Parathyroid Glands - HD

Introduction and Purpose

I don't have anything to disclose.

The purpose of this talk is we'll try to give a brief review of some aspects of the parathyroid glands related to the anatomy, some of the embryology, and mostly in relation of the location of this glands and the pathology in order to see what is the role for imaging and how all this interacts with the medical and surgical decisions in these patients.

Anatomy and Importance of Parathyroid Glands

The parathyroid glands are small, and they are so important, even when they are so small.

They are basically three, four glands, although they can be less than four or more than four.

Some patient can have supernumerary glands and the glands, again, they are small in size and also in weight.

The average size is about between five and six, six millimeters.

And when they have pathology, they can, they enlarge and they are heavier.

Usually the thyroidic glands, the normal thyroidic glands, we cannot see most of the times by imaging, unless they are affected by a pathologic conditions when they enlarge and they start overproducing a thyroid hormone.

In the average patient, the glands are in very predicted location.

The four glands are two superior to inferior, and usually they are positioned at JSN to the thyroid gland, as the name says, para at jn next to the, and they are about specific relation po particularly to the posterior portion of the thyroid gland.

Most of the glands have approximately 80%, follow this pattern.

And there is a smaller percentage that can have a ectopic location.

Utopic location is the ones who are really close and adjacent to the thyroid gland.

What is important to recognize is that the final position of this gland is related to what happens in the development in the embryologic portion of the development of the face and the neck.

Embryology and Development

So the parathyroid glands developed at six weeks and migrate calie up eight weeks.

What is interesting is that the inferior glands develop from the, third, bronchial pouches.

Meanwhile, the superior glands, originate from the fourth bronchial pouch, and I'm gonna see some, I'm gonna show you some schemes about it by six weeks and develop from the ventral portion of the foreign gel, pouches.

But they migrate at, eight weeks and the superior glands, the origin is very closely associated with the thyroid and also the descend with the thyroid, particularly with the lateral, portions, the lateral lobes of the thyroid gland.

The inferior glands, have a close relationship with the thymus and the sand within it.

Here you have, for example, inver in invertebrates in the embryo, about six weeks.

They have these structures called the bronchial arches that are gonna be the precursors of many structures in the face and in the neck.

These bronchial, arches ha have, some clefts in the lateral portion that is derma and have, pouches in the medial aspect of the, of this.

And this is pretty much, endoderm.

The inferior glands are, originate from the third pouch, and these are enclosed association with et thymus.

Meanwhile, the fourth, the, the, the, from the fourth pouches are originating, the, the, superior glands.

And here you can see in this scheme that when they start migrating ly, the fourth, the superior, the superior, glands that are associated with the thyroid, they have a, a shorter migration process.

They start close to the thyroid gland.

Meanwhile, the inferior glands have a longer migration process all the way with the thymus.

Now, in this process of migration, some of these glands can have different, positions.

Eventually, some of the glands, or portions of these glands can stay up, so peer to the thyroid glands.

Some can stay forward to the par to the thyroid gland, and some can go all the way down with the thymus into the mediastinum.

This is important because, from this cattle migration of the parathyroid glands, basically we are gonna have a wide spectrum of locations, and that is gonna be important, for the role of imaging to, identify this.

Again, the spec locations are gonna be related to the thyroid gland or just inferior this, the so-called atopic glands.

But the reality is that you can find glands way up behind the angle of the mandible to about the level of the hyoid bone, but can extend all the way down.

You can see a glands all the way down to the, to the mediastinum.

There are some, unusual locations, that are, can be related to inferior or, or superior glands adjacent to the firings behind the firings, the sugo along the cid sheet, and the ones that go all the way down with the thymus can stay really in the upper portion of the, of the neck, or can be completely all the way down into the, the mediastinum adjacent to the aortic arch.

Some, some of these glands, even can get embedded within the thyroid and have an intra thyroid location, as we are gonna see later on.

Function and Pathology

Basically what, the, the purpose of, of the thyroid gland, and the parathyroid glands have a important role for the, metabolism of the calcium with these actions.

So upon, upon the bones, kidneys and the GI tract, when they are, hyper functioning, basically produce an excess of parathyroid hormone and produce what is, hyperthyroidism.

And most of the time is the, the most common is primary hyperthyroidism.

And the most common cause is the presence of a adenomas.

80 to 85% of the patients with peria hyperthyroidism are gonna have adenomas well established, lesions.

Smaller percentage, can be related to hyperplasia or multiple adenomas.

Most of the time double adenomas.

And a very small percentage of cases can be related to carcinomas.

The vast majority of the patients with primary hyperthyroidism have the form that is called sporadic.

But some patients have a famili form of, hyperthyroidism particularly, visible with a patient with a multiple in neoplasia, like a MN one or MEN two.

Remember that these patients, for example, with the MEN one, they are also associated with pary tumors or with the, or with the pancreatic neoplasm.

In, in, in, in the order m in two, they usually associated with adrenal tumors for pheochromocytomas or with the medullary carcinoma.

There are some other more unusual forms of, of familiar, origins, but this is, in, in much less a percentage.

Nomenclature for Parathyroid Locations

One, one thing I would like to talk, and this is a related also with the migration.

The, the final position of the, of the parathyroid gland in the neck or in the upper mediastinum and all these structures is, a nomenclature that has been described, by surgeons.

This is, the so-called, nomenclature for plus five parathyroid adenomas was developed by surgeons in, in the m Anderson, by Dr. L per surgeon, surgeon.

And basically, the purpose of this, classification was to describe the location of parathyroid adenomas, making a more consistent, and reliable way to describe the position, and in order to get better communication between surgeons, between radiologists and pathologists.

And one of the important thing is this is based on detailed information that is provided by, by imaging.

It was, when, when, when this was, described, it was mentioned that was not enough to say, well, the pathology is located in the superior or inferior glands, but mostly, more information that it needed to see the three dimensional, location of this glands in relation with the thyroid and with other structures.

So this, nomen is based on quadrants and the anterior and posterior depth relative to the course of the recurrent laryngeal nerve, and particularly with a parenchyma.

In the description of Dr. Perilla, she described a classification scheme using the letters A through G.

Now, in this came from his, from her, article.

This is a, from retraction of the, of the, of, of the, of the thyroid gland.

Basically, you can see here the quadrant location for glands that are superior and inferior in quadrants, and labeled from a a a to G.

The superior glands are basically, are ahern to the posterior parenchyma to the posterior, parenchyma of the upper pole.

And some of these glands are really embedded in the par. The parenchyma, even by surgeries, are difficult to see sometimes by radiology are, are hard to, to see.

The glands B are behind, behind or back to the, to the, to the thyroid, to the posterior meet an upper pole of the thyroid gland, glands c that is also a superior, but it is much more inferior in location because the origin you has, the pedicle is from the, from, from, from, from, from the upper head and upper pedicle.

It is a gland that falls behind and posterior and, close to the inferior pole of the, of, of the thyroid gland and close to the clavicle.

But these are posterior glands.

The, d is, it is, difficult.

It is, close to the, to the, it is in the mid region of the posterior surface of the thyroid.

And this is directly over the recurrent pharyngeal, pharyngeal, recurrent laryn gel nerve at the level of the inferior thyroid vessels.

And this is also a difficult, gland for resection.

The gland, category C is close to the inferior pole of the thyroid anterior and the external aspect.

And this is the easy gland.

This is, is easy to see and easy to operate on this one, the f is a gland that follows the, the, the, the, the thy.

And this is a gland that is falling into the thyroid athymic ligament and stay in the superior thymus, and also the glands that are all the way down to the median marker.

Consider f.

And the G is the, is the, the, the adenoma of the clan that is intra thyroidal is the G intra thyroidal.

And basically the, the purpose of describing this is to have a, a very concise, information about the position of this, of this glands, and, and to put that in the radiology report, in the operative report.

And, that, could be, a better understanding about this, particularly in the patients who have had, are going to have repeated surgery.

Imaging Examples of Parathyroid Locations

Here you have some examples in imaging.

This is from a ct.

This is the type B behind the thyroid.

This is a poster to the mid portion of the thyroid.

And this usually this gland, this in the, in the tracheal esophageal group.

This is sag of the trachea, mid portion of the thyroid gland.

This is the gland type E. This is probably the most common.

And, and this is the most common location of this, according to the, to the, to the per lo nomenclature.

This is the gland that is inferior and left, lateral to the, to the lower, lower pole.

This is a thyroid lo this is a gland. This is a type B.

Remember, this is posterior to the gland, in the middle upper pole in the, in the tract esophageal group.

This is longitudinal view of the left lo.

This is, hypo eco elongated structure that is a big adenoma.

And here you can see in the la in the lateral, reform that this is the thyroid lobe.

And in the gel groove, this elongated, gland, so this is the second most common, location.

The most common is this location, the type, the type E.

Role of Imaging in Parathyroid Disease

Now, all this information is, is important for the role or the role of image imaging.

All of all of you know that the years ago, the surgical treatment of primary hyperthyroidism was pretty much a extensive, dissection of the neck, for looking and evaluating the, the glands for, for gland exploration.

But that has been changing to minimal invasive basic approach.

And, for this, purpose, there is a need for really good imaging for localization, not only from the usual locations of these glands, but also on the unusual locations.

And this important because the, in, in, in, in current, with current imaging, the localization of the preparative of parathyroid gland with high resolution, it is, has a great sensitivity up to about 96% of localization of these, structures.

It is considered that the success rate for, of less invasive techniques, equals to the traditional approach.

But not only the, the, the, the, the, the importance also for the imaging is to identify concurrent thyroid pathology.

And, it is, understanding, most of these patients.

So as we hear in previous, lectures, because of the, large prevalence of thyroid, pathology, thyroid nodules is not unusual that when we look for parathyroid adenomas, we look for also for thyroid nodules, and again, is I, the imaging is, essential to detect the ectopic, parathyroid or tissue and recurrent or persistent hyperthyroidism.

Minimally Invasive Parathyroidectomy

Talking about the minimally invasive, parathyroidectomy, basically the, this has, the technique has that is the most effective and most used actually for the evaluation and resection of parathyroid adenoma, particularly in single, in single lesions.

The American Association of Endocrine s in the guidelines for 2016 indicates that the requirement for minimally invasive para therapy, number one, is to have, preoperative location of imaging years ago.

And there is a classic, quote of a interventional radiology, Dr. John do doman from the NIH, saying that the, with, what was that?

The only localization technique that was required to, for, for, for parathyroid surgery was to locate an expert surgeon for parathyroid.

But in this case, basically, it has migrated to the imaging and also this, minimally tech. Nick requires some adjunct, techniques for in surgery, such as, intraoperative monitoring of the parathyroid or hormone, particularly to see if we are dealing with uni or pleuritic glandular disease.

For this, it is needed to have a tech in the OR with, equipment to do an SI of the parathyroid hormone.

Basically, what they do is, they, they, they draw, a blood, A baseline is when the patient before get intubated, draw, a blood, when, when they, times zero is when they excise, the, the, what they expect is the gland.

And then wave and draw blood at five and 10 minutes.

And basically, what what makes the, the di, the, the diagnosis is a drop of more than 50% of the level from the baseline.

Then they are dealing with the right, with, with a, with the right gland, with a, with a culprit gland.

So if they are no drop, they have to, to, to keep it looking.

Imaging Modalities

Now, there are, the imaging modalities, that are available and we use mostly are ultrasound and, nuclear medicine, but other, other, modalities such as CT MR in some invasive, modalities are in use.

The most common, low use are ultrasound and, nuclear medicine with cyt plantar imaging.

And these are, most recently, with the spec, the spec ct.

Ultrasound

Now, ultrasound has been used, for longer time high resolution ultrasound is required, and the technique also includes the color and power doppler imaging and greater compression grade scale, as well as described many years ago from, from, the group from Stanford, the scanning technique, as, that requires high frequency transducer, the patient with extended neck, the thyroid gland used as a reference, important to do transverse and longitudinal images from the submandibular glands to the subclavian vein, and from the midline of the treche to the carotid art to encompass all these areas where the glands can be located.

The parathyroid at the nooma, by ultrasound characteristics are, are going to be solid hypo coic ovoid shape.

Some have, have a beam shape or have been elongated.

Other, shapes can be present.

For example, the longer or the, larger glands or larger adenomas can be multi lobulated can be more modular.

Some can be, triangular, et cetera.

Characteristics, there are hypo oid by the dense, solid component and the cellularity of the adenoma.

And the long axis parallels the long axis of the thyroid. Lole, this is not the only, sonographic appearance, although the vast majority are hyper coic.

They can have be heterogeneous.

Some of these can be hyper coic, because of bleeding, or some can have some fat.

There are some that are, have more content of fat that is, the, the so described lipo adenomas.

But these are tumors that are rare.

Frequently those adenomas can be cystic partially or nearly entirely cystic through cysts are uncommon.

Most of these are non-functional, but, some, adenomas with cystic changes, the vast majority of these are functional, and most of the time it is because the, they can be some bleeding within the, within the gland and eventually have some cystic degeneration.

And here you can see in this system, maybe examination a cys.

This is the cystic gland with activity in the delayed, images.

One thing to, remember about the ultrasound for thyroid adenomas is the use of color and power doppler.

The parathyroid adenomas are highly vascular lesions, and, these, lesions are feed by large, and large, branches of the inferior thyroidal artery, artery that have a characteristic, polar insertion.

And once the, the, this branch gets into the artery and the, the branch gets into the adenoma, they can present with a vascular pattern or artery.

Here you can see in this example, longitudinal albu, a parathyroid adenoma with a large hypertrophic polar branch.

And in this one classic arching appearance and the, the, the, the branching into the deep portion of, of the gland parathyroid, the, ultrasound, has some challenges and some pitfalls.

One of these, obviously, the body habitus patients who are large, who cannot extend the neck very well, are very difficult, or particularly for those glands, like in locations B and C, that are really deep, difficult to differentiate from lymph nodes or thyroid nodules, or patients with multinodular goiter.

Patients with parathyroid hyperplasia, because the glands are small or in ectopic locations, localization, differentiate with lymph node, with Lee East, as was mentioned before, normal lymph nodes, for example, this a big lymph node in located inferior to the gland, but the central echogenic area, the presence of color flow in comparison with the distribution.

Ectopic and Intrathyroidal Parathyroid Glands on Ultrasound

Now, ectopic locations of parathyroid glands, again, they can originate from superior or inferior glands.

This is from a, a large study of patients with ectopic adenoma skin.

And you can, here, you can see the distribution.

The most common distribution for ectopic adenomas are located within the thymus, lesser in the, in, in, as you can see in other locations, including the mediastinum, just deep in the mediastinum in other, areas that are much less common.

Here is a few examples.

Here, you can see by ultrasound, it is possible to see some of these glands that follow, the gland into the thymic ligament region.

This is an ultrasound.

You can see the, this is the gland, this is the right denominate artery.

Here you can see the vascularity, the polar branch here, and look at the location.

And this are located just posterior to the, to the, the cla, the clavicle, the head of the clavicle.

Here, you see in the normal size, in, in the relation with these vessels.

So this patient obviously can extend the neck very well, but also the, the, the, the sonographer can be very, have to be careful about looking all these patients.

And one of the things that are important to, to mention is that the location of this, of, of these glands, and when doing ultrasound, it is important to have deeper, portions, visualize and have good landmarks to, to get the correct localization otherwise.

And for example, the use of, clips and the use of, of, of, of, sometimes even, lower frequency trans user.

This another topic, the normal here, you can see this is, could be a lymph node.

This is very close relationship with the karate.

And here you can see with the use of opular, more of the vascularity of this one.

And this is with the co the, the CT examination, the thyroid, lo and justs lateral was that this, this, this was a patient who had a previous surgery.

And, in patient, patient with an me n one, there are some areas that are gonna be impossible for ultrasound, for example, these ectopics, he is, this is a retron adenoma.

Here, you can see why can of be seen by ultrasound because this is, there is some air.

And here you can see in the transverse location, this is a retro of adenoma, as you can see in, obviously, again, cannot be seen in this, intra parathyroid adenomas, are, are, are rare.

A recent series, located a large number of adenomas in the location in relation with the thyroid.

The vast majority of this is from the University of Pittsburgh, more than, they divided this partially intra and complete the thyroid par in the thyroid when this greater than 50% or completely surrounded by the thyroid, na.

Here is an example of one of these lobulated, partially intra thyroid.

And the main findings they found was that this, should, these scenarios were solid and composition profoundly hypo co relative to the thyroid gland, and with the presence of a polar feeding vessel.

Here is an example of one of these intra parathyroid adenoma in a patient with a family history.

This is from another big serious, when the location of the thyroid gland, most of the intra para adenomas are, 90% are in the lower lateral quadrant and some in the superior pole.

And again, the challenge is differentiate for intra parathyroid adenomas from coexisting thyroid nodules.

Ultrasound is a good, okay, is, is sensitive for solitary adenomas, but falls to patients post failed surgical exploration and with lesser, accuracy for fiber, blood and multina glands.

Nuclear Medicine Imaging

Radio nuclear imaging, basically by plantar imaging, whether with the use of a maybe spec, but the most current location, the most higher sensitivities zone for spec ct.

Here, an example of a lower parathyroid adenoma.

And here this is a superior parathyroid adenoma in location B, the S spec obviously improve the sensitivity for solitary adenomas and double adenomas.

And the benefits is the combination of an anatomical CT for the functional, imaging and discriminate parathyroid adenomas from anatomic landmarks.

This is an example of a spec CT for a mediastinal ectopic adenoma, the spec CT higher sensitivity, and a specificity and superior for cases of ectopic and multi glandular disease.

This is a patient with an MN one hyperplastic gland, and here you can see that this is, in the left parital location.

4D CT

For this, it is a method that takes advantage of the perfusion, the hyper vascularity of the glands, with over, the per change in perfusion over time with rapid contrast uptake and wash out.

It is, IM imperative for doing multiple phases for the acquisition of the 3D reforms and allows lateralization of quadrant localization of the hyperfunctional glands.

And this is, very important for the preoperative, planning particular and re-operation.

So in the four DCT, basically there are three.

The findings are the low international.

In the non-contrast phase, art has been an early, an early arterial phase and wash out of contrast phase.

So contrast in delayed venous phase.

So this important, the, the, the, the multi-phase imaging.

Here you have an example.

The pre contrast examination is, is, is, is, important because of the higher at admiration of the thyroid gland.

This is the nodule here, and this is the arterial phase.

You can see corresponds to this, nodule of lesser attenuation and the wash out in venous face here.

Occasionally you can see the feeding basal the same as you can see in the ultrasound examination.

This one case of a patient with multiple surgeries with m in one with a la left a small hyperplastic gland without contrast, and this in the arterial phase and with a planner, reform in the, in the coronal and in the cytal reform.

So the four e CT is an ex, has an excellent detail for adenomas, localization and detection of ectopic lesions.

And, but, however, has the prime for radiation and increased organ dose, too, this is, a patient with a double adenoma.

Here you can see how is the arterial, at, during the attenuation in the first pass, wash out.

But the most important thing is that you don't see this in the, with a, with a, with a, with in the non-contrast examination.

Interventional Procedures

And lastly, some interventional procedures, some like ultrasound guided FNA for PTSA.

Some people say that it is not, a good idea because these patients tend to have, some, some inflammatory changes in, in fibrosis.

And in some patients is, sometimes we are requested to do, localization just for lateralization, having, sampling the internal jugular veins, for example, in these cases, remember that the, the, the upper, portion of the thyroid, gland and adenomas in these locations are drained through the superior veins, and middle veins into the jugular vein.

So this patient has to be with a neck extended, and the sampling has to be done really low in the base of the neck, as close as possible to have the, the, the localization of the, the, greater level of the, the, parathyroid, the parathyroid, for example, in this particular case, with the greatest, level of param in the right and has to be, the, for lateralization, greater than 10%, of the PTH levels.

Conclusion

So in, in conclusion, the, the current surgical treatment with, minimal invasive surgery requires, requires accurate localization of abnormal parathyroid glands.

Imaging is useful if not essential for surgical planning.

Ultrasound and media scintigraphy are the first line modalities, but challenge persistent recurrent hyper parathyroidism with multi glandular disease and ectopic location, is migrating for increased use of spec CT and four DCT.

These are second line modalities, but in some centers, these are becoming part of the first line modalities along, for example, with ultrasound and, four DCT or spec ct.

Thank you very much.