Background: Technetium-99m sestamibi scintigraphy with single photon emission computed tomography (SPECT) is widely used to guide minimally invasive exploration in patients with sporadic primary hyperparathyroidism (SPH), although its sensitivity in multiglandular disease is limited. We examined the incidence of missed multiglandular disease and associated anatomic findings when sestamibi SPECT was positive for a single intense focus of delayed tracer uptake, termed a lightbulb scan (LBS).
Methods: Prospectively entered data from 764 patients with SPH treated with initial parathyroid exploration from March 5, 2000, to December 31, 2006, were reviewed. A single radiologist performed blinded interpretation of 585 available sestamibi SPECT images, classifying 167 (28.5%) patients with a LBS. Clinical findings were compared among LBS patients with a single adenoma (true positive) and LBS patients with multiglandular disease (false negative).
Results: One hundred fifty of 167 (89.8%) LBS patients had a single adenoma and 3 (1.8%) had carcinoma. Multiglandular disease was anatomically present in 14 of 167 (8.4%) LBS patients compared with 60 of 418 (15.6%) non-LBS patients (p=0.05). Parathyroid hyperplasia occurred less frequently in LBS patients [5/167 (3%)] compared with non-LBS patients [36/418 (8.6%)], (p=0.02), while double adenomas occurred equally often in LBS patients [9/167 (5.4%)] compared with non-LBS patients [24/418 (5.7%)], (p=0.87). Double adenomas in LBS patients were more likely ipsilateral (7/9, p=0.005) and left-sided (7/7, p=0.008). LBS patients with multiglandular disease were more likely to have a history of neck irradiation, prior neck exploration, and concomitant thyroid pathology.
Conclusions: In patients with SPH, sestamibi SPECT studies show a single bright focus of uptake in only 29% of patients. LBS findings do not exclude multiglandular disease. To avoid unacceptable rates of failure at initial parathyroid exploration, the expert surgeon should use validated adjuncts such as intraoperative PTH monitoring or four-gland exploration.