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Inferior constrictor muscle of pharynx

The inferior constrictor muscle (ICM) is the lowest of the three pharyngeal constrictor muscles, forming the posterior and lateral walls of the lower pharynx. It consists of two overlapping components: the thyropharyngeus, arising from the thyroid cartilage, and the cricopharyngeus, arising from the cricoid cartilage. The fibers encircle the pharyngeal lumen, blending with the middle constrictor above and the esophageal musculature below.

The ICM plays a crucial role in pharyngeal constriction during swallowing, ensuring bolus propulsion from the oropharynx into the esophagus. The cricopharyngeus portion also functions as the upper esophageal sphincter, maintaining tonic closure at rest to prevent air entry and reflux.

Function

  • Propels food bolus from the oropharynx to the esophagus during swallowing

  • Acts as the upper esophageal sphincter (cricopharyngeus component)

  • Maintains pharyngeal lumen tone at rest

  • Contributes to coordination of swallowing and airway protection

  • Provides attachment points for pharyngeal fascia and surrounding muscles

Synonyms

  • Inferior pharyngeal constrictor

  • Cricopharyngeus-thyropharyngeus muscle

  • Lower pharyngeal constrictor

MRI Appearance

T1-weighted images:

  • Muscle appears as intermediate signal intensity, similar to skeletal muscle

  • Borders are well-delineated against high-signal fat in parapharyngeal and retropharyngeal spaces

  • Pathological changes such as muscle edema, hypertrophy, or tumor infiltration can alter signal

T2-weighted images:

  • Muscle shows intermediate to slightly hyperintense signal relative to surrounding fat

  • Edema, inflammation, or denervation appears hyperintense, aiding in detection of pharyngoesophageal disorders

STIR (Short Tau Inversion Recovery):

  • Muscle fibers are intermediate signal, while edema or inflammation appear bright hyperintense, highlighting infection, trauma, or neoplastic infiltration

T1 Post-Contrast (Gadolinium-enhanced):

  • Normal muscle shows mild, homogeneous enhancement

  • Pathological conditions (tumor, infection, inflammatory changes) show focal or diffuse enhancement, aiding lesion delineation

CT Appearance:

  • Muscle appears as soft tissue density structure along the posterolateral and posterior pharyngeal wall

  • Clear distinction from surrounding fat planes allows evaluation of thickening, masses, or pharyngeal wall asymmetry

  • Contrast-enhanced CT highlights vascularized lesions or inflammation

  • Axial and coronal reconstructions are useful for assessing cricopharyngeus function and pharyngeal lumen patency

MRI images

Inferior constrictor muscle of pharynx mri axial image -img-00000-00000

MRI images

Inferior constrictor muscle of pharynx