Definition:
Vocal Fold Paresis / Vocal Fold Paralysis is a vocal disorder where the vocal fold(s) don’t open or close properly due to abnormal nerve input to the voice box muscles (laryngeal muscles).  The nerves involved in the tensing and opening of vocal folds are the superior laryngeal nerve (SLN) and the recurrent laryngeal nerve (RLN), respectively.

Also referred to as:
Vocal Cord Paralysis

Various Types:
Vocal Fold Paralysis:  Here, there is a complete interruption of nerve impulse, resulting in no movement of the vocal folds.  The vocal fold may be paralyzed in the midline, intermediate, or lateral position.

Vocal Fold Paresis:  Here, there is partial interruption (or reduced activity) of nerve impulse, resulting in weak or irregular motion of laryngeal muscles

Other information:
In both types of paralysis (full or partial) voice changes, breathing/airway issues, and swallowing difficulties may occur.