Invasive Preoperative Methods

Invasive localization studies are indicated when the combined results of the noninvasive tests are negative, equivocal, or conflicting.

FIGURE 46-8. Sestamibi scan with thymic parathyroid adenoma.

I TABLE 46-2. Characteristics of the Most

Common Noninvasive Localization Studies

Variable

US

CT

MRI

Tl-Tc

Sestamibi

Sensitivity (%)

22-82

40-68

50-85

40-65

70-85

Cost

+

+++

++++

++

++

Operator dependence

+++

+

-H-

No

No

Radiation exposure

No

++

No

+

+

Best localizations

Perithyroid

Ectopic

Ectopic

Perithyroid

Poor localizations

Mediastinum

Thyroid; deep cervical

Mediastinum

Other problems

Surgical clips; requires

Thytoid nodules

contrast material

Tl-TC = thaHium-technetium; US = ultrasonography; CT = computed tomography; MRI

= magnetic resonance imaging.

Fine-Needle Aspiration

Fine-needle aspiration (FNA) of the parathyroid tumor performed under sonographic guidance can improve the results obtained with US. FNA enables cytologic examination of parathyroid hormone (PTH) measurement in the aspirate. When the aspiration is positive for PTH, it confirms the diagnosis of a parathyroid tissue." PTH determination is more helpful than cytologic examination for diagnosing parathyroid lesions because cytologists often have difficulty in differentiating between a parathyroid gland and thyroid tissue, and the sample may also be insufficient.100 Karstrup and associates101 diagnosed 100% of the cases by bioassay but only 60% by cytologic examination. McFarlane and colleagues102 also published excellent results for PTH assay (specificity 100% and sensitivity 70%). Some clinicians have recommended injection of 95% ethanol into parathyroid neoplasms to produce necrosis. Unfortunately, the tumor may recur after the ethanol injection, and recurrent laryngeal nerve injury also occurs. Furthermore, parathyroid tissue is also unavailable for histologic examination or for cryopreservation.

Parathyroid Arteriography

Proper parathyroid arteriography includes examination of both thyrocervical trunks (to look for parathyroid glands in the superior mediastinum, tracheoesophageal groove, or intrathyroid or juxtathyroid location glands), the internal mammary arteries (glands in the thymus and anterior mediastinum) and carotids (juxtathyroid or undescended glands), and sometimes the selective catheterization of the superior thyroid artery. Parathyroid adenomas appear highly vascularized and oval or round (see Fig. 46-9). The sensitivity obtained with digital subtraction arteriography is around 60% to 65%; it is a difficult and expensive technique.15'102'103 In selected cases, it is possible to do an angiographic embolization of the localized adenoma (Fig. 46-9).104

Selective Venous Sampling for Parathyroid Hormone Assay

Angiography is performed primarily to outline the venous drainage, and it can obtain a sample for PTH assay. It is an expensive technique and requires an expert radiologist because it is technically difficult. The samples must be taken as selectively as possible from the smallest venous branches because this helps document the exact location of the parathyroid tumor.105 Nilsson and coworkers,106 however, published significant results with sampling from large veins such as the jugular vein, innominate vein, and superior cava. A twofold gradient between the intact parathyroid hormone (iPTH) concentration in peripheral blood and that in the selective venous sample (SVS) establishes the site of the venous drainage of the tumor. The problem arises in cases in which this gradient is not attained and localization is uncertain.107 The sensitivity of the SVS ranges from 63% to 83%.13.15,37.50,53.83.102,108 Jones and coworkers,109 from the

University of California-San Francisco, reported 64 patients with an exact location in 75% of cases, and the SVS was not useful for the surgeon in only 17% of the cases.

This technique is the most sensitive and lateralizes about 80% of parathyroid tumors.37 107109 Furthermore, it is just as accurate for mediastinal glands as for cervical glands and depends on gland function rather than gland size. It is also helpful when there is more than one abnormal parathyroid gland and can convert an equivocal noninvasive study into a positive one.

The reported sensitivity of localizing studies for persistent or recurrent HPT is shown in Table 46-3.

In cases of recurrent HPT after total parathyroidectomy with autotransplant in the forearm, the first localizing study to do is the iPTH gradient. PTH assay in the basilic vein of both arms draining the graft, with or without ischemic

TABLE 46-3. Localization Methods' Sensitivity (%) in Several Persistent or Recurrent HPT Series

Studies Noninvasive Methods Invasive Methods

AUTHOR, YEAR, TI-TC MIBI VENOUS QUICK

TABLE 46-3. Localization Methods' Sensitivity (%) in Several Persistent or Recurrent HPT Series

Studies Noninvasive Methods Invasive Methods

AUTHOR, YEAR, TI-TC MIBI VENOUS QUICK

REFERENCE NO-

N

ULTRASOUND

CT

MRI

SCINTIGRAPHY

SCINTIGRAPHY

ANGIOGRAPHY

SAMPLING

PTH

Doherty et al, 199249

27

_

35

19

4

_

84

_

.__

Rodriguez et al, 199437

152

53

42

69

60

70

69

McFarlane et al, 1994102

42

67

56

36

42

68

69

Billingsley et al, 199410e

17*

71

38

38

80

-

Numerow et al, 199538

23

58

88

80

Shen et al, 199613

102

57

42

77

68

77

77

-

Jaskowiak et al, 199615

227

48

52

48

42

67

59

76

Peeler et al, 199737

25

45

68

74

Mariette et al, 199B50

38

16

.—

69

63

Fay et et al, 199864

18

88

83

83

Irvin et al, 1999121

33

78

93

Thompson et al, 199940

124

75

58

82

94f

Feingold et al, 2000i2

62

90

78

De Feo et al, 200021

49

27

13

17

57

Gotway et al, 2001"

98

82

85

Kebebew et ai, 2001,E

18'

69

67

93

79

83

;—

Jones et al, 2002109

64

75

"Undescended parathyroid adenomas only. 'In 16 patients. 'Parathyroid carcinomas, HPT - hyperparathyroidism.

"Undescended parathyroid adenomas only. 'In 16 patients. 'Parathyroid carcinomas, HPT - hyperparathyroidism.

blockade, is usually diagnostic when there is at least a twofold increase in relation to the other ami.110111 It is recommended to do at least two positive studies before surgery. Sestamibi, CT scan or MRI, and clinical palpation of the arm may also be necessary.112

In parathyroid carcinoma, CT and MRI are especially useful for detecting mediastinal and thoracic recurrences.18 US can be used for detecting cervical parathyroid carcinoma recurrence. Sestamibi allows for whole-body scanning and therefore may detect distant metastases.

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