2018 Section 6 - Laryngology, Voice Disorders, and Bronchoesophalogy

S INCLAIR ET AL .

FIGURE 3. (A) Translaryngeal ultrasound showing adducted vocal cords. (B) Abnormal ultra- sound showing the left vocal cord in abduction but continued medi- alization and immobility of the right vocal cord.

ated with transcutaneous laryngeal ultrasound. 26 However, in most studies, specificity for detection of vocal fold paralysis (VFP) is comparable to fiber-optic nasal endos- copy and the vocal cords are able to be visualized by transcutaneous laryngeal ultrasound 80% to 100% of the time (Table 2). Advantages of transcutaneous laryngeal ultrasound include its noninvasive nature, low cost, and increased efficiency if performed as part of another ultrasound examination. Pitfalls of transcutaneous laryngeal ultra- sound include less reliability in older and male patients because of thyroid cartilage calcification and potential interobserver variability. In addition, subtle vocal cord abnormalities, such as sequelae of superior laryngeal nerve injuries and vocal cord lesions and their composi- tion (cystic vs solid), especially those < 3 mm in size or those at the most anterior aspect of the vocal cords, are not well appreciated by transcutaneous laryngeal ultrasound. 26–30,32 Laryngeal stroboscopy is a tech- nique utilized to obtain a detailed evaluation of true vocal fold vibration. By using synchronized flashing light, stro- boscopy creates a pseudo-slow motion examination of the mucosal wave and vocal fold vibrations, which occur at speeds of 60 to 1500 cycles per second depending on phonatory pitch. 33,34 The magnified, decelerated view is derived from time-separated but cycle-coordinated sequences from successive vocal fold vibrations, and allows increased insight into subtle pathological findings. Rigid transoral examination is performed with the patient sitting upright, leaning forward, and slightly slouched in Secondary examination modalities Laryngeal stroboscopy.

curve for the technique is relatively short and may be accomplished in 30 to 50 cases. Table 2 26–30 lists findings of vocal cord function when assessed by transcutaneous laryngeal ultrasound compared to fiber-optic nasal endoscopy. Performance of transcutaneous laryngeal ultrasound is relatively simple, especially when already examining other cervical structures with ultrasound. Patients are positioned supine or seated with the neck slightly extended. A linear transducer set to 7 to 10 MHz is most often used for trans- cutaneous laryngeal ultrasound. Higher frequencies are unable to adequately penetrate the thyroid cartilage to allow visualization of the necessary structures. The optimal frequency varies and needs to be adjusted according to individual patient characteristics. Ample gel is used, and the probe is placed over the midportion of the thyroid car- tilage in line with the vocal cords. Alternatively, the probe may be positioned on the cricothyroid membrane and angled upward progressively until the true and false vocal cords and arytenoids are identified. The overall gain is usually increased to help visualize the true cords. The true vocal cords are classically described as hypoechoic, although they are often distinguished in part by a fine hyperechoic line. The false cords are easily identified as triangular-shaped hyperechoic areas. The arytenoids are visualized slightly posterior and lateral (Figure 1). The vocal cords may be examined during quiet respiration, although Valsalva maneuvers readily allow identification of complete vocal cord adduction. Abduction is visualized with inspiration (Figures 2 and 3). In addition to true and false vocal cord motion, vocal cord length and arytenoid position should also be assessed for symmetry that corre- late with normal recurrent laryngeal nerve function. 31 Subtle vocal cord abnormalities cannot be reliably appreci-

HEAD & NECK—DOI 10.1002/HED JUNE 2016

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