Minithyrotomy
Transoral endoscopy of the endolarynx for management of true vocal fold (TVF) pathology often involves intralaryngeal mucosal incisions that may lead to scarring of the mucosa to the body of the vocal fold. Treatment of vocal fold scar and sulcus vocalis represents an especially challenging issue, as transoral endoscopic approaches to these lesions rely on the principle of trading the old scar for a new one in a more favorable position. To address this, Gray et al introduced the minithyrotomy in 1999 as a means of externally accessing and instrumenting the superficial lamina propria (SLP) of the TVF without the need for intralaryngeal mucosal incisions. When scar tissue is divided, it has a strong tendency to re-form unless something is placed between the raw surfaces to prevent this. Placement of a soft-tissue graft thus serves the dual purpose of preventing reformation of the scar and adding volume to or contouring the vocal fold edge.
This operation is designed to create access to the vocal fold lamina propria through the anterior thyroid cartilage without violating the epithelium of the vocal fold or endolarynx. Through this access, manipulation and/or augmentation of the lamina propria compartment is performed to alter properties of lamina propria, such as shape, position, volume, and/or pliability. These alterations are designed to improve glottic closure for improved phonation.
Indications/Contraindications
Common indications include vocal fold scar, variants such as sulcus vocalis type II or type III, and loss of mass due to atrophy (e.g., presbylarynx).
Augmentation of the SLP (with fat or fascia) can be performed to restore favorable true vocal fold (TVF) shape, position, volume and/or pliability, as in cases of bowing and atrophy. The procedure can be performed bilaterally.
Adhesions within the superficial layer of the lamina propria (SLP), which cause mucosal wave disruption, such as lateralizing scar or sulcus vocalis, can be released.
Poor laryngeal exposure will preclude successful performance of this procedure.
Laryngeal radiation is not necessarily a contraindication nor is prior open or endoscopic laryngeal work. Care must be taken, however, to account for any iatrogenic or traumatic alterations of native anatomy.
The procedure can be done with the patient under general anesthesia, or awake with conscious sedation and local anesthetic injections. The skin incision is very small and heals nicely.
In the Clinical Setting
Key Points
Proper placement of the minithyrotomy is essential to permit accurate development of the lamina propria dissection. A 30-gauge finder needle can be passed through the anterior thyroid cartilage in the region of the proposed minithyrotomy to endoscopically assess if the proposed minithyrotomy site is appropriately at the level of the true vocal fold.
Getting acquainted with measuring laryngeal landmark distances with a caliper is helpful; remember that a midline point between the thyroid notch and the inferior border of the thyroid cartilage should mark a point that corresponds internally to the superior surface of the vocal folds.
Proprioceptive feedback for development of the lamina propria tunnel is augmented with visual feedback by looking at the vocal fold from above (with a flexible laryngoscope or telescope) while dissecting in the plane of the lamina propria. Projecting the telescopic image onto a video monitor via a camera is very helpful.
Pitfalls
TVF mucosal perforation during instrumentation of the SLP through the minithyrotomy is the most likely complication of this procedure. If there is a small perforation, a portion of the perichondrial flap can be used as an underlay graft placed with instrumentation through the minithyrotomy. If there is a large perforation or tear of the true vocal fold mucosa, a graft may still be placed, but there is a high rate of postoperative graft extrusion into the airway and very close clinical follow-up is required.
If the minithyrotomy is performed too close to the midline, there is a risk of destabilizing the connection of the anterior commissure to the interior of the thyroid lamina (Broyle′s ligament), which could cause the vocal folds to lose tension. This is a difficult problem to fix and should be avoided.
From a Technical Perspective
When drilling the minithyrotomy it is important not to push too firmly with the drill or one risks violation of the endolaryngeal epithelium and traumatizing the vocal fold. It is essential to use instruments that are not overly sharp when the epithelium is near the instrument tip to prevent epithelial tears.
Note that otologic alligator struts have one jaw that moves and one that is stable. When spreading in the pocket, orient the moving jaw so that it opens laterally, i.e., away from the mucosal edge, to avoid perforation.
Stepwise Procedure
Mount a larynx for open dissection.
OR Pearl: In live patients, this procedure involves direct visualization of the endolarynx during dissection of the SLP. Management of the airway during the case determines what options are available for larynx visualization. If the procedure is performed under local anesthesia/monitored anesthesia care, then flexible transnasal laryngoscopy is performed. If it is performed under general anesthesia, then suspension laryngoscopy and larynx visualization via an endoscopic telescope may be used. Outstanding visualization can be acquired with a telescope through the suspended laryngo-scope. General anesthesia also better limits patient movement, which is advantageous given the small margin for error.
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