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Aim: To demonstrated demyelination and remyelination of the optic nerve histologically by electron microscopy in an experimental model similar to the compression of pituitary adenomas on the optic chiasm., Material and Methods: The rats were fixed to a stereotaxic device under deep anesthesia, and a balloon catheter was placed under the optic chiasm through a burr hole which was in front of the bregma in accordance with the brain atlas of rats. The animals were divided into five groups (n=8): control, mild compression demyelination, severe compression demyelination, mild compression remyelination, severe compression remyelination. The fine structures of the tissues obtained were evaluated using electron microscopy., Results: We found a significant difference in the severity of degeneration when comparing group 1 with group 5 (p < 0.001); there was no degeneration in group 1 rats and severe degeneration in all of the group 5 rats. Oligodendrocytes were found in all rats in group 1 and none of the rats in no group 2. The nuclei were preserved in the group 1 rats but damaged in all of the group 5 rats. There were no lymphocytes or erythrocytes in group 1 and all positives in group 5., Conclusion: This technique, which induced degeneration without causing damage to the optic nerve with toxic or chemical agents, revealed Wallerian degeneration similar to tumoral compression. After compression relief, the optic nerve remyelination process can be better understood, particularly for sellar lesions. In our opinion, this model may guide future experiments to identify protocols to induce and accelerate remyelination.

Aim: To determine the limits, to show the effect of tumor consistency on resection rates and to present the sinonasal morbidity rate in patients with tuberculum sellae meningiomas who underwent endoscopic endonasal approach., Material and Methods: We reviewed the medical data, radiological images, and surgical videos of the patients with pathologically confirmed meningiomas originating from the tuberculum sellae and they were operated via endoscopic endonasal approach between August 1997 and December 2020. We used our endoscopic classification based on infrachiasmatic corridor. In this classification, tumors were divided into those within the infrachiasmatic corridor and proximity of the optic nerve, internal carotid artery, and anterior artery complex and those outside the infrachiasmatic corridor., Results: Gross total resection was achieved in 45/60 (75%) patients. We found that tumor consistency was statistically significant on resection rates. Simultaneously, tumor median diameters on the anteroposterior (≤21.15 mm), transverse (≤19.75 mm), and superoinferior (≤15 mm) axes were statistically significant on resection rates., Conclusion: In summary, the most important factor in selecting the surgical technique is the tumor size. Infrachiasmatic corridor boundaries are the limitations of endoscopic approach. These limitations can change based on surgeon's experience. Also, tumor consistency is a factor that affecting degree of tumor resection rates.

Aim: To determine whether the endoscopic transorbital (ETO) approach could be an alternative and a safer route to access the cavernous sinus (CS) lateral compartment., Material and Methods: ETO technique was studied on 3 cadavers and 6 CSes of these cadavers. Endoscopic dissection was visualized with a 0-degree angle endoscope and recorded with fiberoptic cable, light source and camera system and digital video recording system., Results: Superior orbital fissure (SOF), optic canal (OC), anterior ethmoidal artery (AEA) and posterior ethmoidal artery (PEA) foramens were visualized with periorbital dissection. Anterior wall of CS was reached after drilling the optic strut (OS). When the wall was opened, CS lateral and anteroinferior compartments were visualized. Internal carotid artery (ICA) were visualized from proximal ring to the last 2 cm of paraclival carotid artery. Cranial nerves (CNs) within the CS and the course of the interclinoid ligament were revealed., Conclusion: The transorbital endoscopic method is an alternative approach to other techniques for accessing the lateral and anteroinferior compartments of CS. The advantages, disadvantages and limitations of the technique have been determined.

Aim: To evaluate the cerebrospinal fluid (CSF) flow dynamics in the aqueductus sylvii of patients with obstructive hydrocephalus who underwent endoscopic third ventriculostomy (ETV) and to predict ventriculostomy patency via aqueduct flow measurements., Material and Methods: Twenty-four patients with obstructive hydrocephalus caused by primary aqueduct stenosis who underwent ETV were included in the study. All the patients underwent conventional and cine magnetic resonance imaging before and after treatment. The flow of CSF in the aqueduct of Sylvius and prepontine cistern was assessed, and the diameter of the third ventricle was also measured. Increase in the aqueduct flow velocity after a successful ETV was supported by the assumption physical model that highlights a possible mechanism that explains the clinical findings., Results: The flow pattern and velocity in the prepontine cistern and aqueduct were normal in 17 out of 24 patients who responded to ETV clinically. However, seven patients who did not respond to ETV had an abnormal flow pattern in both the prepontine cistern and aqueduct., Conclusion: The flow pattern in the aqueduct was normalised and velocity was increased compared with those of preoperative values after a successful ETV. The flow of CSF in the prepontine cistern is routinely used for ventriculostomy patency assessment. In addition, aqueduct measurements may be useful in predicting ventriculostomy patency. The physical model provides valuable insights on a possible mechanism that affected the experimental data.

Aim: To determine the feasibility, advantages, and disadvantages of using a robot for holding and maneuvering the endoscope in transnasal transsphenoidal surgery., Material and Methods: The system used in this study was a Stewart Platform based robotic system that was developed by Kocaeli University Department of Mechatronics Engineering for positioning and holding of endoscope. After the first use on an artificial head model, the system was used on six fresh postmortem bodies that were provided by the Morgue Specialization Department of the Forensic Medicine Institute (Istanbul, Turkey)., Results: The setup required for robotic system was easy, the time for registration procedure and setup of the robot takes 15 minutes. The resistance was felt on haptic arm in case of contact or friction with adjacent tissues. The adaptation process was shorter with the mouse to manipulate the endoscope. The endoscopic transsphenoidal approach was achieved with the robotic system. The endoscope was guided to the sphenoid ostium with the help of the robotic arm., Conclusion: This robotic system can be used in endoscopic transsphenoidal surgery as an endoscope positioner and holder. The robot is able to change the position easily with the help of an assistant and prevents tremor, and provides a better field of vision for work.

Aim: The aim of this study was to report our experience with a 64-channel computerized tomography (CT) scanner as the primary choice on the detection of intracranial aneurysms. Comparison of intracranial aneurysms with the simulated images obtained via three-dimensional computed tomography angiography (3D-CTA) in pterional approach was also aimed., Material and Methods: Among 288 consecutive patients who had intracranial aneurysms detected on 64-slice CTA, a total of 337 aneurysms were detected. CTA simulation images and intraoperative images were compared with regards to size, shape, and orientation., Results: In one of the 22 CTA-negative cases, one aneurysm was detected in DSA and an additional aneurysm was detected in a patient operated with CTA. Aneurysm size, shape and direction were error free except a few cases. However, CTA was found to be insufficient to show particularly perforating arteries that were smaller than 2 mm in size., Conclusion: As a fast and noninvasive technique, CTA can be used as an initial examination in subarachnoid hemorrhage. Keeping the fact that there can be insufficiency in showing particularly small aneurysms in mind, DSA should be performed on CTA-negative cases and required cases.

Aim: We examined the cavernous sinus invasion and tumor biological markers that influence the remission rate. Cavernous sinus (CS) invasion was evaluated radiologically. Tumor biological markers consisting of the tumor cell growth parameter Ki-67 and the cancer cell vasculature marker of vascular endothelial growth factor (VEGF) were evaluated., Material and Methods: We examined 28 immunohistochemically proven GH secreting pituitary adenoma patients who had been operated via endoscopic transsphenoidal surgery at Department of Neurosurgery, Kocaeli University Hospital between 2003 and 2008. Pathology preparations were stained with Ki-67 and VEGF. We evaluated remission at the postoperative 6th week. The basal GH level, nadir GH level and IGF-1 levels were evaluated to determine remission., Results: Remission was achieved in 6 of 18 patients (33%) who had cavernous sinus invasion. Remission was achieved in 7 of 10 patients (70%) who did not have cavernous sinus invasion. There was no correlation between the Ki-67 proliferation index and cavernous sinus invasion (p=0.593). There was a positive correlation between VEGF expression and cavernous sinus invasion (p=0.03)., Conclusion: The remission rate found less in the cavernous sinus invasion group. No association was found between Ki 67 proliferation index and cavernous sinus invasion. We found that a positive correlation between VEGF expression and cavernous sinus invasion. VEGF expression can therefore indirectly affect remission via cavernous sinus invasion.

Aneurysms protruding into sellae may mimic pituitary tumors by compressing adjacent cranial nerves. Carotid-Cavernous aneurysms are rarely associated with mortality, and surgical intervention is recommended especially for neuro-ophthalmologic progression. In this report we presented a 51-year-old woman who had severe headache and neuro-ophthalmologic signs with the initial diagnosis of pituitary apoplexy on MRI (Magnetic Resonanse Imaging). However preoperative CTA (Computed Tomography Angiography) revealed a carotid cavernous aneurysm protruding into sellae. The patient underwent endovascular intervention and endoscopic transphenoidal approach for the removal of the hematoma compressing the cranial nerves. The patient's neuro-ophthalmologic symptoms were improved during the follow-up, which may be related due to rapid evacuation of the hematoma.

Aim: Endoscopic third ventriculostomy (ETV) is currently considered the best alternative to shunt systems in the treatment of triventricular hydrocephalus. However, there has been very few published data about the anaesthetic management and the complications of ETV procedure in infants. In this report, we detail our experience with 57 infants, who underwent ETV as an initial treatment for obstructive triventricular hydrocephalus between 2003 and 2010., Material and Methods: Anesthesia chart-records were retrospectively investigated and perioperative data were classified according to the stages of the procedure., Results: In this series, mean heart rate values showed a statistically significant difference in the period concerning the balloon dilatation of ventriculostomy orifice. An episode of bradycardia occurred in 2 patients during balloon dilatation. After the deflation of the balloon, bradycardia resolved immediately without administration of any medication. Video recordings of those two patients revealed that one of them had a narrow and opaque tuber cinereum, and the other had a shallow interpeduncular cistern., Conclusion: During ETV procedure in infants, bradycardia may be a serious complication especially when performing balloon dilatation of the ventriculostomy orifice. We believe that close communication between the surgeon and the anaesthetist is extremely essential in this stage of the procedure.

Aim: Fibrous dysplasia is a benign disease in which medullary bone is replaced by fibro-osseous tissue, and causes distortion and overgrowth of the involved bone and represents about 3% of all bone tumors. There is variability in the manifestation of Fibrous Dysplasia lesions with imaging techniques due to their proportional variations of fibrous to osseous tissue. Radiological differential diagnoses include meningioma, chordoma on MRI and Paget disease on CT imagings., Material and Methods: We report three cases of monostotic fibrous dysplasia, affecting clivus, tuberculum sellae, and sphenoid sinus through the pterygopalatine fossa. We performed pure endoscopic transphenoidal approach for those three cases with the guide of neuronavigation. Extended approach was used via binostril for fibrous dysplasia of clivus and Tuberculum sellae., Results: Radiologic report revealed chordoma and meningioma for the two cases and fibrous dysplasia for the last case. Total resection of tuberculum sellae, subtotal resection of clivus and partial resection of sphenoid sinus lesions were performed. Pathology diagnosis were fibrous dysplasia in all three patients., Conclusion: Histopathological sampling provided by surgical approach should be obtained to establish the final diagnosis. Endoscopic approaches are convenient for skull base lesions even for biopsy or curative resections providing panoramic view and avoid brain retraction.

Aim: The effect of memantine administration on hippocampal neurons of the infantile rats with kaolin induced hydrocephalus was investigated., Material and Methods: Hydrocephalus was induced by injecting kaolin into the cisterna magna of 3-weeks old Sprague-Dawley rat pups. One group received a single daily dose of 20mg/kg memantine i.p. following hydrocephalus induction for a period of two weeks. By the end of the two-week period, animals were radiologically evaluated by magnetic resonance imaging and then sacrificed to get their cerebrums removed. Both immunohistochemical analysis of nitric oxide synthase activity and quantification of spared neurons in CA1, CA2 and CA3 regions of hippocampus were performed., Results: In hydrocephalus-induced rats considerable neuronal loss associated with significantly increased nitric oxide synthase immunoreactivity were determined in all hippocampal regions. However, memantine treated rats showed significantly higher number of spared neuron counts and reduced nitric oxide synthase immunoreactivity in CA1 and CA2 regions compared with the non-treated rats., Conclusion: The findings of the study show that hippocampal neurons may constitute important targets for injury secondary to hydrocephalic process in experimental infantile hydrocephalus. Early anti-excitotoxic treatment with memantine seems to have a neuroprotective effect especially in the CA1 and CA2 subunits of the hippocampus.

Aim: Fenestration of Liliequist membrane (LM) during endoscopic third ventriculostomy (ETV) is extremely important for the success of the procedure. It is noteworthy that LM usually shows a tough and dense stucture in long-standing hydrocephalus cases different from its usual arachnoidal membrane-like structure observed in new-onset hydrocephalus cases. The structural variation of LM in different hydrocephalic states was investigated histologically in this study., Material and Methods: Specimens of LM obtained during endoscopic fenestration in 11 cases were examined under transmission-electron-microscopy. Six cases had long-standing hydrocephalus and five had new-onset triventricular hydrocephalus. None of the cases had a history of infection or hemorrhage., Results: In cases with long-standing hydrocephalus, ultrastructural examinations revealed the existence of regular and dense bundles of type-I collagen among the fibroblast-like cells, which were closely connected by dense desmosomes and gap-junctions. In cases with new-onset hydrocephalus, it was observed that the cells usually had long cytoplasmic extentions and were connected with loose desmosomes. Sparse type-I collagen bundles were observed rarely among the cells., Conclusion: These results suggest that the structure of LM may change with the duration of the hydrocephalic process. This may help explain the tough and dense LM stucture observed during the ETV procedure in cases with long-standing-hydrocephalus.

Aim: There are two major problems for the pituitary adenomas invading the Cavernous Sinus (CS); differentiation of extension and invasion and inability to demonstrate the medial wall via preoperative imaging methods. Two important corridors are defined in endoscopic cavernous sinus approaches; the lateral and medial corridor., Material and Methods: A retrospective analysis was performed in 400 endoscopic transphenoidal approaches and 360 pituitary adenomas underwent endoscopic transphenoidal surgery in our department between September 1997 and December 2010. 48 patients affected by the tumours involving the cavernous sinus were included in this study., Results: We performed an intraoperative evaluation of cavernous sinus invasion considering visualization of the medial wall defect, intracavernous ICA segments, minor tumour extensions through small focal pit holes of the medial wall of CS or confirming carotid segments of CS by micro-doppler. Cavernous sinus involvement was classified into three types according to the medial and lateral corridor extension of the tumor as 25 isolated medial corridor involvement (Type I), 5 isolated lateral corridor involvement (Type II) and 18 total involvement (Type III)., Conclusion: Our classification depends on fully surgical endoscopic approach supported by neuroimaging techniques and anatomical studies and shows a good predictive value for all cavernous sinus involvement.

Aim: Smoking is an extremely important risk factor for subarachnoid hemorrhage and seems to increase rupture risk of unruptured aneurysms by accelerating their growth rate. The aim of the study was to investigate the effect of smoking on the luminal diameter with wall thicknesses of rat basilar arteries and to detect alterations of inducible nitric oxide synthase and endothelin-converting enzyme -1 in the endothelial cells., Material and Methods: Rats were divided into two groups. The level of middle pons slices were embedded in paraffin before they were stained with hematoxylin and eosin. Rabbit anti-human inducible nitric oxide synthase and endothelin converting enzyme-1 antibodies were used., Results: Significant decrease of the vessel luminal diameter and increase of the vessel wall thickness were found in chronic smokers in our study. There was a linear and significant (p= 0,023, r =0,704) correlation between thickness of the wall and endothelin converting enzyme-1 immune reaction. Correlation was not found with inducible nitric oxide synthase (p > 0.05)., Conclusion: This study on the comparison of vessel luminal diameter and vessel wall thickness with inducible nitric oxide synthase and endothelin converting enzyme-1 immune reactions revealed that the main effect of smoking on the vessel wall is associated with endothelin converting enzyme-1.