When searching information about endoscopic thoracic sympathectomy (ETS) or related surgeries on the web or in the scientific literature, it is easy to get confused in the jungle of controversial statements, comments and claims from medical professionals, patients, communities, etc. There has been some effort to standardize certain issues, like the evaluation of quality of life parameters, but there is still too much vagueness when defining details of methods, procedures and outcomes, which makes it almost impossible, not only for patients but also for surgeons, to evaluate and compare methods and results of ETS surgery. This methodological chaos was already mentioned in D. Kopelman and M. Hashmonai's analysis from 2008 ("The Correlation Between the Method of Sympathetic Ablation for Palmar Hyperhidrosis and the Occurrence of Compensatory Hyperhidrosis", World Journal of Surgery, 11/2008, Volume 32, Issue 11).

Judgements on ETS range from miracle cure, with really remarkable results, to anger, regret and condemnation of this surgery. In some countries, the use of ETS has been limited or even prohibited, after a number of patients had suffered or serious complications. For most patients, ETS has represented a significant improvement of their quality of life, but there is a minority of patients who struggle with severe long-term side effects. It is highly likely that this divergence has to be attributed to factors related to the surgical technique, rather than to the patient's individual predisposition for adverse reactions to correctly performed ETS surgery.

In fact, for the layman (the patient), and not only, it may be astonishing to detect that there are so many different ways to perform ETS surgery. And that there is still an incredible chaos regarding the terminology (e.g. ETS T3, T2, T2+T3, T4, R2, R3, etc.). Even more surprising is that correctly performed procedures (and there are only few of them), observing the principle of minimal trauma at the best level to reach a good result, are reported with the same identical label (e.g. ETS T3) in the literature, as techniques that euphemistically can be described as far from optimum. The latter are with little doubt responsible for many unfavorable outcomes of ETS. Needless to say that this makes it difficult or impossible to evaluate and compare any of the short- and long-term results reported in the majority of the published articles.

Since my fellow colleagues Göran Claes and Christer Drott started pioneering ETS surgery in the late -80ies in Borås, Sweden, the author has been following and performing sympathetic surgery for, carrying out 3500+ ETS procedures in over 1800 patients.

During the first years, the commonly employed technique was a rib-oriented R2-3-4 sympathicotomy (imprecisely called ETS "T2-4"), using blend-mode electrocautery, later revised to R2-3 sympathicotomy (ETS "T2-3").

In the early years, slight to moderate side-effects (especially compensatory sweating) were reported by many patients and considered to be a tollerable and acceptable trade-off to get rid of debilitating focal hyperhidrosis. Severe unfavorable side-effects, particularly compensatory hyperhidrosis and, in rare cases, critical bradycardia, did not become immediately apparent. In the 1990-ies with increasing numbers of surgeries, however, detrimental side-effects turned gradually out to be a potential sequel of ETS in a minority of patients.

As a consequence, the author has ever since focused on analysing critically the technical details of ETS, trying to detect and understand the possible factors responsible for untoward side-effects. Over the years, in my surgical approach, technical changes were sequentially implemented, step by step, in order to correct procedural details that had been identified as potential causes for less favorable outcome. Additional knowledge regarding methodological shortcomings had been gained when re-operating patients, originally operated in other units, in whom the result had not turned out as expected. Modifications that appeared to improve the immediate and, most of all, the long-term clinical result were implemented into the author's surgical routine. Often the improvement was so obvious that a controlled verification study could not be carried out, as it would have required to persevere with methods that had proven inferior or even harmful.

This article, therefore, represents a wrap-up of this personal experience and is meant as a critical overview of available methods. It is not based on orthodox evidence based studies or reviews of published studies. It should try to unravel the incredible confusion that reigns in this particular field of surgery and may contribute to shed some light on why there is such degree of uncertainty and difficulty to compare the results of ETS.

In most cases, identifying and interrupting the sympathetic chain is a relatively easy task for any thoracic surgeon familiar with thoracoscopic procedures.

Then why is there such a wide-spread variability regarding the incidence of intra-operative complications and the clinical outcome (desired result vs. undesired sequelae)?

It seems reasonable to focus on technical parameters that may explain this issue, since patient related factors should be neutralized by having included significant numbers of patients in the study.

The following factors regarding the interruption of the sympathetic chain may be crucial when analyzing the topic from a methodological point of view:

1. Where (the exact level)
2. How (the method used to interrupt the nerve)
3. What (number of levels neutralized/destroyed)

Among the large number of publications on thoracic sympathectomy, the majority lack an exact description of these elements.

Why is there such a big discrepancy between the outcome in different individuals (besides patient related factors)?

1. the surgeon makes no effort to respect the boundaries of the ganglia:
   • he focuses on the point where the sympathetic chain crosses the rib to interrupt the nerve
   • In the worst case scenario (and that's not uncommon): he has no knowledge of the location of the ganglia relative to the ribs. It seems incredible, but there are not only a series of peer-reviewed publications, but also published videos, where the author explicitly equates the rib with the location of the ipsinumeric ganglion (e.g. T2=R2, T3=R3 etc.), ignoring the fact that this is never ever the case.
2. missed level:
   • seems to happen more often than expected (there are at least 2 youtube videos published that show the procedure executed at another level than declared).
3. the surgeon is unaware or only vaguely aware of the physical properties and biophysical effects of the device he uses to interrupt the nerve
   • He uses a means to interrupt the nerve that causes more extensive damage to the nerve than originally intended.
   • In the worst case scenario (and that's not uncommon): he has no knowledge about the basic physics of electrocautery and, thence, no control over the extension of damage he is causing to the nerve and the adjacent structures

This makes the outcome to a sort of lottery (to the patient): if the anatomical situation has been advantageous, or if mother nature, in the process of healing, has been forgiving, even too radically or less meticulously carried out procedures may yield satisfactory or, at least, acceptable results.

In 2011, the Society of Thoracic Surgeons (STS) published an Expert Consensus for the Surgical Treatment of Hyperhidrosis, attempting to define “best procedures” and to standardize the nomenclature. Unfortunately, the consensus was based on previous publications, most of them reporting the employed surgical technique too vaguely to allow extracting reliable deductions from the published results. Furthermore, in their conclusions, focus has been put on minimizing hypothetical recurrencies, occurring in almost negligible frequency, instead of reducing the impact of side effects (significant incidence). According to this consensus document, the interruption should be rib-oriented and directed to the top of the aimed-at rib. Most astonishingly, ganglion-oriented sympathectomy is considered unreliable due to the variability of the anatomy and location of the ganglia.

This appears to be really remarkable: the sympathetic chain is the target of action and basis of evaluation of the results of surgery, but the recommendation is to aim at and refer to the underlying scheleton without taking care of the anatomy of the nerve; in other words: do not aim at the organ you are intended to operate, because it may shift up and down, aim instead at a nearby structure that seems anatomically easier to identify and more stable in its location (!). Needless to emphasize that this singular concept introduces and consolidates a system error, reproduced by all surgeons that follow these recommendations, which makes it impossible to determine where on the nerve and to what extent the damage has been carried out.

In addition, no critical analysis has been undertaken regarding the different means used to interrupt the nerve and their physical effect on the tissues.

If the objective of the Expert Panel had been to gain a better understanding of the desired and undesired effects of sympathetic surgery, their recommendations will barely reach the goal. The only result would be to universalize the vagueness of the procedures and reports, because based on hitting the sympathetic chain blindly, with whatever method, without knowing which ganglion is severed and to what extent the ganglion is destroyed. The consequence is that most studies will be relatively useless for gaining better knowledge on the subject.

In addition, there is the lack of standard in reporting side-effects, particularly the incidence and the degree of compensatory sweating, spanning over a wide percentage range in different publications.

In the past 20 years, awareness of side effects has become more wide-spread. Attempts have been proposed to reverse the surgery, repair the chain (reconstruction of the sympathetic chain with different techniques), counteract side-effects with drugs and local treatment. However, a detailed critical scrutiny of the surgical techniques has never been endeavoured, to find an explanation for and, eventually, seek to prevent excessively undesirable results.

When reading published studies, one get the impression that many surgeons are not aware of the real anatomy of the sympathetic trunk and its variability.

It seems not universally known that a sympathetic ganglion almost always is located in the lower part of the intercostal space, beginning at some distance below the lower edge of the rib carrying the same number, and, more often than not, reaches down to or even covers, partly or completely, the next rib (e.g. the T3 ganglion has no contact with the 3rd rib, but reaches or overlies the 4th rib).

That implies that the widely adopted method to use the ribs as main landmark will interrupt the nerve at a casual level, may fail to target the correct ganglion or sever a ganglion that was not intended to be addressed. The extent of damage to the nerve may be fortuitous and unpredictable, even depending on the technique adopted to interrupt the chain. It may result in partial damage to the ganglion and possible creation of a neurologically unstable ganglion.

A considerable number of surgeons are not familiar with the physics of electrocautery, leading to analogous risks, as mentioned in the preceding paragraph, resulting from the uncritical use of this device:

Pure cutting current (continuous unmodulated current >=200V), on the other hand, applied on a minimal surface (needle electrode or tip of L-hook) will cause optimal and concentrated energy delivery to the tissue, resulting in a clean cut with a sealed cut surface and minimal heat penetration into the underlying tissue. At the point of contact, the tissue cells will boil and literally expload in milliseconds, the vapor creates an immediate raise in tissue impedance (resistance) that prevents further penetration of electrical energy and spreading of heat to deeper layers. This electrocautery technique, along with clipping, is more precise, requires relatively low energy and should, therefore, be preferred over other techniques based on heat delivery, including laser.

The same pattern of continuous unmodulated current below 200V will not reach sufficient tissue temperature to vaporize the intracellular water, but leads to Soft Coagulation that spreads gradually through the tissue, without carbonizing it. This technique is the preferred method to stop bleeding in a pinpoint fashion, but should not be used to interrupt the nerve because it is difficult to determine with sufficient precision the extent of thermal damage along the nerve.

Standard Coagulation and Blend mode (cutting + coagulating) requires higher peak voltage settings compared to pure cutting current and has the property to penetrate deeply into the tissue and spread heat uncontrollably along the nerve. Applied long enough, it will carbonize the tissue. Superfluous to mention that its inaccurate use may cause partial thermal damage to the adjacent ganglia or to contiguous structures (intercostal nerve, costovertebral joint etc.), if not employed with extreme caution. Even more dangerous is the use of Fulguration mode in such sensitive environment as the thoracic cavity, characterized by voltage settings as high as to create sparks to reach the tissue even without direct contact. Some surgeons have the (hazardous) habit to apply cut/coag-energy on the electrode while pushing it against the targeted structure (e.g. a nerve), instead of grabbing and lifting it away from the underlying tissue before switching on the current. This technique makes it difficult to limit the depth of mechanical and thermal damage. On the other hand, when pulling the nerve (e.g. with the hook electrode) and applying too low energy, heat will spread rapidly along the nerve and cause more extended necrosis than intended, without or before dividing it.

Frequency: 200 - 3300 kHz (no neurostimulation occurs above 100 kHz)

Nerve tissue is destructed at temperatures at or around 70°C and remains intact at or below 40°C. Unstable nerve tissue due to permanent permeabilization of the axon or cell membrane, an issue not yet addressed in publications dealing with sympathetic surgery, may develop in the layer between necrotic and still healthy tissue, giving rise to chaotic depolarization of nerve fibers and uncontrolled discharge of neurons if the segment includes a ganglion, thus producing pathological nerve signals.

In the early days of ETS (Kux 1977 and later in the 80-ies Claes and Drott), there was a tendency to proceed radically enough in order to guarantee total dryness with least possible risk for recurrence. Consequence of this philosophy was the interruption of the sympathetic chain on different levels, originally severing the sympathetic trunk over the 2nd, 3rd and 4th rib (later in the 90ies reduced to 2nd and 3rd), employing high intensity electrocautery, without identifying the exact location of the ganglia.

Interestingly, this technique is still widely in use, presumably because many surgeons, beginning to perform ETS, rely on the original description of the technique, having in the meanwhile been adopted on thousands of patients.

A turning point has been the report by CC Lin who, besides having introduced the clamping method, postulated the efficacy of the T4 approach for palmar hyperhidrosis, which later was included into the Lin-Telaranta-classification.

Personally, the author was not able to reproduce the excellent results of ETS T4 reported by Lin. In a series of 16 patients, in whom the T4 ganglion was dissected free, isolated and completely destroyed, the side-effects were admittedly greatly reduced, but the desired effect was not reliable: in some patients, the result was asymmetrical, in some the reduction of sweating was insufficient and others experienced a relaps within months. Over half of the patients required repeat surgery, inducing me to climb a step higher and target the T3 ganglion ever since, focussing exclusively on the ganglion, not on the rib.

The explanation for this incongruency became clear when observing Lin performing the surgery at the bi-annual symposium on sympathetic surgery in Tampere, Finland, in 2001. He used to place 1 clip above and 1 clip below the 4th rib (Fig.). From an anatomical point of view, the T3 ganglion was compressed by the upper clip, while the T4 ganglion remained completely unharmed by the procedure. This supported the view that isolating and/or destroying the T3 ganglion would be the best compromise to obtain a good and enduring result in patients with hyperhidrosis of the upper extremity, while reducing side-effects to a tollerable minimum. Neutralizing the ganglion was carried out by interrupting the interganglionic segments above and below the ganglion and the grey ramus communicans, using either clean cutting diathermy (with final or careful soft coagulation of the ganglion itself) or by applying clips without destroying the ganglion. No significant difference regarding the result was noted between the two methods.

Surprisingly, apart from improved side effects, the rate of clinically significant recurrence of palmar sweating dropped to almost nil, compared to the T2 method adopted in the preceding decade.

Similarly, the T3 method according to the Lin-Telaranta-classification for facial hyperhidrosis and, especially, facial blushing, did not deliver reliable results when excluding the T3 ganglion alone. Applying the clip or cutting above the 3rd rib may, however, damage the T2 ganglion sufficiently to get the desired effect. Better, though, the interruption carried out above the upper end of the T2 ganglion (corresponding almost always to the lower edge of the 2nd rib) will block all signals directed headwards without damaging the T2 ganglion. However, this will also interrupt a significant number of afferent fibers, deputed to backfeed information about peripheral skin temperature. When the face starts sweating, these fibers report back that skin temperature is beginning to decrease, thus reducing the efferent response to the sweat glands. Disrupting this mechanism may result in more significant reactive sweating, particularly in individuals with an improperly working “thermostat” (like many of those suffering from facial hyperhidrosis at relatively low outside temperatures or after slight physical activity).

Cutting/coagulating/lasering the trunk mid over the anterior surface or on top of the 2nd rib is never required and carries an avoidable risk of damaging the stellate ganglion, particularly in case of a lower than average location of the ganglion (in around 0.3% of cases it covers the anterior face of the rib, partially or completely, resulting inevitably in a Horner's syndrome).

• A ganglion is never located on the rib that carries the same number. It regularly starts a few millimeters below the lower edge of the rib. It often reaches the upper margin of the next-lower rib or even covers it, at least in part (e.g. ganglion T2 lies close to or stretches over the 3rd rib).
• Clip application at the upper margin of the rib may partially squeeze the rostrally located ganglion, thereby risking to create a neurologically unstable focus.
• A similar unstable nerve segment may result from applying coagulating (or blended) electrocautery current on the rib to divide the trunk.
• Side-effects like bradycardia (low heart rate), hypotension (low blood pressure), unstable thermoregulation, extreme compensatory hyperhidrosis are mainly linked to partial damage or complete destruction of T2. Sympathectomy or block of ganglion T3, if performed with precision, without even touching the T2 ganglion, appears to reduce untollerable side-effects to almost nil, while palmar hyperhidrosis (and axillary) is reliably controlled. Unfortunately, many surgical procedures, defined as “ETS T3” or "R3" are interfering with the T2 ganglion, causing different degrees of mechanical or thermal damage to the ganglion, in most cases without even touching the T3 ganglion. In the majority of published peer-reviewed studies about sympathectomy, description of the procedure is far from precise or completely lacking. Needless to mention the confusion created when trying to interpret the results.
• Interrupting the chain at the top of the 3rd rib, as recommended by the STS consensus, will put the T2 ganglion in jeopardy and should be avoided whenever possible to prevent severe side-effects. Therefore, any intervention on the nerve higher than the lower edge of the 3rd rib should be banned for hyperhidrosis of the upper limb.
• Rib-oriented procedures will hit the real target (i.e. the sympathetic chain) in a fortuitous manner, since the anatomy of the chain itself is quite variable. In fact, the surgeon is disregarding the anatomical boundaries of ganglia and interganglionic segments. The wide array and heterogeneity of technical means and methods to carry out the interruption add to the uncertainty when trying to interpret the reports. In other words, with rib-oriented approaches, we can only vaguely guess what part of the sympathetic chain has been excluded and we have no indication to what extent the nerve has been damaged. Thence, the information from most reports is almost worthless, if the aim was to increase knowledge about the outcome of sympathetic surgery.
• Even worse are those papers that give no closer description of the level and method employed, maybe mentioning just sloppily "T3" or "T2-4", or not even that - and there are plenty of such examples in the literature -, filling the journals with superficial information of little use.
• There is no provocation in expressing these considerations, on the contrary, I consider it provocative that a large surgical community insists in treating a complex and delicate structure as the sympathetic chain blindly, without respect for its anatomy and its segmental boundaries, and using more often than not coarse methods to interrupt it, instead of treating it like a jewel. The sad conclusion is that the majority of publications on the subject is to be perused with considerable scepticism.
• It is appalling to detect that, among publicly accessible videos, a majority exhibit excessively destructive methods and/or disregard for the anatomy of the sympathetic chain. Better not imagining that this may represent a projection for how ETS is performed worldwide. When scrutinizing these documents, one comes to the conclusion that there appears to be no difference between top teaching university hospitals and minor thoracic surgery units. Not even a large number of performed surgeries guarantees a better outcome for patients, if the method employed persistently replicates outdated or approximate technique. Unfortunately, most surgeons seem not aware of the basic physics of electrocautery and the depth of thermal damage caused far too high energy settings. Adding this harsh approach to the haphazard R2, R3 or R4 sympathicotomies (landmarks recommended by the STS-consensus), the surgeon has only a vague, if any, idea about what segment of the underlying sympathetic chain and to what extent it is damaged.
• Among the multitude of methods dealing with interruption of the sympathetic chain, only a small fraction can be considered acceptable as being sufficiently accurate and delicate with the nerve, its ganglia and the surrounding structures. Most methods, widely used and many still in use, do not comply with the criteria of minimum traumatization, anatomically sound approach at correct level. As long as we do not recognize this, and as long every surgeon does it in "his" way, maybe performing only a couple of surgeries a year ("because it is that easy"), perpetuating methods described >20 years ago or using as tutorials some of the many videos ingenuously published on the net, we will continue to increase the number of patients with unfavorable outcomes or even destroyed lives.

ETS is an extremely valuable method to treat palmar hyperhidrosis, but it has to be done correctly, at the correct level, with precision, and using the least traumatic method available. The problem with ETS is not the principle itself, it is the way it is carried out. And unfortunately, with most of the methods described, the patient must rely on his/her luck not to end up with heavy undesired side-effects.

ESB (block with single clip) may also be a good solution for patients with debilitating facial ailments which do not respond to conventional therapy. However, the recurrence rate is higher for facial blushing, and, for facial hyperhidrosis, patient selection has to be particularly strict, because of the significantly higher risk for compensatory/reactive hyperhidrosis in this latter category of patients. Reversal (removal of the clip) will only lead to reduction of compensatory sweating if the nerve had not been completely crushed by the clip.

• The sympathetic chain is not a peripheral nerve with intersections that can be cut, clipped or coagulated with approximation. It should be considered as a series of miniature brain-like structures connected with short nerve segments. After mechanical or thermal trauma, the membrane of the nerve cells in these ganglia, conglomerations of nerve cells, may become permanently damaged and hyperpermeable. The ganglion may develop uncontrolled overactivity and an unstable behaviour, similar to an epileptic focus after brain injury. Different observations support the theory that this mechanism may contribute to or trigger severe undesirable side effects:
   a)  Patients, that have undergone reconstruction of the sympathetic chain with nerve graft, because of unbearable compensatory hyperhidrosis, report often improvement only days or weeks after surgery. The graft itself, however, would require several months to gain, if ever, any function. It seems reasonable to deduct that severing the nerve in healthy tissue, in order to bypass the scar and prepare a connecting point for the graft, seems to block exaggerated signal flow, originating from a pathologically active portion of the ganglion.
   b)  Another element pointing towards unstable ganglia is the surprising effect of membrane stabilizing anti-epileptic substances, found recently in selected patients with debilitating compensatory hyperhidrosis under off-label medication with topiramate.
   c)  Brock et al published a case in whom severe CS after "T2-3 ablation" was successfully treated with additional complete CT-guided percutaneous sympathicolysis of the T2 ganglion, which had presumably only been hurt at the previous sympathectomy.
  Brock M et al., Resolution of generalized compensatory hyperhidrosis related to sympathectomy after T2 sympatholysis. Eur J Cardiothorac Surg 2017(Dec); 52(6):1231-1232.
   d)  In the author's own experience, adopting an anatomically precise and technically accurate method has dramatically reduced the incidence of unbearable side effects in patients operated for palmar hyperhidrosis after 2001, compared to those who had undergone surgery in the decade before.
• The interruption (cut or clip) should be executed with highest possible precision on the interganglionic segment, best in the middle of this segment in order to guarantee a safe distance to the adjacent ganglia.
• A ganglion should be either preserved completely unharmed or, if needed, destroyed completely (after cutting its connections to the other ganglia), but never ever left partially damaged.
• If the ganglia are not clearly visible through the pleura, the pleura should be incised along the entire length of the ganglion to determine its boundaries.
• Use clips or cutting current, avoid coagulation (unless very carefully avoiding collateral thermal damage)
• Interruption should strictly follow the anatomy of the sympathetic nervous system and not the underlying skeleton (ribs).
• When treating palmar hyperhidrosis, ganglion T2 should be left untouched whenever possible.
• For facial blushing and facial hyperhidrosis, one single clip on the interganglionic segment between T1 and T2 (lower edge of the 2nd rib) will do the job. Keep in mind the higher recurrence rate for FB, but additional surgical measures will not change the result. Consider also the higher indidence of troublesome CS in FHH (removal of clips required in 13% of cases).
• Slight recurrence of moisture in the hands/feet is highly preferable to severe compensatory hyperhidrosis, therefore, in all cases, preference should be given to the most limited approach possible to reach a reliable result! If carried out correctly (clean neutralization of the T3 ganglion), the relapse rate is negligible (low single digit range).
• When interrupting the sympathetic trunk “blindly” (i.e. using a rib-oriented approach, with or without opening the pleura over the trunk), severing the trunk at the lower edge of each rib will give best chance to keep clearance from the ganglia.
• Avoid interruption over the rib (front surface) or at the top margin of the rib (the higher the interruption on the rib, the higher the probability of partial damage to the next higher ganglion).
• Avoid neuroma formation (e.g. after cut with scissors without sealing the cut-edge).