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Posterior cricoarytenoid muscle

The posterior cricoarytenoid muscle is a critical muscle of the larynx, often called the “safety muscle” of the larynx due to its essential role in respiration. It is the only muscle responsible for abducting the vocal cords, thus opening the glottis and enabling breathing. Detailed knowledge of this muscle is crucial in clinical practice, especially for ENT specialists and radiologists, due to its vital function and unique imaging characteristics.

Synonyms

  • PCA muscle

  • Dorsal cricoarytenoid muscle

  • Abductor of the vocal cords

Function

  • Sole abductor of the vocal cords (opens the glottis)

  • Allows air passage during breathing

  • Prevents airway obstruction by separating the vocal cords

  • Essential for normal respiration

Origin

  • Posterior surface of the cricoid cartilage’s lamina

Insertion

  • Muscular process of the arytenoid cartilage (posterior aspect)

Nerve Supply

  • Recurrent laryngeal nerve (branch of the vagus nerve, cranial nerve X)

  • Only intrinsic laryngeal muscle innervated exclusively by the recurrent laryngeal nerve

Artery Supply

  • Inferior laryngeal branch of the inferior thyroid artery (branch of the thyrocervical trunk)

  • Minor supply from the superior laryngeal artery

Vein Supply

  • Inferior laryngeal veins

  • Drain into the inferior thyroid vein

MRI Appearance

  • T1-weighted: Intermediate to low signal intensity (typical for skeletal muscle)

  • T2-weighted: Intermediate signal, can appear slightly hyperintense if edema or denervation is present

  • STIR (Short Tau Inversion Recovery): Shows high signal intensity in the presence of edema, inflammation, or denervation changes

  • Normal PCA muscle should have homogeneous low to intermediate signal on T1 and T2, with no bright signal on STIR

CT Appearance

  • Appears as a well-defined, symmetric, soft-tissue structure located posterior to the cricoid cartilage and arytenoid cartilages

  • Similar attenuation to other skeletal muscles

MRI images

Posterior cricoarytenoid muscle MRI AXIAL IMAGE