Thoracic T2 and T3 Ganglia Locations Relative to Their Corresponding Ribs: Implication during Endoscopic Thoracic Sympathectomy

doi:10.21203/rs.3.rs-4620212/v1

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Thoracic T2 and T3 Ganglia Locations Relative to Their Corresponding Ribs: Implication during Endoscopic Thoracic Sympathectomy

https://doi.org/10.21203/rs.3.rs-4620212/v1

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Purpose

Understanding the precise anatomy of the upper thoracic sympathetic trunk is crucial for the effective treatment of palmar hyperhidrosis using the surgical technique of endoscopic thoracic sympathectomy (ETS). The variability in the location of T2 and T3 ganglia in relation to the ribs may contribute to inconsistent clinical outcomes following ETS. Traditionally, a rib-oriented approach has been used, relying on the positions of the second, third, and fourth ribs as landmarks rather than the actual ganglia positions, potentially leading to incomplete or inaccurate ganglion destruction. This study is undertaken to advocate for a ganglion-oriented approach to ETS, which necessitates an accurate anatomical understanding of the T2 and T3 ganglia locations.

Methods

For the study, 40 human cadaveric thoraces were dissected to map the locations of T2 and T3 ganglia relative to the ribs.

Results

The findings showed a high percentage of T2 ganglion is located near the superior border of the third rib, while the T3 ganglion is situated near the fourth rib. Specifically, 43% of the right T2 ganglia and 38% of the left T2 ganglia were in contact with the superior part of the third rib. These results indicate a significant risk of inadvertently damaging the T2 ganglion when using a rib-oriented approach at the third rib level leading to compensatory hyperhidrosis.

Conclusion

Due to the proximity of the T2 ganglion to the third rib, accidental thermal injury to the ganglion may occur when third rib-oriented ETS is performed. A ganglion-oriented T3 ETS can be performed by using the white ramus communicans as a guide to accurately locate the T3 ganglion, ensuring precise sympathectomy and preserving sympathetic innervation to the heart and face. Adopting the ganglion-oriented sympathectomy could standardize ETS procedures and enhance the comparability of surgical outcomes.

palmar hyperhidrosis

T2 ganglion

T3 ganglion

T3 ganglionectomy

endoscopic thoracic sympathectomy

intercostal nerve

white ramus communicans

The correct understanding of the anatomy of the upper thoracic sympathetic trunk is paramount to the successful treatment of palmar hyperhidrosis using the method of endoscopic thoracic sympathectomy (ETS). The variable clinical outcomes after ETS for palmar hyperhidrosis may be due to not taking into consideration the variable location of the T2 and T3 ganglia in relation to the ribs.

As viewed with the videoscope, the locations of T2 and T3 ganglia are not easily discernible; ganglia do not appear as plump round structures. For this reason, a rib-oriented endoscopic sympathectomy approach has been recommended in the past [1]. In other words, the second, third, and fourth ribs are used as guideposts rather than using the actual positions of ganglia to determine the limits of sympathectomy. This approach may result in the interruption of the sympathetic chain in random locations irrespective of the actual ganglia positions. Furthermore, it may lead to ganglia that are incompletely destroyed. Given the variable locations of the ganglia relative to the ribs, ETS should be carried out as a ganglion-oriented and not as a rib-oriented procedure as is usually done. A proper understanding of the topographical upper thoracic ganglia anatomy is the foundation for a ganglion-oriented ETS.

For the treatment of palmar hyperhidrosis, the level of thoracic ganglionectomy that will result in optimal clinical outcome is the T3 ganglion [2]. Sympathetic innervations to the palm pass through and arise from T4, T3, T2, and T1 ganglia within the sympathetic trunk. To achieve a normal level of palm perspiration and to preserve sympathetic innervation to the heart, damage to the T2 ganglion should be avoided. By interrupting the sympathetic signals from T3 and T4 but preserving the sympathetic supply to the face from T1 and T2, the risk of compensatory hyperhidrosis can be lowered while still achieving the desired clinical outcome. Therefore, knowing the locations of the T2 and T3 ganglia is important in achieving optimal ETS clinical results.

The center of the T3 ganglion along the thoracic sympathetic trunk can be located by finding the white ramus communicans (RC) that comes off the third intercostal nerve (ICN) and following the ramus toward the sympathetic trunk. The junction where the ramus joins the sympathetic trunk is the T3 ganglion center [3]. We used this information to compile the locations of T2 and T3 ganglia on the sympathetic trunk by dissecting human cadavers.

Cadaveric Specimen Dissections: Forty embalmed cadaveric thoraces of 25 adult females (aged 53–100 years) and 15 adult males (aged 50–95 years) were procured from the University of New England College of Osteopathic Medicine Donor Program and dissected from January 2021 to June 2022. Bilateral gross and macroscopic dissection (Zeiss Loupes: EM ProS 4.0x/450) was performed. Cadavers were chosen from those without a history or gross appearance of thoracic pathology. The heart, lungs, and mediastinal structures were removed to reveal the vertebral column. The costal and vertebral pleura were then dissected away to reveal the sympathetic trunk and white and gray rami communicantes of the T1-T4 spinal levels. The location of each thoracic ganglion was determined by tracing the white RC to the corresponding intercostal nerve (ICN). For each of the T2 and T3 ganglia, the superior and inferior borders were measured in relation to the superior and inferior margins of the ribs 2–4. The superior and inferior borders of each ganglion were determined by noting the broadening of the trunk into larger diameter ganglion. The measurements consisted of the distance in mm of the superior border of the T2 ganglion from the inferior border of rib 2, the inferior border of the T2 ganglia from the superior border of rib 3, the superior border of the T3 ganglion from the inferior border of rib 3 and the inferior border of the T3 ganglion from the superior border of rib 4. After the ganglia were identified and measured, they were digitally photographed (Nikon D750).

All data were recorded using Microsoft Excel for Mac 2011 (Microsoft Corporation, Redmond, WA). Mean and standard deviation were analyzed using GraphPad Prism 7 (GraphPad Software, La Jolla, CA).

Bilateral dissection of 40 cadaveric specimens yielded 74 (37 right, 37 left) identifiable sympathetic trunks. Six (3 right, 3 left) dissections were discarded due to unacceptable dissection quality or due to unforeseen cadaver pathology. In the 74 accepted sympathetic trunks, all T2 and T3 ganglia were identified, resulting in 148 (74-T2, 74-T3) individual measurable ganglia. The data is shown in Table 1. The mean superior border of T2 was 0.35 mm superior to the inferior border of rib 2 on the right, and 0.79 mm superior to the inferior border of rib 2 on the left. The following is the critical data: the mean inferior border of T2 ganglia was 0.27 mm inferior to the superior border of rib 3 on the right and 0.32 mm superior to the superior border of rib 3 on the left. The mean superior border of the T3 ganglion was 4.0 mm inferior to the inferior border of rib 3 on the right and 4.2 mm inferior to the inferior border of rib 3 on the left. The mean inferior border of the T3 ganglion was 4.1 mm inferior to the superior border of rib 4 on the right and 2.9 mm inferior to the superior border of rib 4 on the left. 43% of the right T2 sympathetic ganglia and 38% of the left sympathetic ganglia had some contact with the superior part of the third rib. Figure 1 illustrates a typical dissection picture.

Table 1: Data Collection. Cadaver dissection results of T2 and T3 ganglia positions relative to ribs 2, 3, and 4 are shown. +/- in data refers to superior (+) or inferior (-) to the border of the indicated rib.

ETS is the treatment of choice for medically uncontrollable palmar hyperhidrosis. The goal of surgical treatment is to improve the quality of life; therefore, the cure of the disease should not be achieved at the expense of worsened quality of life due to surgical complications or severe side effects. Despite best intentions, surgical complication rates have not been optimal. Due to the incongruency of surgical techniques and variable clinical results, the Society of Thoracic Surgeons published their expert consensus statements for the surgical treatment of hyperhidrosis in 2011 [1]. In the consensus paper, a rib-oriented approach was recommended based on the high variability of the ganglion anatomy and the difficult identification of the ganglia due to the presence of fat. After their review of 1,097 published articles from 1991 to 2009, they concluded that the optimal operation for palmar hyperhidrosis is the interruption of the sympathetic trunk at the top surface of rib 3 using electrocautery or the application of metal clips. Alternatively, the interruption could be carried out at the level of the rib 4. The intrinsic problem with this rib-oriented approach is that the sympathetic trunk is interrupted at an approximate level; it is unclear which ganglia are exactly destroyed or partially damaged. Since most published ETS results are based on rib-oriented operations, both retrospective and prospective studies that compare levels of sympathectomy and surgical outcomes do not truly reflect the exact levels of sympathectomy. It is, therefore, not surprising that despite the publication of the consensus statement, the complication rate of compensatory hyperhidrosis did not significantly decrease [4].

The rami communicantes that arise from intercostal nerves are not short stubby connecting nerves, but they may travel long distances caudally or rostrally before connecting to the sympathetic trunk [5–7]. Rami communicantes associated with T2 ganglion and ICN 2 are highly variable compared to rami associated with T3 and ICN3 which have less variability [5–7]. The number of rami communicantes attached to a ganglion may number from one or two for T3 and T4 ganglia, but for T1 and T2 ganglia, the number of rami could be multiple. Although rami communicantes are variable, they are visible, and they can be tracked. Without finding the junction of the RC to the sympathetic trunk, the centers of thoracic ganglia within the sympathetic trunk cannot be easily discerned visually. Zhang et al. published their anatomic dissection study on the variations of the upper thoracic sympathetic chain [7]. They showed that the T3 ganglion is in the intercostal space 68%. Our data show that the T3 ganglion lies on the surface of R4 at 65% and in the third intercostal space at 35%. Our cadaver dissection data show that the T2 ganglion lies close to the superior border of R3 or on the R3 itself. We found that 43% of the right T2 ganglia and 38% of the left T2 ganglia are in contact with the superior part of R3. The T2 ganglia, therefore, can be injured if R3 level sympathectomy is performed, in particular, if coagulation mode electrocautery is utilized. Chung et al also showed that T2 ganglion touches or lies directly over R3 35% of the time [8]. If the sympathetic trunk is interrupted at the top of the third rib as recommended by the consensus statement, there is a high probability that the T2 ganglion will be damaged partially or completely. Consequently, if the target ganglion is T3, the sympathetic trunk should not be disconnected over rib 3, since by doing so, the T2 ganglion may become injured, which will increase the chance of compensatory hyperhidrosis. Based on the anatomic data, one can also surmise that it is imprecise to disconnect the sympathetic trunk over R4 if the targeted ganglion is T4 since cutting over R4 will injure the T3 ganglion 65% of the time.

The method to cut the sympathetic trunk should be chosen with consideration to optimize the best outcome. A modern-day electrosurgery machine, which is used to interrupt the sympathetic trunk, offers three modes of cutting through tissue: pure cut, blend, or coagulation mode. In pure cut mode, a cautery unit performs much like a stainless-steel scalpel unless the power setting is too low, which can lead to soft tissue coagulation. Although there is little control over bleeding when the pure cut mode is utilized, there is minimal thermal injury to the surrounding tissue. It is absolutely necessary to prevent unintended thermal injury to T2 ganglion by not using coagulation mode. A partially injured T2 ganglion may be worse than a completely destroyed T2 ganglion since injured T2 may not coordinate sympathetic signals and become a rogue ganglion. Disconnecting the RC from the T3 ganglion using pure cut mode is similarly important to prevent thermal injury to the intercostal nerves.

The optimal level of sympathectomy still remains a controversy. Controversy remains due to conflicting results and variable operations reported in the past. ETS operation can be systematized, and the surgical outcomes can be better compared in the future if the operation is conducted in a ganglion-oriented manner (e.g., T3 ganglionectomy) instead of using a rib-oriented strategy.

Ethical approval for the study and exemption from obtaining informed consent were approved by the Institutional Review Board from the University of New England College of Osteopathic Medicine and the University of California San Francisco.

Competing interests: The authors have no financial or non-financial interests to disclose.

Funding/Support: None

Authors Contributions:

J Talsma designed, collected, analyzed, and interpreted the data and drafted the manuscript.

CC Peirce collected and analyzed the data, assisted in drafting the manuscript, and critically reviewed the manuscript for important intellectual content.

I Tarfusser analyzed and interpreted the data, assisted in drafting the manuscript, and critically reviewed the manuscript for important intellectual content.

S Kim analyzed and interpreted the data, assisted in drafting the manuscript, and critically reviewed the manuscript for important intellectual content.

O Idowu analyzed and interpreted the data, assisted in drafting the manuscript, and critically reviewed the manuscript for important intellectual content.

Sunghoon Kim conceptualized and designed the study, analyzed, interpreted the data, and critically reviewed and drafted the manuscript.

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Chung IH, Oh CS, Koh KS, Kim HJ, Paik HC, Lee DY (2002) Anatomic variations of the T2 nerve root (including the nerve of Kuntz) and their implications for sympathectomy. J Thorac Cardiovasc Surg 123:498–501

No competing interests reported.

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Thoracic T2 and T3 Ganglia Locations Relative to Their Corresponding Ribs: Implication during Endoscopic Thoracic Sympathectomy

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