1. Pre-operative localization of parathyroid adenoma
Dr Chan Man-yi
Tuen Mun Hospital

2. Primary hyperparathyroidism
Gold standard = bilateral neck exploration
95 – 98% at first exploration
Imaging used only after failed initial surgery
Identify all 4 parathyroid glands, remove abnormal gland(s)
Solitary adenoma – all 4 glands sampled, adenomatous gland removed
Hyperplasia – subtotal 3.5 gland resection with cryopreservation or total parathyroidectomy with autotransplantation into forearm / neck muscle
Carcinoma – radical removal including ipsilateral LN and ipsilateral thyroid
70 – 90% at re-exploration

3. Etiology of primary hyperparathyroidism
Solitary parathyroid adenoma 80-85%
Unilateral neck exploration
Minimally invasive surgery
Foscused parathyroidectomy
Video-assisted parathyroidectomy
Videoscopic parathyroidectomy
Multiple parathyroid adenoma 2-3 %
Diffuse hyperplasia 10-15%
Parathyroid carcinoma 2-3%
Minimally invasive surgery
Unilateral neck exploration
Foscused parathyroidectomy
Video-assisted parathyroidectomy
Videoscopic parathyroidectomy
Equally high cure rate
Advantages
Reduce operative time
allow operation under LA
reduce morbidity (transient hypocalcemia / recurrent laryngeal nerve injury)
reduce hospital costs, shorten hospital stay
Key to success lie in preop localization of pathology gland, identify patient suitable for MIS

4. Minimally Invasive parathyroidectomy
Pre-operative
Intra-operative
Ultrasound
Sestamibi scan CT
MRI
Angiography / selective venous sampling
PTH assay
Ultrasound
Gamma probe
who to operate, where to operate and when to stop operate
Pre-op localization – to look for candidate for MIP, and direct surgical exploration to most likely location
Intra-op – USG / gamma probe – to help locate pathology; PTH to determine cure
USG and mibi – commonly used pre-op imaging
CT / MRI less commonly used for pre-op localization, more commonly used in failed parathyroidectomy to detected ? Ectopic (often mediastinal gland) or when finding of USG and MIBI discordant

5. Ultrasound Sensitivity (55-83%) High frequency linear transducer
Ruda et al, Otolaryngol Head Neck Surg 2005; 132:359–372
High frequency linear transducer
Carotid arteries – hyoid bone – sternal notch
Parathyroid adenoma
Gray-scale image
Oval / bean-shaped
Homogenously hypoechoic
Doppler
Characteristic arc / rim of vascularity
Present in 83%
Lane MJ, Am J Roentgenol. Sept 1998; 171(3:819-23)
(12-15MHx), some write 8-13MHx
Allow anatomical detection of enlarged parathyroid
Posterior to thyroid gland, frequently medial to common carotid artery
Larger ones can be multilobulated
Normal parathyroid glands not commonly seen – 5mmx3mmx1mm vs adenoma have 10x their size; normal glands 50% fat content, isodense as thyroid vs adenoma hypercellular and appear hypoechoic
characteristic extrathyroidal feeding vessel (typically a branch off the inferior thyroidal artery), which branch around the periphery of gland before penetrating deeper, resulting in a characteristic arc or rim of vascularity; (imaging) internal vascularity commonly seen in peripheral distribution; Lan et al noted in 83% of his patient (Lane MJ, Am J Roentgenol. Sept 1998; 171(3:819-23)

6. USG by surgeon Sensitivity of USG Sensitivity of USG + MIBI – 98%
Specific side – 84%
Specific quadrant – 79%
Sensitivity of USG + MIBI – 98%
43 cases, unilat 23, bilat in 20 (11 due to lack of IOPTH, 7 due to localization to opp side, 2 previous neck incision)
Drawback – MIBI % sensitivity, lower then quoted in literature

7. Sestamibi scan Istopic scan with technetium Tc 99m sestamibi
Single isotope dual phase scan
IV injection  early and delayed image
Correlate with larger size / predominance of oxyphil cells / presence of P-glycoprotein
Bhatnagar et al, J Nucl Med 1998;39:
Carpentier et al, J Nucl Med 1998;39:
Tc 99m sestamibi taken up by (mitochondria rich cells) both thyroid and parthyroid glands, abnormal (adenoma / hyperplastic) parathyroid tissue shows increased uptake and retain tadiotracer longer
IV injection of radiogtracer, early and delayed image are acquired; early phase obtained 10-15min after injection, called thyroid phase as Tc 99m sestamibi rapidly concentrated in thyroid gland; delayed phased obtained hour after injection, called parathyroid phase, which emphasize the differential washout of Tc99m sestamibi from abnormal parathyroid glands
MIBI uptake correlate with size of gland and cytological compoition (greater uptake in adenoma with predominance of oxyphil cells c/t chief cells)

8. Advantage Sensitivity (68-95%)
Good at identifying ectopic glands in mediastinum or deep cervical location
Sensitivity (68-95%)
Ruda et al, Otolaryngol Head Neck Surg 2005; 132:359–372
Solitary adenoma 88%
Hyperplasia 44%
Double adenoma 30%
Sensitivity-SPECT
Solitary adenoma 90%
Hyperplasia 4%
Double adenoma 73%
Civelek et al. surgery 2002; 131:

9. Planar imaging
SPECT/CT
SPECT

10. Planar, SPECT or SPECT/CT
Dual SPECT/CT = early SPECT/CT + SPECT / Planar > any dual
Dual SPECT = dual planar
use as a routine procedure before target surgery is still investigational. Preliminary data suggest that SPECT/CT has lower sensitivity in the neck area compared to pinhole imaging. Additional radiation to the patient should also be considered.
2009 EANM parathyroid guidelines.
Dual phase SPECT/CT > dual phase SPECT / planar
Early phase SPECT/CT + any form of delayed imaging > dual phase SPECT / planar

11. USG vs MIBI Sensitivity of USG – 65% Sensitivity of MIBI-SPECT – 68%
Detected only by one modality – 16%
 USG and MIBI complementary
31 cases with both pre-op imaging; USG + dual planar + delay SPECT
OT done, retrospective evaluation of imaging modalities
Sensitive = able to pick up adenoma
Sensitivity of USG + MIBI – 74%

12. USG + MIBI Sensitive = identify adnoma about region
Accuracy = localize adenoma to supreior / inferior gland
All adenomas are correctly localized, superior glands incorrectly locaized t inferior glands, as superior glands tebd to prolapse inferiorly as they enlarge
No sign diff in

13. USG + MIBI Surgical failure w/o PTH – 2% With PTH – 1% P=0.5
Sensitive = identify a positive site of adenoma
Concordant MIBI + USG  focused surgery + PTH  bilateral; 322 concordant; 319 localize and remove adenoma while 3/322 fail PTH drop and find additional disease; 3/319 failed correct hyperclacemia
Discordant MIBI + USG  focused surgery with MIBI result + PTH  bilateral; 201 discordant 125 (62%) correct localization
Planar view
Studies showed that accuracy improved when both imaging studies done pre-operatively
Scheiner et al Clin radiology 2001; 56:
Purcell etal; Arch Surg 1999;134:
DeFeo et al; Radiology 2000; 214:

14. Reoperation?

15. 163 patients with ?missed adenoma Pre-op localization  surgery
6 –ve exploration, all persistent hypercalcemic
2 patient with +ve exploration suffered persistent hypercalcemia, suggest multigland disease
Another 2 Recurrent HPT in FU
163 patients with ?missed adenoma
Pre-op localization  surgery
140 unilateral exploration
18 mediastinal procedure
92% long term resolution of hypercalcemia

16. Sensitivity = 70%
IV – discordant USG and MIBI, 13/14 false +ve given by USG
When USG +Ve, MIBI –ve, successful in 97%, majority in neck
III – 92 patient with at least 1 invasive
MIBI highest PPV in non-invasive
FNA greatest PPV in invasive, but small numble applicable only
Arteriogram vs + stimulated venous sampling – similar
70 out of 71 patient operate base on non-invasive imaging along cured

17. Proposed strategy Diagnosis, exclude other causes of hypercalcemia
Operative reports
Pathology slides
Indication of surgery
Suggest CT over MRI if MIBI identify adenoma in mediastinum, as CT greater PPV

18. ? False positive
17 patient post parathyroidectomy persistent hypercalcemia and “false +ve” pre-op MIBI scan
repeated MIBI +ve for all case, showing the same foci as pre-op scan, eventually adenoma identified with radioguided surgery
Assumed false +ve as surgeon failed to identified adenoma
All repeated scan showed same foci of radioactivity
 Errors in interpertation rather than in scan itself

19. John Doppman 1986 “The best localization study prior to primary exploration in a patient with primary hyperparathyroidism is to locate an experienced parathyroid surgeon”

20. Initial surgery: MIBI + USG if MIP
Both +ve
Concordant result MIP (? IOPTH)
Discordant result  IOPTH mandatory if MIP
One +ve  IOPTH mandatory if MIP
Both -ve  bilateral exploration
Re-operation
MIBI as first line
USG / CT / MRI
FNA / arteriogram / SVS
An experienced surgeon is the key to success

21. END