Weakness or paralysis of the vocal cord’s posterior cricoarytenoid (PCA) muscle, but with normal function of the vocal cord’s other muscles. The PCA muscle abducts (lateralizes) the vocal cord for breathing. The following are indicators of PCA-only paresis:
- Movement: The vocal cord closes normally for voicing, but it does not abduct for breathing. It remains motionless at the midline.
- Position and appearance: Position is normal during phonation, but the vocal cord does not open (lateralize) for breathing. Because the cord does not appear to move (it adducts or closes normally, but from an already-adducted position), PCA-only paresis is often mistaken for complete vocal cord paralysis—TA (thyroarytenoid), LCA (lateral cricoarytenoid), and PCA. Key points of difference between PCA-only paresis and complete paralysis are that, in the former case, the tip of the vocal process is in a normal medial position and the vocal cord has normal bulk and tone.
- Appearance during voicing (under strobe lighting): Completely normal, because the adductors of the cord (TA and LCA muscles) are intact. Hence, as with a normal cord, there is no flaccidity or asymmetry of vibration.
- Voice quality: Entirely normal. Many individuals are told this is due to “compensation” of the opposite cord, but actually it is because the muscles used for voicing (TA + LCA) are intact.