Study for the Incidence of Postsurgical Neuropathic Pain Following Bilateral Axillo-breast Approach of Endoscopic Thyroidectomy: A Pilot Observational, Prospective Study
Corresponding Author: Pratibha Singh, Department of Anesthesiology, All India Institute of Medical Sciences, Gorakhpur, Uttar Pradesh, India, Phone: +91 7800889582, e-mail: firstname.lastname@example.org
Aim: To determine the incidence of postsurgical neuropathic pain following the bilateral axillo-breast approach (BABA) approach of endoscopic thyroidectomy, a minimally invasive approach for thyroid surgeries.
Materials and methods: Fifteen patients undergoing BABA endoscopic thyroidectomy were followed at 15 days, 1 month, and 3 months of surgery. Incidence, character, and severity of neuropathic pain following surgery were assessed. The area of distribution of the pain was also noted.
Results: The incidences of neuropathic pain following BABA endoscopic thyroidectomy were 73.3%, 40%, and 20%, respectively after 15 days, 30 days, and 3 months of surgery. The median (range) NRS pain scores were 4 (3, 5), 2 (2, 3), and 1 (0, 2) on day 15, day 30, and 3 months, respectively. The distribution of pain was mainly in the anterior aspect of the neck (66.67%) and the upper part of the chest (66.67%). The commonest neuropathic pain features were pin pricking, brush allodynia, tingling, and numbness in the involved area.
Conclusion: Despite the enormous technical and surgical benefits of the BABA approach for endoscopic thyroidectomy, the high incidence of both acute and chronic neuropathic pain following surgery needs consideration.
Clinical significance: To draw attention to the alarming complication of neuropathic pain after BABA endoscopic thyroidectomy, which should be addressed to decrease patient morbidity.
How to cite this article: Kumar S, Khuba S, Chand G, et al. Study for the Incidence of Postsurgical Neuropathic Pain Following Bilateral Axillo-breast Approach of Endoscopic Thyroidectomy: A Pilot Observational, Prospective Study. World J Endoc Surg 2022;14(1):1-6.
Source of support: Nil
Conflict of interest: None
Keywords: BABA endoscopic thyroidectomy, Incidence, Neuropathic pain, NRS, Observational study
Surgically-induced neuropathic pain appears as a significant clinical problem for the patient as well as for the surgeon and the attending pain physician. About 10-50% of the patients experience persistent pain following common surgeries.1 Postsurgical pain may persist after wound healing and cause significant discomfort to the patients. This unsettled pain lasting for more than 3 months is generally left unnoticed and puts them in a state of chronic pain after routine surgeries.2 The majority of these patients develop chronic neuropathic pain also (6–68%).3
Laparoscopic surgeries were the biggest success in the early 1980s. This started the era of minimal access surgeries which paved the way for endoscopic thyroidectomy (ET) from the conventional method of open thyroidectomy.4 Traditional open thyroid surgery is an optimal, safe, and effective surgical method for the treatment of thyroid nodules, but there are several advantages of endoscopic thyroid surgery over conventional open surgery, like better cosmetic results and fewer postoperative complications related to the scar. Various approaches for ET have been defined. The bilateral axillo-breast approach (BABA) method is one among them which was first described by Choe et al.5 At our center, BABA-ET is being done regularly. We observed that this procedure leaves an alarming number of patients with neuropathic sensory morbidities involving the areas of surgical instrumentation, as per the clinical evaluation in the pain clinic of our institution.
Till now, we did not find any published literature about the incidence of postoperative neuropathic pain and discomfort after BABA-ET. This study aims to determine the incidence of postsurgical neuropathic pain in patients during the follow-up of the first three months after BABA-ET.
MATERIALS AND METHODS
This was a prospective, observational, single-center, pilot study conducted in a tertiary center in North India after institutional ethical clearance (IEC code: 2020–177–Others–EXP–24) and central trial registry (CTRI no: CTRI/2021/03/ 031,819). Participants included in the study were patients posted for elective BABA-ET, between 18 and 60 years of age of either sex. Exclusion criteria were patient’s refusal, intraoperative conversion to open thyroidectomy, any preexisting anterior neck pain or chronic pain, any disease with preexisting neurological and neuropathic comorbidities, and the inability of the patient to understand the numerical rating scale (NRS).
Douleur Neuropathique 4 (DN4) questionnaire and NRS score were used for the measurement of incidence of neuropathic pain after BABA endoscopic thyroidectomy.
Posted patients for BABA-ET were explained about the study during the preanesthetic check-up. Those who were interested in getting enrolled in the study were given the patient information document and the consent forms available in Hindi and English languages. Patients were explained about the DN4 questionnaire and NRS for the assessment of pain.
After the surgery, the patients were followed up at 15 days, 1 month, and 3 months in the pain OPD. The initial 2 follow-ups (at 15 days and 1 month) were for determining the acute neuropathic pain and the third-month follow-up was for the presence of chronic neuropathic pain. The intensity and character of the pain were noted in each visit using the NRS score and DN4 questionnaire, respectively. The corresponding site of pain was charted on the body diagram. DN4 questionnaire was filled out before the follow-up OPD visit of the patient by an experienced nurse who was not a part of the study.
NRS is a scale ranging from 0–10. The value of 0 on the scale represents “no pain” and a score of 10 represents “worst imaginable pain.” Patients were asked to give a number to their pain on NRS according to the severity of the pain which was then noted. Their pain was then categorized as mild, moderate, and severe according to the NRS of 1–3, 4–6, and 7–10, respectively on the scale.6
The character of the pain was noted using the DN4 questionnaire.7 It contains 10 questions defining the phenotype of neuropathic pain. Seven variables are subjective complaints with their variations on different physical stimuli, and the rest of the three questions are about the clinical findings associated with it. For every positive response, a score of 1 is noted, and subsequently, the total score is calculated for all the ten questions of the questionnaire. Neuropathic pain is diagnosed if the total score of the patient is ≥4/10.
Post-thyroidectomy complications like voice change and swallowing impairment were also recorded in all the time frames of the follow-up.
All patients were taken to the operation theater and general anesthesia was induced. The patients were placed in a supine position with neck extension using a sandbag placed under the shoulders. The table was tilted to 30 degrees in reverse Trendelenburg position. Both arms were mildly abducted to allow insertion of axillary ports. After sterile preparation of the surgical area, diluted adrenaline solution (1:200,000) was infiltrated along the anticipated subcutaneous path. Four ports were made: two ports of 5 mm size in each axilla and two of 10 mm size on the superior edge of each areola. Blunt dissection was done using a tunneler over the chest and the neck. CO2 insufflation was done at 7 mm Hg using a flow rate of 7 L/min. for better optimization and ease of the endoscopic procedure, Neck flaps were extended in all directions as described: till hyoid bone cranially, sternal notch caudally, and till the medial border of sternocleidomastoid muscle bilaterally.
Under endoscopic view, the strap muscles were retracted laterally. Inferior thyroid vascular pedicle along with recurrent laryngeal nerve and inferior parathyroid gland (PTH) were secured followed by dividing the inferior thyroid artery. Dissection of the thyroid gland was done in all the planes while securing the superior pole to preserve superior PTH. The specimen was then extracted from the 10 mm axillary port. All the ports were closed in layers and the elastic adhesive pressure dressing was applied over the surgical area to avoid subcutaneous hematoma. The patients were reverted back from general anesthesia.
Patients were allowed for oral sips after 6 hours of the surgery. Postoperative pain was managed with nonsteroidal anti-inflammatory drugs and weak opioids like tramadol. Patients were discharged after 3 days of surgery.
Selection of study patients: A total of 21 patients scheduled for BABA-ET over a period of 3 months (1st October 2020 to 31st December 2020), were enrolled in the study. Four patients were excluded, one patient had preexisting anterior neck pain, one had fibromyalgia, and two cases were converted to open thyroidectomy. Out of the remaining 17 patients, two patients were drop-outs because they were lost to follow-up in postoperative visits. A flow-chart outlining the enrolment of patients for the study has been shown in Flowchart.
A total of 15 patients, who underwent BABA-ET in a period of 3 months and successfully completed the follow-up for another 3 months after satisfying the inclusion criteria of the study, were included for the statistical analysis.
Continuous variables were presented as mean ± standard deviation or median (range) whereas categorical variables were as frequency (%). As the sample size was small, nonparametric methods were used for tests of statistical significance. Mann–Whitney U test was used to compare the median score between male and female patients. Friedman test was used to test the change in distribution (median score) of the DN4 and NRS score between day 15, day 30, and 3 months followed by multiple comparisons using Bonferroni corrections. Similarly, to compare the proportions of DN4 pain (≥4) between the three-time points, the Cochran’s Q test followed by multiple comparisons was used. Multiple comparisons were used after obtaining an overall significant p-value. p-value < 0.05 was considered statistically significant. Statistical package for social sciences, version-23 was used for the statistical analysis.
A total of 15 patients were analyzed for this study. The mean ± SD and median (range) of the age were 34.53 ± 6.40 and 37 (21–44) years, respectively. Out of 15 patients, 13 were females (86.7%). There was higher age of the male patients as compared to the females although the difference was not statistically significant (median: 40.50 vs 34, p = 0.305).
The incidences of both acute and chronic neuropathic pain were assessed. On postoperative day 15, day 30, and 3 months, the incidences of DN4 pain (≥4) were 73.3%, 40.0%, and 20.0%, respectively (Fig. 1). The median (range) DN4 pain scores at day 15, day 30, and 3 months were 5 (3, 8), 3 (2, 6), and 2 (1, 5), respectively and the difference between the three-time points was statistically significant (p < 0.001) followed by multiple comparisons which were also evident to have significant reductions between day 15 and day 30, day 15 and 3 months, and day 30 and 3 months (each p < 0.05) (Fig. 2). The median (range) NRS pain scores were 4 (3, 5), 2 (2, 3), and 1 (0, 2) on day 15, day 30, and 3 months, respectively and the difference between all the time points were statistically significant (p < 0.001) followed by multiple comparisons indicated as significant reductions between day 15 and day 30, day 15 and 3 months, and day 30 and 3 months (each p < 0.05) (Table 1).
|Observations at time points|
|After 15 days (N = 15)||After 30 days (N = 15)||After 3 months (N = 15)|
|≥4||11 (73.3%)||6 (40%)||3 (20%)|
|Mean ± SD||4.8 ± 1.5||3.3 ± 1.2||2.5 ± 1.2|
|NRS score (0–10)|
|≥4||8 (53.3%)||3 (20%)||0|
|Mean ± SD||3.9 ± 1.3||2.2 ± 1.0||1.1 ± 0.9|
|p-value (DN4)||Friedman test: p < 0.001 (Multiple comparisons: p < 0.05 for all the pairs)|
|p-value (NRS)||Friedman test: p < 0.001 (Multiple comparisons: p < 0.05 for all the pairs)|
Data presented as number (%) or mean ± SD. DN4, Douleur Neuropathique 4 questionnaire; NRS, numerical rating scale
In all the time frames of follow-up (at 15 days, 1 month, and 3 months), the commonest neuropathic features experienced by these patients were pin pricking, brush allodynia, tingling, and numbness in the involved area (Table 2). The neuropathic features most commonly involved the area of instrumentation during the endoscopic procedure. Areas for pain were the anterior aspect of the neck (66.67%), the upper part of the chest (66.67%), the axilla (26.67%), and the submental area (20.00%).
|Components of DN4 score||Observations at time points|
|After 15 days (N = 15)||After 30 days (N = 15)||After 3 months (N = 15)|
|Burning||7 (46.7)||5 (33.3)||1 (6.7)|
|Painful cold||2 (13.3)||1 (6.7)||1 (6.7)|
|Electric shock||4 (26.7)||0||0|
|Tingling||11 (73.3)||8 (53.3)||6 (40.0)|
|Pin and needles||13 (86.7)||9 (60.0)||8 (53.3)|
|Numbness||9 (60.0)||9 (60.0)||8 (53.3)|
|Itching||6 (40.0)||1 (6.7)||1 (6.7)|
|Touch hypoesthesia||8 (53.3)||5 (33.3)||3 (20.0)|
|Prick hypoesthesia||2 (13.3)||0||0|
|Brushing||10 (66.7)||12 (80.0)||10 (66.7)|
Data are presented as numbers (%). DN4, Douleur Neuropathique 4 questionnaire
Postoperative change in voice was seen in five patients (33.3%) at 15 days follow-up. At the end of 1 month, only one patient had a voice change which also had spontaneous resolution at 3 months follow-ups. Mild difficulty in deglutition was present in six patients during the follow-up at 15 days, which resolved spontaneously, and no patient had any such complaints at 1 and 3 months of follow-up (Table 3).
|Postsurgical complications||Observations at time points|
|After 15 days (N = 15)||After 30 days (N = 15)||After 3 months (N = 15)|
|Change in voice||5 (33.3)||1 (6.7)||0|
|Difficulty in deglutition||6 (40)*||0||0|
Data presented as number (%). *Patients had mild difficulty in deglutition
In our practice, we encountered a very high number of patients presenting with clinical features suggestive of neuropathic pain in the surgical areas following BABA-ET. So, this study was an attempt to estimate the incidence of neuropathic pain following BABA-ET. The diagnostic tool used for neuropathic pain in this study was the DN4 questionnaire in which a score of ≥4 out of 10 was considered for the diagnosis of neuropathic pain.7
The study participants consisted of 86.7% female patients, the proportion reflecting a higher prevalence of thyroid pathologies8 and a predilection for less invasive surgeries in female patients for cosmetic reasons.
In our observational study, the incidence of neuropathic pain following BABA-ET was both statistically and clinically significant. This higher preponderance of neuropathic pain was attributed to the increased area of subcutaneous dissection during the surgical procedure damaging the neural structure. There is no data available till now in this context for BABA-ET.
Chong et al.9 observed that after the unilateral axillary-breast approach of ET, 53% and 7% of patients developed chest wall paresthesia within 1 month and after 3 months of surgery, respectively. The surgical procedure included only unilateral axillary endoscope placement using a 2 cm incision and two ports of 5 mm and 10 mm size. Comparing their results with our findings (the incidence of neuropathic pain was 40% and 20%, respectively at 1 and 3 months after BABA-ET), the procedure of BABA-ET involved bilateral dissection using four ports (two of 5 mm and two of 12 mm size), and so, the increased area of instrumentation could have been a reason responsible for higher neuropathic pain at the end of 3 months (7% vs 20%). Additionally, in our study, the assessment of neuropathic pain was done using all the ten parameters of the DN4 questionnaire contrary to Chong et al. who reported using a nonspecific parameter (chest wall paresthesia), and thus, could have also affected the difference.
In another study, Ikeda et al.10 reported only 5% of patients developed anterior neck and chest wall paresthesia at 3 months follow-up after the unilateral axillary approach of ET. The lower incidence of neuropathic pain observed might be due to the difference in surgical technique as one incision of 30 mm was made in unilateral axilla in this approach as compared to the two ports of 10 mm size in bilateral axilla and two ports of 5 mm size in bilateral areola done in BABA-ET. Additionally, in this study also, neuropathic pain was assessed in terms of a broad nonspecific terminology of paresthesia as a comparison to an elaborated DN4 questionnaire used in our study. The author didn’t include the results of acute neuropathic pain at the follow-up duration of 15 days and 1 month.
Kim et al.11 showed that nearly 75% of the patients receiving placebo treatment had anterior chest hypoesthesia after 3 months of robotic ET. The higher incidence of these symptoms may be due to the single large incision of 5–6 cm in the unilateral axilla for the instrumentation, in addition to the increased surgical duration in robotic surgeries.
Several other studies12-14 have also mentioned the occurrence of neuropathic pain following various techniques of ET, supporting the results of the current study and directing our concern over the matter.
In our study, the incidence decreased significantly from 73.3% on day 15–20% after 3 months of surgery. This lowering of incidence might reflect that in most of the cases the pathology caused by the surgical instrumentation was neuropraxia, leading to spontaneous recovery from the injury. Additionally, some rescue analgesics were given in the immediate postoperative period like tramadol having antineuropathic properties15,16 due to their effect on serotonin uptake, and so, might be responsible for the decrement in the incidence over time.
After BABA-ET, the neuropathic pain most commonly involved the anterior aspect of the neck and upper part of the chest corresponding to the area of endoscopic dissection and instrumentation. Other involved sites were the axilla and submental area. Sites of nociceptive pain distribution were opined by Kang et al.17 who observed a more widespread distribution of pain after ET when compared to the open procedure. The authors found additional sites of pain including the upper arm, shoulder, and headache, but they only concluded acute nociceptive pain. The surgical procedure included in the study was transaxillary ET using a single-incision and gasless technique, which is quite different from BABA-ET included in the current study.
Although the occurrence of postoperative neuropathic pain features has been reported in many studies done for various ET approaches, none of them have mentioned the different phenotypes of neuropathic pain. We, in this study, have tried to explore this aspect with the use of the DN4 questionnaire, elaborating on the various neuropathic pain features after BABA-ET.
We observed that the most prevalent character was the pin and needle sensation over the involved area followed by the tingling sensation and brush evoked allodynia. Brush evoked allodynia and numbness over the involved area were the most persistent neuropathic pain features after BABA-ET with no significant spontaneous improvement even after 3 months of surgery and remained a part of chronic neuropathic pain in the majority of patients. We didn’t find any literature on the context of the occurrence of these specific neuropathic features.
Although this study was the first one to focus the attention on the alarmingly high rate of neuropathic pain after BABA-ET, there are several limitations associated. Firstly, the sample size was relatively small. Furthermore, it was a single-centered study, which might have affected the incidence, and there lies a possibility of variance depending on the type of instruments used and the skill of the surgeon operating. So, in the future, multicentric studies with a larger sample size will be helpful to make the results of this study firmer. Finally, the nociceptive pain following the BABA-ET was not addressed. The first follow-up for this study was done on the 15th postoperative day, so, the chances of acute postoperative nociceptive pain are expected to reduce significantly till this time.
The technical improvement in the BABA-ET comes with an unavoidable price of both acute and chronic neuropathic pain. Patients are very commonly left with the pin pricking, brushing, and tingling sensation, mostly occurring over the neck and the chest after surgery which can be very troublesome to the patients. These complaints are very often ignored in the shadows of the other seemingly important postoperative concerns. So, this study tried to draw attention to this alarming complication, which should not be neglected.
Gyan Chand https://orcid.org/0000-0002-4605-3816
Pratibha Singh https://orcid.org/0000-0002-8772-5340
Anil Agarwal https://orcid.org/0000-0002-5231-9609
Prabhakar Mishra https://orcid.org/0000-0003-4769-9106
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