Three-dimensional integration of brain anatomy and function to facilitate intraoperative navigation around the sensorimotor strip

We studied 12 patients with brain tumors in the vicinity of the sensorimotor region to provide a preoperative three-dimensional visualization of the functional anatomy of the rolandic cortex. We also evaluated the role of cortex-muscle coherence analysis and anatomical landmarks in identifying the sensorimotor cortex. The functional landmarks were based on neuromagnetic recordings with a whole-scalp magnetometer, coregistred with magnetic resonance images. Evoked fields to median and tibial nerve and lip stimuli were recorded to identify hand, foot and face representations in the somatosensory cortex. Oscillatory cortical activity, coherent with surface electromyogram during isometric muscle contraction, was analyzed to reveal the hand and foot representations in the precentral motor cortex. The central sulcus was identified also by available anatomical landmarks. The source locations, calculated from the neuromagnetic data, were displayed on 3-D surface reconstructions of the individual brains, including the veins. The preoperative data were verified during awake craniotomy by cortical stimulation in 7 patients and by cortical somatosensory evoked potentials in 5 patients. Sources of somatosensory evoked fields identified correctly the postcentral gyrus in all patients. Useful corroborative information was obtained from anatomical landmarks in 11 patients and from cortex-muscle correlograms in 8 patients. The preoperative visualization of the functional anatomy of the sensorimotor strip assisted in designing the operational strategy, facilitated orientation of the neurosurgeon during the operation, and speeded up the selection of sites for intraoperative stimulation or mapping, thereby helping to prevent damage of eloquent brain areas during surgery.     

Brain sulci and gyri: A practical anatomical review

Despite technological advances, such as intraoperative MRI, intraoperative sensory and motor monitoring, and awake brain surgery, brain anatomy and its relationship with cranial landmarks still remains the basis of neurosurgery. Our objective is to describe the utility of anatomical knowledge of brain sulci and gyri in neurosurgery. This study was performed on 10 human adult cadaveric heads fixed in formalin and injected with colored silicone rubber. Additionally, using procedures done by the authors between June 2006 and June 2011, we describe anatomical knowledge of brain sulci and gyri used to manage brain lesions. Knowledge of the brain sulci and gyri can be used (a) to localize the craniotomy procedure, (b) to recognize eloquent areas of the brain, and (c) to identify any given sulcus for access to deep areas of the brain. Despite technological advances, anatomical knowledge of brain sulci and gyri remains essential to perform brain surgery safely and effectively.     

Accuracy of intraoperative registration during electromagnetic neuronavigation in intracranial procedures performed in children

BACKGROUND AND PURPOSE: The aim of the study was to evaluate registration accuracy in an electromagnetic navigation system applied to image-guided intracranial procedures in children. MATERIAL AND METHODS: In a group of 34 children aged from 2 weeks to 17 years, 38 procedures were performed using electromagnetic navigation, including 24 neuroendoscopic procedures, 10 craniotomies, and 4 shunting or drainage procedures. Thirty-three registrations based on 7 to 10 anatomical landmarks were digitised, and three-dimensional models of patients' heads were constructed using magnetic resonance images (MRI) (23 cases) or computed tomography scans (CT) (10 cases) and used for further analysis. Registration error calculated by the system was used as a measure of registration accuracy. RESULTS: Registration error in the study group ranged from 0.7 mm to 4.4 mm (median 2.1 mm, mean 2.24 +/- 0.7 mm). It was shown that registration accuracy increased with patients' age. Differences between mean registration errors in procedures based on MRI or CT studies were not significant. There was no correlation between the number of landmarks registered and registration accuracy. CONCLUSIONS: Electromagnetic neuronavigation, which does not require firm head fixation, can be used in the youngest age group. Nevertheless, registration accuracy is lower in newborns and infants. Neither imaging modality (MRI or CT) used for creation of a three-dimensional model of the patient's head nor registration of more than 6 landmarks have an impact on registration accuracy.     

Estudio endoscópico endonasal 3D de la anatomía de la base de cráneo

IntroductionTraining in dissection of the paranasal sinuses and the skull base is essential for anatomical understanding and correct surgical techniques. Three-dimensional (3D) visualisation of endoscopic skull base anatomy increases spatial orientation and allows depth perception.ObjectiveTo show endoscopic skull base anatomy based on the 3D technique.MethodsWe performed endoscopic dissection in cadaveric specimens fixed with formalin and with the Thiel technique, both prepared using intravascular injection of coloured material. Endonasal approaches were performed with conventional 2D endoscopes. Then we applied the 3D anaglyph technique to illustrate the pictures in 3D.ResultsThe most important anatomical structures and landmarks of the sellar region under endonasal endoscopic vision are illustrated in 3D images.ConclusionThe skull base consists of complex bony and neurovascular structures. Experience with cadaver dissection is essential to understand complex anatomy and develop surgical skills. A 3D view constitutes a useful tool for understanding skull base anatomy.     

Quantitative comparison of algorithms for inter-subject registration of 3D volumetric brain MRI scans

The objective of inter-subject registration of three-dimensional volumetric brain scans is to reduce the anatomical variability between the images scanned from different individuals. This is a necessary step in many different applications such as voxelwise group analysis of imaging data obtained from different individuals. In this paper, the ability of three different image registration algorithms in reducing inter-subject anatomical variability is quantitatively compared using a set of common high-resolution volumetric magnetic resonance imaging scans from 17 subjects. The algorithms are from the automatic image registration (AIR; version 5), the statistical parametric mapping (SPM99), and the automatic registration toolbox (ART) packages. The latter includes the implementation of a non-linear image registration algorithm, details of which are presented in this paper. The accuracy of registration is quantified in terms of two independent measures: (1) post-registration spatial dispersion of sets of homologous landmarks manually identified on images before or after registration; and (2) voxelwise image standard deviation maps computed within the set of images registered by each algorithm. Both measures showed that the ART algorithm is clearly superior to both AIR and SPM99 in reducing inter-subject anatomical variability. The spatial dispersion measure was found to be more sensitive when the landmarks were placed after image registration. The standard deviation measure was found sensitive to intensity normalization or the method of image interpolation.     

导航辅助内镜下经蝶窦垂体外科的解剖学研究

目的评价导航系统在内镜下经蝶窦垂体手术中的应用。方法在20例尸头标本上模拟内镜下经蝶手术,其中采用GE-Insta Trak 3500电磁导航辅助和无导航辅助各10例。对重要解剖标志及结构变异进行测量与统计,对导航系统精确性进行评估,对导航及非导航辅助下手术的效率与安全性进行比较。结果 GE电磁导航系统误差为(0.28±0.06)mm,实际操作误差为(1.5±0.5)mm。导航系统安装启动平均时间为(11.9±2.0)min。在无解剖变异时导航与非导航辅助下手术时间无统计学差异;若存在解剖变异,前者手术用时较后者明显缩短。结论导航系统辅助内镜经蝶窦手术,在解剖变异、多次手术等解剖关系不明确的病例中,可起到迅速、精确的定位作用,使手术更加安全、高效。     

Application of robotic assistance in surgical treatment of degenerative disease of lumbosacral spine

Robotic assistance has gained increasing popularity in spinal surgery recently. Robotic assistance provides higher effectiveness and safety especially in conditions of complicated anatomy. It also enables the novel, previously unavailable surgical techniques, such as GO-Lif for lumbar spine fusion. The aim of the study is to assess the applicability and effectiveness of the robotic assistance in surgical treatment of degenerative lesion of lumbar spine. 16 patients were operated with robotic assistance device (SpineAssist; MAZOR Surgical Technologies, Caesarea, Israel) between August 2009 and February 2010 in Spinal Department of Burdenko Neurosurgical Institute (Moscow, Russia) with degenerative disc disease. Preoperative assessment included MRI, X-rays and high-resolution CT (slice < 1 mm). The CT is essential for preoperative planning using computed work station SpineAssist. The robot was utilized for automated intraoperative positioning of the instruments according to preoperatively planned trajectories. Basic parameters of surgeries were thoroughly recorded: overall surgery time, radiation dose (all manipulations were performed under fluoroscopic control), accuracy of screw placement relative to preoperative planning, which was assessed using postoperative high-resolution CT with 3D reconstruction. Particular interest of the study was focused on the novel fusion technique for lumbar spine: Go-Lif (Guided Oblique Lumbar Interbody Fusion). This fusion modality enables segment fixation with two screws only, it is comparable with pedicular screws in terms of stability, being far less invasive. It may be used standalone or together with TLIF techniques. Robotic assistance enabled optimal screw placement even in complex anatomical cases (thin pedicles and rotational deformity). No implant-related complications were recorded. Surgery time was much longer in first 2 cases, though in further it decreased nearly to conventional (without robot) surgery time. For radiation dose same tendency was observed--in first 2 cases all surgical steps were fluoroscopically controlled, in further cases--only for primary anatomy registration. Based on control CT, accuracy of implant placement with robotic assistance is 1 mm.     

Anatomía quirúrgica de la órbita. Un estudio sistematizado y claro de una estructura compleja

Background and objectiveThe orbit is a structure of interest for many medical specialties. Surgical approaches to the orbit present significant difficulties for the general neurosurgeon. Whoever decides to practice orbital surgery must have vast anatomical knowledge of this structure. However, although many of the existing publications about orbital anatomy show the complexity of this structure in detail, they fail to facilitate their understanding.The purpose of this study was to systematise and simplify the anatomical study of the orbit from a surgical perspective, to facilitate its understanding.Materials and methodsA review of the international literature on the subject was carried out, and the principle of the rule of 7 was followed for its ordering. For illustration purposes, photographs of cadaveric preparations and digital drawings were used.ResultsThe orbits are 2 cavities located symmetrically on both sides of the nose. They have a pyramidal shape, with 4 sides, a posterior vertex, an anterior base and their axis established from the sagittal plane at a 20-degree angle. A distinctive feature of the orbit is that its elements are organised into groups of seven: 7 bones, 7 intraorbital extraocular muscles and 7 nerves.ConclusionA systematisation of the orbital anatomy was performed with clear illustrations to simplify its study. The understanding of the anatomy of the orbit is vital to classify lesions and provides a solid basis when choosing the most appropriate approach for their treatment.     

经鼻蝶入路至颅底岩尖区的解剖学研究

目的为临床内镜经鼻蝶入路至岩尖区的手术提供参考。方法选择福尔马林浸泡固定的成人尸头10具,行冠状位、矢状位和轴位高分辨率CT扫描,筛选出蝶窦为鞍型的标本9具。内镜下模拟经鼻蝶入路手术处理岩尖区,并对重要解剖结构进行测量。结果经鼻蝶入路处理岩尖区病变手术步骤分为3个阶段：鼻腔阶段、蝶窦阶段和岩尖阶段。处理好蝶窦的后外侧壁是内镜下经鼻蝶入路的关键环节。经视神经-颈内动脉隐窝和斜坡隐窝到达岩尖区是安全的。以鞍前段颈内动脉凸起中点和和斜坡隐窝中心连线的中点为圆心,做直径为10 mm的圆,在该圆内入路可以安全准确到达岩尖。结论经鼻蝶入路到达岩尖区相对安全的区域为视神经颈内动脉隐窝和斜坡隐窝,由该区域入路手术处理岩尖区是可行的。     

Comparison of piece‐wise linear,linear, and nonlinear atlas‐to‐patient warping techniques: Analysis of the labeling of subcortical nuclei for functional neurosurgical applications

Digital atlases are commonly used in pre‐operative planning in functional neurosurgical procedures performed to minimize the symptoms of Parkinson's disease. These atlases can be customized to fit an individual patient's anatomy through atlas‐to‐patient warping procedures. Once fitted to pre‐operative magnetic resonance imaging (MRI) data, the customized atlas can be used to plan and navigate surgical procedures. Linear, piece‐wise linear and nonlinear registration methods have been used to customize different digital atlases with varying accuracies. Our goal was to evaluate eight different registration methods for atlas‐to‐patient customization of a new digital atlas of the basal ganglia and thalamus to demonstrate the value of nonlinear registration for automated atlas‐based subcortical target identification in functional neurosurgery. In this work, we evaluate the accuracy of two automated linear techniques, two piece‐wise linear techniques (requiring the identification of manually placed anatomical landmarks), and four different automated nonlinear atlas‐to‐patient warping techniques (where two of the four nonlinear techniques are variants of the ANIMAL algorithm). Since a gold standard of the subcortical anatomy is not available, manual segmentations of the striatum, globus pallidus, and thalamus are used to derive a silver standard for evaluation. Four different metrics, including the kappa statistic, the mean distance between the surfaces, the maximum distance between surfaces, and the total structure volume are used to compare the warping techniques. The results show that nonlinear techniques perform statistically better than linear and piece‐wise linear techniques. In addition, the results demonstrate statistically significant differences between the nonlinear techniques, with the ANIMAL algorithm yielding better results. Hum Brain Mapp, 2009. © 2009 Wiley‐Liss, Inc.     

Intra-operative cone-beam CT (O-arm) and stereotactic navigation in acute spinal trauma surgery

The purpose of this ambispective cohort study is to describe the emerging role of intra-operative cone-beam CT (O-arm®, Medtronic, Minneapolis, MN, USA), frequently coupled with stereotactic navigation (StealthStation®, Medtronic), in the surgical management of acute spinal trauma. All patients with acute spinal trauma between May 2009 and May 2011 who were treated with the use of the O-arm were identified from a prospectively collected spine database and retrospectively analyzed to characterize indications and outcomes. Over the two-year period, the O-arm was used in 183 spinal operations; 27 of these (15%) involved acute spinal trauma. Within the trauma cohort, 14 injuries were in the cervical spine, nine at the cervicothoracic junction, and four were in the thoracolumbar spine. In 12 patients (44%) pre-existing aberrant and challenging anatomy, commonly ankylosing conditions, were present. Surgical techniques included transarticular atlantoaxial fixation and direct osteosynthesis of a Hangman’s fracture performed entirely percutaneously (via two stab incisions) using O-arm assisted stereotactic navigation. No trauma cases using O-arm assisted navigation had iatrogenic neurovascular injury and none required subsequent revision surgery for implant malposition, compared with a revision rate of 1.2% of patients with non-navigated acute spinal trauma during the same interval. Technical factors associated with successful application of this technology in the setting of acute spinal trauma were detailed. O-arm assisted navigation can overcome anatomical challenges and broaden the available stabilization options in the management of acute spinal trauma. Other advantages include protecting the surgical team from cumulative fluoroscopic radiation exposure and patients from repeat surgery due to implant malposition.     

Books received and brief reviews

A 30-year-old man presented with decreased vision in the right eye of three weeks' duration. Examination indicated a chiasmal syndrome and evidence of subarachnoid hemorrhage. CAT scan showed a large suprasellar mass. Surgical intervention confirmed the presence of a globular lesion filled with blood clots involving mainly the right side of the optic chiasm. Following removal of the clots, the chiasm regained its shape and anatomical landmarks. Biopsy of the mass demonstrated a venous angioma located within the optic chiasm as well as recent and old bleeding. Following surgery the patient did well and recovered vision in the right eye, though a left homonymous hemianopia persisted.     

Microsurgical anatomy of the hypoglossal nerve.

The aim of the present study was to review the surgical anatomy of the hypoglossal nerve (HN), to reveal its relationships on its course and to provide some landmarks to its identification. Ten cadaveric head dissections (20 sides) were performed using microsurgical techniques. The anatomical relationships between the HN and other nerves, muscles, arteries and veins were carefully recorded, and some measurements were made between the HN and related structures. Thus, various landmarks were determined for the easy identification of the HN. In addition, the hypoglossal triangle, which containes major vascular structures, is described. The HN is divided into three main parts: cisternal, intracanalicular and extracranial. The HN arises from the medulla as a line of rootlets situated along the anterior margin of the lower two-thirds of the olive in the preolivary sulcus. It is the newly described 'hypoglossal' triangle in the anterior neck that is bordered by the descending hypoglossus laterally, transverse hypoglossus inferiorly and inferior border of the stylohyoid muscle superiorly. In our specimens, we determined that the HN was 3-7 mm (mean 5 mm) inferior to the digastric tendon, as well as mostly superficial. The occipital artery arose from the posterior surface of the external carotid artery (ECA) 6-9 mm (mean 7 mm) above the carotid bifurcation. There is also an important 'cross' between the occipital artery and the HN. In all cadavers, this crossing point was 7-9 mm (mean 8 mm) superior to the emergence of the occipital artery from the ECA. In conclusion, understanding the detailed anatomy of the HN and using landmarks to identify the nerve are crucial for surgery in the region.     

Surgical anatomy of the anterior clinoid process.

We studied the surgical anatomy of the anterior clinoid process (ACP) and its adjacent structures in cadaver heads. We paid special attention to the anatomical relationships between the ACP and adjacent structures to determine the surgical landmarks for safe anterior clinoidectomy. Thirty-five cadaver heads were dissected and the ACP regions were examined in 55 skull sides. We observed that in eight sides the ACP had been pneumatized from the sphenoid sinus. The caroticoclinoid foramen was revealed in only eight sides. The extra-ocular nerves ran forward to the superior orbital fissure at the inferolateral aspect of the ACP, with the oculomotor nerve being closest. The posterolateral area of the carotico-oculomotor membrane was thin and incomplete in nine sides. The study clarified the anatomical relationship between the ACP and its surrounding structures, and identified the major variations experienced. We used these to identify anatomical landmarks to assist the surgeon in the planning of a safe and effective anterior clinoidectomy.     

内镜经鼻岩尖手术中序贯性组合式解剖标志的确立

目的确立内镜经鼻岩尖手术中序贯性组合式的解剖标志。方法通过内镜经鼻入路对3具(6侧)新鲜冰冻尸颅及5具(10侧)福尔马林固定的成人头颅标本进行岩尖区解剖,观察入路过程中的解剖标志并拍照和摄像记录。结果内镜经鼻岩尖手术可按照入路过程分为5阶段,即鼻腔、鼻咽、鼻窦、翼腭窝、岩尖阶段。每一步骤中均可找到一组相对固定、在术中可作为路标的标志,分别为:鼻腔阶段标志、鼻咽阶段标志、蝶窦阶段标志、筛窦阶段标志、上颌窦阶段标志、翼腭窝阶段标志及岩尖阶段标志。结论内镜经鼻岩尖手术可根据术中依次涉及的腔隙,在每个阶段中参照一组解剖标志,而不是单一标志进行下一步操作。参照这些序贯性组合式的解剖标志,可精确和安全地进行内镜经鼻岩尖区手术。     

Anatomical and computed tomographic analysis of C1 vertebra

Craniovertebral junction surgery requires knowledge regarding the anatomy of this region, particularly the C1 vertebra. Both C1 laminectomy and C1-2 instrumentation necessitate preoperative information about bony landmarks and the vertebral artery. This study compares the results obtained from anatomic and computed tomographic measurements of C1 bony landmarks. 31 C1 cervical vertebrae were measured; the C1 AP diameter, and C1 transverse diameter, the facet diameter, the distance between the anterior tubercle and the anterior aspect of the C1 lateral mass on a lateral view, the distance between the midline and the vertebral artery groove on the outer cortex of the posterior arch of C1 anatomically and computed tomographically. Anatomic measurements were performed by an anatomist using a Vernier caliper accurate to 0.1 mm, whereas the computed tomographic measurements were performed by a radiologist on bone window computed tomography (CT). The mean values and the differences between two measurement modalities were analysed using a paired t-test. There was no statistical difference between the results obtained by anatomical and radiological measurements for six parameters. There was, however, a statistically significant difference between two modalities regarding the distance between the midline and vertebral artery groove on the outer cortex of posterior arch of C1, while slightly different, the difference is within 1 mm and, therefore, not clinically significant. It is concluded that CT reflects most anatomical details of bony landmarks of C1.     

内镜经鼻颅底手术中骨性解剖标志的临床意义

目的探讨内镜经鼻颅底手术中骨性解剖标志的临床意义。方法测量100例干性颅底骨性标本的相关解剖数据;并分析2000年9月～2007年3月进行的172例内镜经鼻颅底手术录像,评价中鼻甲、筛窦、蝶窦腔内骨性隆起、蝶骨翼突等作为骨性解剖标志的临床意义。结果骨性解剖数据:两侧翼突内侧板、枕髁前缘和破裂孔间距分别为26.47mm、16.92mm和19.98mm;视神经管与破裂孔、卵圆孔和下颌关节窝内缘距离约26mm、30mm和44mm。在172例内镜经鼻颅底手术中,与手术入路相关的并发症包括颈内动脉损伤1例,视神经损伤1例,其他并发症包括脑脊液鼻漏14例,蛛网膜下腔出血1例,脑膜炎致死1例;中鼻甲、筛窦、蝶窦腔内骨性隆起及蝶骨翼突是内镜经鼻前颅底、鞍区、斜坡、海绵窦、颞下窝和翼腭窝手术中指导手术的重要解剖标志。结论颅底骨性解剖标志对于内镜经鼻颅底手术有指导作用,正确认识这些解剖标志有助于提高手术安全性。     

影像导航下经鼻内镜视神经减压术(附12例临床分析)

目的 探讨影像导航技术在经鼻内镜的视神经减压术中应用的有关问题.方法 回顾性分析本科自2005～2006年收治的视神经损伤性病变12例,均在影像导航下经鼻内镜行视神经减压手术.结果 影像导航术前准备时间(包括配准、头架定位、常规器械注册等)5～10min,平均7min.手术区域影像标志与实体解剖标志间的误差≤1.5m.4例术前无光感者术后2例有效,其余8例有残存光感者术后5例有效(视力提高1个级别以上).结论 影像导航系统与鼻内镜相结合下的视神经减压术,可以帮助术者在影像导航下准确定位视神经管,颈内动脉等重要标志,并可清晰显示其毗邻关系,可提高手术的精确性和安全性.尤其体现在局部解剖结构因外伤导致的毗邻关系改变的情况下行手术.