The thyroid ima artery (thyroidea ima artery, ''arteria thyroidea ima'', thyroid artery of Neubauer or the lowest thyroid artery) is an artery of the

head and neck This article describes the anatomy of the head and neck of the human body, including the brain, bones, muscles, blood vessels, nerves, glands, nose, mouth, teeth, tongue, and throat. Structure Bones The head rests on the top part of the vertebra ...

. It is an anatomical variant that, when present, supplies blood to the

thyroid gland The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans it is in the neck and consists of two connected lobes. The lower two thirds of the lobes are connected by a thin band of tissue called the thyroid isthmus. The thy ...

primarily, or the

trachea The trachea, also known as the windpipe, is a cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all air- breathing animals with lungs. The trachea extends from t ...

, the

parathyroid gland Parathyroid glands are small endocrine glands in the neck of humans and other tetrapods. Humans usually have four parathyroid glands, located on the back of the thyroid gland in variable locations. The parathyroid gland produces and secretes pa ...

and the

thymus gland The thymus is a specialized primary lymphoid organ of the immune system. Within the thymus, thymus cell lymphocytes or ''T cells'' mature. T cells are critical to the adaptive immune system, where the body adapts to specific foreign invaders. ...

(as ''thymica accessoria'') in rare cases. It has also been reported to be a compensatory artery when one or both of the

inferior thyroid arteries The inferior thyroid artery is an artery in the neck. It arises from the thyrocervical trunk and passes upward, in front of the vertebral artery and longus colli muscle. It then turns medially behind the carotid sheath and its contents, and als ...

are absent, and in a few cases the only source of blood to the thyroid gland. Furthermore, it varies in origin, size, blood supply, and termination, and occurs in around 3.8% of the population and is 4.5 times more common in fetuses than in adults. Because of the variations and rarity, it may lead to surgical complications, particularly during

tracheostomy Tracheotomy (, ), or tracheostomy, is a surgical airway management procedure which consists of making an incision (cut) on the anterior aspect (front) of the neck and opening a direct airway through an incision in the trachea (windpipe). The r ...

and other airway managements.

Structure

The thyroid ima artery is an embryonic artery and it occurs because of the failure of the vessel to close, remaining patent (open). The artery has a variable origin. It mostly arises from the

brachiocephalic trunk The brachiocephalic artery (or brachiocephalic trunk or innominate artery) is an artery of the mediastinum that supplies blood to the right arm and the head and neck. It is the first branch of the aortic arch. Soon after it emerges, the brachi ...

, but may also originate from the

aortic arch The aortic arch, arch of the aorta, or transverse aortic arch () is the part of the aorta between the ascending and descending aorta. The arch travels backward, so that it ultimately runs to the left of the trachea. Structure The aorta begins ...

, the right common carotid, the subclavian, the

pericardiacophrenic artery The pericardiacophrenic artery is a long slender branch of the internal thoracic artery. It anastomoses with the musculophrenic and superior phrenic arteries. Location The pericardiacophrenic artery branches from the internal thoracic artery. ...

, the

thyrocervical trunk The thyrocervical trunk is an artery of the neck. It is a branch of the subclavian artery. It arises from the first portion of this vessel, between the origin of the subclavian artery and the inner border of the scalenus anterior muscle. It is ...

, the

transverse scapular The suprascapular artery is a branch of the thyrocervical trunk on the neck. Structure At first, it passes downward and laterally across the scalenus anterior and phrenic nerve, being covered by the sternocleidomastoid muscle; it then crosse ...

or the

internal thoracic artery In human anatomy, the internal thoracic artery (ITA), previously commonly known as the internal mammary artery (a name still common among surgeons), is an artery that supplies the anterior chest wall and the breasts. It is a paired artery, with one ...

. It ascends in front of the

in the superior mediastinum to the lower part of the

. It differs in size and ranges from as small as accessory thyroid arteries to the size of primary thyroid vessels. The diameter of the lumen of the artery ranges from . The artery may be present as an accessory thyroid artery, but sometimes appears to compensate for incompetence or absence of one or more main thyroid vessels. Since it begins from below the thyroid gland and ascends upwards, it is mostly associated with absence or reduced size of the

. In such cases, it is known as the accessory inferior thyroid artery. In rare cases, the artery has been seen to be compensating for absence of one or both superior thyroid arteries. In cases where the length of the thyroid ima artery is shorter, the artery ends by supplying the

and is known as ''thymica accessoria''.

Function

Postoperative Hypoparathyroidism in Thyroid Surgery Fig4 Recorte

When present, the thyroid ima's chief supply is the thyroid gland, though it also supplies the trachea. The artery may extend and supply the

s. An infrequently observed artery, it is more frequently reported in the context of enlarged parathyroid glands (

parathyroid adenoma A parathyroid adenoma is a benign tumor of the parathyroid gland. It generally causes hyperparathyroidism; there are very few reports of parathyroid adenomas that were not associated with hyperparathyroidism. A human being usually has four parath ...

s). The artery ends by supplying the thyroid gland, or the parathyroid glands, as a single unit or as multiple branches. The artery is also found to be the only supply of the parathyroid gland in rare cases.

Clinical significance

The artery is only present in approximately 3–10% of the population. Thyroid ima artery is of surgical importance; due to its relatively small size and infrequent presence it can cause complications such as severe bleeding. Knowledge of occurrence of the artery is especially important during

sternotomy Median sternotomy is a type of surgical procedure in which a vertical inline incision is made along the sternum, after which the sternum itself is divided using a sternal saw. This procedure provides access to the heart and lungs for surgical proce ...

and

thyroidectomy A thyroidectomy is an operation that involves the surgical removal of all or part of the thyroid gland. In general surgery, endocrine or head and neck surgeons often perform a thyroidectomy when a patient has thyroid cancer or some other conditio ...

. Because the artery is smaller than the other thyroid vessels, and having an origin from one of the bigger vessels, a brisk cut while performing the surgery may cause complications such as severe hemorrhage and significant blood loss. The artery, if dissected, may draw back into the mediastinum and further complicate the condition by causing hemorrhage and clots in the thoracic cavity.

History

The thyroid ima artery was first defined by German anatomist in the year 1772. Hence, it was named the thyroid artery of Neubauer. The artery originates lower than the inferior thyroid arteries, so it is also known as the lowest thyroid artery. ''Arteria thyroidea ima'' is the

Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...

name of the artery.

Other animals

The presence of thyroid ima artery is also observed in other higher primates. The artery has been reported in

gorilla Gorillas are herbivorous, predominantly ground-dwelling great apes that inhabit the tropical forests of equatorial Africa. The genus ''Gorilla'' is divided into two species: the eastern gorilla and the western gorilla, and either four ...

gibbon Gibbons () are apes in the family Hylobatidae (). The family historically contained one genus, but now is split into four extant genera and 20 species. Gibbons live in subtropical and tropical rainforest from eastern Bangladesh to Northeast Indi ...

macaque The macaques () constitute a genus (''Macaca'') of gregarious Old World monkeys of the subfamily Cercopithecinae. The 23 species of macaques inhabit ranges throughout Asia, North Africa, and (in one instance) Gibraltar. Macaques are principall ...

s and

gray langur Gray langurs, also called Hanuman langurs and Hanuman monkeys, are Old World monkeys native to the Indian subcontinent constituting the genus ''Semnopithecus''. Traditionally only one species ''Semnopithecus entellus'' was recognized, but since a ...

s. Variations in the origin were also seen; it was found to originate from the aorta in the thorax, or the carotid in the neck.

References

{{Good article Thyroid Arteries of the thorax Arteries of the head and neck