Raising the Vocal Pitch

1. Cricothyroid approximation, the first procedure ever described to alter vocal pitch. As the name implies, it involves bringing the thyroid and cricold cartilages together by suturing, keeping the vocal cord in tension, thus elevating the vocal pitch. This method was introduced by Isshiki1 in 1976, which he performed in 2 patients, followed by a larger series in 1983 in which he successfully raised the vocal pitch in another 11 patients2. The primary indication in both of his series was androphonia in the female. However, the pitch increase using this approach was often insufficient, and was often accompanied by regression owing to inevitable suture loosening3.

2. Vocal ligament tightening technique, developed by Lejeune et al4,5. The principle of this procedure was again to increase vocal cord tension. This was accomplished by creating an inferiorly based rectangular or triangular flap on the anterior thyroid cartilage in which Broyle¡¯s ligament remained attached. This flap was then pulled forward and secured in place by a tantalum shim. These procedures were performed in patients who had lost tension of thyroarytenoid ligament either from age, trauma or idiopathy. The early results were encouraging though not uniform, but no long term results were known. Based on the same mechanism. Tucker6 proposed a superiorly based flap, which he found gave a superior result due to greater anterior displacement. He performed this procedure in 8 patients who had vocal cord flaccidity. All patients experienced immediate improvement but only 3 maintained it beyond 6 months

3. These methods are capable of raising the vocal pitch . To best understand the physiology and factors influencing vocal pitch, one should be reminded of the following formula.

Where Fo = fundamental frequency

L = length of the vocal folds

T = mean longitudinal stress

P = tissue density

It is clearly demonstrated from this formula that vocal pitch will be raised if one can either shorten or decrease the total mass of the vocal ligaments or increase its tension, or do a combination of these for best results, the mechanism of the previously mentioned techniques addresses only one of these factors, ie. tension of the vocal cord. Though Proctor8 had described how increases in tension cause thinning of the vocal fold, this by no means decreases the total vocal fold mass. Thus, it is still the tension alone that accounts for the increase in vocal pitch in the previous techniques. This may explain why the rise in vocal pitch is inadequate.

In this study, the thyroid cartilage was incised first, followed by excision of the vocal fold while being stretched, and removed them enblock. This step was intended to leave the remaining vocal fold shorter than the antero-posterior diameter of the thyroid cartilage, resulting in shortening and tightening, and decreasing the vocal mass at the same time. Therefore, all factors necessary for raising vocal pitch have been addressed. Furthurmore, as a consequence of excising the anterior portion of the thyroid cartilage, the patients would inevitably gain the additional benefit of losing the thyroid cartilage prominence which they usually long for, which the previously mentioned vocal cord pulling technique does not accomplish. It was interesting to note that none of the patients in this study had abnormally high audible voice despite apparently too high the resultant average fundamental tone.

The inherent disadvantages of this technique are :

1. It requires general anesthesia, and thus subjective voice monitoring or testing is not possible. The length of vocal cord to be excised therefore must be estimated.

2. It is an invasive technique, involving an alteration of the delicate internal laryngeal structure. Though the result was satisfactory, further refinement of surgical technique is required particularly the length of vocal fold to be excised to attain the best outcome. The technique is not recommended in professional singers, due to the risk of altering voice quality.

To address some of these problems we are currently performing this procedure under local anesthesia. Intraoperative patient acoustic feed back enabling a more precise excision of vocal cord.