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Neuroradiology Case of the Week

Case 324

Wade C. Hedegard, MD

Clinical Presentation: A 27-year-old female with a history of papillary thyroid carcinoma and subsequent unilateral vocal cord paralysis presented after falling from a bicycle.

Imaging Findings: Cervical spine CT showed no evidence of fracture or acute injury.  An incidental radiopaque density is identified in the soft tissues adjacent to the right vocal cord.

Diagnosis: Unilateral vocal fold paralysis status post right medialization laryngoplasty with Gore-Tex stent placement

Discussion: Unilateral vocal fold paralysis occurs from a dysfunction of the recurrent or vagus nerve innervating the larynx and causes a characteristic breathy voice. If properly evaluated and treated, a normal speaking voice can be restored. Vocal cord paralysis most commonly occurs following a surgical iatrogenic injury, frequently after thyroidectomy, carotid endartectomy, anterior spine surgery, and thoracic or mediastinal surgery. Paralysis can also occur secondary to endotracheal tube trauma, malignant invasion or rarely after a viral or bacterial infection. The breathy, weak voice is the result of glottal incompetence due to vocal fold paralysis. Normal vocal cord function depends on vocal fold glottal closure secondary to bilateral adduction of the vocal folds. Vocal fold adduction, in combination with subglottic airflow, induces vocal fold vibration. If there is unilateral vocal fold paralysis, this results in partial or complete glottal incompetence. Accordingly, there will be weak, uncoordinated vocal fold vibration and dysphonia.
     The recurrent laryngeal nerve is responsible for both abduction and adduction of the vocal folds. The recurrent laryngeal nerve originates from the vagus nerve, which originates from the brainstem (nucleus ambiguous in the medulla) and travels along the carotid sheath (with the jugular vein and internal carotid artery). Nerve injury may lead to dysphagia in addition to vocal fold paralysis. If a patient presents with symptoms suggestive of unilateral vocal fold paralysis and no surgical history, a chest radiograph should be the initial evaluation to look for a pancoast tumor or mediastinal mass. The next step in the workup could be either a CT or MRI of the neck and upper chest.
     If properly evaluated and treated, a normal speaking voice can be restored in cases of unilateral vocal cord paralysis. Treatement options include voice therapy as well as temporary and permanent surgical interventions. Temporary treatment involves endoscopic injection of a resorbable material into the affected vocal fold, lateral to the thyroarytenoid muscle in the paraglottic space. The resulting medialization of the paralyzed vocal fold restores glottic competence, thereby improving phonation and swallowing function. Temporary vocal fold injections are used when recurrent laryngeal nerve function is expected to return on its own or during the first 6 months after onset of paralysis when the ultimate prognosis is still unknown. Permanent treatment options include vocal fold injections or laryngeal framework surgery. The standard long-term treatment of unilateral vocal fold paralysis is a medialization laryngoplasty from an external approach working through the thyroid cartilage and ultimately placing an implant in the paralyzed vocal fold. Implants frequently include Gore-Tex or sialastic block implants.  Surgical complications are rare, but include airway difficulties and migration of the implant.   

References:

1. Rosen CA, Soose RJ. Vocal fold paralysis, unilateral. eMedicine. June 16, 2006. http://www.emedicine.com/ent/Topic347.htm
2. Som PM, Curtin HD. Head and Neck Imaging. 4th ed, Vol. 2, St. Louis: Mosby, 2003:2231-2235.