| Disclaimer: The information contained within the Grand Rounds Archive is intended for use by doctors and other health care professionals. These documents were prepared by resident physicians for presentation and discussion at a conference held at Baylor College of Medicine in Houston, Texas. No guarantees are made with respect to accuracy or timeliness of this material. This material should not be used as a basis for treatment decisions, and is not a substitute for professional consultation and/or peer-reviewed medical literature. Laryngovideostroboscopy Good morning. Today is Baylor College of Medicine Grand Rounds. Today’s topic will be laryngovideostroboscopy. We will start today with an overview of the talk. We will talk about the case presentation. We will go over the history of laryngovideostroboscopy, which is LVS, the instrumentation involved in the exam. We will discuss laryngeal anatomy. We will talk about phonatory mechanisms, the principles of stroboscopy and the clinical evaluation of stroboscopy. So our case report, P.D. is an 80-year-old white female referred to The Methodist Hospital otolaryngology service with a one year history of hoarseness. She describes her speech as strained and strangled and her symptoms are worse with emotional stress. She denies any other head and neck complaints. Her past medical history is significant for hypertension and a recent onset of tremor. On exam, she is found to have a visible tremor of her lower jaw and tongue and on flexible endoscopy her vocal folds have intermittent rapid shortening with squeezing and quick glottic closure consistent with adductor spasmodic dysphonia. The remainder of her head and neck exam is normal. She was offered a laryngeal Botox injection for definitive treatment, which she completed successfully. She actually has had two treatments to date. She is currently doing well two months post her second treatment with significant improvement in her symptoms. I have some video. This is not her, but this is another patient with similar symptoms and this is just flexible laryngoscopy. This is a patient that we as residents see quite frequently during our training here. While seeing the scope really made me wonder how else can we visualize the larynx and how are other modalities useful and that is what sort of inspired today’s talk. When you look at the history of laryngovideostroboscopy, in 1806 Bossini was credited with designing the first endoscope and that is actually his scary looking device there. In 1829, Babbington described the clinical glottoscope, which is actually very interesting. It had something to retract the tongue and different spatulas to look down and attempt to visualize the glottis. In 1833, the principle stroboscopy was simultaneously discovered by Flasseau and von Stampler. In 1855, Manuel Garcia introduced the laryngeal mirror and indirect laryngoscopy was born. It is actually an interesting story. He was an Italian voice teacher who was not an otolaryngologist. He was walking down the street one day and saw the sun hitting the window and saw the effect of stroboscopy and then actually went out and got a dental mirror and with sunlight was able to visualize his own glottis. In 1878, Ortell was credited with using the first laryngostroboscope and in 1931 Cary and Guillea built the first electronic stroboscope. In 1960, the first major publication on stroboscopy by Shoinar was published and in the 20 th century this modality continues to have technologic advancements in both the stroboscopes and the video recording and we will talk about some of that today. Some definitions – this is basically breaking laryngovideostroboscopy down to all its roots. Endoscopy is a technique used by physicians to view internal parts of the body and laryngoscopy is of course viewing the larynx. Stroboscopy indicates the use of a particular type of light during direct visualization and strobos actually means whirling and videostroboscopy basically means making a permanent record of your findings. Utilization of LVS requires that the clinician can accurately operate the equipment, know the process of phonation, understand the principles of videostroboscopy, understand laryngeal disease as well as the limitations of the stroboscope. Your basic equipment – you have an endoscope, a microphone, a light source, an electronic control unit, camera, monitor, and recording equipment. This is your basic setup for a rigid scope with the camera, the electronic units, and light source and the monitor. The scopes can either be rigid or flexible. We will talk about this in a little bit. The cameras have gone from single chip technology to three chip technology and the video recorders have gone all the way fromVHS to digital recording. The microphone is used to trigger the stroboscopic light source. You actually put it up to the patient’s neck typically. It directs sound waves to the electronic control unit for filtration and amplification. What the microphone does is basically abstract the fundamental frequency of the patient’s voice while they are speaking during the exam. The control unit transmits the extracted fundamental frequency of the voice to the light source for a variable pulse illumination to the endoscope and we will talk about how this works in a little bit. The light source is typically either xenon or halogen. The endoscopes – you can use either flexible endoscopy or rigid endoscopy for stroboscopy actually. Flexible scopes do not inhibit the movement of the oral structures, but do require a powerful light source and provide smaller overall images. The rigid scopes do limit the oral structures, mainly you have to grab the tongue either with a 90 degree or a 70 degree scope, but you do get increased illumination and magnification. These are just two examples; one is a flexible scope and one is a rigid scope. This is actually the new Olympus Chip-tip Flexible Scope. The camera is actually in the tip of the flexible scope and it gives you better resolution as well as enhanced images and here is some video on that. You see you get very good definition. You can see the cords, examining the whole super glottic structure as well as the glottis itself. You can compare that to a standard rigid scope and you can see the increased definition you get as well as the increased magnification. Optics continue to evolve with the newer technologies and now really that the digital era has come along, everything will be shifting to mainly digital recording. This is just a diagram showing again a rigid scope with a high speed digital video. We will actually look at some of this in a little bit, but the signal actually goes right into the system and it goes right into memory for video frame analysis. Cameras that you put on the scopes continue to get better and improve. These are two examples and basically it is the more chips you get the better definition you get. So here is a single chip view and you have very good definition. You can see it is magnified very well, but if you compare that to a three chip camera, which you can enhance basically using a program very similar to an Adobe Photoshop, but you get increased resolution and you can clearly see the better picture. So now that you know how the equipment works, you really do have to appreciate the anatomy. This is just a general slide to show you the structures we are going to be dealing with today. The true and false cord, the epiglottis as well as the piriform sinuses should all be examined during the exam. So, just briefly, as we all know the larynx has a cartilaginous framework, which consists of the thyroid and the cricoid cartilages as well as posteriorly the arytenoid cartilages with the corniculate and the cuneiform cartilages. There are three basic groups of laryngomusculature. You have your abductor, which is basically your posterior cricoarytenoid, your tensor, which is basically your cricothyroid, and everything else is an adductor. What is the purpose of the folds? Well, it is fourfold really; airway protection, respiration, swallowing, and then finally phonation. The vocal folds are covered with a stratified squamous epithelium with no mucous glands. It has a highly specialized lamina propria which separates the epithelium from the underlying muscle and you see your superficial, your intermediate, and your deep layers. The superficial layer is typically your Ranke space and your deep layer is typically referred to as the vocal ligament. When you get some micrographs of this epithelium, it is actually very interesting. The lamina surface is actually covered with this little micro-ridge pattern and this is thought to assist with vibration and phonation. The desquamated layer of the squamous cells is actually functional until it is desquamated, which is different than the rest of the body. The skin, actually, before it is desquamated loses function here. As you can see in this micrograph, there are many organelles and it is thought to believe that this layer does stay functional until it is gone. This layer is also covered by a mucociliary blanket, which lies over the epidermis. Minus the vocal cords, the larynx is covered with a ciliated pseudocolumnar epithelium and this is what produces the mucociliary blanket over the epithelium. It actually has two layers to the blanket. There is a mucinous layer, which is the closest lumenal surface, and a serous layer, which contacts the cilia, and there have actually been studies, mainly on canines, but there are some human studies too, that show that flow of the mucociliary blanket is propelled up the trachea in a superior and posterior circular fashion and it is thought that this blanket keeps the folds healthy and moist under normal conditions. So when you look at vocal fold dynamics, the vibration of the folds gives the appearance of waves in the mucosal surface traveling in recurring cycles, and here is your recurring cycle and actually the cords are described as having a lower lip and an upper lip and you can see the wave traveling through. Propagation of the mucosal vibratory movement involves an alternating sequence of medial closing and lateral opening of the folds spreading from the lower to the upper lips along the medial surface of the fold. This diagram is really just to illustrate that although we see horizontal movement typically when we look at flexible laryngoscopy, there is also a vertical wave traveling simultaneously at the same time between the lower lip and the upper lip. So how does phonation work? Well, during phonation the vocal folds act as an energy transducer that converts aerodynamic power into acoustic power. The transduction occurs mainly in the glottis. Air is the medium for sound transmission and voice quality can be described by its acoustic characteristics. For all intents and purposes, it is basically again just plumbing, there is inflow and outflow. Your input comes from your supraglottal, glottal, and subglottal substructures, and then you have your theories of how phonation occurs, and then you have your output, which are your acoustic characteristics. This is again another slide basically showing the same thing, but your vocal power comes from your thoracic and your abdominal muscles. Your larynx is your oscillator and your supraglottic vocal tract is responsible for resonance. So, there are two main theories of how vibration occurs and how we phonate. One is the myoelastic aerodynamic theory, which was proposed by Vandenberg in 1958. The myoelastic part of it refers primarily to the neuromuscular control in the muscles of the larynx with neuromuscular control of the vocal fold, tension, and elasticity during phonation. This is also responsible for the configuration of the glottic aperture as we adduct. The aerodynamic aspect is basically the role of fluid dynamics in the setting of vocal folds is the vibration once they are adducted and this is where Bernoulli effect of airflow comes into play and that pulls the vocal folds medially as the air passes past them. Then there is the body cover theory. This theory is broken down into two principles, but it basically is responsible for the regulation of the fundamental frequency and the vocal folds have two main layers with different properties. You have your cover, which is the epithelium, the superficial and intermittent layers of the lamina propria and this is pliable and elastic, and you have your body, which is basically the musculature in the deep layer of the lamina propria including the thyroid arytenoid muscle. So when you merge these two theories, which is what I found in reading for this talk, both are pretty much accepted and everybody sort of just merges them together, but vocal fold vibration occurs in the cover and it depends on an interaction between the vocal fold muscles and subglottic pressure. Maintenance of vibration is performed with the folds brought close together by the laryngeal muscles. The cover is pulled together by Bernoulli force. Subglottic pressure pushes the folds apart and the elastic force of the muscles then pushes the folds back together and this repeats in cycles. It is about 100 per second for males and 200 for females. So what is fundamental frequency and frequency of the voice? Well frequency is the physical correlative of the perceptual phenomenon of pitch. It represents the number of times the vocal cords open and close per second and it is measured in Hz. The voice is a complex component comprising many frequencies, but the lowest fundamental frequency is what we preserve as somebody’s vocal pitch and actually in a bass voice that is about 60 Hz and in a soprano voice that is about 1500 Hz, so there is a wide range. At birth, our fundamental frequency is about 490 Hz and that descends to 280 by age ten. As the vocal folds lengthen and mass increases with puberty, the fundamental frequency decreases to 100 Hz in males and 200 Hz in females. So how does stroboscopy work and how do we pull this all together? Stroboscopy is based on Talbet’s law and it basically states that the naked eye can perceive no more than five distinct images per second and once present the image lingers on the retina for about 0.2 seconds. Therefore, if sequential images produced at intervals shorter than 0.2 seconds persist on the retina and fuse with other successive images, it produces an illusion of apparent motion. Basically your eye will catch these little strobes that happen quicker than 0.2 seconds along the field and your body and your brain essentially merges them all to make it basically make sense to yourself. To perceive an intermittently visible object, the visual system also detects what is corresponding and this is what actually merges all the images together. If successive images differing only slightly from each other are presented more rapidly than 0.2 seconds, the viewer will use his or her own innate unconscious knowledge of the world to fill in the gaps and this is motion. A natural correlate of this principle is that a clear image of an object vibrating too rapidly to be visible to the naked eye could be captured by illuminating the object with intermittent short flashes of light and this is where stroboscopy comes in. The flashes can be emitted in one of two ways to capitalize further on this phenomenon. If you flash the light at the same fundamental frequency as the voice, it is called synchronization and you actually get still images. You see the same point of the cycle each time. If you put a slight variation on the frequency, this is what is called asynchronization. In this, you pick up a different part of the cycle each time and this gives you your apparent motion. Synchronization of the vocal fold illumination with frequency of vibration allows the clinician to view any position of the folds to investigate their structure. Again, if you line up the strobe with the fundamental frequency and you vary it slightly, you will see different positions of the cord over and over again. This can also be used to determine if aperiodic vibration is present. So if the cycles are not periodic, but you keep your stroboscope light at the fundamental frequency and you see motion, then you may think that there is something wrong with the periodicity of the cycles, but that may also (and this is a limitation of the stroboscope) reflect problems with the pitch tracker on the microphone or the stroboscopic equipment. The asynchronized mode is typically generated by pulsing light either plus or minus 2 Hz of the frequency being phonated and when the resultant images are viewed successfully, the folds again appear to have movement and appear to form successive cycles, although as we will show in a little bit, these are actually just compiled images from many cycles. Again, that is the limitation with stroboscopy. It is critical to realize that this is apparent motion. It does not provide the detailed vibrations that you can find in viewing high speed photographs or digital images. So the stroboscopic images of one cycle are obtained from portions of several cycles that are not consecutive. The motion occurring between the cycles is unrecorded or lost data, so everything in between all the points that are not picked up by the stroboscope are essentially lost. Moreover, the system is coupled to video recording which typically is limited to 30-60 frames per second, although this is improving as well. The stroboscope offers affordability, ease of use, and a permanent record of the images. Again, this is on a rigid scope and this is a stroboscopic exam and you can see the folds and the apparent motion that you see as well as the vertical and horizontal traveling wave. You can compare this to high speed digital. There used to be high speed photography, now it is really becoming high speed digital video. High speed digital photography captures a greater number of images from each cycle. It is not merging the cycles together. The viewed images are actual recordings of the entire vibratory event. Because you are actually viewing the images from each cycle, periodicity is not a factor and does not affect the system because you are recording actual events. The downfalls of high speed video and photography is that it is expensive and data processing is time consuming. This is actually a new high speed video from the Kay-Elemetric System. These are actual size and you can really appreciate the increased definition, though not appreciably so through the stroboscopic exam. So what do you look at after you perform your stroboscopy, how are you going to evaluate your patients, and what should the otolaryngologist be looking for? Well, perceptual judgments of the vibratory patterns of the vocal cords are based on a knowledge of again the anatomy, the normal gross anatomic appearance to the fold, and the variance of mechanical properties of the fold as a function of frequency and intensity. Observations that you typically look for include symmetry, periodicity, glottic closure, amplitude of vibration, and mucosal wave ratings, and we will talk about each of these. Symmetry is exactly what it sounds like. This is the degree to which two vocal folds provide mirror images of each other during vibration. The symmetry of the timing of opening and closure and extent of lateral excursion of the folds are rated as either symmetric or asymmetric and again this diagram is showing the symmetry. What is amplitude of vibration? This is defined as the extent of horizontal excursion of the vocal folds during their movement and it is rated at normal pitch and normal loudness as well as during soft and loud conditions, and again here is the amplitude and they are symmetric. These look at movement and amplitude. Periodicity is the regularity of successive apparently cycles of vocal fold vibration. It is described as either regular, which is an image which will be static if aligned with the stroboscopic light, irregular where you have apparent motion, or inconsistent where you get motion, then you lose motion, and you get motion again. This is just a simple diagram showing cycles, which are periodic and aperiodic and then jitter and shimmer. So acoustic perturbations describe the random deviations from these cycles and regularity of cycle to cycle. So variations between the cycles are jitter and shimmer. Shimmer is random variability of cycle-to-cycle amplitude and jitter is defined as random variability of cycle-to-cycle frequency. When looking at the mucosal waves, you make mucosal wave ratings and they can range anywhere from absent to great. The waves are considered absent if there is no observable traveling wave that is present on the visible superior surface of the vocal fold and the mucosal wave rating may occur along the entire margin of the fold or restricted to a small segment. It is rated as small if the traveling wave is present, but difficult to observe and restricted to the medial edge of the fold, normal if the wave moves laterally half with width of the two folds, and great if the wave moves to the most lateral portion of the true folds. You also look at glottic closure and you can appreciate that on the exam. It is described actually as complete or incomplete and the pattern of closure is evaluated by matching the glottic configuration at a maximum closure during normal pitch and at typical closure patterns and these are just six typical closure patterns going anywhere from posterior gap to a spindle cell closure to an hourglass closure to complete closure. You also want to look at the supraglottic structures. They are observed to determine how they move as a function of the phonatory path. They normally do not appear to move appreciably, but you do want to look again, as we pointed out before, at the arytenoids, the ventricular folds, the epiglottis as well as the function of how they are all working together. So how do you apply this clinically? Well, the theory and the theoretical applications of LVS have been well publicized and there is actually much in the literature about it. Clinically, we are lagging behind, but there are some articles, which came out in the last decade, which are showing some promise. In 1991, Sataloff studied 350 patients with LVS and reported that he had a 32% diagnostic change based on his stroboscopic exam. Woo followed in the same year, but only reported a 10% change in diagnosis in their series and Casiano in 1992, a year later, followed with a change in diagnosis or additional findings in 43% of 375 patients. But basically there are no prevailing standards for stroboscopic recording. The who, when, and what to record are left up to the examining physician. The patient pathology and the laryngeal condition dictate the test protocol and not all persons with the same pathology exhibit the same vibratory pattern. Nevertheless, there are patterns associated with specific pathologies because of the way the disease affects the body cover relationship and if you do enough of these exams you can really appreciate that. LVS continues to revolutionize the clinical diagnosis and treatment of voice disorders and it permits direct visualization of both the structure and function of the larynx as well as creates a permanent record. The resultant video images captured provide the means of observing shape, movement, vibratory pattern as well as the primary relationship of vocal fold vibration and this allows the clinician to make better diagnoses and provide appropriate treatment based on anatomy and physiology of the system. Interpretation of this data requires knowledge of phonation and the potential pathologies as well as some specialized training, but the LVS remains only one part of a clinician’s exam and as such is a valuable supplement to the other currently diagnostic procedures available to the otolaryngologist. Case Presentation Her PMH is significant for HTN and recent onset of tremor. On exam, she is found to have a visible tremor of her lower jaw and tongue. On flexible endoscopy, her vocal folds have intermittent rapid shortening and squeezing with quick glottic closure consistent with abductor spasmodic dysphonia. The remainder of her head and neck exam is normal. She was offered laryngeal Botox injection for definitive treatment, which she completed successfully. She is currently doing well two-months post-treatment with significant improvement in her symptoms. Bibliography: Anastaplo S, Karnell MP. Synchronized videostrobosopic and electroglottographic examination of glottal opening. J Acoust Soc Am 1988;83:1883-90. Bastian RW, Collins SL, Kaniff T, Matz J. Indirect videolaryngoscopy versus direct endoscopy for larynx and pharynx cancer staging. Ann Otol Rhinol Larynhol 1989;98:693-8. Beaver ME, Stasney CR, Weitzel E, Stewart MG, Donovan DT, Parke RB Jr, Rodriguez M. Diagnosis of laryngopharyngeal reflux disease with digital imaging. Otolaryngol Head Neck Surg 2003;128:103-8. Berke GS. Voice disorders and phonosurgery. 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