various surgical techniques have been developed to optimize esthetic outcomes even in operations for malignancy . unlike other parts of the body ,
thus , it is crucial to minimize postoperative scarring in these areas , especially in neck dissection ( nd ) .
robot - assisted and endoscopic - assisted surgeries are typical examples . kang et al.1 first reported robot - assisted modified radical nd in 2010 .
they performed the operation via a transaxillary approach , but difficulties in approach to level i , an important area for oral cavity cancer treatment , were encountered2 . to overcome this limitation , nd via modified face - lift or the retroauricular approach using robotic surgery
robot - assisted nd has many advantages , such as excellent esthetic outcomes and good visualization during surgery , but its high cost is a problem for most patients .
endoscopic - assisted surgery can be an alternative and more cost - effective option compared to robot surgery , as byeon et al.3 recently , we treated two patients who underwent endoscopic - assisted nd via a retroauricular approach and had excellent esthetic outcomes
. herein , we report these cases and discuss the pros and cons of endoscopic nd .
a 63-year - old male patient visited the department of oral and maxillofacial surgery at dental hospital of yonsei university of college of dentistry in korea .
incisional biopsy had been performed by another hospital , which revealed invasive squamous cell carcinoma .
the ulcerative lesion was present on the lingual side of # 36 , # 37 and was 3.02.0 cm in size .
additional diagnostic imaging , including magnetic resonance imaging ( mri ) and positron - emission tomography ( pet ) , were performed to determine extent of surgery .
there was no mandibular or metastatic lymph node invasion , nor were there metastatic lesions on any other organs ( ct2n0m0 , stage ii ) .
thus , wide excision with marginal mandibulectomy , selective neck dissection ( snd ) ( i - iii ) via endoscope , and repair of the soft tissue defect with megaderm ( l&c bio , seongnam , korea ) were performed .
it took almost 5 hours to complete endoscope - assisted snd ( i - iii ) , with 450 cc of blood loss during the operation .
there was mild marginal mandibular branch weakness , which might also have arisen in conventional nd .
a 56-year - old male was referred from a local clinic for evaluation of a tongue mass .
mri and pet demonstrated no regional or distant metastasis ( ct2n0m0 , stage ii ) .
consequently , wide excision with endoscopic nd , reconstruction of the surgical defect with a radial forearm free flap , and repair of the resulting forearm defect with megaderm were performed .
it took almost 3.5 hours to complete endoscope - assisted snd ( i - iii ) , with 200 cc of blood loss during the operation .
the final diagnosis confirmed the clinical staging ( pt2n0m0 , stage ii ) . unlike in case 1 , no postoperative facial nerve weakness was observed .
incision line and anatomical landmarks for endoscpoic neck dissection were outlined on patient 's neck.(fig .
1 ) a retroauricualr incision was used to approach the sternocleidomastoid muscle ( scm ) and a skin flap was created .
the scm muscle was exposed , then we continued subplastysmal dissection inferiorly and anteriorly until we reach the omohyoid muscle , hyoid bone and the midline of the neck . during skin flap elevation ,
a self - retaining retractor ( sejong medical corporation , paju ; sangdosa , seoul , korea ) was used for good visualization of the surgical field .
a nerve stimulator was used to identify the marginal mandibular branch of the facial nerve .
some portions of level ib , iia , and iii were also dissected under direct visualization .
then , a 30-degree endoscope ( 10 mm in diameter , 30 cm in length ; stryker , san jose , ca , usa ) was applied in the level i area followed by fixation with an endoscope holder ( karl storz , tuttlingen , germany).(figs .
2 , 3 ) dissection of the anterior belly area ( level ia ) was performed ; then , level ib , which contains the submandibular gland , was dissected .
harmonic curved shears ( harmonic ace 36p ; johnson & johnson medical , cincinnati , oh , usa ) were used to cauterize minor vessels and dissect tissues .
the distal facial artery and vein were ligated with premium surgiclips ( covidien , dublin , ireland ) ; the submandibular ganglion , wharton 's duct , proximal facial artery and vein were cut after ligation with surgiclips .
we demarcated the level of omohyoid muscle , which is inferior to the border of level iii , and dissected lymphoadipose tissue superiorly from inferior margin using endoscope .
finally , dissection of the carotid artery and internal jugular vein was performed with posterior retraction of the scm .
micro - vascular surgery was performed in case 2 as usual manuals which have been done in conventional neck dissection.(fig .
4 ) donor vessels such as the proximal portion of facial artery , superior thyroid artery , and related veins were observed well under microscope .
. however , an assistant had to retract the skin flap with an army - navy retractor for visualization of the operative field .
a 63-year - old male patient visited the department of oral and maxillofacial surgery at dental hospital of yonsei university of college of dentistry in korea .
incisional biopsy had been performed by another hospital , which revealed invasive squamous cell carcinoma .
the ulcerative lesion was present on the lingual side of # 36 , # 37 and was 3.02.0 cm in size .
additional diagnostic imaging , including magnetic resonance imaging ( mri ) and positron - emission tomography ( pet ) , were performed to determine extent of surgery .
there was no mandibular or metastatic lymph node invasion , nor were there metastatic lesions on any other organs ( ct2n0m0 , stage ii ) .
thus , wide excision with marginal mandibulectomy , selective neck dissection ( snd ) ( i - iii ) via endoscope , and repair of the soft tissue defect with megaderm ( l&c bio , seongnam , korea ) were performed .
it took almost 5 hours to complete endoscope - assisted snd ( i - iii ) , with 450 cc of blood loss during the operation .
there was mild marginal mandibular branch weakness , which might also have arisen in conventional nd .
a 56-year - old male was referred from a local clinic for evaluation of a tongue mass .
mri and pet demonstrated no regional or distant metastasis ( ct2n0m0 , stage ii ) .
consequently , wide excision with endoscopic nd , reconstruction of the surgical defect with a radial forearm free flap , and repair of the resulting forearm defect with megaderm were performed .
it took almost 3.5 hours to complete endoscope - assisted snd ( i - iii ) , with 200 cc of blood loss during the operation .
the final diagnosis confirmed the clinical staging ( pt2n0m0 , stage ii ) . unlike in case 1 ,
incision line and anatomical landmarks for endoscpoic neck dissection were outlined on patient 's neck.(fig .
1 ) a retroauricualr incision was used to approach the sternocleidomastoid muscle ( scm ) and a skin flap was created .
the scm muscle was exposed , then we continued subplastysmal dissection inferiorly and anteriorly until we reach the omohyoid muscle , hyoid bone and the midline of the neck . during skin flap elevation ,
a self - retaining retractor ( sejong medical corporation , paju ; sangdosa , seoul , korea ) was used for good visualization of the surgical field .
a nerve stimulator was used to identify the marginal mandibular branch of the facial nerve .
some portions of level ib , iia , and iii were also dissected under direct visualization .
then , a 30-degree endoscope ( 10 mm in diameter , 30 cm in length ; stryker , san jose , ca , usa ) was applied in the level i area followed by fixation with an endoscope holder ( karl storz , tuttlingen , germany).(figs .
2 , 3 ) dissection of the anterior belly area ( level ia ) was performed ; then , level ib , which contains the submandibular gland , was dissected .
harmonic curved shears ( harmonic ace 36p ; johnson & johnson medical , cincinnati , oh , usa ) were used to cauterize minor vessels and dissect tissues .
the distal facial artery and vein were ligated with premium surgiclips ( covidien , dublin , ireland ) ; the submandibular ganglion , wharton 's duct , proximal facial artery and vein were cut after ligation with surgiclips .
we demarcated the level of omohyoid muscle , which is inferior to the border of level iii , and dissected lymphoadipose tissue superiorly from inferior margin using endoscope .
finally , dissection of the carotid artery and internal jugular vein was performed with posterior retraction of the scm .
micro - vascular surgery was performed in case 2 as usual manuals which have been done in conventional neck dissection.(fig .
4 ) donor vessels such as the proximal portion of facial artery , superior thyroid artery , and related veins were observed well under microscope .
. however , an assistant had to retract the skin flap with an army - navy retractor for visualization of the operative field .
gagner4 introduced endoscopic surgery as an alternative to conventional open neck surgery for parathyroidectomy in 1996 . since then , various trials for endoscopic surgery on the neck , including thyroidectomy5 , submandibular gland excision6 , sentinel node biopsy7 , and nd3 , have been performed .
this technique was developed gradually and is currently used in the treatment of many patients .
although postoperative period is not enough to discuss about results of postoperative scar , it can not be seen easily in the frontal view because the incision line is hidden along the posterior neck.(figs .
5 - 7 ) second , the procedure is minimally invasive and patients typically recover faster .
the incision line is also shorter than that of the conventional method . although more retraction of the skin flap is needed and causes stretching of the flap , this did not lead to any postoperative complications in the present cases .
we found that accurate nd could be obtained by the endoscopic approach . in the conventional method ,
it is difficult to dissect level iib precisely , but the endoscopic approach provides the best field of view on level ii and favorable fields of view on levels ib and iii .
however , this technique may not be appropriate for unskilled operators who have less experience with endoscopy or are unfamiliar with surgical anatomy .
endoscopy provides limited direct visualization compared to the conventional method , so it can be difficult to recognize the exact area where is being operated and control unexpected hemorrhages
first , the overlying skin tends to be thin and punctured easily , since there is no platysma muscle on level ia .
second , it is difficult to dissect the lymphoadipose tissues on level ia precisely compared with the conventional method because of the limited surgical field
. this technique may also not be appropriate for lesions on the floor of the mouth , near the midline , or along the anterior mandible where lymphatic drainage occurs to level ia .
first , they proposed that endoscopic surgery causes inconveniences to the operator and assistant due to limited space .
second , the robotic system has wrist articulated movement , which enables an unlimited operation field in a narrow working space compared to the endoscope .
third , the robotic system provides more assistance with its arm . however , its high cost is a distinct disadvantage of robotic surgery3,8 .
according to our experience , most patients diagnosed with oral cavity cancer are elderly , and are more concerned about cost than neck scarring . prominent postoperative scarring can be a major problem for patients .
endoscopic nd is a little bit more expensive than the conventional approach , but cheaper than robotic surgery , and causes fewer scars compared to the conventional approach .
thus , we consider endoscopic nd as an alternative to robotic surgery in terms of cost and postoperative scarring .
oral and maxillofacial surgeons should make an effort to gain experience in endoscopic surgery and robotic surgery .
unfortunately , there is no long - term follow - up information on patient outcomes involving these surgeries .
thus , it is impossible to compare oncologic outcomes between endoscopic nd and conventional nd .
 various surgical techniques , such as endoscopic surgery and robotic surgery , are developed to optimize the esthetic outcome even in operations for malignancy . a modified face - lift or retroauricular approach 
 are used to minimize postoperative scarring . 
 recently , robot - assisted surgery is being done in various fields and considered as favorable treatment method by many surgeons . 
 however its high cost is a nonnegligible fraction for many patients . on the other hand , endoscopic surgery , which is cheaper than robotic surgery , is minimally invasive with contentable neck dissection . 
 although it is a difficult technique for a beginner surgeon due to its limited operation view , we suppose it as an alternative method for robotic surgery . herein , we report two cases of endoscopic neck dissection via retroauricular incision with a discussion regarding the pros and cons of endoscopic neck dissection . 
I. Introduction
II. Cases Report
1. Case 1
2. Case 2
3. Surgical procedure
III. Discussion