L is the length of the vocal cord.
T is the medium longitudinal tension.
P is the density of tissue.
Then the three variables are as follows:
So, the f0 depends on the variation of these three parameters. The pitch (and specifically the f0) is directly proportional to the tension and inversely proportional to vocal cord length and mass.
It means that it is possible to elevate the fundamental frequency of glottal vibration (f0) by increasing the tension and/or reducing the mass and/or the length of vocal cords. It can be achieved by three different surgical procedures:
Mass reduction of the vocal folds
Tension increase of the vocal folds
Shortening the length of the vibrating portion of the vocal folds
15.1.3 Surgical Techniques to Increase the f0
22.214.171.124 Injection into the Vocal Muscle of Triamcinolone Acetate Depot
The procedure consists in the injection with triamcinolone into the vocal muscle, which can be performed under local anesthesia in fiberendoscopy or in direct microlaryngoscopy.
Triamcinolone is a long-lasting corticosteroid which has a side effect of the atrophy of soft tissues at the point of intramuscular injection. This side effect is used to reduce the mass of the vocal folds. This technique produces a temporary muscle hypotrophy and the f0 raising of approximately 25–40 Hz. It is an easy technique to perform but with conflicting and sometimes unpredictable results.
126.96.36.199 Advancement of the Anterior Glottic Commissure
This surgery, proposed by Tucker in 1985, is difficult to achieve.
It requires the incision in the thyroid cartilage at the level of the anterior glottic commissure and the insertion of a silicone thickness to keep it advanced. In these cases, So the vocal cords, as well as increase their tension, become longer and thinner and the tension increases. It produces an action on the vocal cord length.
Despite the good results on the speech signal, this surgical technique is not acceptable to the patient because it creates a second Adam’s apple and is not aesthetically acceptable (Fig. 15.1a–d).
188.8.131.52 Endoscopic Anterior Commissure Backward
This procedure, proposed by Wendler, is performed in direct microlaryngoscopy under general anesthesia, and it involves the laser decortication of the anterior third (or often the front half) of the vocal cords.
The purpose of this intervention is to reduce the length of the vibrating portion of the vocal cord and to simulate the dimension of a female glottis. This action creates an anterior synechia, peeling the anterior third of the vocal cords with the laser and then approaching them with a surgical suture; the synechia is also closed using biological glue to avoid any opening. Sometimes, especially if the surgery is not properly performed, synechia can be opened with the use and give a bad voice (Fig. 15.2a–c).
This is the procedure that can lead to the best results in f0 elevation, but it is also the one that is associated with the greatest surgical and postsurgical complications.
184.108.40.206 Cricothyroid Approximation or Thyroplasty Type IV
The procedure is based on an external laryngoplasty with cricothyroid approximation (laryngoplasty type IV). This procedure, proposed by Isshiki in 1980, is the most widespread approach, and it is associated, in most cases, with a surgical remodeling of the Adam’s apple.
This is the surgical technique used by the authors and described in the Sect. 15.2.
It consists in lengthening of the vocal cords (action on the length) performed by attaching the cricoid cartilage to the thyroid cartilage through non-resorbable sutures, simulating a continued spasm of the cricothyroid muscle with a consequent increase of the tension and of the length of the vocal folds (Fig. 15.3a, b).
Radiologic studies confirm that by reducing the distance between the thyroid and cricoid cartilage, the pitch increases (about 18 Hz for each mm of approaching).
15.1.4 The Preoperative Phoniatric Evaluation
Acoustic spectrum of the speech
Manual approximation test
Counseling in the MtF patient candidate for thyroplasty type IV is the most important and delicate moment in phoniatric presurgical evaluation.
In addition to assessing the substantial appearance of the female candidate (somatic and vocal), the phoniatrician has to objectively assess the quality and the manner of speech (through the use of instruments such as GIRBAS and CAPE-V).
The phoniatrician should inform the patient about the surgical approach, should illustrate where the incision will be made, and should inform about the various steps of surgery and postsurgical phases, including the treatment of the postsurgical scar.
The phoniatrician invites later the candidate to explain the reasons that have led him to the surgical choice, their doubts, and their expectations about the surgery, trying to establish a constructive and honest relationship with the patient.
So he should remind the patient that surgery can only act on one of the voice-generating factors, the vocal cords, and remember that the ventilatory function and the cavity of resonance will remain unchanged (i.e., male). After surgery, patients will have to readjust all their body-voice patterns to find the best coupling between vibrator and resonator, also through a modification of Psub.
And this is why speech therapist is essential before and after surgery. It is very important during counseling to suggest the use of speech therapy to the transgender patient.
The aims of speech therapy are as follows:
Removal of mostly incorrect spontaneous forms of compensation
Maintenance of postsurgical results.
Modification of the acoustic parameters of the spoken voice:
Fundamental frequency (f0)
First and second formant (F1, F2)
Modification of suprasegmental features of speech:
Pitch (prosodic contour), intonation, and duration
Pragmatic skills and communicative behavior
In addition, speech therapy, by changing the attitude of the supraglottic structures and tongue, helps to elevate f2. This increase is as important as the elevation of the f0 because vocal tract resonance characteristics may be the second most important acoustic cue to speaker identification.