Preoperative parathyroid radioisotope scanning is of little or no value in patients with multiple endocrine neoplasia type 1 when 4 or more hypertrophied glands are present. Scanning using technetium Tc 99m sestamibi and single photon emission computed tomography will achieve a high level of sensitivity and specificity after 3 or more glands have previously been removed, justifying limited surgical reexploration.
In a prospective study, the preoperative documented report of the predicted site of residual parathryoid was compared with the surgical findings in 13 patients having 19 scans and 17 reoperations.
All patients belonged to one family, previously described as Tasman family 1, and were confirmed by genetic testing as having multiple endocrine neoplasia type 1. In 10 of 13 patients, reexploration was being undertaken more than 10 years after the first operation.
Main Outcome Measures
Scanning was regarded as successful when the documented preoperative report correctly predicted the side and quadrant in which a gland was found at surgery. Surgery was regarded as successful when calcium levels decreased to or below normal levels and were maintained.
All 13 scans before first reexploration were successful in identifying the location of a residual parathyroid. From a statistical viewpoint, this equates to 100% sensitivity and 92% specificity. However, despite accurate localization of 1 residual gland in every patient, 7 supernumerary glands in 4 patients and 1 parathyroid remnant in a fifth patient were not localized so that sensitivity in locating all glands in every patient was only 61%. Scans performed for persistent hypercalcemia 48 to 72 hours after reexploration in 2 patients were unsuccessful in demonstrating any residual parathyroid. Scans performed 3 months after surgery in the same 2 patients and a third patient were successful, with sensitivity and specificity of 100%. Apart from patient 11, who awaits reexploration, normocalcemia was eventually achieved in every patient, with 11 of 12 having an initial period of hypocalcemia.
Three months after reexploration and trimming or resection with transplant of half a gland left at first operation, sestamibi scanning achieved sensitivity and specificity of 100% in locating supernumerary parathyroids in patients with multiple endocrine neoplasia type 1 and persistent hypercalcemia. Before first reexploration, however, scans rarely provided new information, predominantly showing only the hypertrophied half-gland remnant.