Researcher:
Akyoldaş, Göktuğ

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Göktuğ

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Akyoldaş

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Akyoldaş, Göktuğ

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2018 - 201972020 - 202314

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    Can right-handed surgeons insert upper thoracic pedicle screws in much comfortable position? Right-handedness problem on the left side
    (Korean Neurosurgical Soc, 2018) Ozdemir, Nail; Acaroglu, Emre; Akyoldaş, Göktuğ; Şentürk, Salim; Yaman, Onur; Faculty Member; Doctor; Doctor; School of Medicine; N/A; N/A; Koç University Hospital; 203677; N/A; 219524
    Objective : Thoracic pedicles have special and specific properties. In particular, upper thoracic pedicles are positioned in cranio-caudal plane. Therefore, manipulation of thoracic pedicle screws on the left side is difficult for right-handed surgeons. We recommend a new position to insert thoracic pedicle screw that will be much comfortable for spine surgeons. Methods : We retrospectively reviewed 33 patients who underwent upper thoracic pedicle screw instrumentation. In 15 patients, a total of 110 thoracic pedicle screws were inserted to the upper thoracic spine (T1-6) with classical position (anesthesiologist and monitor were placed near to patient's head. Surgeons were standing classically near to patient's body while patients were lying in prone position). In 18 patients, a total of 88 thoracic pedicle screws were inserted to the upper thoracic spine with the new standing position-surgeons stand by the head of the patient and the anesthesia monitor laterally and under patient's belt level. All the operations performed by the same senior spine surgeons with the help of C-arm. Postoperative computed tomography scans were obtained to assess the screw placement. The screw malposition and pedicle wall violations were divided and evaluated separately. Cortical penetration were measured and graded at either : 1-2 mm penetration, 2-4 mm penetration and > 4 mm penetration. Results : Total 198 screws were inserted with two different standing positions. Of 198 screws 110 were in the classical positioning group and 88 were in the new positioning group. Incorrect screw placement was found in 33 screws (16.6%). The difference between total screw malposition by both standing positions were found to be statistically significant (p=0.011). The difference between total pedicle wall violations by both standing positions were found to be statistically significant (p=0.003). Conclusion : Right-handedness is a problem during the upper thoracic pedicle screw placement on the left side. Changing the surgeon's position standing near to patient's head could provide a much comfortable position to orient the craniocaudal plane of the thoracic pedicles.
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    Dynamic stabilization of the lumbar spine using the Dynesys® system
    (Turkish Neurosurgical Soc, 2020) Cevik, Orhun Mete; Akyoldaş, Göktuğ; Süzer, Süleyman Tuncer; Sasani, Mehdi; Öktenoğlu, Bekir Tunç; Özer, Ali Fahir; Faculty Member; Faculty Member; Faculty Member; Faculty Member; Faculty Member; School of Medicine; School of Medicine; School of Medicine; School of Medicine; School of Medicine; 203677; 221691; 219451; 220898; 1022
    AIM: To present the clinical results in patients with minor instability with "Dynesys (R)"a soft spinal stabilization system. Material and Methods: A total of 83 patients were operated upon and the Dynesys (R) system was applied. Indications for surgery included painful degenerative disc disease, degenerative spondylolisthesis and lumbar canal stenosis. Results: The results for the Dynesys (R) system were satisfactory, and we have calculated the overall complication rate to be 20.4% (n=17), which is in agreement with the literature. Conclusion: The Dynesys (R) dynamic stabilization system effectively protects lumbar motion and achieves lumbar stability in patients with lumbar spinal problems. Our clinical result support literature that Dynesys (R) system is a strong alternative to fusion and instrumentation system in patient with chronic instabilities.
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    Long-term results of Gamma Knife radiosurgery for facial nerve schwannomas
    (Taylor & Francis, 2020) Şirin, Alperen; Yılmaz, Meltem; Şengöz, Meriç; N/A; N/A; Akyoldaş, Göktuğ; Peker, Selçuk; Faculty Member; Faculty Member; School of Medicine; School of Medicine; 203677; 11480
    Objective: Long-term outcomes of eleven cases of facial nerve schwannoma were evaluated and the related literature was reviewed to determine the efficacy of Gamma Knife radiosurgery for treating patients with facial nerve schwannoma. Methods: Eleven patients with facial nerve schwannoma (7 women and 4 men; mean age, 44.2 years; range, 19-73 years) underwent Gamma Knife radiosurgery. The most common symptoms were facial palsy (n = 10) and hearing loss (n = 7). Five patients presented with headache. Two patients had undergone prior resection. The patients' clinical and radiographic data were evaluated retrospectively. Results: For the 11 cases of facial nerve schwannoma, mean tumor volume was 3.1 cm(3) (range, 0.4-7.4 cm(3)) and the mean marginal dose applied was 11.9 Gy (range, 11-13 Gy). The mean follow-up period was 84.3 months (range, 66-117 months). Tumor control was achieved in all patients. At the time of writing, four patients experienced tumor volume regression and the other seven were in stable condition. During follow-up, nine patients experienced no change in their facial function, two experienced deteriorated facial function, and none developed new facial palsy. Ten patients who had serviceable hearing prior to Gamma Knife radiosurgery retained their hearing. Conclusions: Gamma Knife radiosurgery achieves excellent results with respect to tumor control for 7 years on average. In addition, Gamma Knife radiosurgery provides good results in facial nerve and hearing function at long term. Our series demonstrates that Gamma Knife radiosurgery is an effective and safe treatment for patients with either primary or residual facial nerve schwannoma.
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    Long-term results of Gamma Knife radiosurgery for foramen magnum meningiomas
    (Springer, 2021) Yılmaz, Meltem; Şengöz, Meriç; Akyoldaş, Göktuğ; Samancı, Mustafa Yavuz; Peker, Selçuk; Faculty Member; Faculty Member; Faculty Member; School of Medicine; School of Medicine; School of Medicine; 203677; 275252; 11480
    Outcomes of 37 patients of foramen magnum meningioma (FMM) were evaluated, and the related literature was reviewed to determine the efficacy of Gamma Knife radiosurgery (GKRS) for treating patients with FMM. We present the largest series reported from a single institution with the longest follow-up to date. The database of patients who underwent GKRS for FMM between 2007 and 2019 was evaluated retrospectively. A total of 37 patients with radiological and pathological features consistent with FMM were included in this series. Thirty-three patients were female, and 4 were male. The median age was 58 years (range, 23-74 years). The most common symptom at diagnosis was headache (64.9%). Twelve patients had a history of microsurgical resection. The median duration from the initial onset of symptoms to GKRS was 12 months (range 1-140 months). Among the 37 tumors, eight (21.6%) were located ventrally, 24 (64.9%) laterally, and five (13.5%) dorsally. The median target volume was 3.30 cm(3) (range, 0.6-17.6 cm(3)). Thirty-five patients (95%) were treated with single fraction GKRS, and two patients (5%) were treated with hypofractionated GKRS. The median clinical follow-up was 80 months (range, 18-151 months), while the median radiological follow-up was 84 months (range, 18-144 months). At the last clinical follow-up after GKRS, 27 patients (73%) had improved symptoms, and none had worsened pre-GKRS symptoms. At the last radiological follow-up after GKRS, 23 tumors (62.2%) remained stable, 13 (35.1%) decreased in size, and 1 (2.7%) increased in size. Tumor control, including stable and regressed tumors, was achieved in 97.3% of patients. Our cohort demonstrates that GKRS is an effective and safe treatment for patients with either primary or recurrent/residual FMM.
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    Minimally invasive translaminar endoscopic approach to percutaneous vertebroplasty cement leakage: technical note
    (Elsevier Science Inc, 2018) N/A; N/A; N/A; N/A; N/A; Şentürk, Salim; Akyoldaş, Göktuğ; Ünsal, Ülkün Ünlü; Yaman, Onur; Özer, Ali Fahir; Doctor; Faculty Member; Doctor; Doctor; Faculty Member; N/A; School of Medicine; N/A; N/A; School of Medicine; Koç University Hospital; Koç University Hospital; Koç University Hospital; N/A; 203677; N/A; 219524; 1022
    Background: Percutaneous vertebroplasty (PVP) and percutaneous kyphoplasty are 2 common procedures that could be applied simply in treatment of vertebral compression fractures. Despite simplicity and safe application of these procedures, there are some drawbacks as well. Cement leakage into the spinal canal is the most common complication of PVP and PKV procedures. The aim of this article is to present a minimally invasive alternative technique for removing cement leakage fragment after the PVP. Methods: A 44-year-old female patient began to complain of L4 radiculopathy after L4 PVP. The lumbar computed tomography demonstrated cement fragment closed to upper medial aspect of the left L4 pedicle. A minimally invasive translaminar endoscopic procedure was performed to remove the cement fragment. Results: Following the endoscopic procedure, the patient's complaints resolved completely and she was discharged on postoperative day 1. The minimally invasive intervention provided shorter operation time, minimal blood loss, and reduced complication rate due to its simplicity. In particular, there was no need to undergo general anesthesia. Conclusion: Endoscopic translaminar approach could be safely performed in patients with symptomatic cement leakage after PVP or a percutaneous kyphoplasty procedure.
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    Use of 3-dimensional modeling and augmented/virtual reality applications in microsurgical neuroanatomy training
    (Oxford University Press, 2023) Şahin, Balkan; Yılmaz, Mehmet Özgür; Barut, Ozan; Tanrıöver, Necmettin; Akyoldaş, Göktuğ; Baran, Oğuz; Aydın, Serdar Onur; Faculty Member; Faculty Member; Researcher; N/A; N/A; KUTTAM; School of Medicine; School of Medicine; N/A; 203677; 291138; N/A
    Background: Understanding the microsurgical neuroanatomy of the brain is challenging yet crucial for safe and effective surgery. Training on human cadavers provides an opportunity to practice approaches and learn about the brain's complex organization from a surgical view. Innovations in visual technology, such as virtual reality (VR) and augmented reality (AR), have immensely added a new dimension to neuroanatomy education. In this regard, a 3-dimensional (3D) model and AR/VR application may facilitate the understanding of the microsurgical neuroanatomy of the brain and improve spatial recognition during neurosurgical procedures by generating a better comprehension of interrelated neuroanatomic structures. Objective: To investigate the results of 3D volumetric modeling and AR/VR applications in showing the brain's complex organization during fiber dissection. Methods: Fiber dissection was applied to the specimen, and the 3D model was created with a new photogrammetry method. After photogrammetry, the 3D model was edited using 3D editing programs and viewed in AR. The 3D model was also viewed in VR using a head-mounted display device. Results: The 3D model was viewed in internet-based sites and AR/VR platforms with high resolution. The fibers could be panned, rotated, and moved freely on different planes and viewed from different angles on AR and VR platforms. Conclusion: This study demonstrated that fiber dissections can be transformed and viewed digitally on AR/VR platforms. These models can be considered a powerful teaching tool for improving the surgical spatial recognition of interrelated neuroanatomic structures. Neurosurgeons worldwide can easily avail of these models on digital platforms.
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    Comparative analysis of autophagy in drug responses and aggressive behavior of adult versus pediatric glioma cell lines
    (Wiley, 2022) Aygun, Bera; N/A; N/A; N/A; N/A; N/A; N/A; N/A; N/A; N/A; N/A; Yenidoğan, İrem; Peker, Nesibe; Deveci, Gamze; Kırmızı, Döndü; Asarcıklı, Fikret; Sözmen, Banu Oflaz; Akyoldaş, Göktuğ; Kulaç, İbrahim; Solaroğlu, İhsan; Erbey, Mehmet Fatih; Gözüaçık, Devrim; Researcher; Researcher; PhD Student; Other; Doctor; Faculty Member; Faculty Member; Faculty Member; Faculty Member; Faculty Member; Faculty Member; N/A; Koç University Research Center for Translational Medicine (KUTTAM) / Koç Üniversitesi Translasyonel Tıp Araştırma Merkezi (KUTTAM); N/A; N/A; N/A; N/A; N/A; N/A; N/A; N/A; School of Medicine; N/A; Graduate School of Health Sciences; N/A; N/A; School of Medicine; School of Medicine; School of Medicine; School of Medicine; School of Medicine; N/A; N/A; N/A; N/A; Koç University Hospital; N/A; N/A; N/A; N/A; N/A; 327591; N/A; N/A; N/A; N/A; 198711; 203677; 102059; 206213; 40248
    Central nervous system tumors are the most common solid cancer and a leading cause of cancer-related deaths in children. Glioma is the most challenging pediatric CNS tumor with therapy resistance and poor prognosis in pediatric patients. Although histopathological analyses revealed similarities with adult brain glioma, emerging evidence suggests that the deregulated molecular pathways in pediatric glioma (p-GM) are different from that of adults. Autophagy, a cellular clearance system and a drug resistance mechanism, has been implicated in glioma progression, invasion, and relapse, yet its role in pediatric patients is not well documented. In this study, we compared the autophagic capacity of adult versus p-GM cell lines and evaluated the effect of autophagy manipulation on drug responses. In addition, migration, extracellular matrix invasion ability, and the metabolism of pediatric and adult gliomas were compared and the contribution of autophagy to the aggressive phenotype was evaluated.
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    The investigation of vasospastic effect of hemostatic matrix used in intracranial operations on cerebral arteries
    (İnönü Tıp Fakültesi, 2019) N/A; Akyoldaş, Göktuğ; Açış, Onur; Faculty Member; PhD Student; School of Medicine; Graduate School of Health Sciences; 203677; N/A
    Aim: We aimed to investigate the vasospastic effect of thrombin-based hemostatic matrix on the basilar arteries in rats. Material and Methods: A total of 28 female albino Wistar rats were used in the study. The rats were randomly assigned to four groups. The rats in group I (control group) were sacrificed without surgical manipulation. We injected 0.1 mL of nonheparinized autologous arterial blood into the cisterna magna of the rats in group II, 0.1 mL of hemostatic matrix into the cisterna magna of the rats in group III, and 0.1 mL of a mixture of nonheparinized autologous arterial blood and the hemostatic matrix into the cisterna magna of the rats in group IV. The experimental rats were sacrificed 48 hours after injections. Three sections were obtained from each rat’s basilar arteries and photographed under a light microscope. Basilar artery cross-section areas were measured using computerized image analysis systems. Results: Mean basilar artery cross-sections of all groups revealed statistically a significant difference between only group I and group II. The mean basilar artery cross-sec-tion areas of groups II, III, and IV decreased by 36%, 19%, and 22%, respectively, in comparison with those of group I. Conclusion: Although our results pertaining to thrombin-based hemostatic matrix were not statistically significant, it is hypothesized that this matrix has a vasospastic effect on arteries. Therefore, it important to remember that when such a matrix is used in cranial surgery, the thrombin contained therein could have a vasospastic effect on cerebral arteries.
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    Gamma knife radiosurgery for the treatment of central neurocytoma: a single-institution experience of 25 patients
    (Springer, 2021) Tugcu, Eylul Su; Akyoldaş, Göktuğ; Samancı, Mustafa Yavuz; Peker, Selçuk; Faculty Member; Faculty Member; Faculty Member; School of Medicine; School of Medicine; School of Medicine; 203677; 275252; 11480
    Central neurocytomas (CNs) are extremely rare tumors that account for 0.1-0.5% of all intracranial neoplasms. Recently, Gamma Knife radiosurgery (GKRS) has become a treatment option in patients with CN. We aimed to evaluate the efficacy and safety of GKRS in 25 CN patients and review the results along with relevant literature. GKRS patient database was searched, and 25 patients who underwent GKRS for CN between 2009 and 2018, were evaluated retrospectively. The study cohort included 15 female and ten male patients with a median age of 32 years (range, 5-60). The most common presenting symptom was headache (88%). The neurological examination was unremarkable in all patients, except for one patient with decreased vision. Twenty patients (80%) had a history of surgical resection. Most of the tumors (92%) were located in the ventricles, and the median tumor volume was 4.8 cm(3) (range, 0.8-28.1). The median marginal dose was 14 Gy (range, 12-15) to a median isodose of 50% (range, 40-50). Following a median follow-up of 80 months (range, 36-138), local tumor control was achieved in 100% of patients. Distant recurrence was observed in one patient (4%). No adverse radiation effect was observed. Regarding non-specific post-GKRS symptoms, one patient experienced a prolonged headache, and one epileptic patient experienced a brief partial seizure. In our patient cohort, GKRS yielded favorable local tumor control (100%) during a median follow-up of 6.6 years. Our series demonstrates that GKRS is an effective and safe treatment option for patients with primary or residual CNs.
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    Gamma knife radiosurgery for pituitary spindle cell oncocytomas
    (Elsevier, 2019) Ozdemir, Inan Erdem; Sengoz, Meric; Akyoldaş, Göktuğ; Hergünsel, Ömer Batu; Peker, Selçuk; Faculty Member; Doctor; Faculty Member; School of Medicine; N/A; School of Medicine; Koç University Hospital; 203677; N/A; 11480
    Objectives: Spindle cell oncocytomas (SCOs) are benign lesions of the posterior portion of the pituitary gland that typically come to neurosurgical attention due to compression of the sellar or parasellar structures, and headaches. Initial treatment options for SCOs include surgical resection, particularly via the transsphenoidal approach. However, given that initial resection tends to be insufficient and subsequent revision surgery carries high complication risk, adjuvant treatment modalities may appear to offer promising solutions for controlling tumor progression. This report focuses on a potential new therapeutic option for SCOs, gamma knife radiosurgery (GKRS). Patients and methods: The authors identified all patients at one center who had a pituitary lesion treated with GKRS between 2005 and 2016. Five patients with histopathologically confirmed SCO who underwent GKRS were retrospectively identified and included in the present study Results: The mean patient age was 52 years (range, 41-61 years). The most common presenting symptom was visual disturbance. All five patients had a history of transsphenoidal surgical resection prior to GKRS therapy. The mean tumor volume was 2.25 cm(3) (range 0.7-5.38 cm(3)). The median tumor margin dose was 12 Gy (range, 12-14 Gy), and the median maximal dose was 24 Gy (range, 24-35 Gy). The median isodose was 50 (range, 40-50). No tumor volume progression was observed during radiological follow-up after GKRS (mean, 52 months; range, 36-84 months). At last follow-up, no neurological, endocrinological, or visual complications had been observed. Conclusion: Given their highly vascular and adherent nature, SCOs can be challenging tumors to treat, in particular when they recur. In our five cases, GKRS provided excellent tumor volume control for approximately 4.3 years on average. These results suggest that GKRS is a safe and effective treatment modality for histopatholo-gically confirmed residual SCO.