Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3863_Библиотеки_им_академика_М_И_Перельмана.pdf
18 Interventional Treatment ofThyroid Nodules
269
pattern created by hypoechoic rounded fascicles. The nerve shows a striated pattern
on longitudinal scans, with several parallel echogenic lines from its internal structures. Detection of small nerves may be challenging, but anatomic landmarks such
as muscles and vessels are useful in detection and tracking.
Nerve injury is one of the most serious complications during RFA.For ablation
of thyroid nodules, the recurrent laryngeal and the vagus nerves are of utmost
importance. Other nerves need to be differentiated for ablation of recurrent thyroid
cancer or metastatic lymph nodes in the central and lateral compartments [21]. The
relationship of neck nerves to adjacent anatomic structures is shown in Fig.18.8.
Vagus Nerve
The vagus nerve is divided into cranial, cervical, thoracic, and abdominal branches.
After leaving the skull through the jugular foramen, the vagus nerve descends in the
neck covered by the carotid sheath (Fig.18.9).
The vagus nerve is usually located posterolateral to the CCA and posteromedial
to the IJV.It is easily visualized on US as a 2–3mm diameter structure. However,
variations in its location relative to the carotid sheath have been reported [22]. The
vagus nerve can be located anterior, medial, and posterior to the common carotid
artery (Fig.18.10).
In a normal thyroid gland, CCA, the vagus nerve, and IJV are positioned in horizontal alignment. In cases of posterolateral bulging of the thyroid mass, their positions can be changed within the carotid sheath. If the CCA is pushed away
inferolaterally and in a vertical alignment, the vagus nerve is positioned anterior or
medial to the CCA, with its exposure more prone to thermal injury (Fig.18.11).
Various symptoms could develop in the case of vagus nerve injury. Because the
cervical portion of the vagus nerve is cranial to the origin of the recurrent laryngeal
nerve (RLN), vagus nerve injury may cause symptoms resulting from a dysfunction
Fig. 18.8 The neck nerves at C6 level; 1, vagus nerve; 2, recurrent laryngeal nerve; 3, superior
laryngeal nerve (not in this gure); 4, cervical sympathetic ganglion; 5, spinal accessory nerve; 6,
cervical plexus nerve; 7, phrenic nerve; 8, brachial plexus. (With permissions from Park [20])
270
Glossopharyngeal
nerve (CN IX)
Vagus nerve (CN X)
Spinal accessory
nerve (CN XI)
Superior ganglion
of vagus nerve
Inferior ganglion
of vagus nerve
A. W. Park et al.
Jugular foramen
Pharyngeal nerve
Carotid sheath
Superior laryngeal nerve
Fig. 18.9 The vagus nerve in the carotid sheath. (With permissions from Park [20])
Type I : 76.9 %
Lateral position
Type III : 1.6 %
Medial position
Type II : 21.1 %
Anterior position
Type IV : 0.3 %
Posterior position
Fig. 18.10 Variations in the location of the vagus nerve; yellow, the vagus nerve; blue, the internal
jugular vein; red, common carotid artery. (With permissions from Park [20])
a
18 Interventional Treatment ofThyroid Nodules
b
271
Fig. 18.11 (a) An altered position of the vagus nerve by a bulging thyroid nodule. E esophagus, T
trachea; yellow, vagus nerve; blue, internal jugular vein; red, common carotid artery (With permissions from Park [20]). (b) US scan showing an anterior location of the vagus nerve by a bulging
nodule in the left lobe of the thyroid gland; solid white arrow, vagus nerve; IJV internal jugular
vein, CCA common carotid artery
of the RLN (e.g., cough, voice change) or dysfunction of the vagus nerve itself (e.g.,
arrhythmia, dysphagia, dyspnea, nausea, hiccups).
The Recurrent Laryngeal Nerve
The Right Recurrent Laryngeal Nerve: The right vagus nerve passes from the posterior aspect of the carotid sheath in the neck base anterior to the rst segment of the
subclavian artery. At this point, the RLN branches exit from the vagus nerve and
rst travel inferoposteriorly to loop around this segment of the subclavian artery
(the fourth brachial arch remnant). It then progresses superomedially along the neck
oor behind the CCA into the right thoracic inlet at the base of the neck and then
extends superiorly more obliquely from lateral to medial direction as it ascends the
neck. The right RLN nally enters the larynx by penetrating the thyrohyoid membrane at the cricothyroid joint level (Fig.18.12). The angle between the right RLN
and the tracheoesophageal groove is 15–45° in 80% of the patients [23].
272
Fig. 18.12 The course of
the right recurrent
laryngeal nerve. (Modied
from Randolph [24])
Fig. 18.13 The course of
the left recurrent laryngeal
nerve. (Modied from
Randolph [24])
A. W. Park et al.
Vagus nerve
Recurrent laryngeal nerve
Subclavian artery
Vagus nerve
Left recurrent laryngeal nerve
Aortic arch
The Left Recurrent Laryngeal Nerve: The left vagus nerve travels from the posterior aspect of the left carotid sheath in the neck base anterior to the aortic arch.
Then the left RLN branches underneath the aortic arch just lateral to the obliterated
ductus arteriosus and passes posteriorly and superiorly to enter the larynx by penetrating the thyrohyoid membrane at the level of the cricothyroid joint (Fig.18.13).
The left RLN is more medial and ascends into the paratracheal or tracheoesophageal groove [23].
18 Interventional Treatment ofThyroid Nodules
273
The Dangerous Triangle vs. the Danger Zone
The concept of a “danger triangle” was proposed by Baek etal. to describe an area
that encompasses the esophagus, trachea, and medial portion of the thyroid gland
around the RLN (Fig. 18.14) [25]. During RFA, the danger triangle should be
avoided due to the high risk of thermal injury to these critical structures, especially
the RLN.However, this concept has been modied on the right side of the triangle,
considering a more oblique course of the right RLN as described above.
The “danger zone” on the right side is an area between the right tracheoesophageal groove and the carotid sheath. This space includes the right RLN and its potential variable locations, the vagus nerve, and the middle cervical sympathetic ganglion
(Fig.18.15). At the mid-to-lower level of the right thyroid gland, the location of the
RLN may vary from medial to lateral inside the danger zone.
Fig. 18.14 Danger triangle vs. danger zone; E esophagus, T trachea; red circle, common carotid
artery; blue oval, internal jugular vein; yellow solid circle, vagus nerve; yellow dotted circle, recurrent laryngeal nerve; yellow heptagon, middle sympathetic ganglion. The dashed yellow circles
show the variable locations of the RLN. (With permissions from Park [20])
Fig. 18.15 Volume
measurement of an
elliptical nodule;
V=abcπ/6. a, the longest
diameter; b and c, the other
two perpendicular
diameters
a
b
c
274
A. W. Park et al.
Procedure
Preprocedural Workup
The 2017 KSThR guidelines for the RFA preprocedural checklist are shown in
Table18.7. These are the most detailed guidelines published, to date [14].
Labs
• CBC/coagulation prole
• TSH (thyrotropin)/Free T4/T3
• Calcitonin: increased possibility of medullary carcinoma
• Thyroid autoantibodies: increased possibility of hypothyroidism during
follow-up
• Thyroperoxidase antibody (TPOAb)
• Thyroglobulin antibody (TgAb)
Table 18.7 Preprocedural checklist according to the KSThR 2017 guidelines (modied from Kim
etal. [14])
Pathologic thyroid nodule Recurrent thyroid cancer
Pathologic diagnosis Pathologic and/or serologic diagnosis
Benign diagnosis at least two US-guided
FNA or CNB
Benign diagnosis at least one US-guided
FNA or CNB in AFTN
Benign diagnosis at least one US-guided
FNA or CNB in thyroid nodules with
highly specic benign US features
US US
Features of the nodule and surrounding
critical structures
Nodule volume
Symptom score
Cosmetic score
Laboratory tests Laboratory tests
Complete blood count
Blood coagulation battery
Thyroid function test
Serum TSH
Serum T3
Serum fT4
Additional imaging study Additional imaging study
CT or MRI
99m
a
Tc pertechnetate or 123I thyroid scan
AFTN autonomously functioning thyroid nodule, CNB core needle biopsy, CT computed tomography, FNA ne-needle aspiration, fT4 free thyroxine, MRI magnetic resonance imaging, RFA radio-
frequency ablation, T3 tri-iodothyronine, Tg thyroglobulin, TSH thyroid-stimulating hormone
(thyrotropin), US ultrasound
a
Selectively indicated
b
Indicated for AFTN
Cancer recurrence at US-guided FNA or CNB
Increased washout Tg level in aspirate or Tg
immunostain of CNB specimen
Increased washout calcitonin level in aspirate or
calcitonin immunostaining of CNB specimen in
patients with medullary cancer
Features of the nodule and surrounding critical
structures
Tumor volume
Complete blood count
Blood coagulation battery
Thyroid function test
Serum TSH
Serum T3
Serum fT4
CT or MRI
b
a
h/
bc
() ()
()
()
18 Interventional Treatment ofThyroid Nodules
275
Pathology
Benign cytopathologic diagnosis (at least two separate times: FNA or CNB) is
required. According to the KSThR 2017 guideline, a single benign diagnosis on
FNA or CNB is sufcient when the nodule has US features highly specic for
benignity.
Imaging
• US features of nodule and neck:
– Number
– Location
– Volume
Thyroid nodules are round or more elliptical, as shown in Fig.18.15.
The formula for calculating the volume of elliptical nodules is as follows:
Ellipsoid volume=height widthlengt
´
´
6Va
´
p
– Composition (Table18.8)
The strategy for choosing between EA and thermal ablation depends on the
composition of thyroid nodules [9, 14].
– Vascularity (Table18.9)
– Echogenicity
– Margin
– Calcications
• Relationship between the target nodule and adjacent structures (skin, strap muscles, trachea, esophagus, vessels, and nerves).
Table 18.8 Classication of thyroid nodules by composition
Classication Composition Selection of ablation
Cystic nodule >90% cyst EA
Predominantly cystic nodule 50–90% cyst EA rst or combined with RFA
Predominantly solid nodule 50–90% solid R FA
Solid nodule >90 solid RFA
Table 18.9 Grading of thyroid nodules by vascularity
Grade Vascularity
0 No intranodular vascularity
1 Intranodular vascularity but peripheral portion only
2 Intranodular vascularity <50%
3 Intranodular vascularity >50%
276
no symptom
A. W. Park et al.
• Computed tomography (CT) or magnetic resonance imaging (MRI): selectively
indicated. CT or MRI examinations may help to evaluate the intrathoracic extent
of benign thyroid nodules.
99m
•
Tc-pertechnetate or
123
I thyroid scan—indicated for AFTN.
Clinical Evaluation
• Symptom score: visual analog scale from 0 to 10 (Fig.18.16) to rank the severity
of discomfort or pain.
• Cosmetic score (Table18.10).
Informed Consent
The following content should be included in an informed consent statement [14]:
• The change in the size of ablated thyroid nodules may be slow (several months
to years).
• The number of expected treatment sessions.
• Possibility of regrowth of the treated nodule and the need for additional
treatments.
• Warning for possible pain with various degrees during the ablation.
• Complications of ablation (reported incidence of 3.3%).
• Ask patients about their history of thyroid surgery, the side effects of any drugs
they are taking, and whether they are taking drugs such as antiplatelets,
anticoagulants, and thyroid hormones. Further observation or admission may
be required after ablation, depending on the patients’ condition following
ablation.
0
Fig. 18.16 Preprocedural symptom score for RFA
Table 18.10 Cosmetic score features for RFA
Score Features
1 No palpable mass
2 Palpable mass but no cosmetic problem
3 Cosmetic problem on swallowing only
4 A readily detectable cosmetic problem
2
a little bit
4
little more
6
even more
8
whole lot
10
worst
18 Interventional Treatment ofThyroid Nodules
277
The Procedure
Total ablation time usually ranges from 20 to 40min for a 2–4cm diameter nodule,
but ablation time depends on the operator’s experience.
Patient Preparation
The aseptic procedure with sterile technique is recommended.
• Supine position with mild to moderate neck extension: pillow under the shoulder
and sponge or thin cushion under the head.
• Skin prep with an antiseptic solution: chlorohexidine or iodopovidone.
• Surgical drape: the opening should be wide enough to allow access to the thyroid
and perithyroid structures.
• Grounding pads for a monopolar radiofrequency electrode (MRFE): the electric
current runs through the patient’s entire body.
Pain Control and Monitoring
Lidocaine (1–3%) is used for local anesthesia at the puncture site and around the
thyroid gland and/or thyroid nodule. The skin incision is not needed, thus preventing unnecessary scar formation. If a patient experiences intolerable pain during
RFA, the power should be reduced or turned off for several seconds. Pain or discomfort usually disappears rapidly, and the procedure may then be continued. Intravenous
(IV) conscious (moderate) sedation could be used for pain control. Voice change
should be monitored intermittently during the procedure by having the patient speak
a few words when RF power is off [26].
Basic Physics
The term “radiofrequency” refers to a high-frequency alternating electric current
oscillating between 200 and 1200kHz. As shown in Fig.18.17, a closed electric
Fig. 18.17 Electric circuit during thyroid RFA. (With permissions from Park [20])
278
Fig. 18.18 Microscopic
phenomena during
thyroid RFA
A. W. Park et al.
circuit is formed through the body. The RF power agitates tissue ions (i.e., Na+, K+,
and Cl) that carry the electric current as they attempt to follow the changes in the
direction of the alternating current (Fig.18.18). For a typical frequency of 500kHz,
the direction of the current (and ion movement) changes a million times per second
[25, 27].
There are two heating areas surrounding the RF electrode: the direct heating area
and the indirect heating area. The direct heating area is close to the RF electrode and
has a high current density. The heat generated in this area is called friction heat.
Although this heat causes immediate damage to tumor tissue, the damage is signicant only in regions very close to (thus, within a few mm of) the electrode.
Simultaneously, tumor tissue that is more remote from the electrode is heated slowly
via thermal conduction from the hot region adjacent to the electrode (conduction
heat) (Fig.18.19) [28].
The nature of thermal damage caused by RF is dependent on both the tissue
temperature achieved and the duration of heating. Elevation of tissue temperature to
40°C does not induce tissue damage. Tissue temperatures between 42 and 45°C,
formally termed hyperthermia, cause tissue cells to become more susceptible to
damage when exposed to chemotherapeutic agents and/or irradiation. Irreversible
cellular damage occurs when temperatures are increased to 46°C for 60min or to
50–52°C for 4–6min. Near-immediate tissue coagulation is induced at temperatures between 60 and 100°C, but temperatures greater than 100–110°C result in
vaporization and carbonization (Fig.18.20) [29, 30]. Microbubbles are produced
and represent gases, primarily nitrogen, that are released from the cells (Fig.18.21),
and then the tissue becomes dehydrated [28]. The dehydrated tissue further leads to
a noticeable decrease in its electrical conductivity.
Equipment
Generator: An RF generator supplies RF power to the tissue through an electrode.
Continuous RF out mode is used for thyroid ablation, which is specially designed
for thyroid RFA.In this mode, the RF power is generated continually and controlled
by an RF output control.
Electrode: Electrodes have various active tips ranging from several millimeters
to a centimeter. Ablation can begin at 5W (3.8mm active tip), 10W (5mm active