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Pre-operative localization of parathyroid adenoma. Dr Chan Man-yi Tuen Mun Hospital. Primary hyperparathyroidism. Gold standard = bilateral neck exploration 95 – 98% at first exploration Imaging used only after failed initial surgery. Etiology of primary hyperparathyroidism
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Pre-operative localization of parathyroid adenoma Dr Chan Man-yi Tuen Mun Hospital
Primary hyperparathyroidism • Gold standard = bilateral neck exploration • 95 – 98% at first exploration • Imaging used only after failed initial surgery
Etiology of primary hyperparathyroidism • Solitary parathyroid adenoma 80-85% • Unilateral neck exploration • Minimally invasive surgery • Foscused parathyroidectomy • Video-assisted parathyroidectomy • Videoscopic parathyroidectomy
Minimally Invasive parathyroidectomy Pre-operative Intra-operative PTH assay Ultrasound Gamma probe • Ultrasound • Sestamibi scan • CT • MRI • Angiography / selective venous sampling
Ultrasound • Sensitivity (55-83%) • 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)
USG by surgeon • Sensitivity of USG • Specific side – 84% • Specific quadrant – 79% • Sensitivity of USG + MIBI – 98%
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;39:1617-1620 Carpentier et al, J Nucl Med 1998;39:1441-1444
Advantage • 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
Planar imaging SPECT/CT SPECT
Planar, SPECT or SPECT/CT • Dual phase SPECT/CT > dual phase SPECT / planar • Early phase SPECT/CT + any form of delayed imaging > dual phase SPECT / planar
USG vs MIBI • Sensitivity of USG – 65% • Sensitivity of MIBI-SPECT – 68% • Detected only by one modality – 16% • USG and MIBI complementary
USG + MIBI • Surgical failure • w/o PTH – 2% • With PTH – 1% P=0.5
163 patients with ?missed adenoma Pre-op localization surgery 140 unilateral exploration 18 mediastinal procedure 92% long term resolution of hypercalcemia
? False positive 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
John Doppman 1986 “The best localization study prior to primary exploration in a patient with primary hyperparathyroidism is to locate an experienced parathyroid surgeon”
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