In order to visualize the vocal folds, experts at the Grabscheid Voice and Swallowing Center of Mount Sinai use scopes that provide light and relay images back to a camera and computer. However, because the voice requires moving vocal folds, we use stroboscopy. When you speak or sing, the vocal folds vibrate periodically – usually between 100 to 220 times per second (Herz). By nearly syncing the light flashes from a xenon bulb with the vibratory rate of the vocal folds, we can see them move at different points in the vibratory cycle. For example, if you are sustaining an “EE” at a middle C, your vocal folds will be vibrating 262 times per second. If the strobe light flashes 263 Hz, then they will appear to vibrate once per second. This enables us to see the fine mechanics of the vibratory cycle and is critical for evaluating the voice. If the vibration is not detected, that means the voice is not either. At the Grabscheid Voice and Swallowing Center of Mount Sinai, our experts have more than 25 years of experience assessing voices with stroboscopy.
Vocal Fold Symmetry Evaluation
Because the voice makes use of two vibrating folds, we are looking for symmetry in many aspects of the vibratory cycle. Some of these include:
- Adduction/abduction: this is the opening and closing of the glottis (space between the vocal folds) as you inhale and speak.
- Vertical phase progression: the vocal folds start each cycle with the lower edge or lip coming together first. We look for symmetrical (Left vs Right) and orderly vertical phase movement.
- Vibratory closure: if the folds are not coming together along their length or if there is a gap at the back edge of the folds, either could indicate anomalies such as unevenness, lesions, or even muscle tension.
- Mucosal wave progression: the white top layer of the folds is called the mucosa. As air pressure builds during each cycle, this surface layer bunches up. When the vocal folds separate, this ‘wave’ of mucosa moves across the folds from the glottis outward toward the edges. Stiffness from tension, scar tissue, or lesions can arrest this wave action, and stroboscopy is the only way to see this.
Types of Stroboscopy Scopes
Two different kinds of scopes are used for stroboscopy. The rigid scope is placed on the tongue and looks over the back edge. It does not go down your throat – just to the back of the mouth. Because the rigid scope can have a larger diameter, it often provides a better, more detailed and well-lit image. Sometimes a thin (3mm) flexible scope is used. This is placed through the nose and sits behind your uvula. This nasoendoscope allows us to see more of the throat and the nasal passages in addition to the vocal folds. Because the camera chip is at the leading tip of this scope, it can also provide a very clear, detailed picture.
What to Expect at Your Stroboscopy Voice Evaluation
You will be seen by a team of specialists at your vocal evaluation visit. Speech therapists who specialize in voice (vocologists) will be looking and listening for how you make use of your voice. An ENT physician who specializes in the voice (laryngologist) will assess the tissues, innervations, and function of the voice. A thorough history is taken of your dysphonia (hoarse voice), as well as other health problems, medications that may affect the voice, and voice use patterns. As we listen to your voice, we are refining the list of factors that may be causing your dysphonia. Based on our assessment, we will use either the rigid scope or the transnasal flexible scope. The stroboscopy exam only takes 1-2 minutes. We will have you try different sounds and pitches with your voice so that we can see how the tissues respond to different demands.
When the exam is done, the team will review the digitized file with you. Together we arrive at a treatment plan that may or may not involve therapy with a speech-language pathologist, medications, or physical treatments such as injections or surgery. Let us know if you would like a copy of the still photos we capture to hang on your refrigerator!