Understanding the three-dimensional (3D) movement of immobile vocal folds (VFs) is very important. Because endoscopic findings reflect only the two-dimensional movement of VFs, it is impossible to obtain a correct diagnosis. The cases presented in this article include not only those of unilateral vocal fold paralysis (UVFP) but also arytenoid dislocation, laryngeal scarring and other statuses. The main diseases are described below.
UVFP : Even in cases of light UVFP, the paralyzed arytenoid is passively displaced cranially during phonation. Some surgical procedures may be applied to manage UVFP, but only arytenoid adduction can resolve this passive movement. I will also describe several specific types of UVFP, such as adductor branch paralysis (AdBP).
Arytenoid dislocation (AD) : AD can be divided into two types: posterior and anterior dislocation. Our 3D computed tomography (CT) study revealed that posterior AD is very rare and often misdiagnosed as AdBP (and vice versa). We detected two subtypes of anterior AD: cranial and caudal. The VFs in cases of caudal AD are located in the mid position, and the patient’s voice is not severely affected; as such, these cases are sometimes misdiagnosed as medial UVFP.
Other types of immobile VF : A number of rare and unique types of immobile VF have been reported, such as scarring after intubation or trauma, fracture, congenital and VF of many other causes. Endoscopy is insufficient for understanding what happens to a patient’s immobile VF However, 3DCT can reveal the actual status of these cases.