Transthyrohyoid Membrane Injection
The transthyrohyoid membrane injection approach allows office-based percutaneous injection of the larynx in the awake patient. It affords visualization of the vocal fold with precise needle placement into the region of choice. The technique offers several advantages over the other major injection techniques, including avoidance of general anesthesia, which is required in direct operative injection; minimization of patient cooperation, which is required in awake transoral injection; applicability in adult patients in whom calcification of the thyroid cartilage prevents transcartilagenous injection; direct visualization of the needle tip, in contrast to transcricothyroid membrane injection (if performed using a submucosal technique).
Indications/Contraindications
Common indications for vocal fold augmentation include vocal fold paresis, paralysis, scar and age-related changes; steroid injection for inflammatory disorders such as granuloma; injection of antiviral medications for the treatment of respiratory papillomatosis; botulinum toxin injection for the treatment of spasmodic dysphonia.
Contraindications might include patient intolerance or unwillingness to undergo an awake procedure.
In the Clinical Setting
Key Points
The right balance of topical anesthetic is essential. Excess topical anesthesia will produce choking and gagging, while inadequate anesthesia will inadequately desensitize the larynz, producing procedural distress.
A spinal needle may be required in those patients with excessive anterior neck adipose tissue.
The correct angle of approach is essential for procedural success. Once the needle is introduced, the ability to adjust the needle tip will be restricted by surrounding soft tissue.
Pitfalls
Vasovagal reactions can occur, particularly at the time of scope placement or needle insertion.
In obese patients or in those who have undergone a cervical surgical procedure, distortion or camouflage of the external laryngeal landmarks may make percutaneous injection difficult. A smaller gauge “finder” needle can be used first to limit patient discomfort and to identify the best site for needle placement.
Greater than 10% overinjection can result in stiffening of the vocal fold, and voicing may be suboptimal.
Injection within the superficial lamina propria should be avoided, as this will impair the vibratory ability of the overlaying mucosa. Secondary surgical correction with evacuation of the excess material may be required if this complication occurs.
Although rare, hematoma at the injection site or hemorrhage within the vocal fold may occur, but is usually self-limited.
From a safety perspective, injection is a low-risk procedure.
Unanticipated reactions to injected materials are theoretically possible. Complications such as bleeding, infection, or airway compromise are exceedingly rare.
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