Ectopic parathyroid adenomas located at the carotid bifurcation: the role of preoperative Tc-99m MIBI scintigraphy and the intraoperative gamma probe procedure in surgical treatment planning

An Approach to a Patient With Primary Hyperparathyroidism and a Suspected Ectopic Parathyroid Adenoma

Primary hyperparathyroidism (PHPT) is characterized by hypercalcemia driven by excess parathyroid hormone (PTH) secretion. PHPT is a common endocrine condition with a prevalence of 1 to 7 cases per 1000 adults. PHPT typically presents in the fifth or sixth decade and shows significant female preponderance. Solitary hyperfunctioning parathyroid adenomas account for 85% to 90% of PHPT cases. The remaining 10% to 15% include cases of multiglandular disease (multiple adenomas or hyperplasia) and, rarely, parathyroid carcinoma (1%). Ectopic parathyroid adenomas may arise due to abnormal embryological migration of the parathyroid glands and can be difficult to localize preoperatively, making surgical cure challenging on the first attempt. The potential existence of multiglandular disease should be considered in all patients in whom preoperative localization fails to identify a target adenoma or following unsuccessful parathyroidectomy. Risk factors for multiglandular disease include underlying genetic syndromes (eg, MEN1/2A), lithium therapy, or previous radiotherapy. In addition to multifocal disease, the possibility of an ectopic parathyroid gland should also be considered in patients requiring repeat parathyroid surgery. In this article, we use illustrative clinical vignettes to discuss the approach to a patient with primary hyperparathyroidism (PHPT) and a suspected ectopic parathyroid adenoma.

99MTc-mibi Radio-guided Surgery in Primary Hyperparathyroidism: A Prospective Study of 128 Patients

Aims and study design

We investigated the role of an intraoperative gamma probe (IGP) technique in 128 patients with primary hyperparathyroidism (HPT). The patients were evaluated before surgery by 99mTcO4/MIBI scintigraphy and neck ultrasound and then operated on by the same surgical team. The IGP technique consisted of the injection of a low dose (37 MBq) of 99mTc-MIBI in the operating room shortly before the start of surgery. Quick parathyroid hormone (QPTH) was routinely measured during the operation.

Results

In 94/97 patients (96.9%) with a preoperative diagnosis of solitary parathyroid adenoma (PA) minimally invasive radioguided surgery (MIRS) was successfully performed; in the other 3/97 patients (3.1%) conversion to bilateral neck exploration (BNE) was required because of the intraoperative diagnosis of parathyroid carcinoma in two cases and multiglandular disease (MGD) in one. MIRS was successfully performed also in 23 patients who had undergone previous thyroid or parathyroid surgery. In 31 patients with a preoperative diagnosis of MGD (n = 5) or concomitant nodular goiter (n = 26) the IGP technique was used during a bilateral neck exploration. Among these patients IGP was useful in localizing an ectopic parathyroid gland in the thymus in one case of MGD and a PA located deep in the neck (n = 2) or ectopic at the carotid bifurcation (n = 1) in three cases with nodular goiter. However, in several other patients with nodular goiter it was difficult for the probe to distinguish intraoperatively between thyroid nodules and PA located close to the thyroid gland.

Conclusions

It can be concluded that a) in primary HPT patients with a high likelihood (according to scintigraphic and ultrasound findings) of being affected by a single PA and with a normal thyroid gland, the IGP technique appears useful in MIRS; b) a 99mTc-MIBI dose as low as 37 MBq appears to be adequate to perform MIRS; c) the measurement of QPTH is strongly recommended in HPT patients selected for MIRS to confirm the radicality of parathyroidectomy; d) MIRS can be useful also in HPT patients who underwent previous parathyroid or thyroid surgery to limit the surgical trauma of reoperation and minimize complications; e) with the exception of PAs located at ectopic sites or deep in the neck, the IGP technique does not seem to be recommendable in HPT patients with concomitant nodular goiter.

[Ectopic parathyroid adenoma: Scintigraphic detection and radioguided surgery]

AIM

The aim of this study was to evaluate the role of (99m)Tc-MIBI parathyroid scintigraphy and radioguided parathyroidectomy on the diagnosis and treatment of primary hyperparathyroidism (PHP) due to ectopic adenomas.

METHODS

We reviewed 105 consecutive patients who underwent radioguided parathyroidectomy due to adenomas between March 2004 and December 2008. Of this group we studied 20 patients (19%) with ectopic adenomas. All patients had biochemical evidence of PHP, a positive parathyroid scintigraphy, radioguided detection with histolopathological confirmation of adenoma and at least 1 year-follow up. The parathyroid scintigraphy consisted on dual-phase planar and tomographic images (SPECT or SPECT/CT). During the parathyroidectomy, intraoperative PTH determinations (0, 7, 15 and 30 min after the parathyroidectomy) were done. The follow up consisted on blood examinations of PTH, calcium, phosphorus and vitamin D and assessment of renal function.

RESULTS

Parathyroid scintigraphy detected all adenomas. Scintigraphic and surgical findings were coincident in 18 cases (90%). The final adenoma localization was paraesophagic in 9 patients, cervicothymic in 5, posterior cervicomediastinal in 4, anterior mediastinal in 1 and parathymic in 1. The parathyroidectomy consisted on 12 minimally invasive surgeries, 2 unilateral cervicotomies, 4 bilateral cervicotomies and 2 sternotomies. No case of persistent or recurrent PHP was observed during the follow up.

CONCLUSIONS

Parathyroid scintigraphy (SPECT/CT) and radioguided surgery are effective methods on the localization and treatment of PHP due to ectopic adenomas. In our study the radioguided parathyroidectomy was successful in all cases and there was no evidence of persistent or recurrent hyperparathyroidism on the follow up.

Detection of ectopic parathyroid adenoma by early Tc-99m sestamibi imaging

Localization of Tc-99m sestamibi (MIBI) by parathyroid adenomas (PA) is well known. Typically the radionuclide washes out slowly from the PAs located in the neck. Rapid washout from some PAs has been reported. Various hypotheses have been postulated for slow and rapid clearance of MIBI from PAs, located in the neck. However, the washout of MIBI from ectopic parathyroid adenoma (EPA) in not well reported. We present a case of EPA with rapid washout of MIBI. Hence, early MIBI imaging plays an important role in the evaluation of EPA.

Tc-99m Sestamibi Localization of an Ectopic Mediastinal Parathyroid Tumor in a Patient With Primary Hyperparathyroidism

A 50-year-old woman presented with pain and tenderness in the right flank. Urogram and ultrasound demonstrated the presence of an 8-mm calculus in the right kidney. There were persistently elevated serum calcium levels ranging from 10.7-11.4 mg/dL (normal range: 8.5-10.5) and borderline low serum phosphate levels of 2.4-2.9 mg/dL (normal range 2.5-4.5). Serum albumin levels were normal. The patient's parathormone levels were elevated and a diagnosis of primary hyperparathyroidism was made. An MRI of the neck failed to reveal evidence of parathyroid pathology. Tc-99m sestamibi imaging demonstrated no abnormal parathyroid tissue in the neck, but clearly showed an abnormal focus in the anterior mediastinum.

Efficiency of gamma probe and dual-phase Tc-99m sestamibi scintigraphy in surgery for patients with primary hyperparathyroidism

PURPOSE

The purpose of this study was to determine the value of the intraoperative gamma probe and the efficacy of dual-phase Tc-99m sestamibi imaging in patients with primary hyperparathyroidism.

METHODS

Twenty-one patients with primary hyperparathyroidism were examined prospectively. Results of same-day dual-phase Tc-99m sestamibi scintigraphy and intraoperative gamma probe evaluations were compared with the intraoperative findings and histopathologic diagnoses. A 15-mm handheld gamma probe was used to measure gamma activity in the neck and upper mediastinum. Nuclear mapping by gamma probe showed a single quadrant of neck that emitted gamma radiation significantly greater than the other three quadrants, which correlated with the sestamibi scan.

RESULTS

Dual-phase Tc-99m sestamibi scintigraphy determined and localized parathyroid lesions in 20 patients (sensitivity, 94%). Of the 20 parathyroid lesions removed, 15 were located in normal positions, whereas five were explored in ectopic sites (one within the thyroid, one in the anterior mediastinum, one in a retrotracheal position, one in the carotid sheath, and one in the retroesophageal region). Although the index of thyroid nodules varied from 15.8% to 22.9%, the index for parathyroid lesions was 77.3% to 112.8%.

CONCLUSIONS

These results confirm that parathyroid lesions, especially at ectopic sites, can be treated successfully in shorter operative times with minimal complications with the help of the intraoperative gamma probe.

Determinant role of Tc-99m MIBI SPECT in the localization of a retrotracheal parathyroid adenoma successfully treated by radioguided surgery

PURPOSE

The authors' aim was to evaluate the role of MIBI SPECT acquired just after planar pertechnetate-MIBI (TcO(4)-MIBI) subtraction scintigraphy in planning radioguided surgery in a patient with persistent primary hyperparathyroidism after initial surgery performed to treat a retrotracheal parathyroid adenoma (PA).

METHODS

A 73-year-old man with persistent primary hyperparathyroidism after a previous left parathyroidectomy and left thyroid lobectomy is described. The patient was examined in our center in a single-day preoperative imaging protocol based on findings of planar TcO(4)-MIBI subtraction scintigraphy, MIBI SPECT, high-resolution neck ultrasound, and computed tomography.

RESULTS

Neck ultrasound did not reveal enlarged parathyroid glands. Findings of a neck-chest computed tomographic scan were also inconclusive. Instead, planar scintigraphy clearly depicted a single focus of MIBI uptake over the thyroid gland in a median position. The SPECT examination precisely localized a PA in the retrotracheal space. The day after imaging, the patient underwent unilateral left cervical surgical exploration. A 16 x 21 mm PA was easily detected using the gamma probe technique after injection of a low dose of 37 MBq (1 mCi) Tc-99m MIBI, and the PA was rapidly removed with limited surgical trauma. Rapid serum PTH and calcium levels normalized after intervention and remained in the normal range during subsequent follow-up.

CONCLUSIONS

The current data indicate the importance of preoperative imaging with MIBI scintigraphy in patients with primary hyperparathyroidism and strongly support the utility of MIBI SPECT acquisition in PAs located deep in the neck and in ectopic sites. Furthermore, the gamma probe can help the surgeon to detect the PA during surgery and to minimize the surgical trauma in patients who have had previous thyroid or parathyroid surgery.

Radioguided surgery in primary hyperparathyroidism

Surgical neck exploration is usually made in primary hyperparathyroidism (PHPT). Localization of the adenoma or detection of hyperplasia may reduce the operation period and limit the extent of the surgery. In this study the effficacy of preoperative Tc-99m MIBI scintigraphy and intraoperative gamma probe was evaluated.

MATERIALS AND METHODS

Six patients with PHPT had preoperative Tc-99m MIBI parathyroid scintigraphy and intraoperative gamma probe (IGP) was used in surgical neck exploration.

RESULTS

Parathyroid adenoma was observed in 2/6 patients on scintigraphy in the right retroclavicular region and the left lobe of the thyroid. Both of them were clearly detected by IGP during the surgery and easily removed by the surgeon in a short time (35 min) with a small incision. Pathologic examination confirmed the parathyroid adenoma. No abnormal MIBI uptake was not observed in scintigraphy in 4/6 patients. Subtotal parathyroidectomy was performed in these patients.

CONCLUSION

Preoperative Tc-99m MIBI scintigraphy and the use of IGP may limit the exploration and also the operation time and reduce surgical complications.

99mTc-MIBI radio-guided minimally invasive parathyroidectomy: experience with patients with normal thyroids and nodular goiters

The surgical approach to primary hyperparathyroidism (HPT) is changing. In patients with a high probability to be affected by a solitary parathyroid adenoma (PA), a unilateral neck exploration (UNE) or a minimally invasive radio-guided surgery (MIRS) using the intraoperative gamma probe (IGP) technique have recently been proposed. We investigated the role of IGP in a group of 84 patients with primary HPT who were homogeneously evaluated before surgery by a single-day imaging protocol including 99mTcO4/MIBI subtraction scan and neck ultrasound (US) and then operated on by the same surgical team. Quick parathyroid hormone (QPTH) was intraoperatively measured in all cases to confirm successful parathyroidectomy. In 70 patients with scan/US evidence of a single enlarged parathyroid gland (EPG) and with a normal thyroid gland, MIRS was planned. In the other 14 patients, the IGP technique was utilized during a standard bilateral neck exploration (BNE) because of the presence of concomitant nodular goiter (11 cases) or multiglandular disease (MGD) (3 cases). The IGP technique consisted of the following: (1) in the operating room, a low 99mTc-MIBI dose (37 MBq) was injected intravenously during anesthesia induction; (2) subsequently, the patient's neck was scanned with the probe by the surgeon to localize the cutaneous projection of the EPG; (3) in patients who underwent MIRS, the EPG was detected intraoperatively with the probe and removed through a small, 2 to 2.5 cm skin incision; (4) radioactivity was measured on the EPG both in vivo and ex vivo, the thyroid, the background and the parathyroid bed after EPG removal. In patients with concomitant nodular goiter, the radioactivity was also measured on the thyroid nodules. Surgical and pathologic findings were consistent with a single PA in 78 patients, parathyroid carcinoma in 2, and MGD in 4. MIRS was successfully performed in 67 of the 70 patients (97.7%) in whom this approach was planned. It must be pointed out that the IGP technique was particularly useful in detecting the PAs located in ectopic site (5 in the upper mediastinum, 2 at the carotid bifurcation) and deep in the neck (6 in the paratracheal/paraesophageal space). Moreover, MIRS was also successfully performed in the seven patients who had undergone previous parathyroid or thyroid surgery. In the other 3 of 70 patients (4.3%), a conversion to BNE was required because a parathyroid carcinoma (2 cases) and a MGD (1 case) were diagnosed during surgical intervention. It is worth noting that in this latter patient affected by MGD, in contrast with the other patients from our series, QPTH remained elevated after the removal of the preoperatively visualized EPG suggesting the persistence of occult hyperfunctioning parathyroid tissue, and another contralateral EPG was found at BNE. Regarding the group of patients in whom a BNE was planned, the IGP helped the surgeon to localize a supernumerary EPG ectopic in the thymus in a patient with MGD, and to localize a PA ectopic to the right carotid bifurcation in a patient with nodular goiter. However, it has to be pointed out that it was difficult for the surgeon to differentiate intraoperatively with the probe the radioactivity of the EPG from that of thyroid nodule(s) in the other 10 patients with HPT with a concomitant nodular goiter, particularly in 6 patients in whom 99mTc-MIBI uptake was higher in thyroid nodule(s) than in EPG. On the basis of these data we can conclude that: (1) in patients with primary HPT with a high scan/US probability to be affected by a single PA and with a normal thyroid gland, IGP appears to be an useful technique with the aim of performing MIRS; (2) a 99mTc-MIBI dose as low as 37 MBq appears to be adequate to successfully perform MIRS; (3) the measurement of QPTH is strongly recommended in patients with HPT selected for MIRS to confirm complete removal of hyperfunctioning parathyroid tissue; (4) MIRS can be useful also in patients with HPT who previously received parathyroid/thyroid surgery with the aim of limiting surgical trauma at reoperation and minimizing the related risk of complications; (5) with the exception of PA located in ectopic sites, IGP does not seem to be a recommendable technique in patients with HPT concomitant nodular goiter.