Parathyroid nuclear medicine localisation - an unusual ectopic gland?
Raya Almazrouei, Aimee Di Marco, Fatima Alkaabi, Amir H Sam, Karim Meeran, Fausto Palazzo. Hammersmith Hospital, Imperial Health Care NHS Trust
99mTc-MIBI SPECT/CT is a commonly used localizing study in patients with primary hyperparathyroidism. It localises up to 70% of adenomas and is particularly good at identifying single ectopic parathyroids. Negative scans may be due to small parathyroid size, adenoma composition, multi-gland disease, body habitus and coexistent thyroid disease. Here we report another potential reason for non-localization in the neck. A 57-year-old woman with a history of renal colic was found to have an elevated adjusted serum calcium (2.86 mmol/L), low normal serum phosphate (0.97 mmol/L), elevated PTH (13.9 pmol/L) and a urine calcium creatinine clearance ratio of 0.021 consistent with primary hyperparathyroidism. Localization studies performed in preparation for surgery included neck ultrasound and 99mTc-MIBI SPECT/CT, which were non-localizing. However, 99mTc-MIBI SPECT/CT scan revealed increased tracer uptake in the right frontal lobe in close proximity to the meninges, consistent with a meningioma on MRI head. The patient underwent neck exploration and a right inferior parathyroid adenoma was excised. 99mTc-MIBI uptake is related to hypermetabolic tissue and mitochondrial content, which could explain the high uptake by the meningioma and potentially the false negative localization study in the neck.