Ahmet Hilmi Kaya

The paramedian supracerebellar-transtentorial approach to the entire length of the mediobasal temporal region: an anatomical and clinical study. Laboratory investigation.

OBJECT The exploration of lesions in the mediobasal temporal region (MTR) has challenged generations of neurosurgeons to achieve an appropriate approach. To address this challenge, the extensive use of the paramedian supracerebellar-transtentorial (PST) approach to expose the entire length of the MTR, as well as the fusiform gyrus, was investigated. METHODS The authors studied the microsurgical aspects of the PST approach in 20 cadaver brains and 5 cadaver heads under the operating microscope. They evaluated the features, advantages, difficulties, and limitations of the PST approach and refined the surgical technique. They then used the PST approach in 15 patients with large intrinsic MTR tumors (6 patients), tumor in the posterior fusiform gyrus with mediobasal temporal epilepsy (MTE) (1 patient), cavernous malformations in the posterior MTR including the fusiform gyrus (2 patients), or intractable MTE with hippocampal sclerosis (6 patients) from December 2007 to May 2010. Patients ranged in age from 11 to 63 years (mean 35.2 years), and in 9 patients (60%) the lesion was located on the left side. RESULTS In all patients with neuroepithelial tumors or cavernous malformations, the lesions were completely and safely resected. In all patients with intractable MTE with hippocampal sclerosis, the anterior two-thirds of the parahippocampal gyrus and hippocampus, as well as the amygdala, were removed selectively through the PST approach. There was no surgical morbidity or mortality in this series. Three patients (20%) with high-grade neuroepithelial tumors underwent postoperative radiotherapy and chemotherapy but needed a second surgery for recurrence during the follow-up period. In all patients with MTE, antiepileptic medication could be decreased to a single drug at lower doses, and no seizure activity has occurred until this point. CONCLUSIONS The PST approach provides the surgeon precise anatomical orientation when exposing the entire length of the MTR, as well as the fusiform gyrus, for removing any lesion. This is a novel technique especially for removing tumors involving the entire MTR in a single session without damaging neighboring neural or vascular structures. This approach can also be a viable alternative for selective removal of the parahippocampal gyrus, hippocampus, and amygdala in patients with MTE due to hippocampal sclerosis.

The termination of superior sagittal sinus and drainage patterns of the lateral, occipital at confluens sinuum in newborns: clinical and embryological implications

Drainage patterns of dural venous sinuses at confluens sinuum are variable and clinically significant. It has been generally investigated in adults; however, we thought that neonatal cadaver study might be more informative in views of embryological and clinical. A total of 33 skull bases of neonatal cadavers were resected to identify termination patterns of lateral sinus (LS), superior sagittal sinus (SSS) and occipital sinus (OS) at the confluens sinuum. Termination patterns of these sinuses were classified into six types: the SSS showed continuity with right transverse sinus (TS) (with OSs) (30.3%) (Type I); or multiple OSs (21.2%) (Type II). The SSS continued with left TS (with OSs) (12.1% (Type III); or with multiple OSs (6.1%) (Type IV). The SSS shows continuity with both TS (9.1%) (Type V). SSS symmetrically bifurcated, the confluens sinuum has a large OS (21.2%) (Type VI). Understanding of the cerebral venous drainage and large variation of the posterior fossa dural sinuses is crucially important for planning surgical intervention to some tumors in the neck which may require ligation of the internal jugular vein.

The perforating branches of the P1 segment of the posterior cerebral artery

The perforating branches of the P1 segment of the posterior cerebral artery are vulnerable to injury. Because of their close proximity to the basilar artery, the vulnerability occurs especially during surgical interventions for vascular pathologies such as basilar apex aneurysms. Therefore, extensive knowledge of the microsurgical anatomy of this area is mandatory to prevent poor post-operative outcomes. We microscopically examined 28 P1 segments obtained from 14 adult fresh cadaver brains (6 silicone injected, 8 freshly examined). The P1 segments ranged between 2.8mm and 12.2mm (mean 6.8mm) in length with a mean outer diameter of 1.85 mm (range 0.8-4.5mm). All 94 thalamoperforating branches identified in 27 P1 segments (mean 3.35 branches per segment) arose from the postero-superior aspect of P1 and were the most proximally originating branch in nearly all specimens (96.4%). In addition in 28 P1s, 12 short circumflex arteries (42.8%; mean 0.42 branches per segment), 16 long circumflex arteries (57.1%; mean 0.57 branches per segment) and 10 medial posterior choroidal arteries (35.7%; mean 0.35 branches per segment) were identified and all originated from the posterior or postero-inferior surface of the P1 segment. When the P1 segment had more than one type of branch, it was the short circumflex arteries that were always more proximal in origin than the others. The medial posterior choroidal arteries were always more distal in origin. All three branches were not observed together in any of the P1 segments. The findings in this, and future, anatomical studies may help to reduce the post-surgical morbidity and mortality rates after surgery for posterior circulation aneurysms.

Circumferential stabilization with ghost screwing after posterior resection of spinal metastases via transpedicular route.

Various surgical methods have been described for treating spinal metastases, namely, en bloc spondylectomy, minimally invasive techniques, and anterior and posterior approaches. The main goals in surgical intervention for these lesions are tumor removal and establishment of strong, durable stabilization. The least invasive method is always preferred. Posterior transpedicular spondylectomy meets all these needs, as this method achieves tumor excision and stabilization of the anterior and posterior spine through one posterior incision and in the same surgical session. The surgeon circumferentially excises a spinal metastasis and then achieves circumferential stabilization in the same session. Numerous circumferential stabilization methods have been used to date, including placement of free bone grafts or cages or acrylic grafts, or insertion of an acrylic graft supported by a Steinmann pin anteriorly and by posterior transpedicular fixators or a Luque rectangle posteriorly. This article describes seven cases of spinal metastasis in which an alternative circumferential stabilization technique known as “ghost screwing” was performed. The first step in this method is circumferential decompression, achieved with laminectomy followed by eggshell corpectomy via the transpedicular route. Then a short segmental transpedicular stabilization system is fixed to the vertebrae cranial and caudal to the laminectomy/corpectomy defect. Prior to fixing the rods in place, an additional screw is mounted on each rod such that the screw shaft protrudes into the defect space. Once the rods are fixed and the two extra screws are optimally positioned, acrylic bone cement is introduced into the defect site, encasing the ghost screws and forming an anterior graft upon hardening. The outcomes in our cases were excellent. All seven patients had uneventful postoperative periods and all experienced pain relief and were able to mobilize early. Direct connection of the anterior acrylic graft to the posterior fixation system via ghost screws makes this system strong and durable, and prevents subsidence or horizontal displacement of the graft. Such complications can be serious issues with other circumferential systems that use independent anterior and posterior fixators.

Localization of pterion in neonatal cadavers: a morphometric study

PurposePterion is defined as a junction of temporal, frontal, parietal, and sphenoid bones. In newborns, pterion may be defined as a region that shows variability in the exact location because of the lack of complete bony structure. The aim of this study is to define the topographic anatomy of this important surgical point, pterion, and the variability of its localization on craniums of newborn cadavers.MethodsOur study was performed using 35 term neonatal cadaver specimens. We measured the distances between the pterion and other critical points and used a scale diagram for the definition of pterional area.ResultsOur scale diagram showed that pterion is mostly localized in regions c, d, e, and f on the length and regions 2, 3, 4, and 5 on the width. Localization was not observed in regions a, b, g, and h, and in areas of squares 1 and 6. The most observed localization of pterion was the e4 (24.28%) area.ConclusionThis study provides a detailed knowledge on localization of this important point, pterion, which will be useful for the clinicians at operation planning and treatment stages, serving for the success in surgery in the presence of this variable topographic cranial anatomy.

Simple technique for removing broken pedicular screw with plain and serviceable screwdriver

Removing the broken pedicular screw after spinal hardware failure is usually problematic. A specially designed simple screwdriver and easy removal technique of broken pedicular screw with this screwdriver are described in this article.

A quick-solidifying, coloured silicone mixture for injecting into brains for autopsy: technical report

The injection of cadaver brains is invaluable for anatomic study, but cadavers that have been properly handled are not easy to obtain. A large number of cadavers pass through forensic departments around the world, and these cadavers could provide hundreds of research specimens, though they remain in the forensic unit for only a short time. The injection of a silicone mixture that quickly solidifies during autopsy would provide greater numbers of fresh specimens for study. The authors describe a technique for injecting a self-curing silicone mixture that can be used on autopsy specimens in a forensic unit. This technique does not interfere with routine autopsy findings. We describe the preparation of the mixture and autopsy specimens, the injection process, and the method for removing injected brains from cadavers. The solidifying process took a 1-h duration in this injection method and was in accord with autopsy procedure. The arterial bed was satisfactorily filled, and even small perforating branches and pial anastomoses were well demonstrated. Injecting autopsy specimens with the quick-solidifying silicone mixture allows anatomical studies of specimens even from cadavers admitted to forensic departments for only a short time. This method can provide neurosurgery laboratories with sufficient numbers of specimens appropriate for various studies.

There are no estrogen and progesterone receptors in cerebral cavernomas: A preliminary immunohistochemical study

BACKGROUND Literature consistently mentions that pregnancy and hormonal therapy probably increase the bleeding rate and seizure expression of cerebral cavernomas. Either increased hormonal activity or embryogenesis related abundant expression of some growth factors such as VEGF, bFGF, and placental growth factor during pregnancy were proposed to initiate angiogenic process and vascular proliferation in cavernomas, thereby increasing their bleeding rate and seizure expression. METHODS To reveal whether estrogen and/or progesterone have direct effect on cerebral cavernomas, their receptor expressions were studied immunohistochemically in recently excised 12 cerebral cavernomas. RESULTS Study showed no expression of either estrogen or progesterone receptors in cerebral cavernomas even the staining worked well in positive control tissues of infiltrative ductal carcinoma. CONCLUSIONS Aggressive behavior of cerebral cavernomas during pregnancy is a commonly proven observation and attributed to some hormonal effects. However, this effect seems not related to effect of estrogen or progesterone on cavernoma tissue via receptor binding.

Bilateral origin of superior cerebellar arteries from the posterior cerebral arteries, and clues to its embryologic basis

The superior cerebellar artery is the most consistent branch of the basilar artery and arises near the bifurcation of the basilar artery. A bilateral origin of the superior cerebellar arteries from the posterior cerebral arteries has been rarely reported in the literature. Reporting variations in brain vessels is important for neurosurgeons to safely and confidently treat pathologies in this region. We report on a specimen with a bilateral origin to the superior cerebellar artery from the posterior cerebral artery and discuss the embryogenesis of this rare variation.

Localized Spontaneous Subarachnoid Hemorrhage as First Manifestation of Cerebral Venous Thrombosis

Cerebral venous thrombosis (CVT) may rarely manifest itself with pure subarachnoid hemorrhage (SAH). For a neurosurgeon, spontaneous SAH always suggests vascular pathologies as aneurysms or malformations. However, though rarely encountered, a spontaneous SAH may be an initial finding of CVT that requires prompt diagnosis with venous angiography to initiate treatment with anticoagulants. Obviously those are contraindicated in aneurysmal subarachnoid hemorrhage. Literature review discovered additional cases presented in this article. CVT may manifest itself with subarachnoidal hemorrhage atypically with a localized pattern rather than diffuse blood. A spontaneous subarachnoidal hemorrhage in atypical localization may be related to venous thrombosis and radiologic evaluation of cerebral venous system should be one of the initial diagnostic efforts in neurosurgical practice of such cases for early initiation of treatment with anticoagulants.