A stroboscopy is a specialized diagnostic procedure used to examine the vocal folds and larynx. It provides a detailed view of how the vocal folds vibrate, essential for diagnosing various voice problems. This non-invasive test helps clinicians identify subtle issues not visible in routine examinations. It is a crucial tool for assessing vocal fold function and detecting abnormalities affecting voice quality.
Understanding Stroboscopy
The fundamental principle behind stroboscopy involves creating an optical illusion of slow-motion vocal fold movement. Vocal folds vibrate at very high speeds, making their motion appear as a blur to the unaided eye. To overcome this, a stroboscopy system uses a rapidly flashing light, synchronized with the patient’s vocal pitch. A microphone on the neck detects the fundamental frequency of the voice, triggering the strobe light.
The flashes are timed to occur at a rate slightly different from the vocal fold vibration frequency. This timing illuminates successive points in the vibratory cycle, and persistence of vision merges these “snapshots” into continuous, slow-motion movement. This illusion allows clinicians to observe intricate movements of the vocal folds in detail, which is not possible with continuous light sources.
When Stroboscopy is Recommended
A stroboscopy is often recommended for persistent or unexplained voice changes. Common symptoms include hoarseness lasting more than two weeks, vocal fatigue, or changes in vocal pitch or quality. Patients might also report difficulty projecting their voice, a sensation of something stuck in the throat, or a history of vocal injury.
This procedure is valuable when a standard laryngoscopy, which provides a general view of the larynx, does not fully explain the voice disorder. Stroboscopy can identify specific vocal fold lesions, such as nodules, polyps, or cysts. It also helps diagnose conditions like vocal fold paralysis or scarring, providing a precise understanding of the underlying cause of a voice problem.
The Stroboscopy Procedure
Before the procedure, there is typically no special preparation required, such as fasting.
During the examination, the patient is usually seated comfortably. A small, flexible or rigid endoscope, a thin tube with a camera, visualizes the vocal folds. A topical numbing medicine may be sprayed into the nose or mouth to enhance comfort and minimize the gag reflex, though some mild discomfort or a sensation of gagging can still occur.
The endoscope is inserted, either through the nose or mouth, to reach the area above the vocal folds. Once positioned, the patient produces various sounds, such as sustained “eee” sounds at different pitches and volumes. As the patient vocalizes, the synchronized strobe light illuminates the vocal folds, allowing observation of their “slow-motion” vibration on a video monitor. The entire procedure is quick, typically lasting only a few minutes.
What Stroboscopy Reveals
The information gathered during a stroboscopy provides insights into vocal fold health and function. Clinicians observe several parameters to assess the vibratory characteristics of the vocal folds. Vocal fold symmetry evaluates if both vocal folds move in a mirror-like fashion, opening and closing at the same time and to the same extent. Asymmetrical movement can indicate a mass or tension difference between the folds.
Another parameter is the mucosal wave, referring to the wave-like motion of the vocal fold’s superficial tissue. A healthy mucosal wave indicates pliable tissue, while a reduced or absent wave can suggest stiffness, scarring, or lesions. Glottic closure, the extent to which vocal folds come together during vibration, is also assessed. Incomplete closure can lead to a breathy voice, while specific patterns of closure can point to particular pathologies.
The presence of non-vibrating segments, or areas of the vocal folds that do not move as expected, is also noted. This can be a sign of underlying stiffness or lesions inhibiting normal vibration. By analyzing these observations, clinicians can accurately diagnose specific vocal fold pathologies, such as nodules, polyps, cysts, or scarring, and develop targeted treatment plans.