Transient false-negative tc-99m sestamibi parathyroid scintigraphy following total thyroidectomy

The case of a female patient with a large multinodular goiter and severe primary hyperparathyroidism (PHPT) is reported. She was treated with total thyroidectomy. At bilateral neck exploration, only 3 normal-sized parathyroid glands were found so that she had persistent PHPT after surgery. At scintigraphy obtained by washout technique 3 hours after surgery, no focal uptake of Tc-99m sestamibi was visualized. Neck ultrasound (US) and spiral CT were also negative. Four months later, repeat Tc-99m sestamibi scan was obtained: a single focus of intense uptake was visualized at the base of the neck. A new spiral CT revealed the presence of a 3 X 2-cm solid mass located between the esophagus and the vertebral column. Three days later, a parathyroid adenoma (PA) was successfully removed at surgery. It can be hypothesized that the negative Tc-99m sestamibi scintigraphy performed 3 hours after the first intervention might be the result of a transient reduced blood supply to the PA directly related to thyroid surgery. Conversely, the positive scintigraphy performed 4 months after intervention might be the result of activation of silent microcirculation vessels supplying blood to the PA.