Introduction
Injection laryngoplasty is performed for treatment of vocal cord paralysis, which may have a variety of causes ( Box 46.1 ). Imaging during a Valsalva maneuver demonstrates the mechanical and physiologic barriers that patients with unilateral vocal cord paralysis endure ( Fig. 46.1 ). Vocal cord augmentation procedures attempt to overcome these barriers by medializing the affected vocal fold, thus allowing for better phonation and alleviating risk for aspiration. Temporary injectable materials, which last a few weeks to a few months, include hyaluronic acid, collagen, and Gelfoam. Long-lasting and permanent agents include calcium hydroxyapatite paste, autologous fat, and polytetrafluoroethylene past (Teflon). These injected materials can be incidentally encountered on imaging obtained for other reasons, such as cancer surveillance. Alternatively, injection laryngoplasty is subject to certain complications that may warrant diagnostic imaging evaluation. Laryngoplasty evolution and potential complications, including Teflon granuloma, will be the focus of the following discussion ( Fig. 46.2 ).
Surgery
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Nonthyroid (i.e., anterior cervical spine, carotid endarterectomy, neck dissection, and cardiac)
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Thyroid/parathyroid resection
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Malignancy
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Lung carcinoma
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Thyroid carcinoma
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Esophageal carcinoma
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Idiopathic
Other
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Trauma
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Intubation
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Neurologic
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Infectious (i.e., tuberculosis)
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Congenital
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Temporal Evolution: Overview
Calcium hydroxyapatite initially displays calcific attenuation on computed tomography (CT) but gradually resorbs over 12 to 18 months, with decreasing bulk and attenuation ( Fig. 46.3 ). Furthermore, calcium hydroxyapatite can stimulate local fibroblast activity and macrophage accumulation, which leads to focal hypermetabolism on fluorodeoxyglucose (FDG)–positron emission tomography (PET) ( Fig. 46.4 ). Although it can last for years, autologous fat also shrinks over time. Therefore fat is often generously or overinjected for vocal cord medialization ( Fig. 46.5 ). However, excess injection of laryngoplasty agents can lead to laryngocele formation with airway obstruction and dysphonia ( Fig. 46.6 ). Teflon is notorious for inciting a foreign body giant cell reaction that leads to granuloma formation, which can cause airway obstruction and dysphonia as well. On CT, a Teflon granuloma typically appears as a concentric soft tissue mass surrounding the hyperattenuating Teflon ( Fig. 46.7 ). The granuloma can also be hypermetabolic on FDG-PET ( Fig. 46.8 ).
