10.14\ Laryngeal Stents

10.14.1  Discussion

The Montgomery® laryngeal stent is a molded silicone prosthesis that conforms to the endolaryngeal­ surface and that is firm enough to support the endolarynx postoperatively yet

is soft and flexible enough to ensure a conforming fit while minimizing injury to soft tissues. These stents are radioattenuating on CT (Fig. 10.77). Montgomery stents can be used for laryngotracheal support or for the treatment of chronic aspiration. Laryngeal stenting requires concomitant tracheostomy.

10.15\ Laryngoplasty and Vocal

Fold Injection

10.15.1  Discussion

Medialization laryngoplasty (thyroplasty) is a type of laryngeal framework surgery used to treat vocal cord paralysis. The procedure consists of creating a thyroid cartilage window and implanting­ devices such as silicone (Montgomery) prostheses. The Montgomery vocal cord positioning prosthesis is a triangular-shaped single block that is typically positioned deep to the thyroid cartilage (Fig. 10.78). However, the classic form of medialization laryngoplasty involves depressing the fragment thyroid cartilage at the window and implanting the prosthesis superficial to this (Fig. 10.79). Other implantable materials

Fig. 10.78  Medialization laryngoplasty with Montgomery prosthesis. Axial (a) and coronal (b) CT images demonstrate the triangular silicone prosthesis (arrows). There is rotation of the arytenoid and medialization of the vocal cord

include cartilage grafts (Fig. 10.80) and hydroxyapatite prostheses (Fig. 10.81).

A variety of agents are used for vocal cord injection, including temporary, semipermanent, and permanent agents (Table 10.4). These materials are injected into the thyroarytenoid muscle or paraglottic space under laryngoscopic guidance. The imaging features vary depending upon the specific agent used (Figs. 10.82, 10.83, 10.84, 10.85, and 10.86). Polytetrafluoroethylene implants demonstrate heterogeneous hyperattenuation on CT and have irregular medial margins­. Silicone implants are also hyperattenuating, similar to the adjacent thyroid cartilage. These materials are hypointense on T1 and T2 MRI sequences. Fat grafts are characteristically radiolucent and hyperintense on both T1 and T2.

a

b

Complications of laryngoplasty include excessive or inadequate augmentation; foreign body granuloma formation, particularly with Teflon; implant rotation or lateralization; migration; and

airway compromise (Figs. 10.87, 10.88, 10.89, 10.90, 10.91, and 10.92). Excess or inadequate medialization is mainly a clinical judgment, and imaging is used for planning revision surgery.

Fig. 10.79  “Classical” laryngoplasty. Axial CT image shows a silicone block implant (*) positioned superficial to the depressed left thyroid cartilage fragment (arrow)

Fig.10.80  Cartilage graft laryngoplasty. Axial CT image shows a partially calcified tragal cartilage graft in the right paraglottic space (arrow)

Fig. 10.81  Medialization laryngoplasty with hydroxyapatite prosthesis. Axial CT image shows a hyperattenuating right vocal cord implant (arrow) shaped to match the contours of a normal vocal cord

Table 10.4  Types of agents used for vocal cord injection

Fig. 10.85  Vocal fold injection with hyaluronic acid. Axial CT image (a) shows enlargement of the left vocal cord with nearly fluid-attenuation material (arrow). The

Doppler ultrasound image (b) shows a corresponding anechoic area without internal vascular flow (arrow)

Fig.10.86  Vocal fold injection with micronized acellular human dermis. Axial T2-weighted MRI shows curvilinear hypointensity surrounded by diffuse high signal in the enlarged left vocal fold (arrow)

Fig. 10.87  Teflon foreign body granuloma. Axial CT image shows mass-like soft tissue material surrounding the left vocal cord implant (arrow)

Fig. 10.88  Laryngocele. Sagittal CT image shows a fluid collection (arrow) above the vocal cord medialization material

Fig.10.89  Laryngoplasty material extrusion. The patient did not experience improvement after attempted laryngoplasty. Axial CT image shows lateral extrusion of the implant (arrow) through the cartilage window and concavity of the left vocal cord. The patient underwent subsequent revision laryngoplasty

Fig. 10.90  Montgomery prosthesis rotated into airway. Coronal CT image shows that the prosthesis projects too far into the airway (arrow). The patient presented with hoarseness after trauma

Fig. 10.91  Laryngoplasty material supraglottic migration. Coronal CT image demonstrates superior extension of the Gore-Tex (arrow) to the level of the right piriform sinus and thickened aryepiglottic fold

Fig.10.92  Insufficient medialization. The patient did not experience improvement in phonation after the surgery. Axial CT image shows bilateral implants in position, but the rima glottidis is relatively wide. Revision surgery was subsequently performed