnormalities, it can be used for longitudinal comparison, and it provides an important tool for reference in medicolegal cases.
Videostroboscopy is typically used in conjunction with flexible laryngoscopy, with the videostroboscopy directly following the laryngoscopic exam in appropriate cases. Vocal fold vibrations are too quick to appreciate with unassisted vision, with hundreds of cycles occurring each second, so we use stroboscopy to “slow down” the image. The term “stroboscopy” refers to the light source rather than the endoscope or camera and can be performed using either a flexible distal chip laryngoscope or rigid telescope. It produces a composite image that appears in slow motion as it utilizes synchronized vocal fold illumination with either a flashing light source or shuttering of a constant light source. The pseudo-slow motion allows us to see the mucosal pliability of the vibrating epithelium and superficial lamina propria (SLP), and highlights asymmetries in glottic closure and vocal fold excursion. This allows laryngeal videostroboscopy to provide a more nuanced view of the vocal folds, and allows for a better assessment of mucosal pliability, vibratory function of the vocal folds, and glottic closure. , The technique allows an examination of how the mucosal “cover” (pliable epithelium and SLP) relates to the “body” (stiffer intermediate and deep lamina propria and thyroarytenoid muscle).
Indications
After a careful history and examination, including subjective assessment of the voice (assessing pitch, quality, grade, roughness, breathiness, asthenia, and strain [GRBAS scale]), the next step in assessing a patient with voice or throat complaints is visualization with diagnostic laryngoscopy and stroboscopy.
Diagnostic flexible laryngoscopy is generally performed first, and provides information regarding the appearance of the laryngeal and pharyngeal structures, vocal fold abduction and adduction, and is also helpful in assessing functional disorders. The exam typically starts while the scope is in the nasal cavity, allowing inspection of the nasopharynx and laryngopharynx in a step-wise fashion. The laryngoscopy can help to identify lesions along this pathway, neurological disorders (such as spasmodic dysphonia or tremor), functional disorders (such as muscle tension dysphonia), and vocal fold motion disorders.
Stroboscopy is recommended in patients with dysphonia, particularly with either normal laryngoscopic exams or voice symptoms out of proportion to the findings on flexible diagnostic laryngoscopy. Videostroboscopy is performed using a flashing light synchronized at a frequency slightly slower than the fundamental frequency of the vocal fold vibration, producing a pseudo-slow motion video recording of the vibratory cycle. It is useful for detecting conditions that affect glottic closure, propagation of the mucosal wave, symmetry, amplitude of the vibration, and periodicity. These conditions include vocal fold paresis or paralysis, exophytic vocal fold lesions, and lesions preventing the lamina propria from vibrating effectively. ,
Technique (Including Patient Preparation and Anesthesia)
The patient is placed in a comfortable upright examination chair adjacent to the laryngoscopy tower and screen. Patient tolerance and compliance are improved in any procedure if there is preprocedure counselling and explanation of the procedural steps, and appropriate verbal consent is obtained. A “clip-on” microphone is attached to the patient’s clothing closest to their mouth (typically a shirt collar).
The nasal cavity is prepared with a topical local anesthetic and decongesting vasoconstrictor, either with a topical spray, gel, or via cotton pledgets. A common preparation is a 50:50 mixture of 4% lidocaine with 0.05% oxymetazoline. For larger scopes (for example, transnasal esophagoscopy), nasal pledgets or additional topical anesthesia may be needed. Nasal pledgets have been associated with less discomfort for laryngoscopic procedures. The topical anesthesia is typically applied at the beginning of the history taking, allowing for the necessary 5–10 minutes for peak action.
Table 38.2
Essential Characteristics to Assess During Videostroboscopy Examination
| A videostroboscopy is performed, and the patient is asked to perform phonatory tasks discussed in Table 1 . The following features are evaluated. | |
| Periodicity | Periodicity is the regularity with which a vibratory cycle occurs in relation to each other |
| Glottic closure pattern |
This is the most consistent pattern of closure of the vocal folds during each cycle for a given patient at the modal frequency
There are several classic closure and gap patterns: Complete closure = the most common closure pattern in males, where there is complete approximation of the vocal folds during phonation Posterior glottic gap = the most common closure pattern in females, where there is complete approximation of the vocal folds during phonation except for a gap typically only between the cartilaginous vocal folds without extension to the membranous larynx (also known as a physiologic gap). A gap that extends into the membranous larynx at modal pitch is typical of muscle tension dysphonia Anterior glottic gap = a common variant in males, where there is complete approximation of the vocal folds during phonation except for a small area anteriorly Spindle-shaped glottic gap = another common variant in males of any age, and older females. It is seen in vocal fold atrophy or inadequate tissue due to scarring or sulcus. This appears as a central spindle-shaped glottic gap during phonation Hourglass glottic gap = this is seen with lesions affecting the mid vocal folds, such as bilateral vocal fold nodules or a unilateral lesion with a contralateral reactive change. This appears as a central area of vocal fold approximation and a posterior and anterior glottic gap |
| Phase symmetry | Phase symmetry of the vibration is assessed by comparing one side to the other, where one side should be a mirror reflection of the other in timing for maximal amplitude of excursion and return to midline |
| Vertical closure | The vocal folds usually sit at equal heights; height difference between vocal folds is seen when there is a difference in positioning or a loss of bulk or tone, such as in paralysis, paresis, or postsurgical cases |
| Mucosal wave: amplitude |
The amplitude of excursion during vibration is a measure of the vocal fold pliability. The amplitude of the mucosal wave is the distance the vocal fold mucosa deviates from midline. Symmetry and the degree of excursion are important to evaluate. During a vibratory cycle, maximal excursion from midline is roughly 1/3 the width of the vocal fold
Higher pitches will result in reduced pliability and amplitude, whereas a lower pitch will result in maximal pliability and more amplitude of the mucosal wave |
| Mucosal wave: magnitude | The mucosal wave is the rippling appearance of the vocal folds during stroboscopy that advances from inferior to superior. The magnitude of the mucosal wave is the depth of the waves that are seen over the vocal folds. The wave is assessed by examining the distance traveled on the superior aspect of the vocal fold |
The patient chair is placed at a height and position such that the clinician can comfortably hold the laryngoscope at the level of the nose without bending, twisting, or reaching excessively. A de-fog solution or the patient’s saliva is applied to the tip of the scope to minimize fogging from the patient’s expired air. The clinician uses a two-handed technique, using one hand to gently stabilize the scope against the patient’s face to guide the scope in and the other to control the vertical movement of the tip using the proximal control lever and to rotate the scope as needed. The tip of the flexible endoscope must take an upward path as it goes over the nasal sill, then is angled downward as it is passed over the nasal floor, taking care not to unnecessarily touch the septum or turbinate mucosa to avoid causing epistaxis or discomfort. To maintain the greatest control and comfort, the part of the scope that is external to the body should be kept straight as it is passed into the nose. The nasal cavity chosen for access is the one with the most open pathway, often the opposite side to a nasal septal spur. Once in the posterior nasal cavity, a step-wise assessment is performed (see Table 38.1 ).
Table 38.1
Laryngoscopy and Videostroboscopy Examination Protocol
| A stepwise examination of the structures encountered on endoscopy is performed. Phonatory tasks are typically performed at the patient’s modal pitch, which is their most comfortable speaking pitch at a comfortable loudness. | |
| Nasopharynx |
Assess nasal and nasopharyngeal anatomy
Assess for abnormal movements such as resting tremors of the soft palate or surrounding structures The patient is asked to say a phrase to assess velopharyngeal closure (e.g., “baby bottle,” “ka-ka-ka,” or “Coca Cola”) |
| Oropharynx, base of tongue, and vallecula |
Assess for abnormalities and asymmetry of tongue, base of tongue, and inferior tonsillar pillars
The patient is asked to stick out their tongue, which also helps to show the base of tongue and vallecula |
| Supraglottis and close-up laryngeal assessment |
Observe respiration at rest and look for asymmetry in anatomy or motion
Advance the endoscope to obtain a close-up view of vocal folds, including a full view showing each ventricle It is helpful to have the patient leave their chin, which tilts the epiglottis forward, giving better access to the larynx |
| Specific vocal fold assessment |
Withdraw the tip of the scope to just above the tip of the epiglottis
Ask the patient to perform the following phonatory tasks: Ask the patient to make a prolonged/i/ (“ee”) at modal frequency to assess for arytenoid and vocal fold symmetry and motion, and look for supraglottic hyperfunction Followed by/i– hi– i– hi– i– hi/ (“ee-hee-ee-hee-ee-hee”) Ask the patient to pitch glide starting at low and moving to high pitch, making the sound/a-u/ (“ahhhwooooo”) Ask the patient to perform brisk inhalation sniffs To assess vocal fold fatigueability, ask the patient to perform multiple/i/-sniff-/i/-sniff maneuvers Read a standardized passage like the “Rainbow Passage” If the patient is a singer, have them perform a sample of their music With these phonatory tasks, assess for motion asymmetry, fatigability, lesions of the vocal folds, atrophy, and hyperfunction |
| Hypopharynx | The piriform sinuses are examined with the patient asked to Valsalva against a closed mouth or perform a low-pitched/i/ (“ee”) to open the piriform sinuses more completely due to the wider angle created during this maneuver |
| Subglottis | Ask the patient to tilt their chin down to optimize the angle to view the subglottis and upper trachea |
| Vocal fold assessment with videostroboscopy |
The light source is then exchanged to the stroboscopy unit, with Table 38.2 highlighting the characteristics to evaluate while the patient performs the following phonatory tasks:
|
Videostroboscopy typically follows the flexible laryngoscopic exam using the same flexible endoscope. The distal tip of the endoscope is usually left in the pharynx, anchored in place using a hand braced against the patient’s face so that it does not migrate distally toward sensitive laryngeal structures while the light source is exchanged by an assistant. The significant aspects of the stroboscopy examination protocol are shown in Table 38.2 . The patient is asked to perform a sustained/i/ (“ee”) vowel sound, and, ideally, multiple full vibratory cycles should be witnessed. The duration of the glottic closure should be approximately half of the vibratory cycle.
Rigid videostroboscopy is an alternative or complementary examination to flexible videostroboscopy. The larger diameter of the rigid scope provides for brighter light and a more detailed exam. Rigid laryngoscopes have either a 70- or 90-degree prism at the distal end that allows downward-angled observation of the larynx from above. The rigid scope gives a better view of the posterior portion of the larynx, whereas the flexible scope has better visualization of the anterior larynx. Rigid videostroboscopy is performed by attaching a video camera to the eyepiece of the proximal end of the scope, while the light cable is attached to the strobe unit. A topical anesthetic of 4% lidocaine spray may be applied to the base of the tongue, soft palate, uvula, and faucial arches to help suppress the gag reflex, though many patients do not require this. The patient is asked to lean forward in the exam chair, bending at the waist, and extending the head up into sniffing position. Defogging solution is applied to the tip of the scope, or the scope can be warmed in moderately hot water/glass bead warming unit to prevent fogging during the exam. The patient is asked to open their mouth and extend the tongue. The endoscopist grasps the tongue with a cotton gauze with the nondominant hand. The endoscope is then advanced into the mouth while resting on the thumb that is grasping the tongue, so there is no contact with the lower or upper dentition. As the scope is advanced toward the oropharynx, the patient is asked to take a deep breath and sustain a long/i/ sound, which tilts the epiglottis forward and allows visualization of the adducted vocal folds. As with flexible videostroboscopy, the patient is asked to produce a prolonged/i/ at modal frequency (∼200–250 Hz for females and ∼100–150 Hz for males), at a softer, higher pitch, and a lower pitch.
Outcomes (Literature)
Flexible laryngoscopy is particularly valuable due to its ability to evaluate the vocal tract in a dynamic state. It is inferior to rigid endoscopes in assessing mucosal health; however, it is effective in providing a global assessment of laryngopharyngeal structure and motion due to its minimal impact on function. Rigid stroboscopy cannot be performed without altering the laryngeal biomechanics through the pulling of the tongue out of the mouth, an unnatural way to phonate. Flexible laryngoscopy is also very useful in the diagnosis of vocal tremor and helps to exclude other pathologies in the assessment of spasmodic and muscle tension dysphonia. , Newer technologies of distal-chip flexible endoscopes do provide superior optics to flexible fiberoptic endoscopes, and coupled with videostroboscopy, facilitate the diagnosis of many voice disorders. Flexible diagnostic laryngoscopy alone is considered inadequate in many cases, as the addition of videostroboscopy can alter the diagnosis in as many as 47% of cases. Despite this, the inter-rater reliability of the videostroboscopic assessment of phase closure, phase symmetry periodicity remains poor.
Complications
Laryngoscopy and stroboscopy are considered very safe procedures in both the adult and pediatric populations. , Literature examining complications of in-office flexible laryngoscopy has indicated major complications such as laryngospasm or airway obstruction as being theoretically possible yet exceptionally rare, with no serious adverse events documented. ,
Mild nasal and/or pharyngeal discomfort from the presence of the scope can occur at the time of laryngoscopy; however it is typically resolved with removal of the endoscope. Mild epistaxis or airway bleeding can also sometimes result; however is very uncommon in experienced hands. Vasovagal syncope is another infrequent complication of flexible laryngoscopy, as the pulse and blood pressure can drop with the presence of the scope in the nose or pharynx. This self-limited reaction is treated by immediate removal of the scope and lying the patient down. As with any reusable instrument that is inserted into the human body, there are theoretical risks of cross-contamination due to inadequate cleaning.
Other Considerations (Controversies, Billing Nuances, Special Equipment, etc.)
Flexible laryngoscopy has largely supplanted the practice of mirror laryngoscopy as the preferred means for examining the larynx, though mirror laryngoscopy does allow for more accurate assessment of the color of pharyngeal and laryngeal tissues and can be performed in low-resource settings. Distal-chip flexible laryngoscopes are becoming more and more common but come at a significantly increased cost over flexible fiberoptic laryngoscopes when combining the cost of the digital processor unit and recording device. The optical resolution, magnification, and increased light in high-definition distal-chip laryngoscopy, as well as other features such as narrow-band imaging, increase the diagnostic accuracy of these scopes versus fiberoptic scopes and are de rigueur in a voice and swallowing center.
Flexible laryngoscopy bills with Current Procedural Terminology (CPT) code 31575, while laryngoscopy with stroboscopy, either flexible or rigid, bills with CPT 31579. As of the time of publication, stroboscopy provides 3.65 relative value units (RVUs) in a nonfacility setting, while diagnostic flexible laryngoscopy provides 2.69 RVUs. One of the two procedures can be billed at one office visit, but not both.
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