Epidermoid cysts are histologically benign, grow slowly and account for 0.2% to 1.8% of intracranial tumors [4]. They have the same characters of CSF in T1 and T2 MRI and it is difficult to differentiate them by these sequences. However, they are restricted in diffusion studies [5]. The treatment of choice is surgical resection. Cases with residual tumors have a more likelihood of a septic meningitis and recurrence or progression [6]. Tumor capsule is most important factor that limits total resection of the tumors is the adherence of the capsule to the neurovascular tangles and brain stem, and trials of dissection of the capsule from these structures would bring more risks than benefits to the patients. As a result, it is advisable to leave the capsule behind or a part of it to avoid any permanent cranial nerve palsy. [7]
In the present study, it was noticed that in 62.5% of the patients an intra-operative missed part was detected after introduction of the endoscope. However, in 37.5% of the sample no missed parts were detected. Our study agrees in this context with the study performed by M. Abolfotoh and colleague which stated that (69%) patients had a “false negative” as residual tumor was found when the endoscope was used. These mutual findings emphasize the utility of the endoscope in visualizing and resecting tumor in microscopic blind spots and around corners [7].
In the present study, in the endoscopic-assisted group, 25% of the patients had new facial palsy. On the other hand, in the microscopic only group, 37.5% of the patients had new facial palsy. Furthermore, after calculating the correlation (p value), there is no significant difference in outcome regarding new facial palsy between the two groups. Our findings correlate with other studies which were done by Göksu and his colleagues, and Koerbel and colleagues who used the endoscopic-assisted technique revealed post-operative facial palsy were 22%, 32%, respectively [8]9.
Regarding the operative time, in the endoscopic-assisted group, 44% of patients had operative time equal or less than 5 and 56% of the patients had operative time between 5 and 7 h. On the other hand, in the microscopic only group, 62.5% of the patients had operative time equal or less than 5 h and 37.5% of the patients had operative time between 5 and 7 h. Consequently, after calculating the p value, there is no significant difference in outcome between the two groups regarding the operative time.
Review of the literature revealed three papers demonstrate epidermoid cyst excision by the endoscope. Schroeder and colleagues illustrated a series of eight cases with endoscopic-assisted resection of epidermoid tumor, however in only four patients the tumor excision was done under direct endoscopic visualization. They reported complete resection in three of eight patients and no residual at 12–98 months of follow-up. The rate of new post-operative CN palsy was (37.5%) overall, but much higher in the three patients who had complete resection of the capsule (66.6%) [4].
Safavi-Abbasi and colleagues described their series of 12 patients had endoscopic-assisted removal of CPA epidermoid cysts. They advised not to use the endoscope for resection of the tumors and advocated to use it for only for inspection of the hidden parts and resuming tumor excision by the microscope. They reported a 75% rate of total resection with only 17% of patients developing new or worsened CN paresis. They reported that there was no difference in long-term outcomes when comparing with the earlier series; however, they recommended the endoscope as a good tool for intra-operative visualization and evaluation tumor residual [10].
Finally, Ebner and colleagues [11] demonstrated the endoscopic application in five of seven patients with recurrent epidermoid tumor. They reported a total excision in four of the five patients. Four patients had temporary cranial nerve palsy and one had permanent nerve palsy.
The study includes more than one surgeon who had done the surgeries. This factor may affect the results of the study due to personal difference in surgery and intra-operative opinion. Some patients were lost to follow-up, so we do not have the full image about their disease course.
Presence of a long learning curve to obtain the skills regarding appreciation of the 2D image of the endoscope and how to hold it while using other instruments during dissection or coagulation are some of the difficulties in the scope of the endoscopic surgery in general. This affects our outcome at least in the first few cases.
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