Divisions >> Otolaryngology-Head & Neck Surgery >> Otolaryngology Surgery Update e-newsletter >> April 2014 Issue >> Clinical Care - Evolving Trends in CT Scan and Unilateral Vocal Fold Motion Impairment
Evolving Trends in CT Scan and Unilateral Vocal Fold Motion Impairment
The etiology of unilateral vocal fold paralysis has changed over time. In a longitudinal, single-institution review spanning 20 years, Rosenthal et al. noted that iatrogenic paralysis from surgery (i.e., thyroid surgery and anterior approach spine surgery) has nearly doubled, whereas paralysis secondary to malignancy (i.e., lung cancer) has decreased 1. More frequent detection of thyroid disease with ultrasound and cross sectional imaging, and improvements in early detection of intrathoracic malignancy, were cited by Merati as explanations for this trend 2.
CT imaging from skull base to the aortic arch is an important component of the evaluation of unilateral vocal fold immobility. When a mechanism of injury is not evident, CT imaging allows a search for occult malignancies that might impact the vagus and/or recurrent laryngeal nerve. However, in cases of incomplete paralysis (paresis), the value of CT is more limited.
The value of CT scan
Vocal fold paresis is assessed with diagnostic modalities such as laryngeal EMG, flexible laryngoscopy, laryngovideostroboscopy and CT scanning of the neck; however, their roles are as yet undetermined 3. Given that the ionizing radiation of CT imaging poses some risk to the patient, Badia et al. performed a single-institution review of the clinical value of CT scanning in the evaluation of vocal fold paresis. Of the 176 patients with unilateral vocal fold paresis, 81 were judged to have an idiopathic etiology and 74% of them underwent CT scanning. Only one patient was found to have a mediastinal lymph node, which ultimately was metabolically negative on CT-PET imaging yielding a 0% final diagnostic yield. This is the first study of its kind and would benefit from data from other institutions, but it strongly suggests the risk/benefit ratio for discovery of occult malignancy in the population of patients with vocal fold paresis is poor.
CT imaging of the larynx has value when paralysis is secondary to a laryngeal neoplasm and when paralysis is traumatic in nature. For suspected arytenoid dislocation, CT is a diagnostic mainstay 4. Hiramatsu et al. — using a novel combination of CT scan and laryngoscopic findings – found that in patients with a non-traumatic vocal fold paralysis, CT reveals a passive gliding motion of the arytenoid with inspiration which is lost in cases of traumatic paralysis 5. The same group found an altered position of the muscular process on CT was a reliable finding in arytenoid dislocation 6. CT can also be useful in the planning treatment for paralysis. Examples include identification of positioning of laryngoplastic implants prior to revision thyroplasty and for identification of migrated injection agents such as calcium hydroxylapatite (aka RadiesseTM) 7, 8.
In summary, CT imaging has recognized value in the assessment of parlaysis and appears to be of less value in the assessment of paresis. CT is also useful in the assessment of laryngeal trauma and in some scenarios, CT becomes useful in planning treatment for vocal fold paralysis.
1 Rosenthal LH, Benninger MS, Deeb RH. Vocal fold immobility: a longitudinal analysis of etiology over 20 years. Laryngoscope. 2007 Oct;117(10):1864-70.
2 Merati AL, Shemirani N, Smith TL, Toohill RJ. Changing trends in the nature of vocal fold motion impairment. Am J Otolaryngol. 2006 Mar-Apr;27(2):106-8.
3 Sulica L, Blitzer A. Vocal fold paresis: evidence and controversies. Curr Opin Otolaryngol Head Neck Surg. 2007 Jun;15(3):159-62.
4 Rubin AD, Hawkshaw MJ, Moyer CA, Dean CM, Sataloff RT. Arytenoid cartilage dislocation: a 20-year experience. J Voice. 2005 Dec;19(4):687-701.
5 Okamoto I, Tokashiki R, Hiramatsu H, Motohashi R, Suzuki M. Detection of passive movement of the arytenoid cartilage in unilateral vocal-fold paralysis by laryngoscopic observation: useful diagnostic findings. Eur Arch Otorhinolaryngol. 2012 Feb;269(2):565-70.
6Hiramatsu H, Tokashiki R, Kitamura M, Motohashi R, Tsukahara K, Suzuki M. New approach to diagnose arytenoid dislocation and subluxation using three-dimensional computed tomography. Eur Arch Otorhinolaryngol. 2010 Dec;267(12):1893-903.
7 Woo P, Pearl AW, Hsiung MW, Som P. Failed medialization laryngoplasty: management by revision surgery. Otolaryngol Head Neck Surg. 2001 Jun;124(6):615-21.
8 DeFatta RA, Chowdhury FR, Sataloff RT. Complications of injection laryngoplasty using calcium hydroxylapatite. J Voice. 2012 Sep;26(5):614-8.