الفهرس 
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Abstract
Endoscopic techniques for cerebellopontine angle (CPA) surgery have been well applied nearly for all the CPA lesion due to its small craniotomies and excellent visualization. The endoscopic-assisted technique provides a completely different view when comparing with the microscope only approaches. Endoscopes have a wide-angle viewing field leading to a panoramic view. Therefore, even lesions which are not located in front of the endoscope tip can be detected early. (1) This is a major advantage in narrow and deep corridors. Endoscopes with angulated lens gives the ability to inspect around a corner or behind neurovascular structures which is very useful in skull base surgery. With the use of the endoscope, the surgeon brings his eye close to the target area with perfect illumination even in the depth.(1)(121) Another significant advantage of the endoscope compared with the microscope is the excellent depth of field. Refocusing which is frequently required with the microscope particularly with high magnification is rarely necessary. Of course, the endoscope has also limitations. The major drawback of the endoscope is the lack of true 3D viewing. (3)(122)(123) Our study proved that in 62 % of the cases, an intra-operative residual lesion was detected after introduction of the endoscope. These finding agrees in this context with other studies dealing with. These findings emphasize the utility of the endoscope in visualizing and resecting tumour in microscopic blind spots and around corners. Our study noted that is a statistically significant difference in outcome regarding the post-operative residual between the two groups. Given the data in the endoscopic-assisted group (3/16) patients have post- operative residual(18.8%). However, in the microscopic only group, (9/16)patients have post-operative residual(56.3%)This prospective study highlighted that there is no difference in outcome regarding facial palsy between the endoscopic-assisted approach and microscopic only approach. This finding was controversial because the previous studies were divided regarding this point, some proved that there is a significant difference and the others denied. In our study there is no significant difference in outcome regarding the post-operative hydrocephalus between the two groups. As in the endoscopic-assisted group, (2/16) patients have post-operative hydrocephalus (12.5%). On the other hand, in the microscopic only group, (3/16)patients have post-operative hydrocephalus(18.75%).This study proved there is no significant difference in outcome in the post-operative CSF leak between the two groups. As in the endoscopic- assisted group, (3/16) patients have post-operative CSF leak (18.75%). On the other hand, in the microscopic only group, ( (2/16) patients have post- operative CSF leak(12.5%). Consequently, after correlation calculation, no significant difference in outcome regarding post-operative CSF leak between the two groups. Regarding the operative time and intraoperative blood loss, the difference in outcome between the two groups was small and insignificant. In summary the main differences between the two approaches which affected the outcome were the intraoperative missed lesion detection and the post-operative residual. The intraoperative missed lesions were removed by help of the endoscope. The post-operative residuals required other lines of management like follow up of the lesion or gamma knife team consultation. The literature has highlighted the application of the endoscope as one of the minimally invasive techniques. Our present study not only covered the nearly all parts and outcomes of the endoscopic-assisted technique, but also compared it with the microscopic technique to figure out any significant difference in outcome between the two approaches. The additional use of the endoscope provides an extra access to a different CPA tumour and was effective in expanding the scope of the traditional approaches. It also increased the surgeon’s ability to evaluate the extent of resection intraoperatively. Most importantly, it improved the ability to achieve additional safe tumour resection, which may be considered the greatest means of reducing long-term patient morbidity. Based on our study results, we believe that endoscopes can be used safely during surgery of CPA lesions. As an adjunct to the operative microscope, this modality improves visualization of bony, neural, and vascular structures while minimizing retraction. Endoscopic exploration of the IAC and other neural foramina after tumor removal using the angled endoscope can demonstrate the presence of residual tumor, left unidentified. based on the study results we recommend the use of the endoscopic assisted technique in excision and treatment of CPA lesions such as vestibular schwannoma, meningioma, trigeminal neuralgia and hemifacial spasm. These recommendations based on the superiority of the endoscopic assisted technique over the microscopic approach in detection of intraoperative missed lesion in canals, corridors and structure of the posterior fossa. In addition, after assessment of the difference in post- operative imaging between the two group, we advocate the use of the endoscopic assisted approach due to its role in reduction the incidence of the post-operative residual