2. Parathyroid glands are located within the
visceral space of the neck, posterior to the
thyroid gland, in the vicinity of the
tracheoesophageal groove.
They may be located either inside or outside
the thyroid capsule.
4. Arises from the 4th branchial pouch, during fetal development,
migrates with the thyroid gland.
Eutopic : located on the posterior aspect of the superior or
middle third of the thyroid lobe in more than 90% of the general
population.
Ectopic :
above the upper pole of the thyroid lobe (<1%)
posterior to the pharynx or esophagus, in either the neck or
the superior mediastinum (1%–4%)
intrathyroidal (<3%)
5. Arises from the 3rd branchial pouch, migrates with thymus.
Eutopic : located at the level of the inferior pole of the thyroid
lobe, in its posterior, lateral, or anterior aspects (61%).
Ectopic: in the anterior mediastinum (4%–5%); intrathyroidal
(<1%–2%).
In the anterior mediastinum, inferior parathyroid glands may be
situated within the thymus, at the posterior aspect of the thymic
capsule, or in contact with the great vessels of the mediastinum
6. four times more common in women than in men and is most
prevalent in the 5th to 7th decades of life
signs and symptoms - hypercalcemia, which may affect multiple
systems
Symptomatic patients at presentation - recurrent kidney stones,
osteopenia, hypertension, peptic ulcer disease, mental status
changes, and fatigue
7. Most cases of primary hyperparathyroidism are caused
by a solitary parathyroid adenoma (88%).
Other less common causes are multiglandular disease
from double adenoma (4%) and multiple gland
hyperplasia (6%), and rarely, carcinoma ( 1%)
increased incidence of parathyroid hyperplasia in MEN
type I and type IIA.
8. To select patients for minimally invasive parathyroidectomy
surgery, the surgeon needs precise localization of the
parathyroid adenoma and to exclude multiglandular
disease
9.
10. •most nodules need to be >1 cm to be confidently seen
on ultrasound
•Parathyroid adenomas are
homogeneously hypoechoic to the
overlying thyroid gland.
•Larger adenomas can be multilobulated
•Color Doppler - show a characteristic
extrathyroidal feeding vessel (typically a
branch off the inferior thyroidal artery),
which enters the parathyroid gland at one
of the poles
11. • Thyroid nodules and cervical lymph nodes mimic parathyroid
pathology.
• Lymph nodes are distinguished from parathyroid adenoma by a
hyperechoic central fatty hilum and absence of vascularity seen
with doppler
• Thyroid nodules appear less vascular than parathyroid
adenoma
• And demonstrate calcification,cystic changes,and heterogenicity
• A hyperechoic capsule favors parathyroid adenomas
• But these sonographic features are inconsistent and parathyroid
adenoma are diff to differentiate from LN or thyroid nodule
12. 12
Figure 1 :Longitudinal USG shows a parathyroid adenoma
(arrow) inferior to the right lobe of the thyroid gland
14. 14
Transverse and longitudinal views The hypoechoic nodule located
posterior to the mid-lobe of the right thyroid is indicated by an
arrow in both the transverse and longitudinal views of the right lobe of
the thyroid. TR= trachea
15. • Enable accurate localization of the parathyroid adenoma and to
depict multiglandular disease
•The 4D CT protocol is composed of multiple phases (typically two to
four phases) and reformatted images in three planes.
•The first three “dimensions” are multiplanar CT: axial acquisition
with coronal and sagittal reformations.
•The fourth “dimension” of 4D CT is change in enhancement
overtime from non– contrast-enhanced, arterial, and delayed
(venous) phase imaging.
16. • The characteristic contrast enhancement pattern of a
parathyroid adenoma - peak enhancement on the arterial
phase, washout of contrast material from the arterial to
delayed phase, and low attenuation on the non–contrast
enhanced images .
• Four-dimensional CT has high accuracy in localizing an
adenoma to a quadrant (87%) when used as a firstline
investigation.
17. The feeding artery is usually a branch of the inferior thyroid
artery, and the artery can be tortuous and enlarged in the setting
of adenoma because of its increased blood flow An enlarged
adjacent vessel may also be an enlarged draining vein
The polar vessel sign can be present in up to two-thirds of
parathyroid adenomas on 4D CT images
20. Step 1: Review for Lesions in Eutopic Locations in
Arterial Phase.
• The superior parathyroid gland has a more consistent location
posterior to the mid-to-upper third of the thyroid gland .
•The inferior parathyroid gland lies inferior, lateral, or posterior to
the lower third of the thyroid
•The arterial phase should be the focus of the initial review
because this is the phase in which the attenuation of the
parathyroid adenoma will be highest, with reported mean
attenuation ranging from 138 to 180 HU
21. Step 2: Review for Lesion in Ectopic Locations in Arterial
Phase
•Ectopic parathyroid adenomas and ectopic parathyroid
hyperplasia account for 20%–25% of cases
•The inferior glands -third branchial pouch and the superior
glands -fourth branchial pouch.
•These pouches are approximately at the level of the bifurcation
of the carotid artery.
•During fetal development, the inferior gland migrates with the
thymus.
•So an ectopic inferior gland may be in any location from the
carotid bifurcation to the anterior mediastinum, including within
the thymus or the thyroid gland.
22. •There is less variation in the location of the superior parathyroid,
which migrates with the thyroid gland. Rare sites for an ectopic
superior parathyroid gland are in the retropharyngeal space or
intrathyroid
•More commonly, a superior parathyroid adenoma -pseudoectopia
due to the enlarged gland falling caudally and posteriorly in the
tracheoesophageal groove .
•Thus a posterior mediastinal parathyroid adenoma is more
characteristic of a superior parathyroid adenoma that has fallen
caudally.
•In contrast, an anterior mediastinal parathyroid adenoma will be
from the inferior parathyroid gland and along the thyrothymic
ligament
23. Step 3: Compare Other Phases for Characteristic
Enhancement
•Characteristic enhancement for a parathyroid adenoma is vivid
contrast enhancement in the arterial phase, rapid washout of
contrast material in the delayed phase, and lower attenuation
compared with thyroid gland in the nonenhanced phase
•The peak enhancement has been described as between 25 and 60
seconds after injection
24.
25. Step 4: Evaluate for Characteristic Morphology
•A parathyroid adenoma is oval or rounded with margins that are
smooth or slightly lobulated
•Other shapes of parathyroid adenomas are teardrop, discoid,
tubular, and pyramidal
•Lobulated margins and cystic component help differentiate a
candidate lesion from a normal lymph node. Normal lymph nodes
have smooth margins and are solid or have fatty hila
26. Step 5: Compare CT Findings with Other Modalities
and History
•If there is a candidate lesion at 4D CT examination, the other
studies should be reviewed to determine if the studies are
concordant
27. The two main mimics of parathyroid adenomas- lymph nodes and
thyroid tissue.
Lymph nodes - progressively increasing enhancement after
injection of contrast material, with peak enhancement at 90
seconds corresponding to the delayed phase.
Thyroid tissue - enhance intensely in the arterial phase but will
also have increasing contrast enhancement between the arterial
and the delayed phases when the attenuation is measured .
In addition, thyroid tissue will have intrinsic high attenuation on
the non–contrast-enhanced images because the thyroid gland is
iodine-containing
28. Three general techniques of radionuclide scintigraphy are
commonly used for the detection and visualization of
hyperfunctioning parathyroid glands:
1. single-phase dual-isotope subtraction imaging,
2. dual-phase single-isotope imaging, and
3. a combination of the two
29. Single-isotope dual-phase
imaging technique was proposed on the basis of the difference
between the rate of 99mTc sestamibi washout from the thyroid
gland and the rate of washout from hyperfunctioning
parathyroid glands, which is typically slower.
This technique requires a single injection of 99mTc sestamibi,
followed by imaging at approximately 10–15 minutes and 1.5–3
hours after the injection.
30. 99mTc sestamibi consists of lipophilic cationic molecules.
The detectability of parathyroid adenomas and hyperplastic
parathyroid glands is related to the presence of mitochrondria-rich
oxyphil cells.
99mTc sestamibi normally is distributed to the parotid and
submandibular salivary glands, thyroid gland, heart, and liver;
uptake is not seen in normal parathyroid glands.
31.
32. a) Images show delayed washout in a large right inferior parathyroid adenoma that
extends from the inferior pole of the right thyroid lobe to the superior mediastinum.
b) early washout in a large thyroid adenoma, which extends from the lower pole of the left
thyroid lobe to the superior mediastinum
a b
33. 33
Figure 12 : Ectopic parathyroid adenoma. Delayed image from a
sestamibi scan shows increased uptake in a surgically proven ectopic
parathyroid adenoma in the superior mediastinum (arrow).
34. Dual-isotope subtraction
imaging techniques is by using 99mTc sestamibi and
123I or 99mTc pertechnetate.
99mTc pertechnetate, which is taken up only by the
thyroid.
subtraction of thyroid images obtained with iodine-123
(123I) or 99mTc pertechnetate from those obtained with
99mTc sestamibi.
Evidence of residual radioactivity on the subtraction
image represents a hyperfunctioning parathyroid gland
35. 35
Fi Parathyroid adenomas detected in a patient by Tc-99m sestamibi
subtraction imaging with I-123. Tc-99m sestamibi subtraction imaging
with I-123 shows an adenoma below the inferior pole of the left lobe of the
thyroid gland.
36. A single parathyroid adenoma is now most commonly
resected through a smaller unilateral incision on one side of
the neck in one quadrant.
The other glands are left unexplored if the venous
intraoperative parathyroid hormone level drops following
resection.
A decrease of more than 50% from the baseline PTH value
at 5–10 minutes after resection is suggestive of a single site
of primary hyperparathyroidism.
37. 39
On a thyroid ultrasound study a
mass is noted posterior to
the left thyroid lobe
This is the same ultrasound
depicted above. The isthmus
and left lobe of the thyroid were
colored blue. The left lower
parathyroid mass was colored
yellow
38. 40
This CT scan study of the same patient shows the
parathyroid adenoma posterior to the left thyroid lobe.
39. 41
This middle-aged woman presented with hyperparathyroidism. A
parathyroid sestamibi scan showed intense activity in the left
lower parathyroid gland, 2 hours after the administration of
the Tc 99 isotope. A slight activity was also detected on the right
side, raising the possibility that another parathyroid adenoma might
be present on the right.
41. Prominent sub-endplate densities at multiple
contiguous levels produce an alternating dense-
lucent-dense appearance simulating the transverse
bands of rugby sweater
(rugger-jersey spine).
42. Sclerosis is seen alternated with radiolucent areas at the level of the
bones of the skull, adopting a "salt and pepper" pattern.
