DESCRIPTION 
OF AN 
ANOMALOUS ORIGIN OF THE RIGHT SUBCLAVIAN ARTERY, 
ASSOCIATED WITH ANOMALIES OF ORIGIN OF 
THE BRANCHES OF BOTH SUBCLAVIAN 
ARTERIES; WITH REMARKS. 
BY 
J. EWING MEARS, M.D., 
PROFESSOR OF ANATOMY AND CLINICAL SURGERY IN THE PENNSYLVANIA COLLEGE OF DENTAL SURGERY ; 
SECRETARY OF THE PATHOLOGICAL SOCIETY OF PHILADELPHIA, ETC. 
Reprinted from the 
American Journal of the Medical Sciences for October, 1871. ANOMALOUS ORIGIN OF RIGHT SUBCLAVIAN ARTERY. 
The specimen represented in the annexed drawing was 
prepared by me some years since-having come under 
my observation whilst engaged as assistant Demonstrator 
in the Jefferson Medical College anatomical rooms. 
Owing to the fact that the subject in which it occurred 
was dissected in parts, by students, it was impossible, 
at the time at which the anomalies were discovered, 
to trace, with that accuracy which is so essential in all 
anatomical descriptions, the distribution of the vessels 
arising by anomalous points of origin from the subclavian 
arteries, or to determine the relations of the surrounding 
structures. It is believed, however, that the vessels can 
be designated with sufficient exactness to warrant a de- 2 
MEARS, 
scription of the specimen, by means of which it will be 
placed on record, with such other specimens of this char- 
acter as have been already described. 
The specimen presents, as will be recognized by refer- 
ence to the figure, the following peculiarities: 
1. Abnormal origin of the right subclavian artery. 
2. As a necessary consequence of the first, an anoma- 
lous origin of the right primitive carotid artery. 
3. Irregularity in the points of origin of the left prim- 
itive carotid, and left subclavian arteries. 
4. Deviations from what is regarded as the normal plan 
of origin in the branches of the subclavian arteries. 
The second and third conditions are incidental, and do 
not concern particularly the present investigations. The 
first and fourth are important, and may be described as 
follows: 
1. Origin and Course of the Right Subclavian 
Artery.-In this specimen, the artery takes its origin 
from the superior and posterior aspect of the aorta on the 
left side, at a point corresponding to the junction of the 
transverse, with the descending portion of the arch, and 
one inch from the point of origin of the left subclavian 
artery. From this origin, it takes its course backward 
and obliquely upward, passes between the oesophagus 
and vertebral column, traversing portions of the second 
and first dorsal vertebrae, and reaches its normal position 
on the upper and outer surface of the first rib. 
2. Origin of the Right Primitive Carotid Ar- 
tery.-This vessel occupies the place of the innominate 
artery, arising from its point of origin, from the com- 
mencement of the transverse portion of the aortic arch. 
3. Positions of Origin of the Left Primitive 
Carotid and Left Subclavian Arteries.-The or- ANOMALOUS ORIGIN OF RIGHT SUBCLAVIAN ARTERY. 
3 
igin of the former is in close connection with that of the 
right carotid artery, and in this respect occupies a posi- 
tion more to the right than is normal; in crossing to its 
distribution on the left side of the neck, it covers a larger 
surface of the trachea than is natural. 
The left subclavian artery arises from the summit of 
the arch of the aorta-the middle point of the transverse 
portion of the arch, which is the normal point of origin of 
the left primitive carotid artery, deviating from its normal 
origin at the end of the transverse portion of the arch. 
4. In the Branches of the Subclavian Arteries 
the deviations from the normal plan of origin are as fol- 
lows : In both vessels the thyroid axis is absent-the 
branches originate as follows : 
1. The Inferior Thyroid Artery on the right side arises 
independently from the first part of the subclavian artery 
at a point on the anterior surface and near to the inferior 
border. 
On the left side, it arises independently from the an- 
terior surface near the superior border from the first part 
of the subclavian artery. 
2. The Vertebral Artery is smaller on the right side 
than on the left, and arises from the superior surface of 
the subclavian artery. On the left side, from the superior 
and posterior surface of the artery. On each side, it is 
given off normally from the first part of the subclavian 
artery. 
3. The Internal Mammary Artery, on each side, takes 
origin from the anterior surface; on the right side, the 
point of origin is nearer to the inferior border, and in close 
connection with the points of origin of the Inferior Thy- 
roid; on the left side, the distance between the two points 
of origin is greater. 4 
MEARS, 
4. The Superior Intercostal Artery, on the right side, 
originates from the upper and back part of the first 
portion of the subclavian artery to the inner side of the 
scalenus anticus muscle. The Left Superior Intercostal 
Artery arises from the posterior surface of the subclavian 
artery, near to the inferior border. 
5. The Transverse Cervical and Suprascapular Arteries 
arise by a common trunk from the subclavian artery, at 
a point corresponding to the junction of the second and 
third portions of the artery, just external to the scalenus 
anticus muscle. On the right side the origin is from 
the upper surface; on the left side it is placed a little 
posterior. 
6. In addition to the above-described branches, a small 
supernumerary artery arises on the right side-a mus- 
cular branch. 
Remarks.-The form of anomaly occurring in the 
origin of the right subclavian artery, as above described, 
has been so frequently observed and described as to 
divest this specimen of particular interest in this respect. 
In a very careful examination of a large number of 
authorities, I have not been able to find the description 
of a specimen illustrating this variety of anomaly, in 
which an association of anomalies in the origin of the 
branches of the subclavian arteries has been observed. 
The association of these anomalies of origin gives to the 
specimen, therefore, an interest which it otherwise would 
not possess, and will justify a more extended notice of it. 
In examining the literature of this subject, my atten- 
tion has been directed to some points in connection with 
the anomalies of this form which may be of interest to 
note. First, as to frequency of occurrence. Professor 
Joseph Leidy, of the University of Pennsylvania, informs ANOMALOUS ORIGIN OF RIGHT SUBCLAVIAN ARTERY. 
5 
me that the Wister and Horner Museum contains, among 
its arterial preparations, at least three examples of this 
anomaly. In his dissections he has met with two in- 
stances. In all the examples which have fallen under his 
observation, the artery has passed behind the oesophagus. 
Dr. Wm. II. Pancoast, Demonstrator of Anatomy in the 
Jefferson Medical College, informs me that he has ob- 
served examples of this anomaly. Other instances may 
have been observed in the anatomical rooms, but, so far 
as 1 know, they have not been reported. Wood (Trans. 
London Path. Society, vol. x.), and other anatomists, 
state generally, that almost every museum contains a 
specimen showing this irregularity. Colles {Surgical 
Anatomy) states that he observed four instances in one 
winter's dissections-two in adults, and two in children. 
Quain {Anatomy of the Arteries) reports four instances 
as observed in the dissection of one thousand subjects, 
giving a proportion of one in about two hundred and 
fifty. J. M. Dubrueil (Des Anomalies Arterielles) states 
that it is remarkable " that among the inversions of the 
origin of the right subclavian artery, the most extraordi- 
nary in appearance is the most common; that in which 
the artery arises from the extreme left of the arch of the 
aorta, and reaches its normal position on the right side 
by passing behind the oesophagus." lie reports two 
instances in which this occurred-one especially note- 
worthy, in view of the fact that the two primitive carotid 
arteries accompanied the right subclavian artery in its 
abnormal course. It is thus described: " la sous-claviere 
droite, situee en arriere et a gauche de sa congenere, et 
dirigee de bas en haut, passait derriere 1'oesophage avec 
les cardtides primitives." Authorities generally agree as 6 
MEARS, 
to the frequency with which the right subclavian artery 
arises from the left side. 
In reference to the point of origin of the right sub- 
clavian artery in these cases, there appears to be some 
variation. Wood alludes to the "singular constancy" of 
the abnormal point of origin of the right subclavian 
artery from the descending aorta, as noticed by Quain. 
Often it coincides with the very point of attachment of 
the ductus arteriosus. Messrs. Bankart, Pye-Smith, and 
Phillips {Guy's Hospital lieports, vol. xiv.) report two 
cases in which the artery arose from the " back of the 
third part of the aortic arch." Meckel {Descriptive and 
Pathological Anatomy) speaks of the right subclavian 
artery being the extreme left trunk of those which arise 
from the arch of the aorta, and passing to the right side 
behind the oesophagus. 
Hyrtl (Lehrbuch der Anatomic des Mensch en) vaguely 
describes the vessel as arising, in these instances, " below 
the left subclavian artery." 
Cruveilhier {Traite d'Anatomic Descriptive) gives a 
similar description. 
Harrison {Surgical Anatomy of the Arteries, p. 19) says 
that he has frequently found the artery arising distinctly 
from the descending portion of the aortic arch. 
Quain, in opposition to the statement of Wood, as 
above quoted, declares that "the position which the 
artery under consideration (right subclavian) occupies on 
the aorta, when it springs on the left side, beyond all the 
other branches, is not constant. Thus, in some cases, it 
is seen to take rise from the upper part of the arch; in 
others, it is derived from the posterior aspect of the arch ; 
lastly, the origin may be found much lower down, even 
from the descending aorta." In regard to the last, he ANOMALOUS ORIGIN OF RIGHT SUBCLAVIAN ARTERY. 
7 
states that it probably " stands alone in respect to the 
depth at which the subclavian artery arises." Reference 
is made to anatomical plates containing drawings of 
specimens in which the different positions of origin are 
shown. 
In the specimen under consideration, the point of origin 
is from the junction of the transverse with the descending 
portion of the arch. The weight of evidence seems to be 
in favor of the descending or third part of the aortic arch 
as the most frequent position of origin. 
The direction which the artery takes is generally 
oblique, the obliquity varying in accordance with the 
position of origin of the vessel. 
The course of the artery, in its passage from the ab- 
normal point of origin to its position on the right side, is 
a question of much interest, relating to the constancy 
with which it passes behind the oesophagus, and to 
certain conditions which are described as attending its 
passage between the trachea and oesophagus. The latter 
will be referred to in another part of this article. Among 
the authorities consulted by me, Meckel, Cruveilhier, and 
Dubreuil alone speak of the passage of the artery in/rm^ 
of the trachea, and behind the other trunks given off from 
the arch of the aorta. The former says that it rarely 
passes in this course; the latter says that it may pass in 
front of the trachea. Neither alludes to cases in which 
this course was observed. 
In reference to the passage of the artery between the 
trachea and the oesophagus, authorities agree that this 
variety is of extremely rare occurrence. Quain so speaks 
of it, and says further, that " it is often mentioned in 
treatises of anatomy; generally, however, without refer- 
ence to particular cases." He refers to cases which are 8 
MEARS 
reported to have fallen under the observation of Meckel, 
Monro, and Zagorsky, and states, as his opinion, that " it 
does not, in either case, appear clearly, from the written 
description or the figure, what the position of the vessel 
was with reference to the oesophagus." I have been able 
to collect three authenticated examples of this form of 
the anomaly. In one of the cases described by Messrs. 
Bankart, Pye-Smith, and Phillips (Guy's Hospital Re- 
ports, vol. xiv.), the artery took this unusual course. Dr. 
S. W. Gross informs me that an example of this kind 
came under his observation in the Jefferson Medical 
College dissecting-rooms during the past winter. 
Dr. Bayford {Memoirs of the Medical Society of Lon- 
don, vol. ii. p. 275; 1793) gives the history of a case in 
which the artery was found to pass in this manner to the 
right side. Dubreuil quotes a case from Desault, Journal 
of Surgery, Paris, 1791, which he states was described in 
the Memoirs of the Medical Society of London, by Dr. 
Brewer. lie remarks that the description was " very in- 
complete;" and it is questionable whether this is not a 
reference to Dr. Bayford's case alluded to above. On 
examination, I cannot find this case in the Transactions 
of the Medical Society of London. 
Relation of the Right Inferior Laryngeal 
Nerve.-In all of these instances of anomalous origin of 
the right subclavian artery, the right inferior laryngeal 
nerve does not wind round it in proceeding to its distri- 
bution. A glance at the deep position of the artery will 
explain the cause of this. In its normal position, the 
artery is on a plane anterior to that of the larynx, and the 
pneumogastric nerve passes down in front, in close rela- 
tion with the vessel. Just at the point of crossing, the 
inferior laryngeal branch is given off, and, in order to ANOMALOUS ORIGIN OF RIGHT SUBCLAVIAN ARTERY. 
9 
reach the larynx behind, winds around the artery and as- 
cends obliquely to the side of the trachea. When the 
artery passes behind the oesophagus, or between the trachea 
and oesophagus, it is placed deep behind the pneumogastric 
nerve, and on a plane posterior to the larynx; the inferior 
laryngeal branch, therefore, although given off at the 
normal point of origin, goes directly to its distribution. 
G. W. Stedman {Edinburgh Medical and Surgical 
Journal, vol. xix., Oct. 1823) relates a case of " singular 
distribution of some of the nerves and arteries in the neck 
and the top of the thorax." The right subclavian came 
oil* from the left side of the arch of the aorta. He states 
that he could not find the recurrent laryngeal nerve, and 
thinks that it was absent, its duty being performed by 
branches given off from the trunk of the pneumogastric. 
John Hart {Ibid., April, 1826) describes "a case of 
irregular origin and course of the subclavian artery, and 
right inferior laryngeal nerve." The artery originated as 
in the case above, and the nervus vagus of right side 
crossed the subclavian artery without giving off recurrent 
nerve in usual manner." " The office of this nerve was, 
however, performed by several branches arising from 
inner side of trunk of nervus vagus; the highest and 
largest became by its distribution the inferior laryngeal 
nerve." He explains the failure of the inferior laryngeal 
nerve to wind round the subclavian artery in these cases, 
by referring to the earlier periods of the existence of the 
foetus, when the larynx is placed behind the ascending 
portion of the arch of the aorta, whilst the brain rests on 
the thymus gland and in front of the ascending portion 
of the aortic arch. The inferior laryngeal nerves pass 
back to the larynx, the left going through the arch of the 
aorta, and the right below the arteria innominata. As 10 
ME A RS, 
gestation advances, the neck lengthens, and the brain is 
removed upward, in accommodation to which the nerves 
become elongated, suspending the arch of the aorta and 
the right subclavian artery in loops. When the right 
subclavian arises on the left side, it passes behind the 
larynx, and is, therefore, not embraced by the inferior 
laryngeal nerve. 
The absence of the right inferior laryngeal nerve is not 
mentioned as usually occurring in these examples. In 
the specimen under consideration no abnormal condition 
of the nerve was observed. 
Compression of the oesophagus by the artery, producing 
a condition of dysphagia, has been observed. The only 
well-authenticated case on record, in which this condition 
existed, associated with an abnormal origin of the artery, 
is that of Dr. Bayford (op. tit.) : 
" The patient, a female aged about sixty-two, had been 
subject to difficulty of swallowing from the earliest age. 
The difficulty increased at the period of puberty, and be- 
came periodically aggravated ; exercise, or any cause 
tending to accelerate the circulation, increased the dis- 
tress ; abstract ion of blood afforded relief. The pain and 
the seat of the obstruction were referred to the upper part 
of the sternum. She finally died, exhausted by fatigue 
and famine. On making an examination after death, 
nothing could be found to account for the condition, ex- 
cept the position of the artery between the trachea and 
oesophagus, and from the obvious connection between the 
state of the circulation and the symptoms, it was reason- 
ably concluded that the vessel was the source of these." 
Dr. Bayford gave the name of "dysphagia lusoria" to 
the disease, which he was the first to describe, in accord- 
ance with the general belief that all departures from the ANOMALOUS ORIGIN OF RIGHT SUBCLAVIAN ARTERY. 
11 
usual arrangements of organs were examples of a "lusus 
natuise." Quain thinks that this condition exists only in 
those cases in which the artery passes between the trachea 
and oesophagus. Other cases of dysphagia are recorded, 
in which the artery was fdund to pass behind the oesoph- 
agus. Careful examination of the reports, however, 
shows that the symptoms were not such as to warrant 
the conclusions drawn. 
In the great majority of the cases in which the artery 
was found to pass behind the oesophagus, no history of 
dysphagia was given. Professor Otto (Seltene Beobacht- 
ungen, Th. 1, S. 100) reports a case in which he had an 
opportunity to observe a patient for more than one month, 
in whom this position of the artery was found, after death, 
to exist; there was no dysphagia whatever. So far as I 
can ascertain, no explanation is offered to account for the 
occurrence of dysphagia in the one case and not in the 
other. A careful examination of the normal position and 
relations of the oesophagus, and of the abnormal position 
and relations it assumes under the influence of the ab- 
normal origin and course of the artery, induces me to 
submit the following explanation. The oesophagus, at 
its commencement in the neck, lies immediately behind 
the trachea. As it enters the thorax, it is directed to the 
left of the median line, emerging from its position imme- 
diately behind the trachea, and passes across the left side 
of t he transverse part of the aortic ach, descending in the 
posterior mediastinum on its way to terminate at the 
cardiac orifice of the stomach. Between the transverse 
part of the aortic arch, which rests in front of the trachea 
and the oesophagus, there exists a space equal in distance 
to the depth of the trachea. When the right subclavian 
artery takes origin from the extreme end of the transverse 12 
MEARS, 
portion of the arch, or from the junction of the transverse 
with the descending portion of the arch, or, again, from 
the descending portion itself, it forms the outer lateral 
boundary of a triangular space of which the transverse 
portion of the arch in front, and the trachea on the side, 
form the other boundaries. In the specimen under con- 
sideration, the antero-posterior diameter of this space is 
fully one inch; the transverse diameter is three-quarters 
of an inch, affording therefore a space in which the tube 
rests without being subjected to any constricting pressure. 
The artery in passing behind the tube forces it forward 
into this space, and the distention caused by a morsel of 
food is in this direction, where ample room exists. 
When, on the contrary, the artery takes the more un- 
usual course between the trachea and oesophagus, the 
latter is compressed against the unyielding vertebral 
column behind, and in front the artery has the rigid 
tracheal tube upon which it can exert no force. 
During inaction of the oesophagus, the artery has suffi- 
cient space, and no interruption is offered to the circula- 
tion. Upon the introduction of food into the oesophagus, 
the bolus meets with a constriction at this point, which it 
is, however, able to overcome, but at the expense of forcing 
the artery against the trachea, and making such pressure 
upon it as will materially interfere with the blood-current. 
This sudden interruption of the circulation in a large 
artery, so near to the great column of blood in the aorta, 
must cause serious disturbance in the circulating mass, 
and induce that condition of feeling so graphically de- 
scribed by Dr. Bayford's patient as the near approach of 
the " agony of death." 
It will be observed that the usual symptoms attending 
stricture of the oesophagus, such as regurgitation of food, ANOMALOUS ORIGIN OF RIGHT SUBCLAVIAN ARTERY. 
13 
etc., are absent, only those being present which relate to 
disturbance of circulation, and through this the evil effect 
is produced. 
This explanation, it appears to me, is in strict con- 
formity with the anatomical relations of the parts, and, if 
any other has been suggested, this may be worthy of 
being considered in connection with it. 
While the oesophagus has such ample latitude in the 
space above described, I can still conceive that an acci- 
dent, such as Mr. Kirby records in the second volume of 
the Dublin Hospital Deports, may occur. In this case, a 
bone, which had been swallowed, was stopped opposite 
to the point at which the artery crossed behind the 
oesophagus, perforated the tube, and wounded the artery, 
causing1 fatal hemorrhage. 
Subgical Anatomy.- In discussing this form of 
anomaly, writers have very properly directed attention to 
the relations of the artery in the first part of its course- 
that is, before it reaches the inner border of the scalenus 
anticus muscle. Sometimes it is necessary to apply a 
ligature on this part, and it should be borne in mind that, 
in these instances, the vessel lies behind the right primitive 
carotid and very deep, separated by fascia and adipose 
tissue. The Lancet for 1839 contains the report of a case 
in which Mr. Liston performed ligation of the right sub- 
clavian artery in the first part, for aneurism. He expe- 
rienced great difficulty in finding the artery, which was 
placed behind the carotid to the distance of full one-half 
an inch, and was separated from it by fascia and adipose 
tissue. Quain, who was present, thought, from the depth 
of the result, that it was an instance of this kind. No 
post-mortem examination was reported to have been 14 
MEARS, ORIGIN OF RIGHT SUBCLAVIAN ARTERY. 
made, by means of which the exact condition could be 
determined. 
I have been interested in observing that the great pro- 
O O 1 
portion of examples of this anomaly have occurred in 
females. Over two-thirds of the cases, in which the sex 
was given, were observed in females. 
Left-handedness.-Hyrtl states that Prof. Oehl, of 
Pavia, found, in two cases of this kind, that the indi- 
vidual was left-handed, and he gives, as a possible 
explanation of this condition, the fact, that, owing to the 
transposition of the origin of the vessel, a feebleness of 
circulation is given to the right extremity. The question 
is interesting and worthy to be noted. 
Branches of the Subclavian Arteries.-Absence 
of the thyroid axis is noted to occur quite frequently. 
In the majority of instances, the branches of the thyroid 
axis arise independently from the first portion of the sub- 
clavian artery, less frequently from the second and third 
portion. In a number of instances, the suprascapular 
and transverse cervical are recorded as taking origin by 
a common trunk, as in this specimen. This latter 
deviation is to be remembered as important in surgical 
operations performed upon the third portion of the sub- 
clavian artery.