Published: March 18, 2025
Michael I. Orestes, MD, interviewed Shumon I. Dhar, MD, about the advantages of incorporating stroboscopy in evaluating patients with dysphonia, how the technology is advancing, and resources to refine your stroboscopy skills.
Why should otolaryngologists who already perform in-office laryngoscopy consider adding stroboscopy?
After taking the history of a patient experiencing dysphonia, endoscopic auditory-perceptual visualization of the larynx is essential for evaluation. The AAO-HNS Clinical Practice Guideline for Hoarseness specifically recommends laryngoscopy for patients with four weeks of dysphonia or those who are suspected of having a serious underlying condition.1
Stroboscopy, when added to laryngoscopy, has been shown to improve diagnostic accuracy in patients who are initially referred with vague diagnoses of non-specific dysphonia or “acute laryngitis”. Stroboscopy improves the diagnosis of benign vocal fold lesions, paresis, and carcinoma. The improved diagnosis after stroboscopy has been shown to lead to changes in final management in 40%–70% of cases.2,3
A wonderful study by Fritz et al. reported that of all the patients referred to their center for tertiary-level evaluation with a “diagnosis” of laryngopharyngeal reflux, 75% were found to have an alternative diagnosis using stroboscopy. The resulting diagnoses included muscle tension dysphonia, vocal fold sulcus/scar, and paresis.4
What do physicians need to know about stroboscopy?
Stroboscopy can be added to either transnasal flexible or rigid transoral laryngoscopy. Stroboscopic light uses the principle that a single image is retained on the retina for 200 milliseconds and when a series of individual images are presented in sequence to the eye, the brain will fuse them, leading to the perception of motion (Talbot’s Law).5 Stroboscopy machines can detect the fundamental frequency of vibration of a subject’s voice (via a contact microphone on the neck) and then turn the strobing light frequency several hertz above it. This leads to the appearance of slow pseudo-motion where individual frames of the glottic vibratory cycle are perceived to be fused together in apparent motion. We can then review the videos frame by frame or in slow motion to enhance our diagnostic acumen.
How do you perform a stroboscopy?
After recording voice samples and performing the basic laryngeal endoscopic exam, we move to stroboscopic examination. We start by watching quiet respiration. Then we instruct the patient to make a modal register “eeee” sound, both soft and loud. Then a series of repeated “eee-eee-eee” sounds. After that, we ask the patient to do a voice glide or glissando, holding the highest frequency. We then focus the exam on the patients’ specific voice complaints and lastly test high soft phonation and inhalation phonation.
What tips do you have for interpreting stroboscopy recordings?
Having a systematic approach to reviewing stroboscopy videos ensures consistency and accuracy. I start with the general appearance of the vocal folds, assessing whether the edge is straight, convex, concave, irregular, or discolored. I also check if the vocal folds are of similar vertical height. Next, I evaluate the pattern of glottic closure—is it complete, hourglass-shaped, or does it have an anterior or posterior chink?
I then assess the vocal fold mobility of each cord, followed by phase symmetry—are the mucosal waves on the right and left vocal folds in sync? I also analyze the phase closure pattern, noting whether the vibration is open-phase or closed-phase dominant. Next, I pay attention to the amplitude or the excursion of the mucosal wave and the magnitude of the wave movement. I then examine periodicity, looking at how consistently the vocal folds vibrate. Lastly, I assess hyperfunction or the activity of supraglottic movement during phonation.
There is no single “correct” way to analyze a stroboscopy video, but developing a system helps ensure consistent interpretation. The Voice-Vibratory Assessment with Laryngeal Imaging (VALI) form is an excellent resource for those who want to deepen their understanding of stroboscopic analysis.6
How do you see the field of video stroboscopy evolving in the next five to 10 years, and how should training programs adapt?
As with everything in medicine, artificial intelligence (AI) is moving diagnostic technology forward at a rapid pace. Deep learning using convolutional neural networks has been successful in identifying serious pathologies, such as squamous cell carcinoma,7 as well as benign findings such as nodules, polyps, and leukoplakia. Newer advances in deep learning programs can outperform novices and approach expert level.8–10 Even for subtle pathologies like vocal fold sulcus, AI can achieve diagnostic accuracy comparable to laryngologist experts.11
Although these developments are impressive and useful, I still feel that there is a need for humans to become familiar with the nuances of stroboscopy. Otolaryngologists will remain the benchmark by which AI is measured as the technologies continue to advance.
Further, there are certainly benefits to performing stroboscopy beyond strictly confirming the initial diagnosis. Understanding a patient’s stroboscopic exam allows us to understand the physiologic changes we are visualizing and seeking to correct through treatment. Seeing how a patient’s exam changes over time, and seeing how treatment affects physiology (and therefore the exam) also allows us to grow as diagnosticians and surgeons. Trainees will continue to benefit from understanding stroboscopy and we must work towards understanding rather than racing towards the diagnosis.
What new resources exist for otolaryngologists who want to up their stroboscopy game?
For me, the key to mastering stroboscopy interpretation is reviewing as many recordings as possible, from those that show obvious disease to subtle manifestations of pathology that are not “textbook”. This repetition is needed for trainees to master stroboscopy interpretation.
When I was initially learning the nuances of stroboscopy analysis, all the resources I came upon were written articles and textbooks. A wonderful resource was the seminal textbook, Stroboscopy, by Peak Woo, MD.5 However, given that stroboscopy is a video-based diagnostic tool, I wanted—but was unable—to find a video-based learning tool.
Years later, a group of young laryngologists (me included) have pooled their resources to create a free, searchable video atlas online, Stroboscopy.org, with numerous recordings of normal patient variations as well as pathological diagnoses (e.g., scars, sulci, cysts, laryngeal dystonia). All videos are curated by an editorial board and sourced from voice professionals across the globe. The site even includes videos on non-stroboscopy topics such as in-office laryngology procedures.
This initiative inspired two committee-sponsored courses offered at the most recent AAO-HNS Annual Meeting: Stroboscopy 101, a panel that delves into the full range of challenges and considerations for incorporating stroboscopy into an otolaryngology practice, and Stroboscopy 201, which focuses on stroboscopic interpretation skills as well as application in clinical practice using examples sourced directly from Stroboscopy.org. We hope to continue offering these courses at future meetings.
I encourage otolaryngologists of all experience levels to visit the website, browse the atlas, and contribute their own stroboscopy videos. The Stroboscopy.org team’s mission is to provide the best resource for learning the science of stroboscopy, which we hope will ultimately lead to better care for patients suffering from diseases related to the voice.
References
- Clinical Practice Guideline: Hoarseness (Dysphonia) (Update) - Stachler - 2018 - Otolaryngology–Head and Neck Surgery - Wiley Online Library. Accessed March 2, 2025. https://aao-hnsfjournals.onlinelibrary.wiley.com/doi/10.1177/0194599817751030
- Cohen SM, Kim J, Roy N, Courey M. Factors influencing referral of patients with voice disorders from primary care to otolaryngology. Laryngoscope. 2014;124(1):214-220. doi:10.1002/lary.24280
- Cohen SM, Kim J, Roy N, Wilk A, Thomas S, Courey M. Change in diagnosis and treatment following specialty voice evaluation: A national database analysis. Laryngoscope. 2015;125(7):1660-1666. doi:10.1002/lary.25192
- Fritz MA, Persky MJ, Fang Y, et al. The Accuracy of the Laryngopharyngeal Reflux Diagnosis: Utility of the Stroboscopic Exam. Otolaryngol Head Neck Surg. 2016;155(4):629-634. doi:10.1177/0194599816655143
- Woo P. Stroboscopy. Plural Pub.; 2010.
- Poburka BJ, Patel RR, Bless DM. Voice-Vibratory Assessment With Laryngeal Imaging (VALI) Form: Reliability of Rating Stroboscopy and High-speed Videoendoscopy. J Voice. 2017;31(4):513.e1-513.e14. doi:10.1016/j.jvoice.2016.12.003
- Azam MA, Sampieri C, Ioppi A, et al. Deep Learning Applied to White Light and Narrow Band Imaging Videolaryngoscopy: Toward Real-Time Laryngeal Cancer Detection. The Laryngoscope. 2022;132(9):1798-1806. doi:10.1002/lary.29960
- Cho WK, Choi SH. Comparison of Convolutional Neural Network Models for Determination of Vocal Fold Normality in Laryngoscopic Images. J Voice. 2022;36(5):590-598. doi:10.1016/j.jvoice.2020.08.003
- Ren J, Jing X, Wang J, et al. Automatic Recognition of Laryngoscopic Images Using a Deep-Learning Technique. Laryngoscope. 2020;130(11):E686-E693. doi:10.1002/lary.28539
- Tran BA, Dao TTP, Dung HDQ, et al. Support of deep learning to classify vocal fold images in flexible laryngoscopy. Am J Otolaryngol. 2023;44(3):103800. doi:10.1016/j.amjoto.2023.103800
- Kavak ÖT, Gündüz Ş, Vural C, Enver N. Artificial intelligence based diagnosis of sulcus: assesment of videostroboscopy via deep learning. Eur Arch Otorhinolaryngol. 2024;281(11):6083-6091. doi:10.1007/s00405-024-08801-y
