[Radio-guided parathyroidectomy. A prospective study in 54 patients with primary hyperparathyroidism]

The contribution of nuclear-medical mapping using 99mTc-MIBI (MIBI) and the use of an intraoperative probe in primary hyperparathyroidism (I degrees HPT) surgery was evaluated prospectively in a series of patients undergoing parathyroidectomy.

Fifty-four patients, who were operated between May 1999 and July 2000, under-went a systematic preoperative evaluation using scintigraphy with a dual tracer 99Tc04/MIBI and image subtraction, and high-resolution neck ecotomography. Surgery was performed using a mini-invasive technique through an incision measuring 2-2.5 cm at the base of the neck in 46 patients; the other 8 patients underwent open surgery with bilateral exploration of the neck. MIBI was injected intravenously in the operating theatre following the induction of anesthesia and after 32 minutes on average, radioactivity was measured using a manual gamma probe. Radioactivity was also counted intraoperatively at the tip of the lung contralateral to the pathological gland, a parameter used as the base activity (B), in the presumed seat of the hyperfunctioning parathyroid (P), in correspondence with healthy thyroid tissue (T) and any associated thyroid nodes (N). Radioactivity was also recorded at the level of the empty parathyroid compartment after removal of the corresponding gland, and on the parathyroid removed ex vivo .

The ratio between the three main parameters, T/B, P/B and P/T was respectively 1.6 (range=1.5 - 1.8), 2.7 (range=1.6-4.0) and 1.6 (range=1.1-2.8). In 4 cases (7.4%), the small size of the parathyroids, adjacent to thyroid nodes, meant that the parathyroid measurement of MIBI was smaller than the thyroid measurement. The histological finding was consistent with: single parathyroid adenoma in 49 cases, multiple adenomas in 3 cases, parathyroid carcinoma in 2 cases. Rapid intraoperative PTH normalised in all patients.

The significant difference in radioactivity levels recorded in the patients, showed that the technique is useful to the surgeon as a means of intraoperative assay for hyperfunctioning parathyroids, even if it cannot obviously replace experience or the value of preoperative scientigraphic and ecotomographic imaging.