Image fusion in a case of ectopic parathyroid adenoma associated with an arteria lusoria

Clinical History

The patient had laboratory findings of primary hyperparathyroidism but on surgical exploration, no parathyroid adenoma or hyperplasia was found in the cervical region.

Imaging Findings

The patient showed signs of primary hyperparathyroidism (PTH: 111–205 pg/ml; Ca²+: 11,4–11,6 mg/dl). On surgical exploration, no parathyroid adenoma or hyperplasia was found in the cervical region. The patient was subsequently investigated in our department. Laboratory findings confirmed a persistent primary hyperparathyroidism: PTH (107 pg/ml), Ca²+ (10.5 mg/dl), P (2.2 mg/dl). A SPECT investigation done suggested retroesophageal localization of the lesion (Fig.1a,1b). A CT examination when performed showed a nodule (33x8x13 mm) protruding behind the left side of the oesophagus and the trachea. An arteria lusoria was documented as well (Fig.2a,2b). We used a dedicated software (X-Warper) to coregister morphologic CT and functional SPECT information(Fig.3a,3b,3c). On doing the second surgical intervention, it was found that the dissection proved to be difficult due to the presence of fibrosis. During the dissection of the paraoesophageal and paratracheal space, a non-recurrent inferior laryngeal nerve was found. By following one branch of the inferior thyroid artery (Fig.4), it was possible to find the adenoma in the position shown in CT and SPECT images. A pathological investigation confirmed the diagnosis of a parathyroid adenoma.

Discussion

The arteria lusoria is a rare anomaly of the right subclavian artery. This artery arises from the aortic arch distal to the left subclavian artery crossing the midline behind the oesophagus. This abnormality remains generally silent, is often an incidental X-ray finding and is often associated with a non-recurrent laryngeal nerve. The embryological nature of such anatomical variations originally results from the vascular disorder known as arteria lusoria in which the fourth right aortic arch is abnormally absorbed, and is therefore unable to drag the right recurrent laryngeal nerve down when the heart descends and the neck elongates during embryonic development. The surgeon must be aware of the possibility of a non-recurrent laryngeal nerve, which directly arises from the cervical vagus and therefore represents a severe potential pitfall during thyroidectomy. When the preoperative studies (e.g. CT) show the presence of a lusorian artery, the surgeon will be aware of this association. As for as ectopic parathyroid adenoma is concerned, in our patient this was the cause of a repeat surgical intervention: it should be noted that when the surgeon does not find the parathyroid adenoma, the retroesophageal position must be considered. In this situation, tracing the branches of the inferior thyroid artery, by gentle dissection, can be very helpful: this can bring blood to the adenoma because blood is supplied to the parathyroid glands from the inferior thyroid artery. Finally, we found that image fusion of CT and SPECT images can be helpful in increasing the diagnostic accuracy and has the potential to give useful presurgical information that may allow reduction of overall surgical time.

Differential Diagnosis List

Final Diagnosis

Retroesophageal ectopic parathyroid adenoma.

URL:	https://www.eurorad.org/case/2914
DOI:	10.1594/EURORAD/CASE.2914
ISSN:	1563-4086