Diagnosis

Left vocal cord paralysis

Findings

The axial fused PET/CT image at the level of the vocal cords demonstrates asymmetric FDG uptake in the right vocal cord with no significant uptake in the left vocal cord. The left vocal cord is mildly lax with slight medial displacement. The fused PET/CT image of the chest demonstrates a mass centered within the left aortopulmonary window with avid FDG uptake. In addition, 2 pleural-based nodules are noted posteriorly within the left hemithorax, which also demonstrate increased FDG uptake.

Discussion

The recurrent laryngeal nerves (RLN) innervate the laryngeal musculature and are essential to phonation, swallowing, breathing, and coughing. The RLN arise from the vagus nerve (CNX) and injury to the RLN or the vagus nerve may be secondary to neoplasm, trauma (including surgical), radiation, or it may be idiopathic. The RLN arises from the nucleus ambiguous in the medulla and exit the cranial vault with through the jugular foramina, coursing inferiorly within the carotid sheath. The left RLN loops under the aortic arch, while the right RLN loop under the brachiocephalic trunk. The RLN then course superiorly along the tracheoesophageal grooves.

This case illustrates left vocal cord paralysis with subsequent increased FDG uptake in the right vocal cord secondary to a compensatory increased workload. The key finding in this case is the hypermetabolic mass within the left aortopulmonary window, which may present clinically with left recurrent laryngeal nerve palsy. The compensatory asymmetric uptake in the right vocal cord is important for the radiologist to distinguish from metastatic disease as it changes management significantly. Correlation with a clinical history of dysphonia, hoarseness, or aspiration may be useful to support the radiologic findings, but in some cases direct visualization with laryngoscopy may be necessary.

In addition to the finding of asymmetric FDG uptake in the contralateral vocal cord, additional CT findings of vocal cord paralysis include paramedian positioning of the ipsilateral vocal cord, tilting of the thyroid cartilage, dilation of the ipsilateral pyriform sinus, and displacement of the arytenoid cartilage.

Related Reading

 1. Komissarova M, Wong KK, Piert M, et al. Spectrum of 18F-FDG PET/CT findings in oncology-related recurrent laryngeal nerve palsy. Am J Roentgenol. 2009;192:288-294.
2. Lee, M, Ramaswamy MR, Mohan R, Nathan CO. Unilateral vocal cord paralysis causes contralateral false-positive positron emission tomography scans of the larynx. Ann Otol Rhinol Laryngol. 2005;114:202-206.
3. Heller MT, Meltzer CC,  Fukui MS, et al. Superphysiologic FDG uptake in the non-paralyzed vocal cord. Resolution of false-positive PET result with combined PET-CT imaging. Clin Positron Imaging. 2000;3:207-211.