Dynamics of Topographic and Anatomical Changes after Thyroidectomy in Patients with Neck Organ Compression Syndrome: Results of Long-Term Follow-Up.

Full Text

The study of the postoperative anatomy of various organs and cavities is currently of great interest. The current literature contains numerous studies describing topographic changes after various surgical interventions and experimental modeling methods for organ and structure displacement [1, 2, 3, 4].
The introduction of computed tomography and magnetic resonance imaging has opened up vast prospects for targeted anatomical research [6, 7]. It has become possible to analyze the structure of organs, structures, and cavities before and after surgery, apply quantitative assessment methods, and utilize statistical analysis of the studied parameters [8].
Research into the postoperative anatomy of the pleural, abdominal, and retroperitoneal cavities is ongoing [9, 10, 11].
It is known that patients with thyroid pathology complicated by cervical organ compression syndrome exhibit certain topographic and anatomical changes [12]. This raises the question of the changes that occur in the postoperative period: does the topography recover after the compression syndrome is eliminated, or does it worsen further due to the absence of the thyroid gland?

Knowledge of the anatomical structures that develop postthyroidectomy may be necessary for planning repeat neck surgeries, assessing the causes of dysphagia, dysphonia, and respiratory distress in the late postoperative period, and interpreting data from examination methods such as ultrasound examination of the neck vessels.

The aim of this study was to examine the dynamics of changes in the anatomy and topography of neck organs and structures after thyroidectomy in the late postoperative period.
Materials and Methods. The study analyzed topographic and anatomical data from magnetic resonance imaging of the neck before surgery and at two, six, twelve, and twenty-four months after thyroidectomy. Seventy-two patients were included in the study. The median age of the subjects was 44 years. There were 7 men and 65 women.

Forty patients underwent surgery for multinodular colloid goiter associated with neck organ compression syndrome, and 32 for autoimmune thyroiditis with neck organ compression.

Magnetic resonance imaging (MRI) was performed with the patient in the supine position using a Siemens Magnetom Harmony 1T scanner with the following parameters: slice thickness of 5 mm, table pitch of 5 mm, and reconstruction index of 1.25 mm. The resulting tomograms were analyzed using RadiAnt DICOM Viewer 2020.2.3. Slices were evaluated in the axial, frontal, and sagittal planes. Precise measurements were taken of the following parameters: the size of the esophagus, trachea, common carotid arteries, and internal jugular veins; The degrees of displacement of the neck organs and structures relative to each other and two mutually perpendicular lines drawn through the middle and anterior margins of the sixth and seventh cervical vertebrae and the first thoracic vertebrae.
The parameters obtained during the study were compared with preoperative values ​​and with data obtained at the second, sixth, twelfth, and twenty-fourth months of the postoperative period.
Statistical analysis was performed using the Statistica 6.0 software package. Conformance to the normal distribution law was assessed using the Kolmogorov-Smirnov test. Descriptive statistics are presented as medians and quartiles: Me (Q1; Q3). The Mann-Whitney test was used for comparisons. Results were considered statistically significant at p < 0.05.

Results and discussion.

Preoperative assessment of the anterior neck anatomy in patients with thyroid disease revealed that 46% of patients exhibited transverse laryngeal displacement in the frontal plane, either to the right or left, depending on the size of each lobe. The median organ displacement was 0.72 cm (Figure 1).

Figure 1. Magnetic resonance imaging of the neck. Axial section. Patient A., 45 years old. Diagnosis: autoimmune thyroiditis, cervical organ compression syndrome. Laryngeal displacement to the left. 1 – larynx; 2 – upper pole of the right thyroid lobe.

Figure 1. Magnetic resonance imaging of the neck. Axial section. Patient A., 45 years old. Diagnosis: autoimmune thyroiditis, cervical organ compression syndrome. Laryngeal displacement to the left. 1 – larynx; 2 – upper pole of the right thyroid lobe. A similar tracheal disposition was also observed (Me=0.54 cm: 0.52; 0.78) with a decrease in its transverse diameter by an average of 0.88±0.40 cm (the median normal tracheal diameter is 1.72 cm: 1.65; 18.0).
As a result of compression, angular displacement of the organ was noted. The median angle of deviation of the trachea from the midline was 19.8° (17.2; 21).
The anatomy of the esophagus in patients with autoimmune thyroiditis associated with a large thyroid gland underwent changes similar to those of the trachea, as the organ was intimately adjacent to its posterior wall. As a result of the compressive effect of the lateral lobes, the slit-like shape changed to a spherical shape with an increase in the anteroposterior diameter and a decrease in the transverse diameter. The median of the first indicator was 0.97 cm (0.72; 1.2), the second – 0.67 cm (0.55; 0.81).
When assessing the neurovascular bundle of the medial triangle of the neck, the following patterns of preoperative anatomy were observed: on the right, it moved posteriorly and to the right, and on the left – posteriorly and to the left. The median parameters of these dispositions on the right were 2.0 cm (1.89; 2.7) and 1.4 cm (1.12; 1.61), on the left – 1.88 cm (1.52; 2.0) and 1.29 cm (1.2; 1.67). The topography of the common carotid arteries relative to the internal jugular veins did not change.
When evaluating magnetic resonance imaging of the soft tissues of the neck in the postoperative period, several patterns of organ and structure displacement after thyroidectomy were identified.
In patients with multinodular colloid goiter, no changes in tracheal topography were detected. In 87% of cases, the esophagus expanded in the anteroposterior direction and shifted toward the left lateral wall of the trachea. The median anteroposterior dimension of the esophagus before surgery was 0.4 cm (0.31; 0.69), at the second month after the intervention it was 0.46 cm (0.28; 0.7), at the sixth month – 1.2 cm (0.98; 1.59, p<0.001), at the 12th month – 2.1 cm (1.88; 2.3, p<0.001). Analyzing CT scans two years after thyroidectomy, the vast majority of patients showed that the trachea was also centrally positioned, and the esophagus was adjacent to the left lateral wall, having a rounded shape with a median anteroposterior diameter of 1.98 cm (1.63; 2.32, p < 0.001).
In this category of patients, the anatomy of the vascular bundle of the medial triangle of the neck was unchanged from the preoperative anatomy two months after surgery. However, from the third to the twelfth months after thyroidectomy, a gradual displacement of the common carotid arteries toward the midline of the neck and anteriorly by an average of 1.6 cm and 1.8 cm was observed, while the internal jugular veins shifted anteriorly and laterally by 1.78 cm and 2.1 cm.
Magnetic resonance imaging performed twenty-four months after surgery revealed the following topographic and anatomical picture: the common carotid artery on the right shifted anteriorly by an average of 1.96 cm and medially by 1.81 cm, adjacent to the right lateral wall of the trachea; the right internal jugular vein was located parallel to the arterial trunk on the right; The left common carotid artery was displaced anteriorly by 1.63 cm and somewhat laterally by 1.25 cm, probably due to the location of the esophagus at the left lateral wall of the trachea, and the left internal jugular vein was located to the left of it, located somewhat anteriorly (Figure 2).

Figure 2. Magnetic resonance imaging of the neck. Patient K., 51 years old. Diagnosis: multinodular colloid goiter. Euthyroidism. Syndrome of compression of the organs of the neck. Condition after thyroidectomy after 24 months. 1 - trachea; 2 - right common carotid artery; 3 - right internal jugular vein; 4 - esophagus; 5 - left common carotid artery; 6 - left internal jugular vein.
Figure 2. Magnetic resonance imaging of the neck. Patient K., 51 years old. Diagnosis: multinodular colloid goiter. Euthyroidism. Syndrome of compression of the organs of the neck. Condition after thyroidectomy after 24 months. 1 - trachea; 2 - right common carotid artery; 3 - right internal jugular vein; 4 - esophagus; 5 - left common carotid artery; 6 – left internal jugular vein.

Following thyroidectomy for autoimmune thyroiditis, the larynx returned to its normal anatomical position within two months and maintained this position on tomograms 24 months after surgery.
From the sixth postoperative month, the trachea shifted toward the midline of the neck and anteriorly. The median disposition was 1.6 cm (1.5; 1.73) medially and 1.17 cm (0.9; 1.22) anteriorly by the twelfth postoperative month, and 1.89 cm (1.74; 2.1) and 1.56 cm (1.46; 1.7), respectively, by the twenty-fourth month. The organ was intimately adjacent to the sternohyoid and sternothyroid muscles. Its diameter gradually increased after surgery, despite persistent wall deformation. The median of this parameter by the second month was 0.78 cm (0.6; 0.93), by the sixth – 0.81 cm (0.73; 1.1), by the twelfth – 1.45 cm (1.2; 1.78, p<0.001), by the twenty-fourth – 1.58 cm (1.13; 1.85, p<0.001).
After thyroid removal, the esophagus was slightly dislocated to the left, with a median displacement of 0.54 cm (0.36; 0.74) by the twenty-fourth month of the postoperative period. Its anteroposterior dimension decreased, and, two years after the intervention, the organ's shape again became oval with a slit-like lumen.
When assessing the postoperative topography of the vascular bundles of the medial triangles of the neck, anterior displacement of the common carotid arteries was noted, with a median disposition on the right of 2.3 cm (1.79; 2.68) by the twelfth month after thyroidectomy, and on the left – 2.16 cm (1.96; 2.45) by the same time.
The internal jugular veins were dislocated along with the arteries anteriorly and laterally. Twelve months after surgery, the median anterior displacement on the right was 2.70 cm (2.55; 3.1), lateral – 1.78 cm (1.6; 1.97); on the left – 2.57 cm (2.26; 2.83) and 1.69 cm (1.34; 1.72), respectively.
A study of magnetic resonance imaging (MRI) scans of patients with autoimmune thyroiditis twenty-four months after thyroidectomy revealed that neck organs and structures continued to shift in the late postoperative period.
The esophagus occupied a position consistent with the anatomical norm. Left-sided positioning was not observed in any patient. The internal jugular veins were parallel to the trachea, and the common carotid arteries were displaced posteriorly, positioned on either side of the esophagus.
The median posterior displacement of the right common carotid artery was 1.15 cm (0.8; 1.45 cm), and that of the left common carotid artery was 1.24 cm (1.1; 1.63 cm). The medians of the anterior displacement of the internal jugular veins increased compared to the twelfth month of the postoperative period and were on the right - 3.35 cm (3.0; 3.71), on the left - 3.56 cm (2.98; 3.75, Figure 3).

Figure 3. Magnetic resonance imaging of the neck. Patient N., 39 years old. Diagnosis: autoimmune thyroiditis. Subclinical hypothyroidism. Syndrome of compression of the organs of the neck. Condition after thyroidectomy 24 months later. 1 - trachea; 2 - left internal jugular vein; 3 - left common carotid artery; 4 - esophagus; 5 - right common carotid artery; 6 - right internal jugular vein.
Figure 3. Magnetic resonance imaging of the neck. Patient N., 39 years old. Diagnosis: autoimmune thyroiditis. Subclinical hypothyroidism. Syndrome of compression of the organs of the neck. Condition after thyroidectomy 24 months later. 1 - trachea; 2 - left internal jugular vein; 3 - left common carotid artery; 4 - esophagus; 5 - right common carotid artery; 6 – right internal jugular vein.
The diameters of the common carotid arteries and the right internal jugular vein did not change before and after surgery in all subjects without exception. The median for the arteries was 0.89 cm (0.74; 1.23), and for the right vein, 1.34 cm (1.0; 1.52).
The diameter of the left internal jugular vein in multinodular colloid and autoimmune thyroiditis increased, reaching 1.89 cm (1.57; 2.18) by the sixth month postoperatively, 2.57 cm (2.19; 2.85) by the twelfth, and 2.63 cm (2.11; 2.8) by the twenty-fourth.
Discussion. Any surgical intervention, regardless of its extent, leads to changes in the topographic anatomy of both the organ and the surrounding structures.
Data has accumulated on the topographic and anatomical changes that occur after surgical procedures on the organs of the thoracic and abdominal cavities, as well as the retroperitoneal space.
For example, in the work of I.I. Kagan and M.N. Vasyukov (2021), anatomical changes before and after pulmonectomy were described, and topographic and anatomical patterns of post-pneumonectomy changes in the thoracic cavity were developed and substantiated [13].
P.V. Samoilov (2015) presented data on the topography and anatomy of the mediastinum after the Lewis procedure. The study examined chest computed tomography data from patients without gastrointestinal pathology and patients with thoracic esophageal cancer. It was found that the transverse diameter of the posterior mediastinum increases during the postoperative period. Simultaneously, it shifts to the right. This causes the esophagus to expand, and the trachea, left main bronchus, aorta, and heart to shift [14].
A few studies have noted that the formation of scar connective tissue in the laryngeal bed after hemi- or thyroidectomy can affect the topographic anatomy of the recurrent laryngeal nerve, which, in turn, does not exclude the possibility of its paresis in the late postoperative period [15].

Changes that occur after thyroidectomy are likely related to the lack of a stabilizing effect of the thyroid gland on the organs and structures of the neck. We believe that this postoperative anatomy, including the spherical transformation of the esophagus, occurs as a result of swallowing and respiratory movements, as well as pulsation waves of the common carotid arteries.
Conclusion. Thus, magnetic resonance imaging is an effective method of intravital visualization, allowing us to study the regular processes of displacement of organs and structures of the anterior neck in patients after thyroidectomy.
The data obtained during the study suggest that multidirectional topographic changes in the anatomy of neck organs and structures can occur for a considerable period of time after thyroid removal. Moreover, the patterns of displacement differ in patients with different pathological processes in the organ. These data may be useful for assessing functional changes at various postoperative times, as well as for the appropriate planning of repeat neck surgeries.

About the authors

Arina Zhirnova

Author for correspondence.
Email: oringirl@mail.ru
ORCID iD: 0000-0002-3678-1940
SPIN-code: 6400-7121
Scopus Author ID: 6603224837
ResearcherId: Q-91702017
Russian Federation

Sergey Nikolaevich Lyashenko

Orenburg State Medical University

Email: serglyashenko@mail.ru

Профессор, заведующий кафедрой оперативной хирургии и клинической анатомии им. С.С. Михайлова 

Russian Federation, 460000, Orenburg, Sovetskaya Street, 6

References

Supplementary files