the recurrent laryngeal nerve ( rln ) injury during surgeries on thyroid and parathyroid remains the most significant commonly found complication of endocrine surgery in the neck , and it can result in significant morbidity including temporary or permanent paralytic dysphonia and dysphagia .
rates of nerve injury published in the literature typically range from 1% to 2% and are significantly higher for re - operation .
it has long been accepted that anatomic identification of both the rln and the external branch of the superior laryngeal nerve ( ebsln ) is the safest way to reduce nerve injury rates to a minimum   and certainly injury rates are lowest when surgery is carried out by experienced endocrine surgeons or thyroid surgeons in specialized centers with high caseloads . nonetheless , identification and preservation of the rln
an anatomically intact nerve may still show altered function postoperatively due to multiple factors , such as neural stretch during goiter retraction .
the study group comprised of forty - seven patients who underwent thyroid or parathyroid surgery at tulane university medical center from october of 2007 to april of 2009 .  
the protocol for assessment of the laryngeal nerves included routine preoperative and postoperative laryngoscopy at one to two weeks .
stroboscopy and electromyography ( emg ) assessment were not used in this study . a standard mivat / p gasless approach to the thyroid gland was performed under general anesthesia .
the surgeon stands at the lesion side , the camera operator on the other side , and an assistant at the patient 's head .
all vessel ligation during the procedure was done using the harmonic scalpel ( ethicon , nj ) .
additionally , the harmonic scalpel was also used to divide the isthmus in lobectomies , to isolate the gland from the trachea . after routine attempted anatomical observation of the rln , stimulation of the nerve
was done with a hand - held nerve stimulator with either the medtronic varistim iii nerve stimulator ( medtronic inc . ,
minneapolis , mi , usa ) or the nervona system ( nervona , ca , usa ) at currents of 1 to 2  ma on completion of dissection [ 2 , 5 ] .
the rln was stimulated at the most proximal exposed site of the nerve ( figure 1 ) .
data for continuous variables are expressed as median and range , unless specified otherwise . the outcome measures primarily the morbidity and mortality .
a total of seventy - seven nerves in forty - seven patients were included in this study .
there were twenty - three total thyroidectomies ( 48.9% ) , nineteen hemithyroidectomies ( 41.3% ) , 10.6% and ten parathyroidectomies ( 10.6% ) .
out of seventy - seven rlns , there was one permanent unilateral rln injury ( 1.29% ) in a patient with advanced papillary thyroid cancer managed by postoperative cord injection .
no hemorrhage or cervical hematoma was observed , and none of our cases developed wound infection ( figure 2 ) .
one of the most common operations throughout the world is thyroidectomy , and it has a low morbidity rate if performed by skilled surgical teams .
conventional thyroidectomy requires a transverse cervical incision that leaves a visible scar on the anterior surface of the neck .
the application of minimally invasive techniques for thyroid surgery was primarily motivated by the attempt to improve the cosmetic result of this operation .
the aesthetic point of view is particularly important for young women , who constitute a large part of patients affected by thyroid diseases .
most mivat / p allows for a prompt postoperative recovery and is performed as an outpatient procedure in some clinical settings .
it has been recently demonstrated that endoscopic   and video - assisted [ 911 ] procedures for thyroid and parathyroid surgery have some advantages over conventional methods of surgery in terms of not only cosmetic results but also analgesic requirements and postoperative recovery .   on the other hand , it should be pointed out that these procedures are not easy or feasible in all clinical settings .
they are technically demanding and require a surgical team skilled in both endocrine and endoscopic surgery .
the endoscopic and video - assisted procedures require learning and a training period that can be time consuming , especially at the beginning of the experience .
however , with training , learning , and experience , along with the continuous development in scientific medical technologies , mivat / p will be done in more centers and more candidates will be qualified for these kinds of surgeries .
the recurrent branch of the laryngeal nerve ( rln ) innervates all of the laryngeal muscles except the cricothyroid muscle , which regulates the tension of the vocal cords and is innervated by the external branch of superior laryngeal nerve .
if damage to the rln is unilateral , the patient may present with voice changes including hoarseness .
bilateral nerve damage can result in breathing difficulties and aphonia , the inability to speak .
the right recurrent laryngeal nerve is more susceptible to damage during thyroid surgery due to its relatively medial location . the nerve injury in this series was on the right side .
such anomalies include nonrecurrence of the rln , rln displacement by thyroid nodularity or paratracheal lymphadenopathy , extralaryngeal branching of the rln , and variations of the nerve course in relation to the inferior thyroid artery and ligament of berry . in a recent analysis of rln anatomy in 491 thyroid surgery cases ,
60.8% of rlns were found in the expected tracheoesophageal groove position , whereas 4.9% were lateral and 28.3% were posterior to the trachea .
of greatest concern are those cases where the rln is found on the anterior surface of the thyroid gland , a particularly high - risk area for nerve injury .
the surgical importance of this nerve relates to its proximity to the superior thyroid vessels . to preserve the rln
, most surgeons tend to avoid rather than expose the nerve , suggesting selective ligation of the upper pedicle vessels .
miccoli and colleagues introduced the minimally invasive video - assisted thyroidectomy procedure in 1998 . during mivat /p
, most surgeons do not use ionm to search for the rln . in our series consisting of forty - seven operations
, we were able to visualize the rln in 100% of the cases . among these ,
the nerve ran entirely medial and separate to the superior thyroid artery in most of the patients .
ionm of the rln during thyroid and parathyroid surgeries has been claimed in some studies to reduce the rate of nerve injury [ 15 , 16 ] ; however , other studies have shown it to be of no benefit and no reduction in the risk of rln injury [ 1720 ] compared with anatomic identification .
however , hermann et al . showed that ionm could be useful in identifying the rln especially when anatomically altered by prior surgery or large masses .
numerous studies have shown that only routine exposure of the rln is associated with very low rates of injury in high - volume centers ( less than 0.3% ) . during mivat / p ,
the surgical incision is really small in most cases to allow palpation of the nerve or the larynx as methods of identification . in our institution
, we have been using ionm as a method of rln identification during mivat / p operations .
now we are reporting our experience retrospectively . at the beginning of implementing both technologies together , we hypothesized that this method of monitoring the rln would decrease / prevent the risk of iatrogenic injury with lesser risk to the patient .
our initial clinical results were very promising showing that the use of ionm is easy and feasible in mivat / p , and it was rather safe with no intraoperative complications or conversion to traditional open approach .
though the operating space in these kinds of endoscopic surgeries is relatively narrow , there was no difficulty using the ionm simulator probe .
the tip of the monopolar probe is flexible , which helped the surgeon to go beyond the view of his field .
the rln may get injured while it still looks intact without the nerve being actually cut .
this can be caused by different sorts of injuries , which include , but are not limited to , traction , pressure , ischemia , ligation , crush , electrical or suction injury [ 23 , 24 ] . the role of ionm is not only during surgical dissection .
its role extends after the operation as it can help detect how the rln is functioning at the end of the procedure .
this provides the opportunity to stage contralateral surgery in case of suspected rln injury , thus avoiding the risk of rln injury bilaterally .
we also would like to mention that in our experience , we never had device failure or any unexpected events with the use of ionm during mivat / p .
our experience of ionm with mivat / p showed that ionm could be a very useful adjunctive method for rln identification besides endoscopic visualization and magnification .
this possibly will decrease rln injury and improve the quality and outcomes of mivat / p operations .
kern   discussed an important point that nerve monitoring during surgeries can possibly decrease the medico - legal liability .
however , the literature needs a study with a wider scale of patients to accurately prove our citations . to show a decrease in rln paralysis rates from 2% to 1% per nerves at risk , a study group of approximately 1,000 patients would be necessary .
standardization of the technique and wider availability of these technologies in centers performing these kinds of operations would be of great benefit .
 
 objective . 
 our goal is to study the feasibility of using intraoperative neuromonitoring ( ionm ) in minimally invasive video - assisted thyroidectomy and parathyroidectomy ( mivat / p ) with emphasis given to the identification of recurrent laryngeal nerve ( rln ) . methods . 
 consecutive series of forty - seven patients with seventy - seven recurrent laryngeal nerves at risk undergoing both mivat / p and ionm were enrolled in this retrospective , nonrandomized analysis study . 
 all operations were performed by the same surgeon within an academic institution setting . 
 all patients underwent vocal cord evaluation postoperatively . demographics and intraoperative and postoperative complications following surgery were collected . 
 results . out of seventy - seven rlns , there was one permanent unilateral rln injury ( 1.29% ) in a patient with advanced papillary thyroid cancer , managed by cord injection . 
 there was another transient rln paresis that resolved spontaneously ( 1.29% ) . 
 there were no instances of equipment malfunction or interference 
 . conclusions . to our knowledge , this is the first reported mivat / p series from the united states of america with a standardized ionm technique . 
 the technical feasibility of ionm seems acceptable and may serve as a meaningful adjunct to the visual identification of nerves . 
 neuromonitoring during mivat / p is effective in providing identification of laryngeal nerves and enables surgeons to feel more comfortable with mivat / p . 
 comparative series are needed for further evaluation . 
1. Introduction
2. Patients and Methods
3. Statistical Analysis
4. Results
5. Discussion