Keywords
laryngoplasty, thyroplasty, vocal cord paralysis, glottic insufficiency
Introduction
Medialization laryngoplasty or thyroplasty type I was first described and later popularized by Ishiki during the 1970s. Netterville first reported on the immediate medialization of the true vocal fold following skull base or head and neck surgeries involving the sacrifice of the vagus or recurrent laryngeal nerves.
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Glottic insufficiency affects all laryngeal functions and may be caused by vocal fold:
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Atrophy (i.e., presbylarynx, neuromuscular degenerative disease)
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Weakness (i.e., paresis)
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Paralysis
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Glottic insufficiency impairs the function of the laryngeal sphincter leading to :
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Poor protection of the tracheobronchial airways during swallowing (i.e., aspiration)
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Reduction of efficiency and strength of the cough reflex
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Elimination of physiologic positive pressure on expiration (helps to inflate the lungs)
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Wide range of dysphonia and vocal fatigue
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Decrease in the efficiency of a Valsalva maneuver; thus patients may exhibit problems splinting the thoracoabdominal muscles, which help with lifting and facilitating bowel movements
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An immediate intraoperative thyroplasty is based on an empirical medialization of the true vocal fold. The patient’s true functional deficit cannot be assessed reliably under general anesthesia; thus the need for a subsequent revision is higher than a secondary thyroplasty performed under awake sedation.
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The vast majority of patients will enjoy a satisfactory outcome resulting in adequate protection of the tracheobronchial tree against aspiration and normal or near-normal voice (vocal fatigue may be a persistent problem).
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Professional voice performers may require adjunctive procedures, such as arytenoid repositioning, to reach an optimal result.
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A seemingly adequate postoperative result may deteriorate in time due to re-accommodation of the implant (i.e., GOR-TEX strip) or vocal fold atrophy (more common in patients with a high-vagal lesion).
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Surgical medialization of a paralyzed cord displaces the affected vocal fold toward the midline and augments its bulk to improve the glottic closure (it facilitates neuromuscular compensation by the unaffected contralateral side).
Key Operative Learning Points
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A medialization laryngoplasty or thyroplasty type I involves the medialization of a paralyzed or paretic true vocal fold by the insertion of a paraglottic implant such as :
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Silicone (premade and custom implants)
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Polytetrafluoroethylene (GOR-TEX; W.L. Gore and Associates, Newark, DE)
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Titanium alloy
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Hydroxyapatite
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Cartilage
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Fascia
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Acellular dermis
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Adjustable balloon
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Most frequently, an intraoperative thyroplasty involves implantation without the benefit of being able to be certain of the position of the window with respect to the position of the vocal fold or the immediate effect of the implantation upon the quality and strength of the voice or cough.
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The surgeon creates a window in the thyroid cartilage and medializes the vocal cord using dimensions that have been determined to yield adequate results for most patients operated in the traditional way ( Fig. 6.1A ).
Fig. 6.1
A, Approximate dimensions and position of the thyroplasty window. During an immediate thyroplasty, the window is opened as close to the inferior edge of the thyroid ala as possible while still preserving an inferior strut. B, The strap muscles and the perichondrium of the thyroid cartilage were divided at the midline and are being retracted from the thyroid ala en bloc. Stabilization of the larynx with a single or double hook greatly facilitates this dissection and opening of the window.
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20%–30% of patients will require revision surgery.
Preoperative Period
History
This procedure may be planned preoperatively in the patient with a history of having a tumor originating in the vagus nerve (i.e., vagal schwannoma or a glomus vagale requiring removal of the vagus nerve) or requiring the sacrifice of the vagus nerve in removing an adjacent tumor (i.e., carotid body tumor). In such situations, this procedure must be discussed with the patient. There are also instances in which the need for intraoperative thyroplasty may not be anticipated, such as accidental transection of the recurrent laryngeal nerve during thyroid surgery in which the patient may not have been prepared for this additional procedure.
Physical Examination
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Examination of the neck must rule out the presence of masses, scars, or excessive subcutaneous adipose tissue, all of which may affect the choice and difficulty of the exposure.
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A preoperative flexible fiberoptic laryngoscopy ascertains:
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The position of the vocal fold (VFs) and arytenoids (horizontal and vertical planes) during normal and forced ventilation, vocalization, and cough
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The muscle tone of the vocal folds
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The bulk of the vocal folds
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The integrity of the mucosa
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Functional assessment of all lower cranial nerves is critical.
Imaging
Not necessary.
Indications
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The decision to perform an immediate intraoperative thyroplasty is multifactorial and includes such variables as the needs and desires of the patient (e.g., profession, fitness, hobbies and interests), age, premorbid laryngeal and pulmonary function, and presence of other cranial nerve deficits.
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An immediate intraoperative thyroplasty is indicated in patients who:
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Undergo sacrifice of the vagus or recurrent laryngeal nerve during an oncologic resection
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Suffered iatrogenic or penetrating trauma to the neck with injury to the vagus or recurrent laryngeal nerves
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Contraindications
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An immediate intraoperative thyroplasty is contraindicated in patients who show:
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Glottic airway stenosis due to edema or abductor paralysis (or paresis) of the contralateral true vocal cord
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Presence of a congenital or acquired coagulopathy (relative contraindication)
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Strong aversion to accept the risks of the surgery or the possibility of needing a secondary revised procedure
Preoperative Preparation
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If the possibility of an intraoperative medialization is anticipated, the surgeon must ascertain the function of the contralateral vocal fold by indirect mirror or flexible laryngoscopy.
Operative Period
Anesthesia
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Continue the type of anesthesia established by the primary procedure.
Positioning
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Position the neck in a neutral position or slightly extended. Type of anesthesia, neck positioning, and placement of the incision during an immediate intraoperative thyroplasty may be dictated by the needs of the oncologic surgery or the need to control the great vessels of the neck.
Perioperative Antibiotic Prophylaxis
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Administer broad-spectrum perioperative prophylactic antibiotics and systemic corticosteroids.
Monitoring
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Continue standard anesthesia monitoring.
Instruments and Equipment to Have Available
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Flexible laryngoscope
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Unipolar electrocautery with insulated tip
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Insulated bipolar electrocautery
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Single hook retractor
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Double hook retractor
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Senn retractor (dull)
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High-speed drill
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2-mm cutting or hybrid burr
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1- and 2-mm bone curettes
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Cottle or Freer periosteal elevator
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Duckbill elevator
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Medical grade silicone block (medium density) or premade silicone implant
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0.4-mm thickness GOR-TEX patch (alternate)
Key Anatomic Landmarks
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Notch and midline of thyroid cartilage
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Inferior border of the thyroid ala
Prerequisite Skills
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Experience with laryngeal framework surgery
Operative Risks
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Airway compromise
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Misplacement of the prosthesis
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Overcorrection or undercorrection
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Extrusion
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Dysphonia
Surgical Technique
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The intraoperative thyroplasty is usually accomplished through the oncologic incision or an extension.
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Divide the strap muscles and perichondrium of the thyroid cartilage at the midline.
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Stabilize the laryngotracheal complex using a single or double hook lodged at the inferior or superior border of the thyroid cartilage. This also facilitates the rotation of the thyroid cartilage, better exposing the thyroid ala. Elevate the ipsilateral strap muscles and perichondrium of the thyroid cartilage to expose its ala.
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Retract the perichondrium and strap muscles with a Senn retractor to expose the cartilage of the thyroid ala (see Fig. 6.1B ).
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Transect the insertion of the sternothyroid muscle using a bipolar electrocautery, thus exposing the entire inferior border of the thyroid ala.
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The dimensions of the window vary according to the dimensions of the thyroid ala (in turn vary with height, gender, and age):
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Ranges between 4 × 8 mm to 5 × 10 mm
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Position the window 3 to 4 mm above the inferior border of the ala and 5 to 10 mm posterior to midline (for women and men respectively) (see Fig. 6.1A ).
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A window may be opened with a 67 Beaver blade (for cartilage) or a high-speed drill with a 2-mm coarse diamond or hybrid burr (for calcified cartilage).
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The latter is most commonly used because most adults have undergone some ossification of the inferior aspect of the thyroid ala.
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Drill out the window at perpendicular angles (i.e., avoiding “saucerization”) until the inner cortex of the thyroid ala is thin enough to be eggshell fractured, thus allowing its removal with a 1- to 2-mm bone curette.
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When the cartilage is soft, it can be transected with a #67 Beaver blade and elevated with a middle ear spatula or Cottle elevator.
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One must avoid saucerization or thinning of the lower strut, which could lead to fracturing and will destabilize the implant.
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Following exposure of the inner perichondrium, a bone curette, Cottle, or duckbill elevator is inserted between the alar cartilage and the inner perichondrium to widely dissect this space.
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Incise the inner perichondrium along the axis of the window.
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This incision allows the implant to medialize just the area corresponding to the vocalis muscle (as opposed to medializing the entire inner perichondrium).
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A small artery is commonly encountered at the posterior aspect of this incision, requiring control with a bipolar electrocautery.
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Choice of implant material is surgeon dependent; however, carving an implant from a medium-density medical grade silicone block allows customization, does not suffer compression like the polytetrafluoroethylene strip, and is more cost effective.
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Implants are carved so they are wider and longer than the window, thus avoiding extrusion of the implant through the window.
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A “peg” that protrudes through the window prevents migration of the implant in the coronal or sagittal planes ( Fig. 6.2 ).
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