The entry of neuroendoscopy into the field of transnasal pterygoidectomy for pituitary tumors is undoubtedly a milestone in the history of the development of surgical treatment of pituitary tumors. Although the traditional microscopic technique of transnasal butterfly resection of pituitary tumors is well established, neuroendoscopy has brought significant improvement in the quality of surgical treatment [1]. In addition neuronavigation techniques and intraoperative nuclear magnetic techniques have also provided excellent adjuncts to transsphenoidal pituitary tumor surgery. Here we report 375 cases of purely endoscopic transnasal pterygoid resection of pituitary tumors from December 2006 to December 2009.
1. Case data A group of 375 patients underwent simple endoscopic transsphenoidal pituitary tumor surgery from December 2006 to December 2009. There were 177 male cases and 198 female cases. The age ranged from 12 to 87 years, with a mean of 38.3 years. There were 320 cases of headache, 114 cases of abnormal amenorrhea, 37 cases of lactation, 63 cases of acromegaly, 23 cases of Cushing’s syndrome, 73 cases of visual acuity and visual field changes, 9 cases of actinic nerve palsy, 31 cases of elevated glucose, and 11 cases without any symptoms. The cases were followed up for 3-36 months and followed up successfully in 295 cases.
Neuroimaging: all were scanned by CT and MR of the head, and the tumors were located in the saddle area with diameters of 0.3-6.5 cm. 58 cases had diameters <1 cm, 290 cases had diameters of 1-4 cm, and 27 cases had diameters >4 cm. The cavernous sinus was invaded in 41 cases (10.9%). Tumor growth into the three ventricles was observed in 17 cases (4.5%). The tumor invaded the slope in 33 cases (8.8%).
Blood endocrine examination increased blood prolactin (PRL) in 137 cases, blood growth hormone (GH) in 63 cases, blood adrenocorticotropic hormone (ACTH) in 23 cases, blood thyroid stimulating hormone (TSH) in 2 cases, and PRL+GH in 3 cases. There were 20 cases of hypoendocrine function. The endocrine function was normal in 187 cases. The tumors with mildly elevated prolactin and immunohistochemical PRL (-) were classified as non-functional pituitary tumors, while those secreting multiple hormones were classified as endocrine and symptomatic type I pituitary tumors.
2.Surgical method Surgical instruments Neuroendoscope from Storz Medical Instruments, Germany, 4 mm diameter rigid mirror, automatic flushing pump. monitor and video acquisition system from Sony. The PLA General Hospital introduced the first high field strength iMRI (1.5T Calgary Crane System from IMRIS) in China at the end of 2008. The neurological navigation is Metronic or Brain Lab’s navigator.
Surgical operation: General anesthesia with conventional endotracheal intubation, patient in supine position, head tilted back 15-30° according to surgical requirements. The face and nasal cavity are disinfected with iodophor. The nostril is selected according to the characteristics of the tumor. The nasal mucosa was constricted by dilating the surgical channel with 0.01% norepinephrine and saline tampon under 0° endoscopic guidance along the approach between the middle turbinate and nasal septum. In the pterygoid sinus crypt, the opening of the pterygoid sinus is revealed. The bony structure of the anterior inferior wall of the pterygoid sinus is revealed by incising the mucosa of the septum along the opening of the pterygoid sinus inward and backward, and the bony lower part of the septum is enlarged and removed with a grinding drill, 1.0-2 cm in diameter. The saddle base is grinded with a grinding drill at the beginning of the middle of the saddle base and enlarged with biting forceps. The dura is electrocautery and cross-cut with a sharp knife, and the dura is cauterized to contract and expose the tumor, and the tumor is removed in pieces with a scraper, suction and microretrieval forceps. When the tumor is large enough, the residual tumor can be removed under direct endoscopic view by probing into the tumor cavity with the endoscope as the tumor is removed. When a large tumor is resected, the 45° endoscope is replaced to explore the dead space of the tumor cavity. After removal of the tumor, the tumor cavity was hemostatically gauzed and the saddle base was closed with an artificial dura. If there is intraoperative cerebrospinal fluid leak, a sandwich repair is made with a double-layer artificial dura. A nasal expansion sponge was placed between the middle turbinate and nasal septum.
Intraoperative MRI and neuronavigation: The first high field strength iMRI was introduced to the PLA General Hospital at the end of 2008, and 25 cases were used in this group, all of which were 〉3cm large adenomas and 〉4cm giant adenomas. The number of cases of neuronavigation in this group was 30.
Results1 Surgical outcome: 295 cases were successfully followed up. There were 234 cases (79.3%) of total resection, 56 cases (19.0%) of subtotal resection, and 5 cases (1.7%) of partial resection. Postoperative visual field improvement 27/31 (87.0%). The proportion of abnormal endocrine indexes reached normal after surgery: 68/88 (77.3%) for prolactin, 55/63 (84.1%) for growth hormone, and 18/23 (78.2%) for corticotropin. The improvement of endocrine symptoms was consistent with the changes in the above-mentioned examination indexes. Preoperative actinic nerve palsy recovered 5/9 (55.5%) postoperatively. The four cases of tumor recurrence or rapid growth of residual tumor during the follow-up period were all adolescent patients.
3. Surgical complications No death. Serious disability 1 (0.3%), a giant adenoma of 5.5 cm in diameter with tumor invasion and enlargement of the interpeduncular fossa, the patient developed symptoms of brainstem ischemia after surgery, the patient was in coma the next day, and was in a shallow coma when transferred to a rehabilitation hospital at one month and lost to follow-up. Residual stroke after surgery led to secondary surgery in 2 cases, including the above case, and the other case did not have any neurological dysfunction after secondary surgery. There were two cases of transient loss of vision (0.5%), both of which recovered before discharge. Seven cases (2.1%) of transient palsy of the articular or abducens nerve were due to surgical access to the cavernous sinus, all of which recovered within one month after surgery. Intraoperative cerebrospinal fluid leak or possible spinal fluid leak was repaired in 56 cases (14.2%), and the materials used were artificial dura mater, none of which was repaired with autologous tissue. Postoperative prophylactic lumbar pool cerebrospinal fluid drainage was performed in 13 cases. There were 2 cases (0.5%) of postoperative cerebrospinal fluid nasal leakage, all of which were cured by bed rest and lumbar pool cerebrospinal fluid drainage, and none of them had secondary repair. One case of subarachnoid hemorrhage (0.3%), with symptoms of one side of the motor nerve palsy and headache, was cured by draining bloody cerebrospinal fluid for 4 days without any residual symptoms. There were 6 cases (1.6%) of post-discharge nasal hemorrhage, one of which was embolized via external carotid artery; 14 cases (3.7%) of transient enuresis.
4. Results of the application of intraoperative MRI and neuronavigation Of the 25 cases of intraoperative MRI surgery, 17 cases underwent reoperation, which improved the degree of tumor resection. The combination of neuroendoscopic pituitary tumor surgery and high field intensity intraoperative MRI was tried for the first time in China, and the residual tumor was scanned and relabeled under navigation several times intraoperatively to guide the continuation of surgery. On two occasions, apparent strokes of the residual tumor were found, avoiding the possibility of secondary surgery. The 30 cases in which neuronavigation was applied were cases in which the anatomy of the pterygoid sinus was disturbed in the second operation or in which the tumor invaded paracranially or even crossed the cavernous sinus, and neuronavigation played a correct role in guiding the operation.
5. Discussion Since the emergence of transsphenoidal surgery in the last fifty years, the quality of surgery has been significantly improved and the surgical techniques have gradually matured. However, the development of neurosurgery is often accompanied by the development of related medical technology and breakthroughs, and the development and gradual improvement of endoscopic technology is the current hot spot of medical technology development. Neuroendoscopy is playing a wider and wider role in the field of neurosurgery, among which the technique of endoscopic transsphenoidal surgery to remove pituitary tumors has become more mature in foreign countries. In China, this technique has been promoted by Zhang Yazhuo and others, and it is also carried out in a considerable number of units and widely recognized.
The neuroendoscopic transsphenoidal pituitary tumor resection alone is still based on the traditional transsphenoidal surgery, and the access and basic anatomy of the surgery remain unchanged, as do the basic surgical techniques and strategies. The main difference between neuroendoscopic transnasal butterfly pituitary tumor surgery and the traditional surgical approach lies in the minimally invasive and expanded and clear visual field. None of the cases in this group showed splitting of the nasal vestibule and perforation of the nasal septum, even in pediatric patients with very small nostrils. Postoperatively, the nasal septum was only packed between the middle turbinate and the septum with expanded sponges to prevent adhesions, and the ipsilateral nostril could even be ventilated. It is not necessary to enlarge the anterior wall of the pterygoid sinus as much as microscopic surgery when dealing with cavernous sinus tumors. All these make the postoperative recovery fast and comfortable for the patient and make the surgery minimally invasive.
The expanded and clear endoscopic field of view is perhaps more critical for pituitary tumor surgery than the minimally invasive nasal cavity of endoscopic surgery. The endoscopic illumination for image taking and the angle of the endoscope allow for much expanded and clearer anatomy of the transnasal skull base endoscopically than microscopy. Endoscopic exposure of the saddle area allows clear identification of the bilateral optic canal bulge, bilateral internal carotid bulge, saddle base and slope depression. This group of endoscopic procedures appeared to be more comfortable in revealing the saddle base than under the microscope because there were more references, and the saddle base could be identified very accurately when the situation of the pterygoid sinus was very complicated. For large adenomas with high upward growth, the endoscope has a clear advantage. When microscopic surgery is performed to remove huge upward growing tumors, many cerebrospinal fluid leaks are caused by occluding the saddle base as far as possible to the anterior cranial fossa, many suprasellar hemorrhages are caused by blindly pulling the saddle septum, and many residual tumors are caused by not seeing the dead space under the saddle septum. In contrast, endoscopic surgery can change a considerable part of non-direct vision surgical operation into direct vision operation, which reduces the damage of blind operation and increases the degree of tumor removal. For tumors invading the cavernous sinus, microscopic surgery can only maximize the anterior wall of the anterior pterygoid sinus hoping to look directly at the anterior inferior wall of the cavernous sinus. However, the anterior inferior wall of the cavernous sinus can be easily reached endoscopically, and the lens can be placed in the saddle to look directly at the passage of the tumor from the medial wall of the cavernous sinus into the cavernous sinus, from which the tumor can be removed with much less potential for internal carotid artery and cranial nerve injury. The complications of this group of endoscopic procedures are described in detail in this study, and in only one case out of the total number of cases did irreversible severe neurological impairment occur. This is a significant improvement over our previous transnasal pterygoid pituitary tumor surgery, and most reports in the literature, both nationally and internationally, have clarified the same point. The safety of our group of endoscopic procedures also reached the mainstream level in the foreign literature. The use of endoscopic transnasal butterfly surgery is the key to this improved surgical outcome, in addition to the continued accumulation of surgical experience.
Compared to conventional microscopy, endoscopic transnasal butterfly pituitary tumor surgery also has some weaknesses. The main one is that the surgeon cannot perform all the movements. The operator either has to support the mirror with one hand, which is one less hand to operate with. Or if the mirror is given to the assistant to support, then the mirror and the movements will be very demanding to work with. It is also very inflexible if a fixed frame is used. Some large centers abroad have ENT surgeons as assistants to help the operator, and our group’s solution to this problem is to improve some instruments so that unskilled assistants can also help the operator. However, with the improvement of endoscopes and endoscopic instruments, these difficulties can be overcome.
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