Load-Bearing Capacity and Design Advantages of a Custom-Made, Thin Pure-Titanium Cranioplasty (CranioTop).

BACKGROUND: Adequate and stable coverage of cranial contour and continuity defects of any origin is a common challenge in neurosurgical clinics. This study presents the results of investigations concerning the mechanical load-bearing capacity and design advantages of custom-made implants made from a thin, pure-titanium sheet (CranioTop) (CLinstruments, Attendorn, Germany) for covering complex cranial defects. METHODS: In 9 test series, the stability of three differently shaped and sized thin titanium sheet implants was tested using vertical, uniaxial compression with 3 different compression stamps, to investigate the behaviour of these implants in relation to punctiform as well as planar forces. RESULTS: All 9 model implants showed elastic behavior in the synchronously recorded force/displacement diagrams at an impression of up to 2 mm. The forces at 2 mm deformation were between 170.1 and 702.7 Newton. CONCLUSION: Cranioplasty using CranioTop is a stable procedure for covering skull defects, even those of large dimensions. An added advantage is the significant reduction in effort required to prepare the area of the bone margins compared to other current techniques of cranioplasty.

Virtual reality-based evaluation of neurovascular conflict for the surgical planning of microvascular decompression in trigeminal neuralgia patients.

OBJECTIVE: Trigeminal neuralgia (TN) is a lightning bolt of violent, electrifying, and stinging pain, often secondary to the neurovascular conflict (NVC). The vessels involved in NVC are mostly arteries and rarely veins. Evaluation of NVC in the deep infratentorial region is inseparably connected with cranial imaging. We retrospectively analyzed the potential influence of three-dimensional (3D) virtual reality (VR) reconstructions compared to conventional magnetic resonance imaging (MRI) scans on the evaluation of NVC for the surgical planning of microvascular decompression in patients with TN. METHODS: Medical files were retrospectively analyzed regarding patient- and disease-related data. Preoperative MRI scans were retrospectively visualized via VR software to detect the characteristics of NVC. A questionnaire of experienced neurosurgeons evaluated the influence of VR visualization technique on identification of anatomical structures involved in NVC and on surgical strategy. RESULTS: Twenty-four patients were included and 480 answer sheets were evaluated. Compared to conventional MRI, image presentation using 3D-VR modality significantly influenced the identification of the affected trigeminal nerve (p = 0.004), the vascular structure involved in the NVC (p = 0.0002), and the affected side of the trigeminal nerve (p = 0.005). CONCLUSIONS: In patients with TN caused by NVC, the reconstruction of conventional preoperative MRI scans and the spatial and anatomical presentation in 3D-VR models offers the possibility of increased understanding of the anatomy and even more the underlying pathology, and thus influences operation planning and strategy.

Cerebral Anatomy Detection and Surgical Planning in Patients with Anterior Skull Base Meningiomas Using a Virtual Reality Technique.

Anterior skull base meningiomas represent a wide cohort of tumors with different locations, extensions, configurations, and anatomical relationships. Diagnosis of these tumors and review of their therapies are inseparably connected with cranial imaging. We analyzed the influence of three-dimensional-virtual reality (3D-VR) reconstructions versus conventional computed tomography (CT) and magnetic resonance imaging (MRI) images (two-dimensional (2D) and screen 3D) on the identification of anatomical structures and on the surgical planning in patients with anterior skull base meningiomas. Medical files were retrospectively analyzed regarding patient- and disease-related data. Preoperative 2D-CT and 2D-MRI scans were retrospectively reconstructed to 3D-VR images and visualized via VR software to detect the characteristics of tumors. A questionnaire of experienced neurosurgeons evaluated the influence of the VR visualization technique on identification of tumor morphology and relevant anatomy and on surgical strategy. Thirty patients were included and 600 answer sheets were evaluated. The 3D-VR modality significantly influenced the detection of tumor-related anatomical structures (p = 0.002), recommended head positioning (p = 0.005), and surgical approach (p = 0.03). Therefore, the reconstruction of conventional preoperative 2D scans into 3D images and the spatial and anatomical presentation in VR models enabled greater understanding of anatomy and pathology, and thus influenced operation planning and strategy.

Impact of Virtual Reality in Arterial Anatomy Detection and Surgical Planning in Patients with Unruptured Anterior Communicating Artery Aneurysms.

Anterior-communicating artery (ACoA) aneurysms have diverse configurations and anatomical variations. The evaluation and operative treatment of these aneurysms necessitates a perfect surgical strategy based on review of three-dimensional (3D) angioarchitecture using several radiologic imaging methods. We analyzed the influence of 3D virtual reality (VR) reconstructions versus conventional computed tomography angiography (CTA) scans on the identification of vascular anatomy and on surgical planning in patients with unruptured ACoA aneurysms. Medical files were retrospectively analyzed regarding patient- and disease-related data. Preoperative CTA scans were retrospectively reconstructed to 3D-VR images and visualized via VR software to detect the characteristics of unruptured ACoA aneurysms. A questionnaire was used to evaluate the influence of VR on the identification of aneurysm morphology and relevant arterial anatomy and on surgical strategy. Twenty-six patients were included and 520 answer sheets were evaluated. The 3D-VR modality significantly influenced detection of the aneurysm-related vascular structure (p = 0.0001), the recommended head positioning (p = 0.005), and the surgical approach (p = 0.001) in the planning of microsurgical clipping. Thus, reconstruction of conventional preoperative CTA scans into 3D images and the spatial presentation in VR models enabled greater understanding of the anatomy and pathology, provided realistic haptic feedback for aneurysm surgery, and influenced operation planning and strategy.

Normal pressure hydrocephalus as a failure of ICP homeostasis mechanism: the hidden role of Monro-Kellie doctrine in the genesis of NPH.

OBJECTIVE: The theme of this paper is to outline that the genesis of normal pressure hydrocephalus (NPH) is governed by the intracranial pressure (ICP) homeostatic principle. The development of this new concept is based mainly on rethinking the well-known Monro-Kellie doctrine in the way that ICP homeostasis mechanism is not only a mechanism that works to prevent pathologically high ICP but also a mechanism that aims to protect from pathologically low ICP. METHODS: The NPH-related literatures are reviewed and reinterpreted to generate a new paradigm for the cascade of pathophysiological events that leads to the genesis NPH, as well as the mechanism of clinical beneficial effects and complications of the shunting procedure. RESULTS: According to this new paradigm, the suboptimal cerebral perfusion that is associated with the impairment of the cerebral autoregulation is the initial step in the genesis of NPH. When the overall volume of blood that circulates intracranially is diminished, a chronic low ICP with episodes of pathologically low ICP occurs. Since the cranial vault is not collapsible, those episodes of low ICP are compensated by the accumulation of cerebrospinal fluid (CSF) to keep the ICP in normal ideal range. The impairment of brain toxin-flushing mechanism because of CSF pooling combined with the already-established suboptimal cerebral perfusion leads to functional disinhibition of the cerebral cortex. CONCLUSION: Recognizing the importance of ICP homeostatic mechanisms in the genesis of the NPH is a simple yet novel view that could change the way we look at NP and can give a basic and fundamental theoretical frame work to achieve better understanding of NPH.

An endoscopic, cadaveric analysis of the roof of the fourth ventricle.

We performed endoscopic dissections of the roof of the fourth ventricle in eight fresh human cadaveric heads to characterize the endoscopic anatomy of the roof of the fourth ventricle and the anatomical configuration of the structures forming its roof. We also made three-dimensional (3D) silicone casts of the fourth ventricle in seven formalin-fixed specimens to evaluate the 3D configuration of the structures that create the roof of the fourth ventricle. The roof of the fourth ventricle can be divided into three zones. The upper zone is formed by the superior cerebellar peduncle and superior medullary velum and is associated with the lingula. The middle zone is formed by the inferior cerebellar peduncles and inferior medullary velum and is associated with the nodule in the midline and with the peduncle of the flocculus. The lower zone is formed by the tela choroidea and is associated with the tonsils. The 3D shape of the roof the fourth ventricle resembles that of a rhomboid-based pyramid; the edges of the base represent the borders of the ventricle, and the apex is the cerebellar fastigium. The lateral recess is shaped like a triangular-based pyramid, with its base connected to the cavity of the fourth ventricle and its tip opening into the lateral cerebellomedullary cistern through the foramen of Luschka. Our results may help in the endoscopic exploration of and microsurgical approaches to the fourth ventricle through its roof.

A microanatomical map of the structures hidden in the middle fossa based on the facial nerve hiatus: measurements and their variability.

The aim of this study was to investigate the relationships/variations between the facial nerve hiatus (FNH) and middle cranial fossa neuro-vascular structures. Twenty CT-scanned middle cranial fossae of fresh adult cadavers were used; the greater superficial petrosal nerves, and critical neuro-vascular structures were identified. Using the FNH as a reference point, a neuronavigation system was used to measure the distance between each structure and the FNH. The coefficient of variation (CV) was used to quantify the degree of variation among each distance. The mean distances and standard deviations between the various landmarks and the FNH, and the associated CV were analyzed. Furthermore, a microanatomical map of the structures hidden in the middle fossa based on the greater superficial petrosal nerve was generated. The most reliable relationships of the FNH were with the internal auditory canal (CV = 14.59), and with the vertical portion of the intrapetrous internal carotid artery (CV = 15.54). Our data demonstrate that the FNH can be used as anatomical landmark to plot the position of several hidden neurovascular structures when performing a middle-fossa skull base approach. However, the pattern and the variation of these structures had to be recognized.