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.