A meta-analysis of superior thyroid artery variations in different human groups and their clinical implications.

We have investigated whether the presence, numerical variations and site of origin of the superior thyroid artery (STA) are influenced by the ethnic group and gender, whether the origin and caliber of this vessel are symmetrical, to what extent a non-selective thyroid angiography, either conventional or by digital subtraction, is effective in visualizing it, and whether this information may be useful in selected clinical conditions. A meta-analysis has been performed, including 24 library- and Medline-selected publications on Caucasoids (European and non-European) and East Asians and a set of original data on European Caucasoids. A total of 3453 Caucasoid and 931 East Asian items, including entire bodies, half bodies and arteries, were used. After testing the homogeneity of the available data sources in relation to the anatomical variables under study we calculated a cumulative value for each selected anatomical parameter and evaluated differences by non parametric statistics. Effectiveness of non-selective thyroid angiography was determined using sensitivity, specificity, positive and negative predictive values. A higher frequency of origin from the external carotid artery was present in Caucasoids than in East Asians. In contrast, a higher frequency of origin from common carotid artery was observed in East Asians versus Caucasoids. No gender differences were found for any of the parameters analyzed in East Asians. In addition, an equal probability of either asymmetrical or symmetrical origin on the two sides of the neck for STA was found in East Asians. In contrast, a symmetry of caliber for STA was found in European Caucasoids. Finally, only a moderate effectiveness of non-selective thyroid angiography, either conventional or by digital subtraction, was determined for visualization of STA in European Caucasoids. Statistically significant variations in some STA anatomical parameters occur between Caucasoids and East Asians. These differences, together with the high frequency of asymmetry for STA origin in East Asians and low effectiveness of STA visualization by non-selective angiography in European Caucasoids, may result in useful information for clinical reasoning in selected conditions of the thyroid region.

Anthropological variations in the anatomy of the human thyroid arteries.

Knowledge of anatomic variability of the superior (STA), inferior (ITA), and lowest accessory (IMA) thyroid arteries may be helpful in certain clinical conditions. However, details of this variability have not been thoroughly described. Specifically, whether the presence and site of origin of STA, ITA, and IMA are influenced by the anthropological group, to what extent their origin is symmetric or asymmetric, and the role played by this variability in visualizing each thyroid artery by nonselective thyroid angiography is not known. To clarify this we conducted a meta-analytical study on Caucasian and Asian subjects, the latter including only Japanese and Koreans. In Caucasians and Asians the presence of superior vessels compared to inferior vessels was more frequent and the probability of symmetric or asymmetric arterial origin for STA were equivalent. However, better recognition of inferior rather than superior vessels was achieved by nonselective angiography in Caucasians. Finally, different frequencies of presence and site of origin for each artery were identified in Caucasians compared to Asians. Our results suggest that the higher frequency of IMA in Asians than in Caucasians should result in a search for an IMA-dependent feeding artery of inferior parathyroid adenomas, primarily the mediastinal ones, especially in Asians both by imaging and transcatheter ablative approaches. In addition, we have found that a small percentage of Caucasian subjects lack an STA on the left side. Therefore, anatomic arterial compatibility should be carefully evaluated in the preoperative stage of laryngeal transplantation maintaining in situ the donor's thyroid by terminal anastomoses between donor and recipient STAs. Finally, the lack of any individual thyroid artery in either Caucasians or Asians might influence the distribution of autonomic supply that runs with thyroid vessels to the thyroid parenchyma. This appears functionally relevant in cases of traumatic or surgical lesions of the cervical sympathetic chain involving thyroid nerves. In fact, a restricted local autonomic control of thyroid activity might be related to individual rami of thyroid nerves.