The presence of a conchal sphenoid sinus is typically considered to be one of the contraindications for the use of transsphenoidal route due to the difficulties of intraoperative localization and exposure of the sellar floor. With advances of the application of microscopy and the application of neural navigation technology, we are able to safely carry out transsphenoidal resection of pituitary adenomas with conchal sphenoid sinus. Compared with the non conchal sphnoid sinus pituitary adenoma, the channel of the transsphenoidal surgery will be smaller, the operation space will be limited, it is more difficult that the surgical instrument be operating in this narrow corridor. We consider that surgical resection of pituitary adenoma with conchal sphnoid sinus under microscope have more advantages than endoscopic transsphnoidal surgery due to microscope surgery need less surgical instruments than endocopic surgery. the distance of the internal carotid artery of the cavernous segment should be carefully measured preoperatively, which determines the size of corridor of TSS surgery[i], which is the adverse aspect to exsect pituitary lesion with conchal sphnoid sinus; during the procedure of drilling conchal sphnoid sinus we should be intermittently apply the probe of neuronavigation to confirm the distance of carotid arteries and to adjust the direction of surgery path to prevent injury the internal carotid arteries accidentally.
But in these four patients of pituitary adenoma with conchal sphnoid sinus, we found, during TSS procedure, that sphenoid boney tissue is relatively loose and easy to drill away, hemostasis of bone surface is not difficult, the sellar floor dura mater is smooth, few vessel, easy to open, Except one case which have very small intercavernous sinus is not caused a significant impact to operation, which may be due to bilateral cavernous sinus blood circulate through a large number of cancellous bone communication instead of the intercavernous sinus of sellar dura, so poor blood supply through sellar dura, bleeding was significantly reduced more rather than those with pneumatized well sphenoid sinus. Loose bone within the sinusoids is easy to drill, bleeding could be stop immediately by the heat and bone meal, when necessary, bone wax can also be used to stop bone bleeding easily. At the same time, we found that the size of pituitary adenoma with conchal sphnoid sinus are smaller, the average diameter is about 1.9cm, and the tissue of tumor is soft easy removal, and lesions are without rich blood supply, less bleeding. These finds need further research because there are exist same papers already published about that some pituitary adenoma with conchal sphnoid sinus have larger diameter[ii]. Therefore, we believe that pituitary adenoma with conchal sphnoid sinus can relatively safe be resected by transsphenoidal surgery with aid of the neuronavigation and achieve satisfactory therapeutic effect, this type PA is no longer a contraindication to transsphenoidal surgery.
To study the anatomy of sphenoid sinus we will find that sphenoid sinus can be divided into conchal type, saddle type, and saddle according to the degree of pneumatolysis; There is study show that the degree of pneumatization of sphenoid sinus play an important role to safely carry out TS surgery, suggest that the circumstance of sphenoid sinus should be full evaluated preoperatively[iii]. Our experience is not only must carry on the MRI scaning preoperatively, also must carry on the thin layer CT scanning of saddle area that would give us more information to comprehensively understand degree of pneumatolysis of sphenoid sinus, and to know the relationship between the internal carotid artery and sphenoid sinus. Conchal type of sphenoid sinus occurrence rate is very low, Song Tao team found that the incidence of sphenoid sinus of nonpneumatized is 6% in Chinese population[iv], that is consistent with our center study found. Conchal type of pituitary adenoma is a taboo for transsphenoidal surgery in the past, this is due to the thickening of the sphenoid sinus bone cause obstacles to surgery corridor, making the surgeon lost and increasing the risk to injury the internal carotid artery; The application of neuronavigation can better solve this problem, with the aid of neuronavigation improve the success rate of surgery; reduce the rate of complication of operation[v]. In addition, because the bone structure of sphenoid sinus and skull base those structure scanning by MRI is less clear than CT scanning and Studies have shown that error of navigation registration base on CT image is smaller than MRI, we choose CT‘s neuronavigation, the accuracy is reliable. we are not machinery in accordance with the instruction of the navigation, but we should combin with the experience of surgeons and the observation of sella anatomy, at the same time, to judge the right direction of surgery.
In this study we think pituitary adenomas with conchal sphenoid sinus, the surgery corridor is narrow, so microscopic resection with the aid of neuronavigation has more certain advantages than endoscopic TSS. microscopic surgery use the surgical instruments less than endoscope TTS, so the microscopic TTS are easier to operate, less time needed for surgery; endoscopic observation Angle more wide than microscope[vi], but we found that this type of pituitary adenomas tumors are smaller, no obvious intercavernous sinus, don't need more viewing Angle in resection of pituitary adenoma with conchal sphenoid sinus. although neural endoscopic resection of pituitary adenoma surgery is more and more widely applied, according to our experience, microscopic transsphenoid surgery applying to conchal type of pituitary adenoma has some advantages. at the same time we found that between pituitary adenomas with conchal sphenoid siuns and other type pituitary adenomas exist certain differences, such as anatomical differences, tumor biological behavior characteristics and so on, it remains to be further research.
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[ii] Song Y, Wang T, Chen J, Tan G. Endoscopic transsphenoidal resection of sellar tumors with conchal sphenoid sinus: A report of two cases. Oncol Lett, 2015, 9(2):713-716.
[iii] Hamid O, El Fiky L, Hassan O, Kotb A, El Fiky S. Anatomic Variations of the Sphenoid Sinus and Their Impact on Trans-sphenoid Pituitary Surgery. Skull Base, 2008, 18(1):9-15
[iv] Lu Y, Pan J, Qi S, Shi J, Zhang X, Wu K. Pneumatization of the sphenoid sinus in Chinese: the differences from Caucasian and its application in the extended transsphenoidal approach. Journal of anatomy. 2011;219(2):132-42.
[v] Furtado SV, Thakar S, Hegde AS. The use of image guidance in avoiding vascular injury during trans-sphenoidal access and decompression of recurrent pituitary adenomas. J Craniomaxillofac Surg. 2012;40(8):680-684.
[vi] Zaidi HA, Awad AW, Bohl MA, Chapple K, Knecht L, Jahnke H, et al. Comparison of outcomes between a less experienced surgeon using a fully endoscopic technique and a very experienced surgeon using a microscopic transsphenoidal technique for pituitary adenoma. J Neurosurg. 2016;124(3):596-604.