Cricoarytenoid ankylosis is easily mistaken for laryngeal paralysis. In neither condition can the patient move the vocal cord. In laryngeal paralysis, he cannot move it because he has lost motor nerve supply. In cricoarytenoid ankylosis, he cannot move it because the posterior attachment of the vocal cord is solidly fixed at the cricoarytenoid joint.
The "passive-mobility" test of Jackson will differentiate between the two conditions.1 Ankylosis of the cricoarytenoid joint immobilizes the arytenoid cartilage so that it cannot be displaced outward by the tip of a laryngeal forceps; in laryngeal paralysis such displacement is easily possible. In unilateral cricoarytenoid ankylosis, the general region of the arytenoid joint may appear different from the opposite side and thus give some indication of the pathologic change. Another diagnostic point concerns the ventricular bands, which in cricoarytenoid fixation may move and approximate each other in the midline but in laryngeal paralysis generally cannot.
SAUNDERS WH. Cricoarytenoid Ankylosis or Laryngeal Paralysis? AMA Arch Otolaryngol. 1956;63(3):260–261. doi:10.1001/archotol.1956.03830090032007
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