Eur J Anat, 6 (2): 109-113 (2002) Variants of the thyrocervical trunk and its branches in human bodies A. López-Muñiz, C. García-Fernández, L.C. Hernández and S. Suárez-Garnacho Department of Morphology and Cellular Biology, Faculty of Medicine, University of Oviedo, E-33071-Oviedo, Spain SUMMARY variability of the TT and its branches, which must be considered of interest given the fre- The thyrocervical trunk or thyrobicervicoscapu- quency with which this region is involved in lar trunk of Faraboeuf (TT) is a branch of the both diagnostic and therapeutic procedures. subclavian artery. In most cases, the following arteries arise from here: inferior thyroid artery Key Words: Thyrocervical trunk – Anatomical (ITA), transverse cervical artery (TCA) and the variants – Infundibular dilation suprascapular artery (SSA). However, this trunk can show many variants. We dissected the supraclavicular region of 22 INTRODUCTION human bodies (12 males, 10 females) with the aim of studying the subclavian artery, and prin- The thyrocervical trunk or thyrobicervicoscapu- cipally the TT (22 right trunks and 18 left ones), lar trunk of Faraboeuf is a branch that originates its disposition and number of branches, the exis- from the anterosuperior side of the subclavian tence of infundibular dilation, and the thickness artery, distal to the vertebral artery, generally at of the branches. A statistical analysis of the data the level of the internal thoracic artery. was performed. Our results show that the most In most cases it is a short, thick trunk from frequent type of TT is that of 2 branches. No sig- which the ITA (the principal branch), the TCA nificant differences were found between the and the SSA arise, the ascending cervical artery number of branches of the TT, nor with respect (ACA) originating from the ITA (Williams and to sex or side. The infundibular region of the TT Warwick, 1985). This artery can exhibit many is an anatomical variant of considerable interest, variants and these may not even be present if its this variant being more frequent in males on the branches originate directly from the subclavian right side and in trunks with a greater number of artery itself (Testut and Latarjet, 1978). branches. The most frequent variants in our Among the variations described, the study with respect to the classic description infundibular dilation of the origin of the trunk were: the presentation of the ascending cervical or one of its branches in the case where they artery (ACA) as a branch both of the TCA and of originate independently is especially important. the TT; that of the TCA as a branch of the SSA or This morphology, which is similar to that seen the subclavian, and the origin of the SSA direct- in other arteries (Abrams and Jönsson, 1983; ly from the subclavian artery itself. The calibre of Goebel et al., 1985), is the result of incomplete the branches of one side or another was differ- reabsorption during embryonic development ent, the most frequent observation being that the and can mistakenly be considered pathological branches of the right side were thicker than if its possible existence is not taken into con- those of the left. Our results confirm the high s i d e r a t i o n . Correspondence to: Dr. A. López Muñiz. Dpto. de Morfología y Biología Celular,Facultad de Medicina, Universi- Submitted: May 20, 2002 dad de Oviedo, E-33071-Oviedo, Spain. Accepted: July 26, 2002 Phone: 985 103056; Fax: 985 103618. E-mail: [email protected] 109 A. López-Muñiz,C. García-Fernández,L.C. Hernández and S. Suárez-Garnacho MATERIAL AND METHODS statistical test of Z distribution was used. Calcula- tions were made using Microsoft Office Win d o w s In the present study we dissected 22 human Excel 5.0 and the SPSS 10.0 statistical package. bodies (12 males and 10 females), in each case studying the subclavian artery and its branches: principally the TT (22 right trunks and 18 left RESULTS trunks). Only cadavers with no vascular pathol- ogy were included. Variability of the trunks Of the 40 subclavian arteries studied, we found Anatomical intervention TT in 38 (95%), 4 of which had four branches The supraclavicular region was dissected. The (Fig. 1A), 12 three branches (Fig. 1B) and 22 two skin and subcutaneous cellular tissue was cut branches (Fig. 1C). The only two cases in which until the superficial cervical fascia was rea c h e d . this was absent corresponded to the right side in Under the superficial fascia there is a second cel- two males (Fig. 1D). lu l o f i b r ose plane: the investing layer of deep cer- Separated according to side, of the 22 right vical fascia, divided into two parts by the omohy- subclavian arteries dissected we found a trunk of oid muscle. In the deep face of this second plane four branches in 2 cases, of three branches in 4, the following structures are found: in the upper of two in 14 cases and no branches in 2. On the part, the branches of the cervical plexus; in the left side (18 subclavian arteries), we found 2 lower part, the external jugular vein and the SSA. trunks with four branches, 8 with three and In order to gain better access to the lower part another 8 with two (Table 1). of the region, a 6-8 cm portion of the clavicle Statistical comparison between the side and must be sectioned. The prevertebral layer of deep the number of branches of the TT was not sig- cervical fascia was cut; the scalenus anterior mus- nificant (p=0.231). The linear regression between cle was separated, the deeper part of the fascia the number of branches on each side with was lifted, and the scalenus posterior separated. respect to the other was not significant. The The subclavian artery is found behind the ten- same occurred with Spearman’s correlation. don of the anterior scalene and the SSA is When separated according to sex, of the sub- clavian arteries dissected in females the TT was observed here. In the celluloadipose tissue that present in 20 cases (100%). None had four fills the underlying space, the intrascalenic por- branches; 6 had three, and 14 had two. In males tion of the subclavian artery is found and the TT (20 subclavian arteries) we found trunks on 18 with its branches, the ITA, the ACA, the TCA, and occasions (90%): 4 presented with four branch- the SSA, can be identified (Testut et al., 1965). es, 6 with three and 8 with two. Statistical comparison between sex and the Statistical analysis number of branches was not significant (p=0.65). The following parameters were analysed: the Correlation analysis did not show statistical sig- number of branches of the TT; the number of nificance. infundibular dilations; the arterial variant according Of the infrequent branches of the TT, we to its origin (frequency), and the thickness of the observed the internal thoracic artery in 4 cases arterial branches (frequency). Each parameter was (10%) (Fig. 1E). studied according to sex and age. In each res u l t we obtained the mean, standard deviation and Infundibular dilation standard error . For data with Gaussian distribu- Of the 40 subclavian arteries dissected we tions, an analysis of variance (ANOVA) and a later found 6 infundibular dilations (15%): all in the study using Student’s “t” and Newman-Keuls tests TT and none in independent branches (Fig. 1F). we r e perfo r med. For the study of dependent vari- Distribution according to side: 4 infundibular ables (comparison between the left/right side of dilations were right sided and 2 left sided. the same body), linear reg r ession and Spearma n ’ s Distribution according to sex: 4 infundibular co r r elation were employed. Finally, for the evalu- dilations in males, all on the right side and 2 on ation of the non-parametric percentage data, the the left side in females. Table 1.- Percentages of the number of branches of the thyrocervical trunk (TT) according to side and sex. Number of Side Sex Total branches of the TT Right Left Male Female 4 9% 11% 20% 0% 10% 3 18% 44.4% 30% 30% 30% 2 63% 44.4% 40% 70% 55% Absence of TT 9% 0% 10% 0% 5% 110 Variants of the thyrocervical trunk and its branches in human bodies Fig. 1.- A: Thyrocervical trunk with four branches. B: Thyrocervical trunk with three branches. C: Thyrocervical trunk with two branch- es. D: Thyrocervial trunk absent. E: Internal mammary artery with origin in the thyrocervical trunk. F: Infundibular dilation of the thyrocervical trunk. 1: subclavian artery (arteria subclavia ); 2: thyrocervical trunk (truncus thyrocevicalis ); 3: inferior thyroid artery (a. thyroidea infe - rior); 4: suprascapular artery (a. suprascapularis ); 5: transverse cervical artery (a. transversa cervicis); 6: ascending cervical artery (a. cervicalis ascendens); 7: internal thoracic artery (a. thoracica interna ); 8: infundibular dilation (infundibulum ); 9: phrenic nerve (nervus phrenicus). Distribution according to the number of The results of statistical analysis of the branches of the TT: 2 infundibular dilations were infundibular origin according to side and sex in trunks with four branches (both on the right were not significant, with p=0.846 and p=0.843, side in males) and 4 in trunks with three branch- respectively. es (2 on the right side in males and 2 on the left side in females) (Table 2). 111 A. López-Muñiz,C. García-Fernández,L.C. Hernández and S. Suárez-Garnacho Table 2.- Percentages of infundibular dilations according to the number of branches of the thyrocervical trunk (TT), side and sex.