Framework surgery usually provides long-term benefit to voice quality and function and consists of medialization thyroplasty (type I), with or without arytenoid adduction [1–3]. The other main option is laryngoplasty by endoscopic injection: a substance is injected into the vocal cord to increase its volume and medialize the paralyzed fold. In fact, several biocompatible materials are available for this purpose, but the ideal substance for vocal fold augmentation still does not exist because all of these materials have some drawbacks [4, 5].

Static repositioning of the paralyzed vocal cord in the midline phonatory position by means of laryngoplasty either through injection or external medialization is highly successful at improving laryngeal function closure. Recent evidence, however, suggests that early endoscopic intervention with resorbable materials reduces the need for transcervical reconstruction. In general, different injection materials, either permanent (Teflon, PDMS) or temporary (Gelfoam, Cymetra, Restylane, Radiesse) and different approaches (transoral vs. percutaneous) have been used to medialize the paretic vocal fold to improve voice and prevent aspiration. IL can be performed under local or general anesthesia, using a fiber optic or microscopic control. If the implanted material is reabsorbable, a fiber optic injection is usually preferred; on the contrary, if a long-term result with permanent materialsis sought, a microscopic approach is performed, because a more precise and accurate injection of the substance is required, also because of the irreversibility of the procedure.

In case of unilateral vocal fold paralysis (UVFP), the surgery is performed at least 6 months after the start of symptomatology, not only because of the possible reversibility of the paralysis, but also for the possible change of position, volume and/or profile of the vocal fold (progressive muscular atrophy or, on the contrary, synkinetic reinnervation with restoration of the trophism). Different timing for the surgery can be related to particular situations, such as the patient’s needs (professional singer), important dysphonia, repeated episodes of food inhalation, often related to superior laryngeal nerve involvement. Microlaryngoscopy is a surgical approach to the larynx that permits the exposition of the glottic plain and the implementation of many phonosurgery procedures [6].

Historically, Kirstein introduced the suspension laryngoscopy in 1897, allowing for the first time bimanual instrumental manipulation of the surgical field [7]. In those days, the suspension gallows technique was too complex and anesthesia techniques were not always optimal. These problems led to the development of the fulcrum technique by Brünings in 1912 [8] and Seiffert in 1922 [9], which has been widely adopted. After the development of proper laryngoscopes in combination with a laryngoscope holder by Kleinsasser, this method became standard.

Usually, general anesthesia is used for microlaryngoscopy. As the surgeon and the anesthesiologist share the same area, a good collaboration between them is mandatory. Good general anesthesia is necessary to obtain profound sedation for contrast intubation reflexes of the surgical laryngoscopy and forces exerted to the larynx, and also to maintain good ventilation, with larynx immobility and muscular relaxation during surgery. The anesthesiological technique is not univocal: the anesthesiologist must be able to guarantee the anesthesiological plan to be appropriate for the procedure provided by the operator. The ideal technique should be simple to perform, ensure adequate protection of the airways with adequate oxygenation and CO₂ removal, secure induction and maintenance of anesthesia, with a minimal impact on the cardiovascular and respiratory systems, ensure a satisfactory operative field without movement, and allow gentle wakening without pain, coughing, or laryngospasm. Typically, anesthesia is performed by intubation with a small endotracheal tube that does not interfere with surgery in the anterior two-thirds of the vocal folds.

Endotracheal intubation provides the safest ventilation and enables a stable operating field for precision surgery, as required in phonosurgery. The technique with intermittent apnea (up to 2–3 min in adults) or the “in and out” technique (positioning the tube in the trachea for optimal assistance, with 100 % oxygen and eventually the use of inhalation anesthetics, and airway protection, up to pulling out the tube only at the moment of the surgical act), under the surgeon’s view of the rigid laryngoscope, may also be valid whenever the operative field is not adequately visualized in the presence of the tube [10]. For special indications, jet ventilation, which consists of the administration of 100 % oxygen or gas mixture with high frequency and high pressure through an accessory canal of low caliber, positioned in the glottic, supraglottic or transtracheal region, is a useful and sometimes indispensable technique [11–14].

Correct patient positioning is also the key to adequate laryngeal exposition and intubation, with lower pressure on the tongue base and gingival arch. The patient has to be positioned in dorsal recumbency on the operating table, with a slightly elevated movable headboard, to allow the “Boyce–Jackson position,” also known as the “du guetteur” position according to French authors or the “sniffing” position according to English-speaking authors [3, 15, 16]. This position is characterized by a slight flexion of the neck on the thorax and by an extension of the head on the neck (Figs. 5.3 and 5.4). In this way it is possible to obtain good anterior commissure exposure, facilitated from external back pressure to the larynx. The laryngoscope is thus suspended on a chest support, and the surgeons’s arms are supported by arm rests.

In 1.5–8.5 % of cases, difficult anesthesiology and, consequently, surgical larynx exposure may occur, related to particular anatomical situations (narrow mandibular arch, retrognatia, mandibular protrusion, cervical spine rigidity, short neck, obesity, previous radiotherapy). In these cases, a correct preoperative evaluation, with Cormack–Lehane and Mallampati scores and hyoid–mental or sternum–mental or else thyromental incisure distance, can prevent difficult and dangerous intraoperative scenarios.

Under extreme conditions, a rigid laryngoscopy with a flexible fiber optic control with curved instruments can be used. It is important to carry out the procedure using the wider laryngoscopy available, in order to deflect ventricular bands and visualize the superior portion of vocal folds without touching them to avoid mucosal stretching, which could change morphology of some vocal lesions.

Several laryngoscopies of various calibers must be available, to adapt to the laryngeal anatomy. As with any instruments, practical experience with a particular kind of laryngoscope enables the surgeon to become more proficient in its use.

Kleinsasser, Bouchayer, and Sataloff instruments are usually used for laryngeal exposition. Typically, a 400-mm focal length lens provides good visualization and allows adequate working space. Some surgeons, however, are more comfortable with a 350-mm focal lens [3, 16]. In the case of optic systems with variable focus, it is possible to regulate the distance in this range, for a facilitated introduction of instruments and for comfortable surgery.

An adjustable operative table, with adjustable eye pieces and a chair with arm support are other variables that are important for the correct and ergonomic position of the surgeon performing microlaryngoscopy.

The point of infusion depends on the material used. For fat injection it is preferable to use an infusion point between the medial third and the posterior third of the vocal fold, deep to the paraglottic space, in the lateral portion of the thyroarytenoid muscle, penetrating the material through the posterior portion of the vocal fold, lateral to the vocal process, medializing it, and through the median and anterior thirds, obtaining a volumetric increase and correction of the arcuate profile. For hyaluronic acid the site of injection is substantially the same as that for fat, when it is used as augmentative material in microlaryngoscopy. This substance, which is an important component of the superficial layer of the lamina propria, is often used with a subepithelial infusion to regularize the vocal fold profile or to perform a hydrodissection of a superficial sulcus or a scar, increasing the tissue viscoelasticity.

A CaHa implant (hydroxyapatite) is made of a suspension of microspheres of CaHa (25–45 μm in diameter), in a gelatin carrier of sodium carboxymethylcellulose, which is slowly released and reabsorbed into the human tissue, partially replaced with fibroblasts; then, microphages partially remove microspheres, so that the volume of the vocal fold after 6–9 months is reduced, and a hypercorrection is preferable. The site of injection is at the level of the lateral portion of the thyroarytenoid muscle or in contact with the thyroid cartilage, with an injection point lateral to the vocal process, which favors intrarotation, and another to the medial third, as for Vox® implants (Fig. 5.5).