Doctors and other medical specialists have always been on the lookout for techniques that would allow them to visualize the internal organs and structures of the body without the inconvenience of actually having to slice a patient open and look for themselves. Much of the diagnostic prowess of modern clinicians rests on the use of advanced applications of the electromagnetic spectrum to penetrate the skin and develop a picture of what lies beneath. X-Ray, Magnetic Resonance Imaging, and Positron Emission Tomography have all become routine medical imaging procedures.
But one of the oldest techniques developed for this purpose is simply using lights, cameras, and mirrors to look into the body through the variety of natural orifices available without engaging in any knife work. This technique is called endoscopy and when the larynx and vocal apparatus specifically are being investigated, it is called laryngoscopy or laryngeal imaging. Laryngoscopy is a common and powerful technique used by speech language pathologists in diagnosing various speech and language disorders. Laryngial imaging is not a simple procedure so it is more likely to be used by medical SLPs who are working in medical settings like hospitals.
Image-based analysis of the vocal folds vibrating can play an important role in diagnosing voice disorders. When the left and right vocal folds oscillate symmetrically, they can generally be ruled out as the source of vocalization problems. Direct observation via laryngeal imaging is the fastest and easiest way to confirm their behavior.
The technique is also sometimes used to investigate and provide therapy for dysphagia.
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Laryngeal Imaging Allows SLPs to View Vocalization in Action
Endoscopy was originally developed to investigate the larynx and only later was adapted to looking at other internal organs. As the first type of endoscopic imaging, it is also among the most common and most frequently used.
Although they might not be able to name it immediately, most Americans instinctively recognize this original type of laryngoscope from decades of medical television shows.
Every scene in a modern TV drama showing a patient being intubated—usually a moment of high drama—includes a cool, intense professional staring down a laryngoscope to thread the endotracheal tube through the patient’s vocal cords to keep their airway open.
The curved blade, mirrors, and lights of a basic laryngoscope look pretty intimidating and they effectively prevent the patient from even attempting to make a normal effort at speaking. In some cases, local anesthetic is used, making it even harder to observe the larynx in a normal way. Apart from observing gross topological malformation, this is very limiting for speech pathology uses.
Fiber Optics and High Speed Cameras Revolutionized Laryngeal Imaging
Fiberoptic endoscopes were developed in the early 1950s but didn’t become widely available until the 1990s. The thing, flexible tubing allows entry to be made through the nasal passages as well as the mouth, allowing more or less normal function of the rest of the body’s speech production apparatus—a valuable state for diagnosing abnormalities.
High-speed digital imaging has revolutionized this aspect of SLP diagnostic practice. The previous technology used in laryngeal imaging, slow-motion stroboscopy (SMS), allowed video frame rates of between 25 and 50 frames per second. This rate was not fast enough to capture the complete sequence of vibrations in the cords, so the resulting images were composites that required a lot in the way of expert interpretation by the SLP. The HSDI method, on the other hand, runs at 4000 frames per second… a rate easily fast enough to visualize the complete behavior of the vocal tract.
The downside to this high-speed technique is that it generates a lot of imaging to be reviewed. A skilled SLP is required to analyze the results. New AI-based imaging analysis efforts are attempting to use computer-analysis to automatically perform some tasks, such as identifying and tracking the position of the glottal gap.
Becoming Qualified to Perform Laryngeal Imaging
As you might imagine, special training is required before you are allowed to shove a camera into someone’s throat or nose. According to ASHA (American Speech-Language-Hearing Association), strobovideolaryngoscopy of any sort may be used by SLPs only for the purposes of assessing voice production and vocal function, or as a therapeutic aid and biofeedback system during treatment. They are not qualified to use the technique for medical purposes, so they frequently work together with otolaryngolists or other physicians both in performing laryngoscopy procedures and when evaluating the results.
State Licensing in Endoscopy
Because of this overlap in function, you will also need to consult your specific state licensing laws to determine if you can perform laryngoscopies as a speech-language pathologist. Many states do not explicitly address the issue, while others, such as Missouri and New Jersey, place it firmly within the SLP scope of practice. But others, such as Indiana, view endoscopy as an exclusively medical procedure and either prohibit SLPs from performing it or require they do so under the direct supervision of an individual with a medical license.
ASHA has a good summary of state-by-state endoscopy requirements on their website.
ASHA has developed standard policies on the knowledge and skills expected of SLPs making use of videoendoscopic imaging for both voice and swallowing disorders. It includes a model curriculum covering both administering the procedure and interpreting results. However, ASHA does not formally endorse any training or certification programs dedicated to laryngeal imaging.
The organization does recognize a Clinical Specialty Certification in swallowing disorders, the BCS-S (Board Certified Specialist – Swallowing). This expertise can be valuable for SLPs performing laryngeal imaging to investigate or treat swallowing-related conditions. The certificate is offered through the American Board of Swallowing and Swallowing Disorders. The credential is only open to currently certified CCC-SLPs. It requires:
- At least 7.5 continuing education units specific to dysphagia treatments within the past three years.
- A minimum of 3 years of post CCC-SLP practical experience with a focus in dysphagia treatment or research. Clinical track qualifiers must have 350 clock hours of evaluation or treatment activities, while academic track qualifiers must have 100 hours of that work and a position in academics or administration with a focus on dysphagia treatment.
- Perform additional activities, such as publishing or mentorship, demonstrating advanced experience in dysphagia treatment.
Having met these standards, you can obtain the BCS-S by paying a $100 fee and passing a written examination.
There are also two ASHA Special Interest Groups (SIGs) that have input and expertise on laryngeal imaging:
Training on the use of endoscopes is often offered by equipment manufacturers. Because most of the uses are medical in nature, SLPs in hospital settings will have more access to training and mentorship on the use of laryngoscopes. Physicians may be the best training resource for the basic procedure. However, SLPs have to rely on other SLPs to learn the specific techniques and information required to interpret imaging results for voice and dysphagia diagnosis and therapy.