PREOPERATIVE MR-IMAGING IN HYPERPARATHYROIDISM - RESULTS AND FACTORS AFFECTING PARATHYROID DETECTION

OBJECTIVE. To determine the sensitivity of MR imaging for the detectio n of abnormal parathyroid glands in patients with biochemical evidence of hyperparathyroidism and to identify the factors affecting detectio n. SUBJECTS AND METHODS. Between 1985 and 1992, 82 patients with bioch emical proof of hyperparathyroidism were referred for MR imaging of th e parathyroid glands prior to surgery, Axial T1- (600/20 [TR/TE]) and T2-weighted (2500/40, 80) spin-echo images were obtained using an ante rior neck surface coil, The interpretation of the MR image was compare d with the findings at surgery and also correlated with gland histolog y, volume, and weight. Cases in which a false-positive or false-negati ve diagnosis was made were reviewed to determine the factors affecting detection. RESULTS. MR imaging detected 71 of 92 (77%) surgically pro ven abnormal glands (sensitivity, 77%; 95% confidence interval (CI), 6 8-86%) and misdiagnosed five (1.6%) of 314 normal glands as abnormal, There was no difference in the detection of enlarged glands in patient s presenting for the first time (n = 71) (sensitivity, 77%; 95% CI, 66 -86%) compared with patients with recurrent hyperparathyroidism (n = 1 2)(sensitivity, 77%; 95% CI, 46-95%). There was no significant differe nce in the detection of adenomas (sensitivity, 77%; 95% CI, 65-86%) co mpared with hyperplasia (sensitivity, 71%; 95% CI, 42-92%). Of five pa tients with ectopic parathyroid glands (1.6%), four had had previous s urgery, All five glands were successfully located (three mediastinal, two in the neck), Factors contributing to a false-negative MR imaging diagnosis included small gland size and thyroid disease, Four of five false-positive diagnoses were due to enlarged lymph nodes being mistak en for parathyroid glands, CONCLUSIONS. MR imaging is an accurate tech nique for investigation of hyperparathyroidism. Pitfalls include low s ensitivity for the identification of small glands, misinterpretation o f enlarged lymph nodes as parathyroid adenomas, and misinterpretation because of thyroid disease, MR imaging is particularly useful in the i nvestigation of patients who remain hypercalcemic following initial su rgery.