The weepy nerve-different sensitivity of left and right recurrent laryngeal nerves under tensile stress in a porcine model.

PURPOSE: Recurrent laryngeal nerve palsy in thyroid surgery is still a threatening complication. Our aim was to analyze the impact of prolonged tensile stress on the recurrent laryngeal nerve (RLN) in an animal model using continuous intraoperative neuromonitoring (C-IONM). METHODS: Constant tensile stress was applied to left and right RLNs in 20 pigs (40 RLN). In a pilot study, five animals were subjected to a tensile force of 0.34 ± 0.07 N for 10 min and changes in amplitude were documented using C-IONM. In the main study, a force of 1.2 N was applied until the signal amplitude was reduced by 85 %, in 15 pigs. Nerve conductivity was analyzed by threshold current measurements. RESULTS: Good correlation was found between stress and amplitude decrease in the pilot study as well as between signal decrease and duration of trauma in the main study. Great variations were found inter- and intra-individually. These variations were most prominent at 85 % signal reduction (median 36 min, range 0.3-171 min). There was no side specificity (left 0.3-171 min, right 0.3-168 min, respectively, p = 0.19). However, in each individual animal, there was a sensitive (0.3-98.9 min) and less sensitive nerve (26.8-171 min). These differences became highly significant at 85 % of signal reduction (p = 0.008), where the vulnerability is 1.4 to 146.4 times higher on one side (mean 4.3). CONCLUSIONS: Our study demonstrates the presence of a sensitive RLN that was 4.3 times more vulnerable than the contralateral nerve (range 1.4-146.4 times, p = 0.008). Thus, the right and the left nerves cannot be assumed to be of equal sensitivity to trauma. In our data, the more sensitive nerve does not occur predominantly on one side and was named the "weepy nerve."

Endoscopic ultrasound-guided lymph node ablation with a novel radiofrequency ablation probe: feasibility study in an acute porcine model.

BACKGROUND AND STUDY AIMS: Radiofrequency ablation (RFA) is an accepted method of tissue destruction for solid organ tumors. Endoscopic ultrasound (EUS)-guided RFA has been used for lesions in the pancreas and liver, but there is limited experience of lymph node ablation using EUS-guided RFA. The aim of this study was to determine feasibility and safety of prototype EUS-guided RFA of mediastinal lymph nodes. METHODS: This was an endoscopic experimental feasibility study in a porcine model. After EUS-guided puncture of targeted lymph nodes, the stylet of a 19-G needle was replaced by a prototype RFA probe. RFA was performed by ERBE generator (bipolar settings: 10 watts, effect 2, 2 minutes). The animals were euthanized, and the targeted lymph nodes were identified and removed for histology and measurement of the effect achieved. RESULTS: A total of 18 mediastinal lymph nodes were ablated (mean size 20.8 ±â€Š6.6  mm in the long axis). The average length of exposed probe was 10.0 ± 3.0 mm. The mean length and diameter of necrosis was 9.8 ±â€Š3.6  mm and 5.5 ±â€Š1.6  mm, respectively. Linear regression comparing needle length with necrosis diameter revealed a coefficient gradient of r = 0.92 (P = 0.0001). With EUS-RFA a mean of 17.6 ±â€Š10.3 % (range 8.0 % - 53.2 %) of the respective lymph node area was ablated. No complications (i. e. hemodynamic instability, local bleeding, tissue damage) occurred during the procedure. Technical problems included stripping of the probe by the EUS needle and bending of the tip of the probe. CONCLUSIONS: EUS-RFA of lymph nodes was performed safely and successfully using a prototype EUS-compatible probe. This method may have the potential for future use in patient care.

Feasibility and safety of endoscopic full-thickness esophageal wall resection and defect closure: a prospective long-term survival animal study.

BACKGROUND: The first experiences with endoscopic closure of esophageal perforations in animal survival studies encouraged us to extend these procedures to full-thickness resections of pieces of the esophageal wall (FTEW). OBJECTIVE: To learn the feasibility, safety, and long-term effects of FTEW removal and defect closure. DESIGN: Feasibility animal study. SETTING: Approved animal facility. INTERVENTIONS: Twelve pigs were used for 3-month survival studies, autopsy, and histologic examination. Resection of a 2-cm piece of wall was performed with needle-knife and forceps/snare. Closure was performed by using prototype endoscopic suturing. MAIN OUTCOME MEASUREMENTS: Feasibility and complication assessment of this new endoscopic method. RESULTS: There were no complications relating to incision, resection, or closure. All pigs recovered quickly. In 2 animals a larger piece of wall causing a larger defect was removed, resulting in much air penetrating into the mediastinum, causing difficult ventilation. This was resolved with thoracic drain. In 3 of 12 animals a toxic substance slipped into the mediastinum, resulting in an abscess in 1 pig and misfire of an anchor as a result of obscured vision. This caused temporary illness of the animal but not death. Autopsy and histologic study confirmed no mediastinitis and well-healed scars in all but one. LIMITATION: Animal study. CONCLUSION: FTEW has proven to be feasible. Long-term survival demonstrated no mediastinitis and only 1 abscess after contamination of the mediastinum. These first experiences encourage further animal studies because the prospect of endoscopic full-thickness removal of esophageal lesions in patients might be very advantageous.