NIM vs Neurosign in nerve sparing total thyroidectomy. Multicentric experience.

INTRODUCTION: Injury to cranial nerve represents 5% of negligence litigation against general surgeons and of all malpractice jury verdicts in endocrine surgery 60% accounts for recurrent nerve injuries and 15% for anoxic brain injuries from RLN injuries, unrecognized post-operatively. During Total Thyroidectomy is reported an incidence of failure to find the nerve in 5- 18% of cases and if we think that routine identification of the RLN during thyroid surgery has reduced the injury rate from 10% to less than 4% and that the incidence of nerve paralysis was 3 to 4 times greater in cases where the nerve was not exposed than in cases where was routinely exposed, then we understand the importance of a clear identification during every thyroid dissection MATERIALS AND METHODS: 880 Total Thyroidectomies during the last 4 years, since Jannuary 2007 until December 2010, (610 F, 270 M; mean age 44,5 years old, range 14-83). All patients were examined pre and postoperatively (1-6 months after) by direct laryngoscopy or laryngofibroscopy to check vocal cord mobility (medium follow up 25.5 months range 3-50 months). The Authors reviewed charts from two randomized groups, selected by a double blind, statistically designed study and again compared in a multivariate analysis (Stat 2004 ltd): 1) 480 total sutureless thyroidectomies, performed during the previous year with continuous intra-operative nerve monitoring using dedicated endotracheal tube with a last generation Nerve Integrity Monitor Pulse II (N.I.M. pulse II®) 2) 400 total sutureless thyroidectomies: performed with continuous intra-operative nerve monitoring using dedicated Laryngeal Electrode, a self-adhesive device designed to fit onto standard reinforced endotracheal tubes (Neurosign® 1040 - 4 Channel EMG) RESULTS: There were no statistically significative difference between the two groups for distribution of age, sex, epidemiological characteristics, type of pathology etc. The incidence of major complications in thyroid surgery in the first two groups (total Thyroidectomy performed by NIM and by Neurosign), as well as compared with the data of the literature are absolutely overimposable; only significative difference is a reduction of the costs in the second group (Neurosign). The 1st group (NIM) specificity is 90.2% (433/480). There were 6 cases of temporary RLN paralysis (temporary paralysis rate: 1.25 % of patients), 3 true positive and 3 false negative. Finally there were 3 cases of permanent RLN paralysis (0.75%), 2 truepositive and 1 false-negative developed after 10 days (demyelination by thermal injury). The 2nd group (Neurosign) specificity of 89 % (356/400). There were 6 cases of temporary RLN paralysis (rate: 1.5 %, p > 0.5), 2 true positive, 1 false positive and 4 false negative. Finally 2 cases of permanent RLN paralysis (0.5% p > 0.5), 2 true-positive. DISCUSSION AND CONCLUSION: Our data confirm a useful application of NIM and Neurosign in thyroid dissection nerve prevention. We don't believe that those procedures can be useful for learning thyroid gland surgery, because can't preserve from an accurate dissection and nerve identification technique, but can only support in nerve-at-risk thyroidectomy or during dissection can support expert surgeon's decision, having a clear pre-operative (post-anesthesiologist) and post-operative predictive value. Those procedures are anyway expensive and time consuming (25000-30000 € for the E.M.G. system and almost 200-250 € for each dedicated endotracheal tube in NIM group). So Neurosign group has over-imposable results in terms of complications specificity and accurancy (no statistically significative differences), but it's a much cheaper procedure!