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94 Mediastinoscopy
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OPERATION
An inflatable bag is positioned behind the shoulders,
1
with the head resting on a donut, in order to maximize
cervical extension. The neck and anterior chest down to the
xiphoid are prepared and draped.
1
A transverse 3 cm incision between the anterior borders
2
of the sternocleidomastoid muscle is made 1 cm above
the suprasternal notch. The dissection is taken through the
platysma down to the strap muscles (the sternohyoid and the
deeper sternothyroid), the midline is identified, and the
straps are separated. If any significant bleeding is encountered, this situation indicates that the dissection is off the
midline. To become reoriented, it is always helpful to have a
feel of the trachea below. After dissecting the straps, the pretracheal fascia is elevated and opened, and the tracheal rings
should be clearly visualized.
2a
2b
2c
Blunt dissection with the index finger is performed. The
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3
innominate artery is felt anteriorly and the trachea posteriorly. This maneuver is extremely important in delineating
the planes of dissection. Further blunt dissection is performed in order to break the pretracheal fascia on the right
and on the left of the trachea.
Operation 95
3
Innominate artery
N3
Aortic arch
Azygos
vein
4
Innominate vein
N3
2R
4R
10R
11
4L
7
2L
6
5
12
13
10L
8
9
14
Pulmonary
artery
This illustration demonstrates the mediastinal lymph
4
node distribution.
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An excellent knowledge of
5a
astinal structures is mandatory for
the safety of the procedure. This
cadaver dissection demonstrates the
brachiocephalic trunk crossing the
trachea from left to right.
the anatomy of the medi-
5a
In this illustration the
5b
dissected out. Notice the relationship of the azygos vein to the right
border of the trachea. Notice also the
relationship between the right pulmonary artery and the right main
bronchus, and the proximity of the
left recurrent laryngeal nerve to the
left border of the trachea.
brachiocephalic trunk was
5b
Further reading 97
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The mediastinoscope is inserted below the pretracheal fascia
and introduced gently. The suction tip is used for dissection
purposes. Any suspicious structure should be punctured with
the aspiration needle first after ascertaining that the structure
is not a blood vessel and that it is a lymph node. A cupped
biopsy forceps may be used for the biopsy. It is preferable not
to use the electrocautery on the left side due to the left recurrent laryngeal nerve.
If the procedure is being performed for lung cancer staging, some surgeons will start sampling the lymph nodes on
the contralateral side of the lung lesion. If these nodes are
positive for malignancy, then the patient will be staged as N3
disease and will not be a surgical candidate. The pathology of
the ipsilateral lymph nodes will not change the final decision.
OUTCOME
Due to the proximity of the mediastinal lymph nodes to
major blood vessels and bronchial circulation, bleeding can
be a major problem. Major bleeding that necessitates thoracotomy or mediasternotomy for control is reported in
0.2–0.5% of patients. Minor bleeding that can be controlled
with local pressure or coagulation is reported in 1.5% of
patients. In cases of major bleeding that is not controlled with
local pressure the surgical approach should be adjusted to
each patient separately depending on the source of the bleeding and the location of the tumor. Resection is peformed at
the time of the exploration.
Tracheal rupture is reported in patients with significant
fibrosis of the mediastinum, and this problem is treated with
local covering of the laceration with oxidized adhesive.
Recurrent nerve paralysis, mainly on the left side, pneumothorax and lung injury, and wound infection are also
potential complications. Sporadic cases of stroke have been
reported in patients with atherosclerosis. Finally, tumor seeding may occur in the pathway of the scope.
FURTHER READING
Carlens EL. Mediastinoscopy: a method for inspection and tissue biopsy
in the superior mediastinum. Diseases of the Chest 1959; 36:
343–52.
Hammoud TZ, Anderson CR, Meyers FB, Guthrie JT, Roper LC, Cooper DJ,
Patterson GA. The current role of mediastinoscopy in the evaluation
of thoracic disease. Journal of Thoracic and Cardiovascular Surgery
1999; 118: 894–9.
Patterson GA, Ginsberg RJ, Poon JD, et al. A prospective evaluation of
magnetic resonance, computer tomography and mediastinoscopy in
the preoperative assessment of mediastinal node status of
bronchogenic carcinoma.
Surgery 1987; 94: 679–84.
Journal of Thoracic and Cardiovascular
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Mediastinotomy
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JOSEPH S. FRIEDBERG MD, FACS
Associate Professor of Surgery, Division of Thoracic Surgery, Penn–Presbyterian Medical Center, Philadelphia, Pennsylvania, USA
11
HISTORY
Mediastinotomy, also commonly referred to as anterior
mediastinoscopy or the ‘Chamberlain procedure’, was
reported in 1966 as a technique for assessing the resectability
of lung cancers in the left upper lobe. Since that time, the
operation has changed little, but the indications have broadened to establish the procedure as an excellent operative
approach for acquiring macroscopic tissue samples from
tumors in the anterosuperior mediastinum on either side of
the sternum. Although some proponents of video-assisted
thoracic surgery (VATS) have challenged mediastinotomy as
an outdated procedure, mediastinotomy has endured as a
‘minimally invasive’ surgical procedure in its own right and
one that all thoracic surgeons should have in their armamentarium.
PRINCIPLES AND JUSTIFICATION
The role of mediastinotomy should be viewed separately with
respect to its place in staging lung cancer and its role as a diagnostic procedure for anterosuperior mediastinal masses. For
anterosuperior mediastinal masses, the indication is to obtain
a tissue diagnosis when other modalities have failed or are
inadequate. One of the most common indications for this
procedure at our institution is to obtain a sufficiently large
tissue sample of suspected lymphoma such that the specimen
is adequate for routine and special-stain pathological examinations as well as flow cytometry. Generally, a presumptive
diagnosis of thymoma is viewed as a contraindication to
mediastinotomy for biopsy. Partial excision of an encapsulated thymoma can result in tumor dissemination; and therefore, many thoracic surgeons proceed directly to en bloc
resection of the mass if thymoma is the leading diagnosis.
The use of mediastinotomy for staging of lung cancers is
essentially limited to cancers involving the left upper lobe.
This lobe drains preferentially to the aortopulmonary window (level 5) and the anterior mediastinal station (level 6).
This lobe also drains to the nodal stations accessible via standard (cervical) mediastinoscopy. The staging rendered by the
presence of metastatic disease in the lymph nodes accessed via
cervical mediastinoscopy equals or exceeds the staging generated by the presence of metastatic disease in the lymph nodes
accessed via left anterior mediastinotomy. Many thoracic
oncologists will treat patients with known N2 disease (stage
IIIa) with neoadjuvant therapy (preoperative chemotherapy
with or without radiation) before surgical resection. Level 5
and 6 lymph nodes are categorized as N2 lymph nodes in
compliance with the TNM staging system for lung cancer.
Strong evidence exists, however, that lymph nodes at these
stations are more likely to impart the prognosis rendered by
positive N1 lymph nodes, especially if they are resected at the
time of surgery. As a result, positive level 5 or 6 lymph nodes
that are resectable do not serve as a contraindication to proceeding with a left upper lobectomy in a patient who is otherwise a surgical candidate. Unless the mediastinotomy is being
carried out to confirm unresectable malignant involvement
of the aortopulmonary window (as suggested by left vocal
cord paralysis), the decision whether or not to perform a
biopsy of those lymph nodes preoperatively is determined by
the surgeon’s commitment to neoadjuvant therapy. Many
thoracic surgeons, even those who routinely perform cervical
mediastinoscopy, have adopted a selective approach to left
anterior mediastinotomy.
When mediastinotomy is performed for staging lung cancer, this procedure should be preceded by cervical mediastinoscopy. The recovery of any malignant lymph nodes
from the mediastinoscopy obviates the need to proceed with
mediastinotomy. If the lymph node biopsy specimens from
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the paratracheal stations are negative, however, then the cervical incision should be left open while the mediastinotomy is
performed. This maneuver allows the surgeon to introduce an
index finger through each incision to allow bimanual palpation of the aortopulmonary window and para-aortic region.
An alternative procedure to mediastinotomy is VATS.
Whether to proceed with VATS instead of mediastinotomy is
determined by the goal of the operation. If biopsy of an accessible mass or sampling of the level 5 and 6 lymph nodes is the
goal, then mediastinotomy should be performed. If additional information is required, such as concomitant evaluation of the pleura, lung, or other mediastinal structures, then
VATS is a better choice. A VATS procedure can provide more
information, but it requires single-lung ventilation, is not an
outpatient procedure, and requires some type of drainage
tube in the chest postoperatively. Mediastinotomy is generally a less painful procedure for the patient than VATS.
The same risk factors that make a patient a poor surgical
candidate for other operations apply to mediastinotomy as
well. Specific contraindications are few and are essentially
limited to previous mediastinotomy or a history of heart surgery in which a mammary graft was harvested. Previous
mediastinotomy is a relative contraindication, and performing a reoperative mediastinotomy could be considered to
obtain more tissue from a mediastinal mass that had been
previously biopsied uneventfully, but failed to yield sufficient
diagnostic material. The author would consider the presence
of a patent internal mammary graft to the heart as an absolute
contraindication to mediastinotomy because of the potential
risk of a fatal complication resulting from inadvertent damage to the vessel.
The potential morbidities of the operation include bleeding from injury to major vascular structures, injury to the
recurrent laryngeal nerve or phrenic nerve, pneumothorax,
incisional tumor implantation, and chylothorax. The author
was unable to identify any published reports of mortality
associated with this operation but is aware of one anecdotal
case in which death resulted from injury to the pulmonary
artery. Postoperative discomfort is variable: some patients
require no narcotic analgesia and return to work in several
days whereas others need narcotic pain medication for more
than a month. In the vast majority of patients, the procedure
is very well tolerated. Cosmetically, a thin patient can expect
to have a visible indentation on the chest if the costal cartilage
was resected.
PREOPERATIVE ASSESSMENT AND
PREPARATION
No procedure-specific preparations are made for patients
undergoing a mediastinotomy beyond the standard preoperative preparations for other thoracic surgical procedures.
All patients should have a computed tomographic (CT)
scan to guide the surgeon; and when the mediastinotomy is
being performed to stage lung cancer, it should be carried out
after cervical mediastinoscopy but during the same
operation.
ANESTHESIA
Standard general anesthesia without single-lung ventilation is
most commonly used for mediastinotomy. The procedure
can be performed under local anesthesia. If the goal is to
biopsy a mass abutting the chest wall, if deemed safe, general
anesthesia is preferred and standard.
OPERATION
A single dose of preoperative antibiotic is given, and the usual
deep venous thrombosis preventive measures are taken
(pneumatic compression stockings and/or subcutaneous
heparin sodium). The patient is positioned supine with the
arms tucked at the sides. If the procedure is being performed
to stage a lung cancer, then the patient is positioned for a cervical mediastinoscopy with the head at the very end of the
operating table and a rolled towel or inflatable thyroid bag
under the shoulders to maximally extend the neck. If the procedure is being performed to obtain tissue from a mediastinal
mass, then elevation of the shoulders is optional. If the operation is being performed to stage lung cancer, then the
cervical mediastinoscopy is performed first, and a left mediastinotomy is performed only if the frozen section pathological examination indicates no metastatic tumor in any of the
superior mediastinal lymph nodes from which tissue was
taken. In either case, a wide preparation is used so that any
incision can be performed in an emergency should an untoward event occur.
Incision
If the operation is being performed to biopsy a mediastinal
mass, then the incision is made over the appropriate site as
dictated by the CT scan. A useful way to estimate the best
location for the incision is to identify the CT cut with the
most anteriorly accessible area of the mass and to estimate its
distance, based on the number and thickness of the intervening slices, to the CT cut in which the manubrium is first visualized. The top of the manubrium can then be used as the
landmark to estimate the correct position to place the incision. If the operation is being performed for staging a left
upper lobe lung cancer, then the incision is placed over the
second costal cartilage on the left side, with the sternomanubrial junction used as the landmark.
Once the appropriate site has been determined, a 3–6 cm
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1
incision is created in a transverse manner starting
approximately 1 cm lateral to the sternal border. In the
absence of any contraindications, I inject the operative site
preemptively with a generous amount of 0.25% bupivacaine
hydrochloride (Marcaine) before making the incision. After
the skin is divided, the pectoralis muscle is exposed, and the
fascia is incised along the length of the incision with electrocautery. The underlying muscle fibers are then split along
their axis. This step can usually be accomplished with blunt
digital dissection. Once the costal cartilage is exposed, placing
a self-retaining retractor in the incision to pull back the skin
and muscle is useful. Even through a small skin incision, the
retractor can be moved medially and laterally to expose an
additional 1–4 cm of the cartilage.
Operation 101
1
Approach
If the mass is abutting the undersurface of the chest wall,
2
or if the interspace is very large, then the intercostal muscle can be divided along the superior surface of the underlying rib. Otherwise, the perichondrium is incised with
electrocautery along its length and a rib instrument or
periosteal elevator is used to liberate the cartilage from the
investing perichondrium. This portion of the procedure
should be performed without violating the pleural space. The
cartilage can be distinguished from the attached bony skeletal
elements by both appearance and feel. Frequently, one can
incise the margins of the costal cartilage with a scalpel and, by
grasping the cartilage with a stout instrument such as a
Kocher clamp, pop it free. If this technique is not successful,
the cartilage can be divided with a standard rib-cutting
instrument.
2
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Mammary vessels
At this point the surgeon is looking at the posterior
3
perichondrium, which is divided sharply along its length.
The structures in jeopardy for the next portion of the procedure are the internal mammary vessels. The intrusiveness of
these vessels is variable. The majority of the time, the vessels
can be bluntly mobilized and retracted medially out of harm’s
way. Great care must be taken with the mammary vessels as
they are very fragile, and although bleeding from a torn artery
is generally not life threatening, it can be difficult to control
due to retraction out of the immediate field. If the mammary
bundle cannot be retracted, it should be pre-emptively ligated
and divided.
4
3
Biopsy
With the mammary vessels cleared from the field, the
4
mediastinal pleura is then swept laterally, which exposes
the mediastinum without violating the pleural envelope. This
maneuver is best performed with digital dissection, although
it can also be performed under direct vision using a small
peanut dissector. If the procedure is being performed for
biopsy of a mediastinal mass, then the mass should be visible
at this point, and tissue can be removed. Sounding the mass
with a 25- or 22-gauge needle before taking any biopsies is
always prudent if the surgeon has any doubt as to what is
visualized, what lies beyond the mass, and how the mass will
behave once it is incised. The options for performing the
biopsy include dissecting with a scalpel to carve out a specimen, taking bites with a standard mediastinoscopy forceps,
or using a device designed for obtaining core needle biopsies.
The vascularity of the mass, its firmness, its size, and the
experience of the surgeon will dictate the best approach.
Tumor assessment
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Operation 103
If the procedure is being performed for staging
5a,b
palpation is the next step after exposing the mediastinum. At
this point a helpful approach is for the surgeon to place one
index finger in the cervical incision and the other index finger
in the mediastinotomy incision. This maneuver allows the
surgeon to develop a mental ‘road map’ of the aortopulmonary region and to assess the degree of involvement of the
lymph nodes with the mediastinal structures. The arch of the
aorta is the most obvious and useful landmark to help the
surgeon gain bearings.
of a left upper lobe lung cancer, then digital
5a
5b
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