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ENDOCRINE SURGERY
70
physiological stimulation from the mildly elevated TSH level, which was undetected.
Another possible explanation is the radiation
exposure to the head and neck during childhood, which increases the risk of not only
malignant nodules but also benign multinodular goiter. Nevertheless, in most instances no
specific cause is identified, although a defect in
genetic makeup has been suggested [9, 10].
Multinodular goiter is the most common thyroid disorder, with a wide spectrum of clinical
presentation and severity. Most goiters are discovered incidentally and are asymptomatic at
presentation. They are slow growing and may
cause only little discomfort. Subtle forms of
symptoms may go unnoticed for many years
and not infrequently patients may only be
aware of a dominant multinodular goiter,
which present as a single palpable nodule. Conversely, large and massive goiters continue to
exist in iodine-deficient regions, particularly in
the developing countries. Large goiters in the
neck not only affect the cosmetic appearance,
but lead to predominant signs and symptoms
that are closely related to the enlarging mass,
impinging onto the adjacent structures and
causing significant compressive symptoms of
dysphagia, dyspnea, choking sensation, or
even hoarseness of voice.
Further downward growth of a goiter occurs
in the path of least resistance into the thoracic
inlet forming a substernal goiter. Most substernal goiters are asymptomatic and detected only
on routine medical examination with chest
radiograph. However, large substernal goiters
may present with symptoms of chest discomfort
and significant obstruction to the venous
return. The venous obstruction of the jugular
veins may be made apparent by having the
patient elevate the arms above the head, indicating a positive Pemberton’s sign. Not infrequently the compressive symptoms with chest
discomfort may be misinterpreted as cardiopulmonary symptoms. Once detected there is an
urgent need for intervention as any sudden
glandular bleeding may exacerbate the compressive symptoms, leading to life-threatening
emergency. Other reasons for removal are suspicion of malignancy and prevention of future
complications. Although the majority of multinodular goiters are in euthyroid state, hyperfunctioning or rarely hypofunctioning has
been reported.
Embryology and Surgical
Anatomy of Thyroid Gland
The practice of thyroid surgery should always
be based on a thorough understanding of the
embryology and surgical anatomy. It is
imperative for surgeons to appreciate the anatomical planes, enlargement variations, and
abnormalities in relation to the surrounding
structures to map for the best options of safe
surgical approach. The thyroid gland develops
from the median endodermal thickening in the
floor of the primitive pharynx. This thickening
invaginates from the foramen cecum with a
downward growth and descends passing ventral to the developing hyoid bone and laryngeal
cartilages. At this stage, the developing median
thyroid gland is connected to the tongue by the
thyroglossal duct. The pyramidal lobe is
formed from the remnant of the distal end of
thyroglossal duct. The median thyroid lobe
continues to divide into two medial thyroid
lobes connected by the isthmus. Here the thyroid gland acquires the shape of a butterfly and
resides anterior to the second and third tracheal rings. Most would not appreciate the presence of the lateral thyroid lobe, also known as
the posterior horn of thyroid gland, which
arises from the fourth branchial cleft and ultimobranchial body on both sides. The lateral
lobes develop from the ectodermal origin,
which is rich in parafollicular cells, and later
fuse with the medial thyroid lobes to form the
thyroid gland [11]. This fusion of the thyroid’s
C cells is closely associated with other ectodermal endocrinopathy such as in MEN 2A. It is
not surprising to learn that as a result of the
incomplete fusion of the lateral and medial
lobes, a tubercle with higher concentration of
calcitonin is formed. The tubercle was named
after Emil Zuckerkandl, who described this
incomplete fusion back in 1902 [12]. The importance of the Zuckerkandl tubercle when present
is that, if not appreciated and removed during
thyroid surgery, it may be a persistent source of
unrelieved compression symptoms and remnant for future recurrence [13]. Furthermore
the understanding of the anatomy of Zuckerkandl’s tubercle is important as a guide to safe
dissection. The tubercle enlarges laterally and
above the recurrent laryngeal nerve, forming a
medial cleft, and at this point of dissection, it
71
MULTINODULAR GOITER
a
Fig. 5.1. (A) Early exposure and elevation of the Zuckerkandl’s tubercle (arrow) invariably will allow the recurrent laryngeal nerve
to be easily and safely encountered. (B) The uncommon variation where the recurrent laryngeal nerve (arrow) runs lateral and lying
on the Zuckerkandl’s tubercle (ZT).
may appear as if the recurrent laryngeal nerve is
passing directly into the thyroid gland. Hence
early exposure and elevation of the Zuckerkandl’s tubercle will invariably allow the recurrent laryngeal nerve to be easily and safely
encountered. This is an important constant anatomical landmark to encounter the recurrent
laryngeal nerve (Fig. 5.1A) [14, 15]. A unique
feature is the uncommon abnormal variation
where the recurrent laryngeal nerve runs lateral
and lies anterior on the enlarged Zuckerkandl’s
tubercle, thus to some extent placing it at
increased risk of damage during dissection
(Fig. 5.1B) [16].
Special care should be taken to avoid undue
traction and dislocation of the tubercle before
the nerve is encountered. Another important
point is that the normal superior parathyroid
gland, also being derived from the fourth branchial cleft, is commonly found in close association, cephalad to the tubercle [11, 14–16]. The
presence of Zuckerkandl’s tubercle is frequently
recognized only when full mobilization of the
respective lobe has been achieved [15, 16].
When the tubercle is obvious particularly
when it is more than 1 cm in size, it is noted to
be associated with 81% of appreciable compressive symptoms from either the enlarged retrotracheal or the retro-esophageal extension [13,
16]. The significance of the compressive symptoms due to the size of the tubercle is well
recognized, but perhaps more important is the
b
location of the tubercle from either a retro-tracheal or a retro-esophageal extension regardless
of the size of goiter. It is possible that the embryological formation of the tubercle continues to
enlarge over a period of time caused by hyperplastic or neoplastic changes as postulated in
the formation of multinodular goiter (Fig. 5.1).
More often than not, all large goiters are significantly associated with the increase in the size of
the tubercle [13]. Pelizzo et al. proposed a classification based on the size of the tubercle and
its fusion with the principal medial thyroid lobe.
The classification proposed was grade 0 –
unrecognizable, grade 1 – only a thickening of
the lateral edge of the thyroid gland, grade 2 –
smaller than 1 cm, and grade 3 – larger than
1 cm [14].
The Zuckerkandl’s tubercle is an important
anatomical landmark commonly found in
large multinodular goiter, which has a sound
embryological basis with significant clinical
implications. The value of preoperative lateral
neck radiograph to detect the enlarged
tubercle is substantiated with the widening of
retro-visceral or prevertebral soft tissue measurement at C4, C5, and C6 levels (Fig. 5.2A). It
would seem that the C4 level is the most promising predictor of enlarged Zuckerkandl’s
tubercle and any widening of 16.5 mm or
more observed in the lateral neck radiograph
has 100% specificity to diagnose the enlarged
grade 3 tubercle [17].
ENDOCRINE SURGERY
72
a
Fig. 5.2. (A) The widening of retro-visceral or prevertebral soft tissue measurement at C4 level is the most promising predictor of
enlarged Zuckerkandl’s tubercle. (B) Lateral radiograph showing direct posterior compression narrowing the airway with severe
symptoms of dyspnea, stridor, and dysphagia.
Clinical Presentation
of Multinodular Goiter
The signs and symptoms of multinodular goiter
are predominantly related to the enlarging mass
leading to significant compression and impingement onto the local adjacent structures. To
some extent, the location and extension of the
goiter may be more crucial than its absolute size
to cause compressive symptoms as has been
described earlier. The compressed trachea or
esophagus or both may result in common symptoms of dysphagia, dyspnea, coking sensation, or
stridor, made worse when patient is in recumbent position. On the contrary when there is
hoarseness of voice, a presumptive diagnosis of
malignant goiter with infiltration into the recurrent laryngeal nerve must be considered, as
rarely it may occur from enlarging mass stretching on the nerve. Similarly Horner’s syndrome as
a result of local pressure on the sympathetic
ganglions and nerves is a rare occurrence.
There is numerous definition and classification proposed to categorize thyroid enlargement.
Large goiter has been defined as a protrusion
beyond the chin or jaw, and according to the
World Health Organization classification, large
goiter is a stage 3 goiter visible from a distance
of several meters. Stage 1 is where the thyroid
enlargement is not visible but palpable and
Stage 2 is where the thyroid enlargement is
clearly visible on close inspection. Perez
b
classification of large goiter is when a goiter
weighs 80 g or more after excision or has the
largest neck circumference crossing the goiter
being 40 cm or more [18].
Large goiters are common in iodine-deficient
regions and although long-standing large goiter
in the neck is clinically apparent with cosmetic
problems, it appears to be tolerated by many
patients in endemic regions. Surgery is inevitable in those with large goiter with significant
compressive symptoms. The effects of compression onto the vital structures and distortion of
the anatomy increase the difficulties of surgery
and pose a unique challenge to surgeons. It is
clear that unilateral dominant goiter with lateral
compression can displace the hyoid, trachea,
and larynx to the contralateral side. However,
in bilateral nodular enlargement, lateral compression on both sides of the trachea and larynx
may cause a critical narrowed slit airway. In
such circumstances horizontal finger pressure
maneuvers by the patient anterior to the trachea
may help a little to temporarily ease the airway.
Direct posterior compression from the retrotracheal or retro-esophageal extension may
also cause significant compression symptoms
as seen in the lateral radiograph (Fig. 5.2B).
Thyroid enlargement descending lateral and
posterior into the narrow thoracic inlet may
cause considerable neck discomfort and the
sensation of tightness. The downward growth
is often restricted anteriorly by the pretracheal
muscles, which are inserted into the posterior
73
MULTINODULAR GOITER
part of the clavicle and sternum. Nonetheless
the rare entity of presternal extension in the
midline has been reported [19]. The continuation of downward growth of a goiter below the
level of the manubrial notch and thoracic inlet
may be drawn by the process of swallowing and
increased in the negative thoracic pressure. The
lower pole is the usual starting point of a growth
to descend, but occasionally the growth may
start from a lateral lobe. Initially the thyroid
enlargement moves in and out of the thorax
with swallowing, and further downward prolongation would require an increasing thoracic
pressure upon coughing to plunge the mass
out of the thorax. This plunging goiter is easily
removed through a cervical approach. As more
and more mass volume forms and with further
downward growth, the goiter reaches a size that
precludes its movement out of the thorax. Various stages of downward growth have been proposed to describe the process of descend [20].
A stage 3 goiter is where only a fibrous band
attaches to the goiter and stage 4, a complete
isolated mediastinal goiter disconnected from
the principal thyroid gland in the neck [20].
Such isolated substernal goiter adds to the difficulties in diagnosis and invariably may resort to
a sternal split for removal.
Diagnostic Modalities
All patients diagnosed with multinodular goiter
must be screened for thyroid function to determine the serum level of free thyroxine (T4) and
TSH levels. Imaging studies are useful to assess
the extent of displacement and constriction of
the trachea and esophagus. A chest radiograph is
a simple investigation that will often show deviation of the trachea and the presence of a substernal tumor. Although trachea displacement
and compression is frequently documented in
most cases this is rarely critical to warrant emergency surgery. Lateral chest radiography may be
helpful to detect posterior compression and presence of enlarged Zuckerkandl tubercle. Barium
studies may demonstrate clearly the indention of
the esophagus from the posterior or the lateral
side. Ultrasound is an important and noninvasive bedside imaging study, which is now
increasingly being accepted as part of the armamentarium of endocrine surgeons. Not only
important information of the size, number, and
location of the nodules can be measured but also
important adjacent structures to any local compression. Computer tomography and magnetic
resonance imaging provide additional information on the location and extension of the goiter.
Both are highly accurate to detect the severity of
tracheal or venous compression and help to categorize the substernal goiter with best possible of
approach for surgery. Furthermore both imaging
studies may be necessary to distinguish a goiter
from a vascular tumor or aneurysm. Radioisotope scanning is helpful in defining the limits as
well as in identifying the nature of the mass.
Flexible laryngoscopy is a routine assessment
for all patients undergoing surgery in particularly those patients with voice changes and for
reoperative surgery. Thyroid scan is a useful
preoperative assessment particularly to confirm
isolated substernal goiter from other mediastinal
mass. Malignancy should be considered in longstanding multinodular goiter when there is sudden enlargement within a dominant nodule,
hoarseness of voice, presence of lymph nodes
coupled with past history of neck irradiation
particularly in childhood. The fine-needle aspiration may be helpful in multinodular particularly
if suspicious of malignancy in a dominant
nodule. It has been reported that 4–17% of multinodular removed at operation were found to
harbor malignancy [21–23]. This high incidence
rate may be unduly influenced by diagnostic and
selection bias in surgery. It is likely that the
surgery was performed in patients diagnosed
with multinodular goiter with high suspicion of
malignancy. Fortunately most are low-grade
thyroid cancers and are typical of the papillary
varietyand not clinically active. Samson reported
17% of small papillary carcinomas of the thyroid
gland in routine autopsies of patients not known
to have any thyroid disease or past irradiation
[24]. At this stage it is not certain whether these
lesions noted in autopsies would show any overt
clinical evidence of malignancy.
Therapeutic Options
Iodine prophylaxis via the dietary intake of
iodized salt is the most effective means of prevention and treatment for endemic goiters.
Treatment for multinodular goiter is indicated
ENDOCRINE SURGERY
74
when there is presence of local compression
symptoms, rapid enlargement in short period
of time, suspicious or proven malignancy, and
cosmetic consideration. No medical or surgical
treatment is necessary if the goiter is asymptomatic and not growing in size. Although levothyroxine therapy has been widely used to
shrink and arrest further growth of nodular
goiter, there is little evidence to support its
efficacy and the benefit is limited [24, 25]. However, some would still favor this suppressive
therapy, but it should only be reserved for
younger patients with early small nodules [26].
Over the years radioiodine therapy is increasingly being considered in the treatment of multinodular goiter, and it offers an alternative
strategy to surgery. Radioiodine therapy has
intriguingly shown consistent results of volume
reduction from 35 to 40% in the first year and
from 40 to 60% in the second year of treatment
with minimal side effects [27, 28]. More recently
the application of recombinant human thyrotropin has demonstrated to increase the uptake of
radioactive iodine (RAI) and enhanced the effect
of radioactive iodine therapy [28–30]. On the
other hand, it is clear that the enhancement
effect has implication of an increased risk for
developing hypothyroidism [29, 30]. The introduction of fractionated radioiodine therapy in
large nontoxic goiter has been reported with
success [30]. So far there is growing interest to
expand the indication for radioiodine therapy
not only to those with small goiters, elderly
with comorbidities, or those patients with substantial risk of surgery, but also to those with
large goiters and who opted for nonsurgical
approach. Given the benefit of doubt, there is a
clear need for ongoing prospective randomized
data with long-term outcome to substantiate the
routine application radioiodine therapy in the
management of multinodular goiters.
Although the renewed interest in multimodality treatment of multinodular goiter has been
made available, surgery remains to be the first
choice of treatment. The main indications for
surgery are for suspected or proven malignancy,
effects of local compressive symptoms, those
with large and substernal goiters. The surgical
options for the management of multinodular
goiter include bilateral subtotal thyroidectomy,
subtotal resection with contralateral lobectomy,
or total thyroidectomy. At present total thyroidectomy is the preferred option for the
management of benign multinodular goiter
[31–33]. Total thyroidectomy is an appropriate
surgical procedure when both lobes are
involved. It avoids further surgery in cases of
proven malignancy and prevents any possibilities of future recurrence. The argument against
total thyroidectomy for a less-extensive procedure is based on the fear of excessive morbidity
to the laryngeal nerves and parathyroid glands.
It was reported that total thyroidectomy is
associated with an increased rate of recurrent
laryngeal nerve palsies and hypoparathyroidism
in comparison with less-extensive surgery [34].
On the contrary total thyroidectomy is increasingly being accepted as the choice of surgery for
multinodular goiter provided if it could be done
safely with minimal morbidity to the laryngeal
nerves and the parathyroid glands. All efforts
should be made to preserve the parathyroid
glands during surgery, but if this is not possible
parathyroid autotransplantation of at least one
gland should be made to reduce the incidence
of hypoparathyroidism [35]. The potential benefits of total thyroidectomy relate to complete
removal of the disease and prevent reoperative
surgery for recurrence disease, which indeed
carries a higher risk and morbidity [36, 37].
Conversely hemithyroidectomy is adequate
for removal of dominant multinodular goiter
involving one lobe of the thyroid gland [38].
Although the incidence of tracheomalacia has
been reported to range from 0.001 to 1.5% this
complication remains a rarity [39]. It is more
likely to occur in those patients with long-standing
large benign goiters. In such a situation, the
sensible decision is to perform a tracheostomy at
the end of the surgery [40].
Substernal Goiter
In 1749, Haler was the first to describe a comprehensive account of substernal goiter [41],
and the first successful surgery for substernal
goiter was performed by Klein in 1820 [42]. The
reported incidence of substernal goiter in the
general population varies from 0.02 to 0.5%
based on all chest radiograph-screening reports
[43]. Substernal goiter has been reported to
range from 1 to 15% of all thyroid surgery and
accounts for about 5% of all mediastinal mass
removed at thoracotomy [44, 45]. The definition
75
MULTINODULAR GOITER
of substernal goiter has not been uniformly
standardized and accepted [46]. Substernal
goiter was defined as a lesion of the thyroid
gland extending to the fourth thoracic vertebra
on chest radiograph [46], or extending down to
the aortic arch [47]. Hedayati and Mc Henry
literally consider every thyroid that extends
below the manubrium as substernal goiter
[48]. Lahey’s definition of substernal goiter is
where the greatest diameter of the thoracic mass
by roentgenogram is well below the thoracic
inlet [49]. A popular view and the most widely
applied definition of substernal goiter was
described by Katlic, where more than 50% of
the thyroid gland is below the suprasternal
notch [50].
Zylak proposed a system to categorize the
mediastinum with computerized tomography
scan. The mediastinum is being divided into
three longitudinal compartments extending from
the level of the thoracic inlet to the diaphragm
[51]. The middle mediastinal compartment is
exclusively a vascular space that incorporates the
pericardium and its contents, the great veins, and
the anterior aorta and its major branches. The
anterior mediastinal compartment is bounded
anteriorly by the sternum and posteriorly by
the middle mediastinal and contains the thymus. The posterior mediastinal compartment
is bounded anteriorly by the pericardium and
great vessels, posteriorly by the prevertebral
fascia and anterior longitudinal ligaments,
and laterally by the respective parietal pleura.
It contains the esophagus, descending aorta,
azygos and hemiazygos veins, thoracic duct,
lymph nodes, and neural structures [51]. The
growth of a mediastinal goiter along the path of
least resistance is delineated by the anatomic
constraints in a confined space.
Classification of Substernal
Goiter
Substernal goiters are classified as either primary
or secondary. Primary or isolated substernal
goiter is totally confined to the thoracic cavity
and in most instances remains asymptomatic
and undetected. Less than 1% of goiters are
truly isolated in the thorax, and it is believed
that the primary substernal goiter is congenital
in nature and arises from aberrant thyroid tissue.
In majority of cases isolated substernal goiters
are totally without any connection with the
cervical thyroid gland and reside in the anterior
mediastinum. Isolated anterior substernal goiters
have their own blood supply derived from the
nonanatomic mediastinal vessels. On the other
hand isolated posterior substernal goiters are
extremely very rare and only few cases have
ever been described in literature [52]. Secondary
substernal goiter is presumed to originate from
the embryological descent of the thyro-thymic
tissue and continues growth downward along
the plane of the cervical and mediastinal fascia.
Here the blood supply derives principally from
the inferior thyroid arteries and venous return
is through the inferior thyroid veins. Most substernal goiters are of secondary goiters and descend into the anterior mediastinal compartment.
Numerous classifications of substernal goiters
have been introduced, but there is lack of general
consensus to categorize them systematically. It is
certainly important to classify substernal goiter
in relation to the surrounding structures as it
could offer vital clinical information and best
possible options of safe surgical intervention.
Higgins’ classification includes substernal, partially intrathoracic, and completely intrathoracic
based on the percentage of neck versus intrathoracic disease [53]. Cohen and Cho classified the
goiter based on the percentage of mediastinal
component of substernal goiter; grade 1 indicates
25% or less of the goiter is in the mediastinum,
whereas grade 2 is between 26 and 50%. Grade 3
implies 51–75% and grade 4, more than 75% of
the goiter is in the mediastinum [54]. Perhaps
the most useful in the clinical practice is the
anatomic classification proposed by Shahian
based on the mediastinal compartment and
either a primary or a secondary goiter [55]. It
gave a comprehensive illustration of the contralateral posterior mediastinal goiter with either a
retro-tracheal or a retro-esophageal extension.
Given the difficulties that may be encountered during the surgery, first it is important to
define the lower end of substernal goiters, which
may be located well below the level of aortic arch
and as far down to the diaphragm. Second it is
equally important to learn the direction of growth
and impingement onto any vital structures, and
third it may require a proper strategyand a careful
assessment for the best route of surgical approach
for safe resection. We proposed a classification of
substernal goiter based on the Zylak’s division of
Table 5.1. Classification of substernal goiter
Type Subtype Description Operative approach
Anterior A I isolated Sternal split
AII substernal extension Collar – Sternal split
AIIIA crossed-over anterior Collar – Sternal split
AIIIB crossed-over posterior Collar and Sternal split
Posterior(Back) B I Isolated Thoracotomy
BII Substernal extension Collar – thoracotomy
BIIIA Crossed-over anterior Collar – thoracotomy
BIIIB Crossed-over posterior Collar – thoracotomy
1 Retro-tracheal extension
2 Retro-esophageal extension
Abbreviation: A: anterior, B: posterior (back).
76
ENDOCRINE SURGERY
the mediastinum into three longitudinal compartments. This classification not only takes into
account the anatomic compartment but also the
possible variation of substernal goiters growing in
the mediastinum coupled with the best possible
surgical approach (Table 5.1).
It is clear that in a confined space the
substernal goiters frequently compressed onto
the trachea and the large veins, and to some
extent causing critical narrowed airway, venous
engorgement, and even superior vena cava
obstruction. Fortunately most anterior substernal can be removed entirely through a cervical
approach with a low complication rate. The
anterior crossed-over substernal goiter to the
opposite side is rather unique in the sense that
it descends downward and crosses over from
a
the right to the left side (Fig. 5.3) or vice versa.
One quarter of mediastinal goiters are in the
posterior mediastinum. It arises from the posterior and lateral aspects of the thyroid gland in
the neck and descends into the thorax. Two
thirds of the posterior mediastinal goiter exclusively occur on the right side [55]. This is due to
the position of the aortic arch and descending
aorta, which occupies the left side of the thorax,
and thus preventing the goiter from descending
on the left side. Contralateral or crossed-over
substernal goiter is a rare clinical entity in the
posterior mediastinum. Often the crossed over is
part of the extension from left-sided gland to the
right side of the posterior mediastinum either
crossing behind the esophagus or sandwiched
between the trachea and the esophagus (Fig. 5.4).
b
Fig. 5.3. CT scan (A) and gross specimen (B) showing the anterior crossed-over substernal goiter from the right to the left side.
77
MULTINODULAR GOITER
a
b
Fig. 5.4. (A) CT scan showing the crossed-over posterior substernal goiter extending below the level of carina. (B) A large gross
specimen of the crossed-over posterior substernal goiter completely removed through the collar incision using Lahey’s technique.
78
ENDOCRINE SURGERY
a
b
Fig. 5.5. (A) The anterior substernal goiter crossed over the aortic arch to the opposite right side of the posterior thorax. (B) Gross
specimen of the anterior substernal goiter crossed over right side of the posterior thorax.
79
MULTINODULAR GOITER
Such glands are usually retrievable through the
neck. Occasionally in large goiter, one might
have to resort to a right lateral thoracotomy
through the fourth or fifth intercostal space to
allow adequate exposure and removal [56]. On
the contrary, crossed-over substernal goiter
from the anterior to the posterior mediastinal
compartment or vice versa is extremely rare. It
appears that because of the confined space and
structures in middle mediastinal compartment,
the growth of a substernal goiter occurs from
the anterior left-sided goiter and crossed over
the aortic arch to the opposite right side of the
posterior thorax (Fig. 5.5). It may also cross
over and impinge onto the brachiocephalic
vein into the right posterior mediastinal compartment. The impingement on the brachiocephalic vein or on the aortic arch formed the
‘‘saddle goiter’’. Further downward growth into
the posterior of right thorax may be mistaken
for a true posterior ipsilateral substernal goiter.
At this point it is important to define the trachea, as most posterior goiter will push the
trachea toward the anterior. On the contrary
this unique feature of anterior substernal goiter
that crossed over the aortic arch to the posterior
mediastinum pushes the trachea to the back.
Similarly a posterior mediastinal goiter, either an
ipsilateral or an contralateral goiter, may continue
to enlarge extending to the anterior mediastinum
particularly on the right side. The surgical implication of anterior goiters crossed over to posterior
or vice versa may be important as it changes the
scenario from a simple attempt of removal
through a cervical approach to often a sternal
split rather than a thoracotomy. It would be hazardous to attempt the removal through a cervical
approach without understanding the various compartments involved and the direction of the
growth. Secondary posterior substernal goiters,
either an ipsilateral or a contralateral extension,
may be removed through a cervical approach
(Fig. 5.4) except very large goiter with incomplete
removal in previous surgery would require the
right posterolateral thoracotomy (Figs. 5.4 and
5.5). Special attention and care must be taken in
those patients whose airway is severely compromised. It may be necessary to resort to tracheal
intubation while patient is awake under topical
anesthesia in order to avoid airway difficulties
during induction. Tracheal intubation ensures
the continuity of breathing during the surgical
procedure, as traction and dissection may exert
pressure against the narrowed airway. It is clear
this is associated with high incidence of significant postoperative sore throat and laryngeal
edema especially those with large goiter and
with severe compression [57].
Operative Techniques
Anterior Substernal Goiter
Primary (isolated) anterior substernal goiters
are rare clinical entities and arise primarily
from the ectopic intrathoracic thyroid tissue.
However, more often then not they are in fact
residual portion of a goiter in the thyro-thymic
remnant, which was incompletely removed in
previous surgery. A sternal split is perhaps all
that is required to achieve a complete removal
of an isolated anterior mediastinal goiter which
lies entirely within the thorax. One should not
attempt to remove the goiter from cervical
approach as most primary substernal goiters
derive their blood supply directly from nonanatomic vessels in the anterior mediastinum.
On the contrary almost all secondary anterior
substernal goiters can be removed through a
cervical approach without much difficulty [58].
The cervical approach allows excellent exposure
and proximal control of the blood supply to the
substernal goiters. After raising the superior and
inferior cervical flaps it is important to divide the
straps muscle on both sides to enhance the anterior exposure. To facilitate the surgery it is a
good practice to start from the opposite thyroid
gland with least substernal extension to provide
more space in the neck. The nextcrucial step is to
divide the middle thyroid veins and expose the
lateral and the posterior prevertebral space. This
is an avascular space, which provides access for
safe dissection away from the carotid sheath and
a cleavage point to separate the goiter from the
thyroid bed. It is equally important to have a
Ryle’s tube inserted to allow identification of
the distorted esophagus.
The identification and preservation of the
external laryngeal nerve can be performed by
exposure of the cricothyroid space. The priority
at this point is to control the blood supply
by tying the superior thyroid vessels individually. The thyroid gland can be gently dislocated
to identify the Zuckerkandl tubercle and permit