Laryngeal Endoscopy and Stroboscopy

Endoscopy (endo—“within”; oscopy—“to look at”), in the context of medicine, is a procedure that allows a healthcare professional to look inside the body with the use of an endoscope. As illustrated in ▶ Fig. 6.1, endoscopes can be made of rigid or flexible material. They contain a fiberoptic system that conveys light from an external source into the body, and a lens system which transmits the reflected image of the internal body surfaces. An eyepiece at one end of the scope allows the examiner to see the reflected image or allows for the attachment of a camera for capturing and recording of the image. The camera can also be connected to a computer or video monitor screen. When the larynx is examined using endoscopy, the process is a type of laryngoscopy (larynx + oscopy), although you do not have to have an endoscope to look at the larynx (it can also be viewed with a mirror). Some professionals prefer the term phonoscopy or phonoscopic examination when laryngoscopy is performed by a speech–language pathologist (SLP) for the purposes of evaluating vocal function. 1 This term distinguishes laryngoscopy for voice examination from laryngoscopy for swallowing examination (e.g., fiberoptic endoscopic examination of swallowing [FEES]). Both otolaryngologists and SLPs perform laryngoscopy as a part of standard clinical evaluations. Stroboscopy incorporates the use of a stroboscopic (flashing) light or a rapidly shuttered camera to result in the illusion of slow motion. The stroboscopic image allows for the observation and description of vibratory cycles and specific characteristics of vibratory dynamics. Stroboscopy has often been referred to as “videostroboscopy,” with the “video” prefix referring to the use of a video camera for motion image capture and playback.

Examples of rigid and flexible endoscopes.

Fig. 6.1 Examples of rigid and flexible endoscopes.

6.3 Principles of Stroboscopy

Many of us have been in a club or at a dance where a rapidly flashing strobe light was turned on, making the people in the hall appear as though they were moving in slow motion. This same illusion is used in laryngeal stroboscopy to provide a detailed view of the vibratory characteristics of vocal fold motion. We must remember that, during typical voice production, the vocal folds are vibrating at hundreds of times per second. Like looking at a hummingbird’s wing during flight, without some method of slowing down this vibration, our view of the vibrating object would be blurred and indistinct—we know that the structure is moving, but the details of the vibratory movement would be unclear. However, a strobe light (periodically interrupted light) may be used to visualize a rapidly moving object. If the object(s) (e.g., vocal folds) is/are moving in a relatively periodic (repetitive) fashion, the object(s) will appear to move in slow motion if the frequency of the strobe light is slightly different than the frequency of vibration (e.g., vocal frequency = 200 Hz; strobe light frequency = 195 Hz). If the frequency of the strobe light is the same as the frequency of vibration of the moving object(s), then the resulting image will appear to be a still image or “freeze frame.” Both of these views are available in most systems used for the stroboscopic evaluation of the larynx, though the key characteristics of vocal fold vibration (e.g., closure pattern, symmetry of vibration, and mucosal wave—see subsequent section) are all observed and described during a “slow-motion” view.

It is important to recognize that we have referred to the slow-motion view observed during stroboscopy as the “illusion” of slow motion. This is because what may appear as a slow-motion view of one cycle of vocal fold vibration is actually made up of different snapshots of multiple cycles of vibration in which the stroboscopic light has illuminated different positions of vocal fold movement during successive vibratory cycles. Just as the individual still frames of a film appear to show continuous movement when viewed rapidly in succession, we see the individual illuminations of successive cycles of vibration as one continuous cycle (i.e., a stroboscopic cycle). This is in contrast to a newer method of laryngeal evaluation referred to as high-speed video in which (depending on the system) thousands of images per second are digitized and multiple images are obtained per cycle of vibration.

▶ Fig. 6.2 illustrates how videostroboscopic image perception works. Each row represents a successive vocal fold oscillation. The red dot within an individual circle represents different points within one vibratory cycle, representing a complete cycle (opening-open–closing-closed) moving around a 360-degree circle. Circles in consecutive rows that are highlighted in red represent flashes of a strobe light that will illuminate the visual field. The rate of the strobe light is timed to flash a few milliseconds slower than the actual period of vibration (the amount of time it takes for one vibratory cycle to occur). This results in the vocal folds being illuminated at different points of the vibratory cycle in each successive flash. Although each flash of the strobe creates a separate image that is detected by an examiner’s eye, these discrete images will perceptually blend into a one continuous moving image due to the property of persistence of vision.

An example of how strobe light flashes different phases of successive vibratory cycles. See text for further description.

Fig. 6.2 An example of how strobe light flashes different phases of successive vibratory cycles. See text for further description.

(From Kendall K, Leonard R. Laryngeal Evaluation, 1st ed. New York: Thieme Publishers, 2010.)

Another way to conceptualize visual perception of stroboscopy is shown in ▶ Fig. 6.3. The top waveform symbolizes successive vocal fold oscillations, with the open phase represented by the peak of each oscillation. The lightbulbs underneath represent a flash of the strobe light which illuminates the vocal folds. These flashes occur at different points of the vibratory cycles, but not during the same oscillation. Visually we perceive the motion as a continuous stroboscopic cycle of vocal fold vibration—we do not perceive the fact that different oscillatory cycles are being illuminated. Some may argue that our interpretation of vibratory dynamics in laryngeal videostroboscopy does not represent actual disturbances in any one vibratory cycle—and this is true. However, research evidence shows that the information obtained from videostroboscopy is significant and can add to or change diagnoses in a large percentage of cases. 2,​ 3,​ 4 Evidence strongly supports that visual analysis of vocal fold vibration illuminated with stroboscopic light is highly sensitive to most vibratory disturbances.

An example of how strobe light flashes different cycles of vibration. Each pulse represents one vibratory cycle.

Fig. 6.3 An example of how strobe light flashes different cycles of vibration. Each pulse represents one vibratory cycle.

(From Kendall K, Leonard R. Laryngeal Evaluation, 1st ed. New York: Thieme Publishers, 2010.)

6.4 Laryngoscopy/Stroboscopy Frequently Asked Questions

In many graduate SLP programs, basic knowledge of laryngoscopy and stroboscopic examination may be provided, but students often do not get a depth of experience to develop skills in these procedures. Many clinicians develop endoscopic skills and advanced knowledge after graduation through mentored experiences and continuing education. This leaves many new SLPs with questions about their role in the use of endoscopy for clinical evaluation and treatment. To directly address some of the more frequent questions posed by SLPs new to laryngeal endoscopy and stroboscopy, we have organized this introduction into a set of frequently asked questions (FAQ), which will set the stage for the remainder of the chapter.

6.4.1 Does the Use of Endoscopy and Stroboscopy Fall within the Scope of Practice of SLPs?

Yes. And possibly. You are probably confused by this answer. Allow us to explain. According to the American Speech-Language and Hearing Association (ASHA), the clinical services provided by SLPs include “…using instrumentation (e.g., videofluoroscopy, electromyography, nasoendoscopy, stroboscopy, endoscopy, nasometry, and computer technology) to observe, collect data, and measure parameters of communication and swallowing or other upper aerodigestive functions.” 5 ASHA goes further, explicitly stating in a position statement that “It is the position of the American Speech-Language-Hearing Association (ASHA) that vocal tract visualization and imaging for the purpose of diagnosing and treating patients with voice or resonance/aeromechanical disorders is within the scope of practice of the speech–language pathologist.” 6 Thus, our national certifying body makes it very clear that visualization of the vocal tract, including the larynx, using endoscopy and stroboscopy is within our scope of practice. As additional supportive evidence, a recent expert panel of ASHA’s “Special Interest Group 3: Voice and Voice Disorders” also published guidelines for recommended voice evaluation procedures, which included laryngoscopy with stroboscopy. 7

While ASHA provides certification recognized by the federal government, the right to work as an SLP in any state is regulated by a licensing board. Currently, most state licensing boards allow for laryngoscopy within the SLP scope of practice. However, some states have specific wording in their scope of practice statements that regulates how an SLP might utilize this tool. For example, in California, SLPs are not allowed to diagnose with endoscopy, and must refer any suspected lesion to a physician for further evaluation. In Michigan and Indiana, an SLP can utilize endoscopy only “…under the authorization and general supervision…” of a physician. In Tennessee, an SLP can use endoscopy but only when they “Obtain written verification from a board-certified otolaryngologist that the SLP is competent in the proper and safe use of an endoscope.” It is the SLPs’ individual responsibility to be familiar with ASHA’s scope of practice (when performing duties as an SLP with a certificate of clinical competence) and the scope of practice for the state in which they are licensed.

6.4.2 Other Than My SLP License/Certification, Do I Need a Special Certificate or License to Perform Endoscopy and Stroboscopy?

No. But possibly. Sorry to keep doing this to you. According to ASHA’s code of ethics, Principle of Ethics II Rule B, “Individuals shall engage in only those aspects of the professions that are within the scope of their competence, considering their level of education, training, and experience.” 7,​ 8 This means that there is no ASHA-required “certificate” or specific training required for utilizing endoscopy and stroboscopy as a certified SLP, but an individual must be certain that they are competent to perform and interpret endoscopic procedures. However, we previously mentioned that each state also publishes a scope of practice which might stipulate requirements for SLP’s use of endoscopy, including training requirements. An example was the state of Tennessee, which requires an otolaryngologist to provide written confirmation that an SLP is competent to perform these procedures. It is the responsibility of the SLPs to verify with their state licensing board on educational/training requirements for performing endoscopy.

6.4.3 How Does One Obtain and Demonstrate Endoscopic and Videostroboscopic Competencies?

ASHA gives further guidance on this. The only specific stipulation is that “Some of the training should take place in a clinical setting allowing the SLP to work with more experienced professionals and a number of patients.” Otherwise, SLPs can obtain competencies “…by a variety of means,” including 9

  • Traditional classroom learning provided in the context of accredited training programs.

  • Extended one-on-one work with an SLP or otolaryngologist who has had extensive experience with all aspects of endoscopy in an interdisciplinary environment.

  • Extended performance of endoscopy clinical services under the supervision of an SLP and otolaryngologist who has had extensive experience with all aspects of the procedure.

  • Organized training provided outside established educational degree programs (continuing education workshops/seminars).

  • Review and interpretation of previously recorded endoscopic examination.

  • Experience leading to expertise in performing and interpreting endoscopy in the clinical environment.

At the state level, remember that it is the responsibility of the SLPs to verify with their state licensing board regarding any specific educational/training requirements for performing endoscopy. In ▶ Appendix 6.1, we provide our recommended guidelines for obtaining and demonstrating competency in performing endoscopic and stroboscopic laryngeal evaluations for voice disorders. We emphasize that these are the recommendations of the authors, and not guidelines endorsed by any state or national agency.

6.4.4 If I See a Lesion, Can I Diagnose It as a Specific Medical Condition Such as Vocal Fold Polyps?

No. ASHA policy is very clear on this, and is stated as follows: “Physicians are the only professionals qualified and licensed to render medical diagnoses related to the identification of laryngeal pathology as it affects voice. Consequently, when used for medical diagnostic purposes, strobovideolaryngoscopy examinations should be viewed and interpreted by an otolaryngologist with training in this procedure.” 10 This means that when an SLP uses laryngoscopy with stroboscopy for diagnostic evaluations, the examination needs to be reviewed by an otolaryngologist who will provide a medical diagnosis (if warranted) for the laryngeal condition. SLPs can perform laryngoscopy with stroboscopy independently in the majority of states. However, these examinations should be reviewed collaboratively (preferred) or separately by the otolaryngologist before any final diagnosis is made. How do you know what a medical diagnosis is? You can refer to the International Classification of Diseases, 10th Revision, Clinical Modification (ICD-10) as a guide for diagnostic classifications. ▶ Table 6.1 illustrates the more common ICD-10 codes associated with voice disorders. These are the diagnoses that will be provided by the physician—not the SLP. Some state licensing boards also make this explicit in their scope of practice.

Table 6.1 ICD-10 codes associated with medical diagnoses of voice disorders

ICD-10 code



Dysphonia—used for hoarseness


Aphonia—used for loss of voice


Other voice and resonance disorders—used for vocal hyperfunction


Unspecified voice and resonance disorder—used for a general change in voice


Paralysis of the vocal cords and larynx, unilateral


Paralysis of the vocal cords and larynx, bilateral


Polyp of vocal cord and larynx


Nodules of vocal cords


Other diseases of vocal cords:

  • Abscess of vocal cords

  • Cellulitis of vocal cords

  • Granuloma of vocal cords

  • Leukokeratosis of vocal cords

  • Spasmodic dysphonia

  • Atrophy of vocal cords

  • Cyst of vocal cords

  • Pseudocyst of vocal cords


Edema of larynx—would be appropriate for Reinke’s edema


Chronic laryngitis

With that said, as an SLP becomes more knowledgeable and skilled in the evaluation and treatment of voice disorders, they will find that the precision of their diagnostic hypotheses becomes more accurate. In addition to the medical diagnosis provided by an otolaryngologist, our role is to describe the physiological impairment that we see on laryngoscopy and stroboscopy. This description should include a report of any visible mass (using non-diagnostic terms such as “lesion”), tissue discoloration, or movement anomaly. It might also include adjectives such as “exophytic,” “irregular,” “hyperfunction,” “erythematous,” “plaque-like,” “fluid-filled,” “immobile,” “spasm,” and “tremulous” among others, but we leave it to the otolaryngologist to diagnose whether these signs are actually nodules, polyps, cysts, paralysis, spasmodic dysphonia, or primarily hyperfunctional in nature (e.g., muscle tension dysphonia). Thus, the SLP can diagnose impaired physiology, but applying a medical diagnostic label to the disorder is the role of the physician. Ideally, the SLP and otolaryngologist can review these exams together as part of interprofessional collaborative practice, and take advantage of each other’s mutual knowledge and skill to guide the process of differential diagnosis.

6.4.5 As an SLP, Can I Use Both Rigid AND Flexible Endoscopes to Perform Endoscopy?

Yes, for ASHA. Possibly, for state licensure regulations. There are more state regulations pertaining to the use of a flexible endoscope during the performance of a FEES than pertaining to the general use of a flexible endoscope for voice examination.

6.4.6 Can I Use an Oral or Nasal Topical Anesthetic to Make the Exam More Comfortable for the Patient?

Possibly. ASHA defers to the state licensing boards on this topic. SLPs routinely use oral and nasal topical anesthetic to decrease oral or nasal sensitivity to endoscopes passed through the mouth or nose. Whether the SLPs can directly administer the anesthetics, if they need another medical professional present during administration, or if they need another medical professional to administer, the decision will be dictated by state regulations. Specific wording from ASHA on this topic includes “…speech-language pathologists should address issues of scope of practice as defined by state licensing boards and institutional regulatory committees, professional liability and patient and practitioner safety before engaging in procedures on individuals medicated for sedation or topical anesthesia. These issues should be defined in specific, written protocols that the … speech-language pathologist develop in collaboration with physicians, dentists, and other medical professionals who are responsible for patient care.” 11 In this same technical report, ASHA stipulated the requirement to practice collaboratively with medical professionals when administering topical anesthetics, indicating “…collaboration with appropriate medical professionals is required, as topical anesthetics and vasoconstrictors may have undesirable side effects that place patients at risk for adverse medical complications.” Many SLPs interpret this to mean that if one is to administer topical anesthesia, they should be in a medical environment with trained health professionals (e.g., nurses, physicians) present (in the facility—not necessarily in the room unless dictated by state regulations) and in communication with the SLP (they are aware that the SLP administers topical anesthesia). ASHA has gone further in their descriptions of the SLP use of topical anesthesia in the context of endoscopic swallowing evaluations, stating that skills needed to perform this procedure include the competence to “Apply topical anesthetic when clinically appropriate and permitted by the licensing regulations of individual states.” 12

ASHA’s recommendations justify the SLP practice of topical anesthetic administration in a published guideline, noting “Clinicians may choose to use topical nasal anesthetics alone or in combination with vasoconstrictors to facilitate more comfortable transnasal passage of the flexible endoscope.” 13 The administration of nasal vasoconstrictors can increase patient comfort by enlarging the space inside a nostril through constricting small blood vessels and tissue for a brief period. However, ASHA has also published precautions that should be followed by the SLP, which include the following 6:

  • Have available immediate emergency medical assistance when using topical anesthesia or flexible fiberoptic nasoendoscopy.

  • Hold a current Basic Life Support Certificate if performing flexible fiberoptic nasoendoscopy or using topical anesthesia.

  • Obtain informed consent of the patient and maintain complete and appropriate documentation when performing flexible fiberoptic nasoendoscopy or when using topical anesthesia.

6.5 Rationale for Laryngeal Endoscopy and Stroboscopy

Among the clinical concepts that SLPs might take away from this book, the following are essential: (a) functional voice disorders can exhibit perceptual, acoustic, and aerodynamic characteristics that are very similar to organic voice disorders and (2) different organic voice disorders can exhibit perceptual, acoustic, and aerodynamic characteristics that are similar to each other. In short, a wide range of voice disorders, including those with a functional origin, those associated with benign lesions, and those associated with more severe organic disorders can all have similar perceptual, acoustic, and aerodynamic characteristics. As examples, the auditory–perceptual features of a speaker with laryngeal cancer can sound exactly like a speaker with primary MTD, with acoustic and aerodynamic measurements also indistinguishable. As another example, an individual with laryngeal papilloma can sound exactly the same as an individual with a vocal fold polyp, where acoustic and aerodynamic measurements also appear similar. However, the treatments for laryngeal cancer, MTD, papilloma, and vocal fold polyp are all very different from each other. These phenomena justify the need to visualize the larynx prior to the development of a treatment plan. Effective treatment plans require accurate diagnoses, and accurate diagnoses of voice disorders require laryngeal visualization.

The question is who performs the laryngoscopy? Here, we present the Golden Rule of voice therapy, which all readers should make efforts to memorize and store in long-term memory for the rest of their careers: Prior to initiating voice therapy, an otolaryngologist must view the larynx (via laryngoscopy) and determine if any medical diagnoses are present. The SLP can certainly conduct a comprehensive voice evaluation including a behavioral and qualitative assessment, laryngeal function study (acoustics and aerodynamics), and laryngoscopy with videostroboscopy, but before initiating voice therapy the patient must see an otolaryngologist. The laryngeal images viewed by the otolaryngologist might be obtained by their own procedure, or from video obtained by the SLP. In most cases, the physician will obtain the images themselves during their initial clinical examination of the patient. Otolaryngologists can perform laryngoscopy in one of the following three ways: indirectly using a laryngeal mirror (indirect laryngoscopy), directly using a flexible endoscope routed through the nose (flexible laryngoscopy), or directly using a rigid endoscope routed through the oral cavity (rigid laryngoscopy). The most widely used method of laryngeal visualization during initial examinations by otolaryngologists is flexible laryngoscopy. 14

We have just made the case that laryngoscopy is critical for accurate diagnosis of voice disorders, and that an otolaryngologist must perform laryngoscopy or review laryngoscopic images and provide any medical diagnosis prior to initiation of voice therapy by an SLP (the “Golden Rule”). What about laryngoscopy with videostroboscopy (we will refer to this as LVS from this point on)? Unfortunately, most general otolaryngologists do not utilize LVS as part of their initial or follow-up examinations on patients with complaints of voice problems. Fortunately, most laryngologists and most SLPs working in voice clinics do. This is a good thing, because evidence shows that LVS can modify diagnostic decisions, provide additional diagnostic information, and/or change treatment decisions in up to 47% of patients. 4 The reasons for this are multifactorial, but the most important justification for LVS is that it allows you to assess vocal fold vibratory dynamics and glottal closure pattern, while laryngoscopy without stroboscopy does not. There are many cases in which patients with seemingly normal/typical laryngeal structures show only abnormal/atypical signs when observed during LVS. Vocal fold vibratory dynamics and glottal closure patterns, discussed later in this chapter, inform the otolaryngologist or SLPs about the health of the vocal fold tissue and the extent to which a lesion or tissue change impacts the layered structure of the vocal fold(s) and, in turn, their vibratory characteristics. This information can be the difference between decisions of obtaining a biopsy versus more conservative management, or diagnosing a functional voice disorder instead of a neurological voice disorder.

6.6 Instrumentation

Clinical utilization of laryngoscopy (specifically, phonoscopic examination) with stroboscopy for SLP requires instrumentation that will allow a field of view centered on the larynx and the ability to store and review a recorded image. This requires a specific combination of equipment, illustrated in ▶ Fig. 6.4, including the following:

  1. A rigid or flexible endoscope.

  2. A light source to illuminate the field of view and provide an intermittent flash (strobe).

  3. A microphone to detect vocal fundamental frequency, which synchronizes the stroboscopic flash and may be used to record the voice signal (depending on the system, this may be achieved via one or two microphones).

  4. A video camera to capture the image.

  5. An analog (e.g., videotape) or digital recording device (e.g., computer or DVD recorder) to store the video.

  6. Capability to replay and/or edit the recording.

    The basic equipment setup for laryngoscopy with stroboscopy.

    Fig. 6.4 The basic equipment setup for laryngoscopy with stroboscopy.

Some systems also come with a foot pedal to control the characteristics of the light source and to trigger video recording. The endoscope, whether flexible or rigid, allows for an appropriate field of view. There are many endoscope options available commercially in the United States and Europe, and there are many options for the other necessary equipment for LVS. Two of the most important elements of a stroboscopy system are the choice of endoscope and the type of light source used to visualize the larynx. These are described in more detail below.

6.6.1 Endoscopes

Two categories of endoscopes are used during LVS: rigid or flexible, and sometimes both. ▶ Table 6.2 compares and contrasts characteristics of these two options. Rigid endoscopes are made of metal and come with a lens at the tip that is angled at either 70 or 90 degrees (▶ Fig. 6.5). The lens angle is a matter of preference, but one difference is that the 70-degree lens does not require as deep an insertion into the pharyngeal region to allow visualization of the laryngeal structures versus a 90-degree endoscope. At the opposite end, the lens is an optical eyepiece which can be viewed directly or coupled to a camera. Just in front of the eyepiece on the underside of most rigid endoscopes, there is a fiberoptic cone to which a light cable can be attached. Alternatively, the endoscope may be constructed with the light cable fixed to the endoscope. The fiberoptic cable allows light to project internally through the endoscope to illuminate the larynx. Rigid endoscopes are passed through the mouth, with the patient leaned forward, protruding their tongue while sustaining the /i/ vowel. The resolution achieved with rigid endoscopes is much better than standard flexible fiberoptic endoscopes, providing a clear, well-illuminated, and larger view of the larynx and vocal folds. Camera settings can allow for adjustments to brightness, contrast, and color to best visualize tissues.

Table 6.2 Characteristics of rigid versus flexible laryngeal endoscopes (laryngoscopes) for laryngeal endoscopy with stroboscopy (videostroboscopy)


Rigid laryngoscope

Flexible laryngoscope

Rigid metal construction

Flexible plastic/rubber construction

Inserted through oral cavity

Inserted through nasal cavity

When needed, topical anesthesia to oropharynx

When needed, topical anesthesia to nasal cavity

70 or 90° angled lens

Different shaft diameters available—angle of tip adjustable

Can be coupled to standard or high-definition cameras

Chip-in-the-tip high-definition scopes available

Rigid metal construction

Flexible plastic/rubber construction


Larger image with greater resolution

Any vocalization possible

Greater visible detail of vocal pathology

Less likely to elicit gag reflex

Requires topical anesthesia less frequently—fewer barriers to use by SLP

Video endoscopes can provide images rivaling HD rigid scopes

Tolerated by vast majority of patients

Tolerated by vast majority of patients

Does not require lubricating gel

Patient can be examined in more natural sitting position


Limited to vowel production

Smaller image with less resolution using standard fiberscopes

More likely to elicit gag reflex

Requires topical anesthesia more frequently than rigid laryngoscope

Requires unusual positioning for patient

Video endoscopes very expensive

Example of lens angle in a 70-degree laryngoscope.

Fig. 6.5 Example of lens angle in a 70-degree laryngoscope.

The typical flexible endoscope used for laryngoscopy is made of flexible plastic and rubber and is constructed with mechanical parts not present in a rigid endoscope (▶ Fig. 6.6). One end of the endoscope contains the main control body to which a number of components are connected. These include an eyepiece, a fiberoptic cone, and a control knob to control angulation of the endoscope tip, and depending on the endoscope model, various ports can be inserted and routed along with the main shaft of the endoscope. The main shaft is flexible and contains light-conducting glass fibers (thus, they are sometimes referred to as fiberoptic endoscopes). The main shaft can vary in diameter between 2 and 4 mm, with smaller diameter scopes used for pediatric populations. At the end of the shaft is a bendable tip whose angulation is manipulated by the control knob on the control body of the endoscope.

Example of the control knob and flexible tip of a flexible laryngoscope.

Fig. 6.6 Example of the control knob and flexible tip of a flexible laryngoscope.

Flexible endoscopes are passed through a nostril (they are also referred to as nasoendoscopes) so that the tip rests in the pharyngeal space, pointed down toward the larynx. They do not interfere with articulation like a rigid endoscope, so that the patient can produce any type of speech sound the clinician asks of them. However, the image size projected through the lens is smaller than that through a rigid endoscope, and has less resolution. However, recent technological advances have made available video endoscopes with a charged couple device (CCD) chip and electronics at the distal end of the bendable tip wired back through the shaft and controlled by a video processor. These are also referred to as “chip-in-the-tip” or “distal chip” endoscopes, and are equivalent to having a video camera built into the tip. These endoscopes can significantly increase resolution and resulting image clarity even when the image is enlarged on a video screen. Images from current high-definition video endoscope technology rival those from rigid endoscopes, although current flexible video endoscopes have larger diameter shafts which can make the examination less comfortable for some patients.

The choice of endoscope used for LVS depends on desired image quality, the type of vocalizations needed for diagnostic purposes, and patient tolerance. Currently, the best image quality can be obtained from rigid endoscopes and chip-in-the-tip flexible endoscopes, especially high-definition versions. Some flexible fiberoptic endoscopes do not illuminate and/or capture sufficient light to thoroughly assess vocal fold vibratory dynamics, which can make accurate interpretation of an LVS examination difficult (▶ Fig. 6.7). Rigid endoscopes, however, limit vocalizations to a sustained vowel-like productions. Flexible endoscopes allow the clinician to assess vocal fold and laryngeal behavior during varied vocal tasks, including connected speech produced with habitual patterns. This can sometimes provide valuable information that would be lost if only a rigid endoscope is used.

Images taken from the same patient only minutes apart with a flexible endoscope (a) and a rigid endoscope (b).

Fig. 6.7 Images taken from the same patient only minutes apart with a flexible endoscope (a) and a rigid endoscope (b).

(From Kendall K, Leonard R. Laryngeal Evaluation, 1st ed. New York: Thieme Publishers, 2010.)

Most patients, with the proper procedural technique, can tolerate rigid endoscopy for LVS. There is a small subset of patients who, no matter how skilled the clinician or how great the amount of topical anesthetic applied, are unable to suppress their gag reflex so that adequate frames of video can be obtained. In these cases, the only option is to switch to a flexible endoscope. And to make things even more interesting for you, there is a small subset of patients who tolerate a rigid endoscope, with or without topical anesthesia, much better than a flexible endoscope due to nasopharyngeal hypersensitivity.

6.6.2 Light Source

Market-leading videostroboscopy systems use either light-emitting diodes (LEDs) or a combination of halogen and xenon bulbs for constant and stroboscopic illumination. LED lighting has the advantage of efficiency, bulb lifespan, low heat output, and economical pricing. However, depending on the quality and construction of the LED array, illumination may not be as good as halogen/xenon light, especially when viewed through a flexible endoscope. Newer LED technology is advancing and overcoming this shortfall. Color temperature will also vary depending on the light source, making the visual perception of tissue color somewhat different depending on the type of light being used.

Most stroboscopy systems allow for manual light adjustment during the exam which, along with camera color balancing technology, can visually approximate true tissue color. Light intensity and color balance must be continually monitored, however, as these factors can alter visual perception of the epithelial surfaces and affect potential diagnostic decisions. Alternatively, color balance can be manipulated by the examiner to better detect specific visual characteristics, such as vascular features of the vocal folds and surrounding laryngeal tissue. Clinicians should become familiar with the light source and camera controls specific to their stroboscopy equipment so that adjustments can be made when needed.

The stroboscopic light flash rate is set at a frequency slightly lower than the actual Fo being produced to give the visual illusion of slowed vibratory movement. The speaker’s Fo can be detected via a microphone placed on the anterior neck (e.g., a contact microphone) or on the endoscope itself, and the signal is fed back into the light source to modulate the strobe flash rate. Other systems can create a stroboscopic effect using a constant light that is shuttered at a high frequency by camera technology. Most stroboscopy systems allow for at least two modes of examination: (1) a slow mode which produces the illusion of slow motion and (2) a locked mode which produces the illusion of a freeze-frame or still image when the vocal folds are vibrating in a periodic fashion.

6.7 Laryngoscopy and Stroboscopy Procedural Technique

Experience performing laryngoscopy with stroboscopy will lead to clinician’s skill and comfort in the procedural aspects of the exam in addition to personal preferences in the examination approach. The following are the authors’ recommendations for laryngoscopy with stroboscopy procedure, although it is understood that there may be a wide variation in clinician preference for many dimensions of this protocol. The key to this examination, regardless of procedural approach, is obtaining a focused and well-lit visualization of the larynx and full view of the vocal folds along their entire horizontal length.

6.7.1 Preevaluation

  1. Exam records—if the patient has previously been evaluated by an otolaryngologist, those records should be obtained and reviewed prior to the evaluation. Information from these previous laryngeal exams can help guide the subsequent clinical protocol.

  2. Equipment and materials should be set up so that they are in easy reach of the examiner. In addition to the stroboscopy system, supplies needed for rigid and flexible examinations will include

    1. Personal protective equipment—at minimum, gloves.

    2. Gauze (rigid laryngoscopy)—This will be used to hold the patient’s tongue during the examination. We prefer 4 × 4 pads which are then unfolded and then refolded lengthwise.

    3. Cup of warm water (rigid laryngoscopy)—This will be used to warm the tip of the endoscope to prevent fogging once inserted into the patient’s mouth.

    4. Lubricant (flexible laryngoscopy)—This may help ease passage of the endoscope through the nasal cavity. Lubricant may be applied to the flexible shaft near the endoscope tip, being careful not to smear any material on the lens.

  3. Endoscope preparation.

    1. Endoscopes are coupled to the camera head securely and either placed on top of a sterile pad within easy reach of the examiner or mounted to an equipment rack if purchased for the system.

    2. Once secure in the camera head, the endoscope light cable is connected to the external light source.

    3. The light source is activated while the endoscope is placed over a white surface (for automatic color balancing) and an object with one or more images for focusing. The video monitor will need to be turned on for this step. We use a piece of gauze for automatic white balancing, or a sheet of white paper. If the computer keyboard is white with black letters, we use those to focus the image, or otherwise a sheet of white paper with printed letters.

    4. When using a flexible endoscope, we then apply a thin film of lubricant to the end of the shaft near the tip.

    5. When using a computerized recording system with software that controls the video capture, we use this time to enter patient examination data and prepare the software for recording a new examination. For systems that come with report templates as part of the software, this is a good time to include patient demographic and history information.

6.7.2 Greeting and History

It is customary for the SLP to greet the patient in the waiting room. Some clinics may prefer to have a nurse or aid greet the patient and bring them back to the exam room. In either case, time is taken to say hello, introduce yourself to the patient, and ask the patient how they are doing. This conversation often takes place while walking with the patient to the exam room, or immediately upon entering the room. By careful listening to a patient’s responses during these initial greetings, the clinician can get an idea of potential anxiety that can later be mitigated prior to and during the examination.

After initial greetings and once in the examination room, we recommend introducing yourself in a formal manner so that the patient has a clear idea of your position and role in the examination about to take place. An example script one might use is as follows (assuming you have already greeted the patient by telling them your name):

“I am a speech-language pathologist by training, and one of my areas of specialty is evaluating and treating voice problems. One of the ways that I evaluate the voice is by looking at the larynx—or voice box—where the vocal folds are located. I can do this with an endoscope—a special camera that allows me to see what is going on inside your neck where your larynx and vocal folds are located. You were referred here today so that we can get some pictures and video of your larynx. This exam is relatively easy for most people and, if we get good images, it should only take 5 or 10 minutes to complete. I will explain to you how we will get these pictures, but first let me know if you have any questions about what I just explained.”

The next step is to obtain history information from the patient which would help explain their referral for the examination. When otolaryngology records are available prior to the examination, important history information can be obtained which can be used to devise follow-up questions for the patient’s report of history. We typically begin this part of the exam by asking the patient, “Can you tell me why you were referred here today (or why you are here today, for those who are self-referrals)?” or “Tell me what has been going on with your throat and your voice.” Important follow-up questions are the same as those described in the history section of Chapter 3.

6.7.3 Procedure Explanation

Now that you have a concise history, and the patient understands who you are and what you are about to do, you provide them with further explanation of the examination process. Below are examples of scripts you might use for rigid and flexible examinations, respectively. When showing the patient the rigid or flexible endoscope, it is important not to “threaten” them by pointing it or thrusting it toward them. Hold the endoscope close and in front of your body. The following is an example of what you might say for a rigid laryngoscopic examination:

“To get pictures of your larynx and vocal folds I am going to use this scope (hold the endoscope while standing in front of them but away from their face.) I am going to ask you to sit forward in the exam chair, lean your torso forward and stick out your neck almost like you were trying to sniff something that was in front of you (give a visual model for the patient). I will then ask you to open your mouth and stick out your tongue, and I will gently hold your tongue with some gauze. I will gently place the tip of the scope inside your mouth—don’t be intimidated by the length of this shaft because only a small portion of the scope will sit in your mouth.”

“During the exam I will ask you to take easy breaths and then say the /i/ sound—like this (give an auditory model of the /i/ vowel, holding it out for about 5 seconds at a comfortable pitch and loudness). It can be difficult to say the /i/ sound with me holding onto your tongue and the tip of the scope in your mouth. It is the attempt at /i/ that is important—you might hear me say ‘try for more of an /i/ sound’ during the exam. This is because some patients start out saying /a/ instead of /i/. The /i/ sound is best because it opens the throat and will give us the best view of your larynx and vocal folds. If you have trouble saying the /i/ sound, sometimes it can help if you smile while saying it, or gently close your teeth around the scope. Remember to take a breath every 4 or 5 seconds, and then just keep saying the /i/ sound until I tell you to do something different. It will also help if you keep your eyes open during the exam so that you can see what is going on—I will remind you to breathe and open your eyes if you forget.”

Follow this by having the patient practice sticking out their tongue and prolonging the /i/ vowel for about 4 or 5 seconds, and then take a breath in between productions. When the patient has demonstrated competency in doing this, ask them if they have any questions before you begin.

6.7.4 Positioning and Endoscope Technique

Clinician Position

In the combined experience of the authors, we have found that, for right-handed individuals, positioning oneself on the right side of the patient (as they are facing you) is best. Alternatively, left-handed individuals may find placing themselves on the left side (as they are facing you) is best. However, there is no hard rule and the clinician should determine what configuration will allow them to best handle the endoscope while being able to view and record the video image. Some clinicians also choose to sit in a chair while performing the laryngoscopic exam. When a foot pedal control is used to control the light source and recording, it will be placed within easy reach of the examiner’s foot while they are standing or sitting.

Patient Position

For rigid laryngoscopy, the patient sits in the examination chair, which might be elevated so that the patient’s mouth is at the clinician’s eye level. Per previous instructions to the patient, they are asked to sit forward in the chair, lean forward, and protrude their chin as if they were sniffing something in the air, and stick out their tongue (▶ Fig. 6.8). The vast majority of patients will be able to complete the examination in this posture. On occasion, patients may have anatomical differences, whether congenital or acquired (e.g., subsequent to treatment for head/neck cancer), or behavioral reactions to the procedure that necessitate experimentation for the posture that will allow the best visualization of the larynx. In these cases, the examiner needs to be patient and calm, and allow for more time in the process. Having the patient lean farther forward in the chair, sit upright, or even reclined back are just some of the alternative positions that might be attempted to obtain adequate images.

Patient and examiner positioning for rigid endoscopy.

Fig. 6.8 Patient and examiner positioning for rigid endoscopy.

(From Kendall K, Leonard R. Laryngeal Evaluation, 1st ed. New York: Thieme Publishers, 2010.)

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Feb 25, 2020 | Posted by in OTOLARYNGOLOGY | Comments Off on Laryngeal Endoscopy and Stroboscopy
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