Levator glandulae thyroideae muscle

The levator glandulae thyroideae muscle (a.k.a. musculus levator glandulae thyroideae or levator glandulae thyroideae of Soemmerring) is an anatomic variant, consisting of a band of fibrous/fibromuscular tissue, connecting the pyramidal lobe of the thyroid to the hyoid bone. When muscle fibers are present it is an accessory muscle.

Gross anatomy

It is most commonly found on the left side of the neck . A true midline structure is very rare . Although the pyramidal lobe is usually present, it is neither a constant, nor necessary, finding in those with this variant fibromuscular structure .

In the 1960s, in a large Japanese study of 210 cadavers with a levator glandulae thyroideae, Mori classified them into five main types :

Origin

The levator glandulae thyroideae originates from the inferior margin of the hyoid bone most frequently. Alternately, it may be rarely found to arise from the thyroid cartilage, or even the trachea .

Insertion

When present, the levator glandulae thyroideae most commonly inserts into the pyramidal lobe, much less commonly, the superior isthmus of the thyroid.

Innervation

• small branch of the external laryngeal nerve
• few case reports have shown supply from twigs of the ansa cervicalis instead

Action

• elevates the thyroid

History and etymology

The Prussian neuroanatomist, Samuel Thomas Soemmerring (1755-1830) described this thyroid variant in a report published in 1794. Although historically Soemmerring is remembered most strongly for his cutting-edge work on the anatomy of the cranial nerves .