VOICE FEMINIZATION

The average length of vocal cords is 22.79 ± 3.27 mm in men and 18.99 ± 1.82 mm in women. The length of the membranous vocal cord is 14.97 ± 2.01 mm in men and 11.17 ± 0.68 mm in women. Thus, the membranous vocal cord is about 25% longer in men than women. The thickness of the vocal cords also differs between sexes: 6.07 ± 1.11 mm in men and 5.03 ± 1.10 mm in women. Thickness is approximately 20% greater in men. Therefore, for transsexual patients transitioning from male to female, the membranous vocal cord length should be shortened by about 25% to approximately 11 mm, and thickness reduced by 20% to achieve voice feminization.

Voice feminization first appeared in history in the 16th century in Italian operas with castrati. The church prohibited women from singing, so castrati performed their first vocal performances at the Sistine Chapel in 1562. After castration, the larynx and vocal cords, freed from the masculinizing effects of androgen hormones, produce a high-pitched childlike voice containing high harmonics. Nowadays, voice feminization surgeries are also performed in conditions such as androgenital syndrome, ovarian tumors producing male hormones, testicular feminization, and aplastic anemia treated with androgen hormones. Let us examine these techniques in detail.

VOCAL CORD LENGTH SHORTENING

The first voice feminization surgery by shortening vocal cords was described by Donald in 1982 in 3 cases by creating a web in the anterior third of the vocal cords through laryngofissure and entering the endolarynx. Wendler, in 1989, described vocal fold anterior one-third epithelium removal and web creation with suturing under general anesthesia using a rigid laryngoscope. Gross in 1999 published a modification of this technique using muscle sutures. Later, CO2 laser and absorbable Vicryl sutures were used for epithelial removal and suturing, and Radiesse voice gel was also used to create the web without sutures. The vocal fold shortening with retrodisplacement of the anterior commissure (VFSRAC) technique, defined by Kim, creates a vocal cord web with non-absorbable sutures, producing an average fundamental frequency increase of 76.6 Hz by permanently shortening the thyroarytenoid muscle. According to research by Paltura and colleagues, the anterior web formation only increases fundamental frequency, while formant frequencies in male-to-female transsexual patients remain close to male values. Since shortening vocal cords does not alter the supraglottic air column, the resonator cavity remains constant and the acoustic spectrum resembles that of men.

VOCAL CORD THINNING

The first experimental attempt to reduce vocal cord mass for voice feminization was described by Tanabe in 1985. Triamcinolone injection was performed after a longitudinal and deep cut on the vocal cords, but voice quality deteriorated and acoustic thinning results were unsatisfactory. In 2006, Orlof introduced the Laser-Assisted Voice Adjustment (LAVA) technique. This method vaporizes the membranous vocal cord with CO2 laser without involving the vocal muscle to increase stiffness and raise fundamental frequency by an average of 26 Hz, not reaching female voice levels. A more invasive technique, Laser Reduction Glottoplasty (LRG), including CO2 laser ablation of the vocalis muscle epithelium and ligament, was introduced by Koçak in 2009. It was applied in patients unresponsive to cricothyroid approximation surgery, resulting in an average 45 Hz increase in fundamental frequency.

VOCAL CORD TENSION INCREASE

Several techniques such as cricothyroid approximation, anterior commissure advancement (ACA), cricothyroid subluxation, and elongation thyroplasty have been described to increase vocal cord tension. The cricothyroid muscle is the main muscle that controls vocal cord tension, raising the pitch and thinning the voice. It is used when this muscle loses function (e.g., superior laryngeal nerve paralysis) or in hormonal imbalances, androphonia, male-to-female transition, or voice appearance/social status mismatch cases. In congenital laryngeal malformations and after laryngeal trauma where vocal cord tension is necessary, tension laryngoplasty can be applied for voice restoration. It is also used in high vagus paralysis with vocal cord paralysis for voice and swallowing problems.

Kitajima et al., in 1979, showed that anterior approximation of the cricothyroid distance linearly increased voice frequency. The most common technique, cricothyroid approximation, narrows the cricothyroid space by suturing the thyroid cartilage anteriorly to the cricoid cartilage to mimic cricothyroid muscle tension and raise voice pitch. However, only about half of patients achieve satisfactory results. It can result in unnatural falsetto-like voice and narrowed voice range. Long term, sutures may damage or loosen cartilage, reducing initial voice feminization. Due to insufficient ossification of thyroid cartilage in younger patients, this method is not recommended below 30 years old. Differences in cricothyroid joint anatomy affect surgical success, and preoperative CT is suggested for patient selection. Thus, cricothyroid approximation is often combined with other feminization methods today.

The surgery can be performed under local anesthesia with sedation or general anesthesia via a 4-5 cm horizontal neck incision aligned with skin creases. Since it is mostly performed on male-to-female transsexual patients, thyroid chondroplasty removing the prominent laryngeal prominence can also be done. Absorbable sutures are passed below the anterior commissure of the thyroid cartilage and lateral to the midline to narrow the cricothyroid space.

Anterior commissure advancement (ACA) was designed for vocal fold laxity cases like presbylaryngitis but is not sufficient for transsexual voice feminization alone. It was combined with cricothyroid approximation to increase pitch but voice thinning remains limited.

EXTERNAL APPROACH

Kunachak first described in 2000 an external surgical method shortening vocal cords by resecting anterior one-third of the thyroid cartilage and vocal cords and overlapping tissues. This aggressive method sometimes caused unexpected pitch increases to 320 Hz. While thinning the voice, disadvantages include dysphonia and diplophonia from vocal cord asymmetry, inability to produce high pitch if the new anterior commissure is loose, and disrupted laryngeal feedback reflex from vocalis muscle cutting. Modifications by Thomas added thyrohyoid approximation to reduce pharyngeal space and alter resonance, called feminization laryngoplasty. However, the tongue and hyoid movements strongly influence pharyngeal resonance, making thyrohyoid approximation difficult and potentially causing hyperfunctional side effects.

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