Endoscopic Skull Base Surgery in Assiut University, Single Center Early Experience

Background: Endoscopic transnasal skull base surgery had started long time ago in different centers around the world for excision of skull base lesions with good results and more cost effectiveness. The aim of this study is to dis-cuss our early results in endoscopic skull base surgery and the development of the learning curve. Patients and Methods: We analyzed our experience regarding 25 patients presented to us in Neurosurgery Department, Assiut University Hospital, Assiut University, Assiut, Egypt in a period of 3 years (2015, 2016, 2017) and operated by endoscopic transnasal approach. All patients signed an informed consent. Results: With the highest percentage was pituitary adenoma 56%, pituitary apoplexy 12%, craniopharyngioma 12%, CSF rhinorrhea 12%, Planum sphenoidal meningioma 4% and suprasellar granuloma 4%. 88% of patients were operated without complications, 8% mortality rate postoperative, 12% complication rate and 76% complete improvement postoperative. Conclusion: Endoscopic skull base surgery is a safe approach to the skull base that needs a good experience, practice and good anatomical knowledge. Teamwork between a Neurosurgeon and ENT surgeon is a must for patient safety.


Introduction
The idea of reaching the skull base lesions endoscopically through the nasal rout has been started long time ago since the early start to find the ideal approach for  [4].
Guiot was the first neurosurgeon who used the endoscope to inspect the seller cavity after microscopic transsphenoidal surgery in 1960 followed by Michael Apuzzo in 1977 who started to use the endoscope to assist the microscope during the transsphenoidal surgery [1] [5].
In 1996, co-operation between neurosurgeon Hae-Dong Jho and otolaryngologist Ricardo Carrau at the University of Pittsburgh, made them start to perform a fully endoscopic skull base procedures with a strictly endonasal approach [1] [6].
Juo and Carrau reported and discussed their approach in a series of 50 patients at the Sixth European Workshop on Pituitary Adenomas (Berlin, July, 1996) [1] [7].
Since that time Jho-carrau endoscopic endonasal skull base approach was adopted and pioneered by multiple centers worldwide.
Endoscopic use in the endonasal skull base approach allowed more clear, superior panoramic view than microscope with the possibility of exploration of angels and deep structures that was very difficult to be seen by microscope. The new technique results in overall decrease in complication rate, improved tumor excision, better preserved nasal airway functions, better patient compliance and shorter hospital stay [1] [3] [7].
In Assiut University Hospital, we started our team work with Otolaryngology department since 2015 and did our first purely endoscopic transsphenoidal approach at the same year. We started with pituitary adenoma cases and after some time of gaining experience we started to do more difficult cases with more complicated pathology like meningiomas and craniopharyngiomas.
In this article, we reviewed our results in three years and discus the achievement and progress in our learning curve.

Patients and Methods
This is retrospective descriptive study to review the results of 25 patients who presented with skull base lesions that can be approached endoscopically throw a transnasal approach.
All cases presented to us at Neurosurgery department, Assiut University, Assiut, Egypt during a period of time of 3 years (January 2015 to December 2017).
Patients were carefully selected in a base of lesion accessibility transnasally and acceptance of the patients on the approach.
Our plane is to study the following variables: • Demographic data. Open Journal of Modern Neurosurgery • Rates of different pathologies presented to us.
• Presenting symptoms and signs.
• Rate of hormonal abnormalities in our study.
• Approaches used by our team.
• Extent of resection of excisable lesions.
• Outcome and improvement rate.
• Recurrence rate during the follow up period.
• The development of our learning curve.
All patients were informed about the approach, technique, possible complications, postoperative course and the alternative treatment possibilities, and they signed an informed consent with previously mentioned information.
We used the following storz endoscopic equipment's: • Hopkins ® straight forward telescope 0˚ and 30˚.
• Image 1 S camera head with 3 chip full HD view.
• Cold light fountain xenon nova ® 175 light source.
• Karl Storz clearvision ® II system for irrigation and intraoperative rinsing of the telescope lens.

Inclusion Criteria
All cases presented with seller-supra-seller lesions or any skull base pathology that need surgical intervention and can be operated throw trans nasal endoscopic approach.

Exclusion Criteria
• Lesions that appear to have para-seller extension.
• Lesions that appear to be invasive in nature.
• Inclusion of one or more of neurovascular structures within the lesion.
• Patients refuse the approach.

Preoperative Investigations
All patients diagnosed with a skull base lesions prepared with a preoperative investigation: Detailed history, general and neurological examination, ophthalmological examination (fundus, visual field and visual acuity) by ophthalmologist, nasal examination by otolaryngologist, complete hormonal profile, CAT scan of the head and paranasal sinuses and MRI of the head.

Operative Approach
After general anesthesia, patient positioned in supine position with head centered and slightly elevated 20˚, slightly tilted to the right and placed over a In cases of CSF rhinorrhea according to the site and the size of the defect, we mainly repair it with gel foam, fat, fibrin glue and vascularized nasal septal flap.

Follow Up
The mean follow up period was one year ± 6 months. An immediate follow up CAT scan is always done within the first 48 hours after surgery and a follow up MRI after 6 months. Follow up hormonal profile after 24 hour and after one month. Follow up urine output in the first 5 days after surgery.

Statistical Analysis
Data was collected in Excel sheet (Microsoft office 2016) then analysis was done.
The results were expressed in term of percentage.

Ethical Considerations
The study was conducted after getting ethical clearance and the permission from Assiut University teaching hospital administration. Thorough explanation of the purpose of the study and how data will be treated with respect and confidentiality was provided to the participants. All patients and their first-degree relatives informed about their condition, the disease, about the risks of surgery and anesthesia and also informed about the other surgical treatment options. All patients signed an informed consent.

Results
Open Journal of Modern Neurosurgery males and 12 females with a percentage 52% and 48% respectively.
The most common pathology was pituitary adenoma (56%) and pituitary apoplexy (12%) representing total (68%) as a pituitary related pathology. 3 patients with craniopharyngioma (12%). 3 patients with CSF rhinorrhea representing (12%), one case of planum sphenoidal meningioma and one case of suprasellar granuloma. All cases are diagnosed preoperatively by MRI of the brain, intraoperative gross pathology and postoperative histopathological examination (Table 1).

Preoperative Hormonal Profile
7 patients had disturbed hormonal profile preoperative, one patient with increased ACTH, 4 patients with increased prolactin and 2 patients with increased growth hormone.
Approaches used in our series were as following.
The most majority of the used approaches were the trans-sphenoidal transsellar approach which used in 17 patients (68%) all were pituitary adenoma cases.
In 3 cases of CSF rhinorrhea we made the skull base repair according to the

Extent of Resection
The total number of patients with a pathology needed to be excised was 22 patients. Gross total resection (GTR) was achieved for 16 cases (72.7%), near total resection (NTR) was achieved in 2 patients (9%) and partial resection (PR) was done for 4 patients (18.2%).

Hospital Stay
The mean hospital stay in our series was 5.32 days postoperative ranging from 3 to 10 days.
The outcomes in our series were as following.
There We have only one case of recurrent pituitary adenoma 2 years after the first operation during the study which needed reoperation (Table 3).

Discussion
Ancient Egyptians were the leaders and pioneers in medicine and surgery. They did brain surgeries for some intracranial diseases as founded in Egyptian papyrus writings from 17 th century BC which is believed to be written by Imhotep.
Ancient Egyptians were the first mankind to reach the brain throw the nose and skull base. They used this approach to do excerebration (evacuation of the brain) during the process of mummification [8].
In recent history, the trans-sphenoidal approach was reintroduced as a safe, minimally invasive approach to reach the pituitary gland and skull base pathologies to decrease the complications and cost of cranial surgeries [1] [3]. In middle of 2015 we upgraded our endoscopic system with a storz ® HD camera and monitor, also all the surgical instruments were upgraded.
As a benefit from using that advanced equipment's and gaining more experience in the approach we started to do the pituitary adenoma cases more efficiently and in much shorter intraoperative time, also we started to approach into more difficult pathologies like planum sphenoidal meningioma, craniopharyngioma, supraseller granuloma and CSF leak repair for the skull base.
In this study we reviewed our results in 25 patients who presented to us in  [9].
Pituitary adenoma was also the most common pathology in Mascarenhas et al. study 51.6% followed by craniopharyngioma 20.6% [9].
Regarding the extent of resection, the rate of GTR in our series was 72.7%, NTR was 9% and PR was 18. The mean hospital stay in our series was 5.32 days postoperative ranging from Open Journal of Modern Neurosurgery sons the make endoscopic skull base surgery has a more cost effectiveness than microscopic and cranial approaches for management of the same skull base lesions [11].
Recent studies also defined the endoscopic endonasal skull base approaches as a safe and effective alternative surgical approach for managing skull base lesions in pediatrics and elderly patients above 70 years old [12] [13].
Regarding the learning curve development, we believe that every neurosurgeon and ENT surgeon must start their endoscopic skull base surgery development with 3 very important steps, first carful anatomical study of the endoscopic skull base anatomy, second carful observation of endoscopic skull base surgeries with one of the professional endoscopic skull base teams, and third to do a lot of cadaveric dissection and hands on anatomical study with the endoscope.
Starting to operate after completing the first steps in learning curve is actually a start of the real learning curve as patient is the best teacher.
One way to assess the learning curve development is to evaluate the results and complications rate across time. Smith et al. estimated the number of cases needed to advance beyond the learning curve and reach the plateau in outcomes is to be between 18 and 34 patients [14].
Kshettry et al. divided his series into early cohort (20 patients) and late cohort (23 patients), they noticed that the extent of resection was significantly different between both groups, as the GTR was achieved in 65% of cases in the late cohort compared to 20% in the early cohort. Also, the same was for complication rate as they found that it was 14% in the early cohort and only 4% in the late cohort [15].
They concluded that there is significant improvement in the results and decrease in complications after operating 20 cases.
In this study there were 3 complicated cases and 2 of them ended by death.
CSF rhinorrhea in one case after partial excision of a planum sphenoidal meningioma, this case was in the first year of the study (2015) and duo to lake of enough experience, it was very difficult to dissect the tumor from the optic nerves and we preferred to stop to preserve the remaining vision, also during the repair we only inserted fat followed by a layer of facia Lata which resulted in postoperative CSF leak. After this case we started to do gasket seal repair and cover it by a naso-septal flab in all our cases with high flow leak intraoperative.
The 2 other complicated cases were also in the first year and early second year of this study which also was our early experience, both cases died postoperative.
One craniopharyngioma complicated with hypothalamic dysfunction and sever

Conclusion
Endoscopic skull base surgery is a safe approach for management of selected skull base lesions with a low complication, mortality rate and postoperative hospital stay which make this approach more cost effective. Learning curve needs at least one year of practice to reach its plateau. Certain time must be spent in studying the endoscopic skull base anatomy, cadaveric dissection and observation of a professional skull base team.

Limitations of the Study
• Early experience.
• Relatively small number of patients especially in craniopharyngioma and meningioma patients. • Equipment's limitations.

Recommendations
A further study is needed with more patients and specifies the teamwork experience in each lesion separately.

Conflicts of Interest
The authors declare that they have no competing interest.