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Inferior thyroid vein

The inferior thyroid veins are paired veins that provide venous drainage of the lower poles of the thyroid gland, the trachea, and adjacent cervical structures. Unlike the superior and middle thyroid veins, which drain into the internal jugular vein, the inferior thyroid veins descend anterior to the trachea and empty into the brachiocephalic veins (right, left, or both).

They usually form a plexus of veins anterior to the trachea just below the thyroid isthmus, known as the thyroid venous plexus. The left inferior thyroid vein most commonly drains into the left brachiocephalic vein, while the right inferior thyroid vein drains into the right brachiocephalic vein or sometimes directly into the superior vena cava. There is marked anatomical variation, and the inferior thyroid veins may form a common trunk before draining.

Clinically, these veins are important during tracheostomy, thyroidectomy, and mediastinal surgeries, where injury can lead to significant venous bleeding. They are also relevant in central venous catheter placement and in evaluation of mediastinal venous drainage pathways.

Synonyms

  • Vena thyroidea inferior

  • Inferior thyroid plexus vein

Function

  • Drains venous blood from the lower poles of the thyroid gland

  • Contributes to venous return from the trachea and cervical esophagus

  • Empties into the brachiocephalic veins and occasionally into the superior vena cava

  • Plays a role in mediastinal venous connections and central venous drainage

Tributaries

  • Venules from the inferior thyroid gland

  • Tracheal and esophageal venules

  • Thyroid venous plexus

MRI Appearance

T1-weighted images:

  • Appears as a signal void (black lumen) coursing anterior to the trachea

  • Surrounded by fat planes that enhance contrast with adjacent soft tissue

T2-weighted images:

  • Vein appears as a linear signal void within the lower neck/mediastinum

  • Thrombus, when present, may appear as intermediate to high signal depending on stage

STIR:

  • Fat suppression highlights venous course against mediastinal fat

  • Useful for identifying perivascular edema or inflammatory changes

T1 Post-Gadolinium (Gd-enhanced MRI):

  • Inferior thyroid vein enhances brightly and homogeneously

  • Filling defects correspond to thrombosis or compression

  • Useful for mapping mediastinal venous anatomy prior to thyroid or tracheal surgery

MRA (Magnetic Resonance Angiography):

  • Visualizes venous plexus and connections to brachiocephalic veins

  • Helpful for preoperative venous mapping in neck and mediastinal procedures

CT Appearance

Non-contrast CT:

  • Difficult to visualize directly; appears as a small tubular density anterior to the trachea

  • Sometimes recognized by its course and fat planes

CT Post-Contrast (CT Venography):

  • Inferior thyroid veins opacify as enhancing venous channels draining into the brachiocephalic veins

  • Demonstrates thyroid venous plexus anterior to the trachea

  • Multiplanar and 3D reconstructions helpful in distinguishing veins from lymph nodes or masses

  • Detects dilatation, thrombosis, or anomalous drainage patterns

CT images

Inferior thyroid vein axial ct image -img-00000-00000

CT images

Inferior thyroid vein sag ct image -img-00000-00000