Iterative neuronavigation using 3D ultrasound. A feasibility study

Intra-operative ultrasound (iUS) can generate 2D images in real-time as well as near real-time 3D datasets of the current situation during an intervention. Tracked ultrasound can locate the images in 3D space and relate them to patient, devices, andpre-operative planning data. Therefore, tracked US is an efficient means for controlling the validity of pre-operative planning, recognition of changes (brain shift) during the intervention, replanning of the operational path due to situational changes (iterative navigation), and finally, controlling the results (residual tumor). This paper describes a neuronavigation system exploiting this potential of interventional tracked US for permanent control of intervention progress and iterative adaptation of the planned procedure to the current situation.     

New ultrasound techniques and their application in neurosurgical intra-operative sonography

Abstract

We describe a variety of new ultrasound techniques by their physical background, potentials and applications regarding usefulness during intra-operative neurosurgical procedures. Transducers like highfrequency and small rotating probes fitting into neuroendoscopes, imaging techniques as extended field-ofview technique, harmonic imaging, echo-enhancers, 3-D imaging and the real-time integration of neurosonography with pre-operative CT- or MR-data are mentioned. The technical or physical principles are explained, followed by a discussion of these techniques from available literature dealing with their intra-operative neurosurgical applications and the experience of the authors with the techniques. With higher frequencies micromillimeter imaging is possible and small probe allows endoneurosonography. Echo-enhancers and harmonic imaging improve the signal-to-noise ratio and 3-D imaging and extended field-of-view techniques allows a better understanding of the pathoanatomy. With the real-time integration of intra-operative ultrasound images and pre-operative CT or MR images additional information, like hemodynamic pattern, are available for the neurosurgeon. Although until now only a limited number of reports about new sonographic techniques during intra-operative application in neurosurgery exist, the methods seem to be promising in creating images easier to understand, incorporating more information about pathoanatomy and supplying the neurosurgeon with information additional to that provided by CT and MRI. [Neurol Res 2001; 23: 697-705]     

Combined MR measurements of magnetization transfer,tissue diffusion and proton spectroscopy. A feasibility study with neurological cases

Abstract

Magnetic resonance imaging (MRI) of diffusion and magnetization transfer was combined with 1Hspectroscopic imaging (CSI) to evaluate the clinical potential of in-vivo profiles of various brain pathologies. Ten patients (multiple sclerosis, cerebrovascular disease, leukodystrophy, Alzheimer dementia) and five healthy volunteers were investigated with diffusion-weighted MRI, magnetization transfer imaging, and CSI. Proton spectra were analyzed as ratios of NAA/Cr and Cho/Cr calculated from the peak areas of N-acetyl-aspartate (NAA), (phospho)-creatine (Cr) and choline (Cho). The apparent diffusion coefficient (ADC) and the magnetization transfer ratio (MTR) were determined in identical voxels to ensure identical partial volume effects compared to CSI. Compared to MTR and ADC assessments, the lower spatial resolution of CSI clearly indicates a hindrance at 1.5 T. In most demyelinating lesions, NAA/Cr reduction paralleled attenuated MTRs and elevated ADCs. By contrast, in acute stroke and some acute MS lesions the ADC was reduced, while MTR and NAA/Cr were also decreased. In Alzheimer's dementia, ADC was increased, MTR unchanged and Cho/Cr increased. In a case of leukodystrophy, ADC was pronouncedly increased, MTR and NAA/Cr both reduced, and Cho/Cr normal. Combined measurements of ADC, MTR and CSI are feasible and provide differential in-vivo information on various brain pathologies.     

Thalami and corona radiata in juvenile NCL (CLN3): a voxel-based morphometric study

Juvenile neuronal ceroid lipofuscinosis (CLN3) is characterized by progressive cerebral atrophy. The purpose of this study was to re-evaluate the three-dimensional magnetic resonance (3D-MR) images of patients with CLN3 using voxel-based morphometry (VBM) to achieve a detailed understanding of the affected brain regions. T1-weighted 3D-MR images of 15 patients with CLN3 (age range: 12–25 years, mean age 17.6 years) and 15 age- and sex-matched controls were analyzed using VBM. VBM showed strikingly focal alterations in the brains of CLN3 patients: the gray matter volume was significantly decreased in the dorsomedial part of the thalami of CLN3 patients. In addition, the volume of the white matter was significantly decreased in the corona radiata, containing cortical efferents and afferents in the transition between the internal capsule and the subcortical white matter. These data suggest that the dorsomedial part of the thalamus and the corona radiata may have a central, previously unrecognized role in the pathogenesis of CLN3.     

A modified rabbit model of stroke: evaluation using clinical MRI scanner

Abstract

Objective: Occluding the middle cerebral artery of small animals with an intraluminal filament to build a stroke model has gained increasing acceptance. In light of the growing demand for magnetic resonance imaging (MRI) studies using the clinical MRI scanner, large animal models can be superior to small animal models. In this work, we developed a modified rabbit model of stroke, which was assessed using clinical MRI scanner and compared with a most commonly silicone-coated filament model.

Methods: We presented a focal cerebral ischemia in rabbits. The key feature of this modified method is the use of a guide wire as a 'nylon suture'. At 3 days after ischemia, the percentage of brain infarct volume, neurobehavioral score, intracranial hemorrhagic incidence and dynamic changes of T₂ and apparent diffusion coefficient values were assessed respectively and compared between the focal cerebral models.

Results: Wire-induced models had more severe brain infarct size with less dispersion (32.7 ± 6.5%, coefficient of variation=0.20) than that with filament models (25.4 ± 8.9%, coefficient of variation=0.31; p<0.05). There were more significant MRI changes in the early stage, higher rate of technique success (wire, 20/20; filament, 17/20) and less intracranial hemorrhage (wire, 0/20; filament, 3/20) in wire-induced models than in filament-induced rabbits (p<0.05).

Conclusion: Our data suggest that wire-induced method can provide a useful tool for the earlier research of ischemia.     

神经导航辅助下前颞下经硬膜外前岩骨锁孔入路的显微解剖学研究

背景蝶岩斜区手术入路的选择和设计成为神经外科界关注和探索的难题之一.此部位手术多采用颞下入路、扩大中颅窝入路、Kawase入路、额颞眶颧入路等,但这些入路颅外组织损伤较多,存在大范围的无效暴露及不必要的结构破坏.为此,本实验应用微创锁孔入路的新理念,在颞下入路基础上,模拟前颞下经硬膜外前岩骨锁孔入路,并将神经导航技术运用到该入路中,进行显微解剖学研究,探讨其可行性,为临床应用提供依据.方法①导航资料的建立尸头切口周围6-8枚钛钉标记,行螺旋CT连续、无间隙扫描,影像资料输入Stoker神经导航系统.在导航系统Contour功能栏内,分别标出前岩骨、耳蜗、内听道的轮廓,指导术中岩骨的磨除范围.②模拟前颞下经硬膜外前岩骨锁孔入路尸头向对侧旋转约90°,取耳屏前约1 cm、颧弓上缘上行长约4 cm的直切口,在颧弓根部用磨钻磨开一小骨孔,以铣刀取下直径2.0～2.5 cm的小骨瓣.自中颅窝底抬起颞部硬脑膜,切断脑膜冲动脉.在下颌神经表面切开硬膜,进入海绵窦外侧壁浅、深两层之间,用显微剥离子向圆孔、眶上裂分离硬膜融合区,暴露海绵窦外侧壁,通过海绵窦三角显露内部结构.用神经导航定位耳蜗、内听道,依次磨除Kawase菱形区及三叉神经节下方的岩尖部,暴露上、中斜坡及桥小脑角等结构,观察并比较暴露结构的不同.③神经导航记录确定海绵窦三角、Kawase菱形区、最大限度磨除前岩骨后形成的菱形区的各点坐标,应用空间任意两点的距离函数由Excel算出长度,应用三角形面积公式算出面积.结果 1.海绵窦外侧壁由浅、深两层构成,深浅两层之间存在潜在的间隙,其内没有神经、血管穿过,动眼神经、滑车神经、三叉神经走行于该间隙之下.剥离该间隙,可以暴露海绵窦外侧壁全貌.暴露的相关海绵窦三角为①滑车神经上三角可暴露海绵窦后上腔、内侧腔,颈内动脉水平部上面、后曲部及其脑膜垂体干分支②Parkinson三角可暴露海绵窦前下腔、后上腔、内侧腔,颈内动脉后升部、水平部、后曲部及其脑膜垂体干分支,海绵窦下动脉,外展神经;③Mullan三角(前内侧三角)可暴露颈内动脉水平部、前曲部,海绵窦下动脉,外展神经④前外侧三角可显露卵圆孔与圆孔间的蝶骨表面.2.Meckel腔位于海绵窦后部韵外下方,小脑幕附着缘和岩上窦下方,是颅后窝向颅中窝突入的硬膜陷窝,形成一个中颅窝和后颅窝之间沟通的自然通路.Meckel腔包裹三叉神经根、节及三个分支至各自的出颅孔.3.计算出Kawase菱形区的面积为(248.2±12.4)mm2,最大限度磨除前岩骨后形成的菱形区面积为(318.4±36.2)mm2.两者比较有显著性差异(t=27.53,P《0.05).4. 通过三叉神经上间隙暴露上斜坡、基底动脉中部通过三叉神经下间隙暴露内听道下方的部分中斜坡、脑桥下部、脑桥延髓沟、延髓上部、椎基底动脉交接部、椎动脉近端、小脑前下动脉脑桥前段和脑桥外侧段.磨除三叉神经压迹下方的骨质,可进一步暴露展神经、Dorello管孔、小脑前下动脉的起始点.结论前颞下经硬膜外前岩骨锁孔入路具有可行性.通过一个直径2.0～2.5 cm的小骨窗,可以充分显露海绵窦、Meckel腔及三叉神经分支等结构,对原发或侵及上述部位的肿瘤可以直视下完全暴露.如病变扩展至后颅窝,通过最大限度磨除前部岩骨,暴露上、中斜坡,进行切除.但因岩斜区和海绵窦区解剖复杂,该锁孔入路在解决微创问题的同时,仍然存在传统入路相似的不足.     

A retrospective fetal ultrasound study of brain size in autism.

BACKGROUND: Despite evidence of possible abnormalities during fetal development, no study to date has attempted to investigate fetal brain growth in autism. Fetal head circumference (HC) and biparietal diameter (BPD) are highly correlated with fetal brain volume and are measured on fetal ultrasounds. METHODS: We used retrospective fetal ultrasound data to examine fetal head and body size during midgestation in children later diagnosed with autism. Second trimester fetal ultrasounds were collected for 45 autistic subjects and 222 control subjects. The HC, BPD, abdominal circumference (AC), and femur length (FL) measurements were extracted from the ultrasound records and standardized. The standardized growth parameters and discrepancies between them were compared in autism and control subjects. RESULTS: The autism group did not differ significantly from control subjects on individual measures of standardized HC, BPD, AC, and FL. Fetal HC was normal in the autism group. Preliminary findings suggest a tendency for fetal BPD to be large relative to HC in the autism group. An index of fetal body size, AC was significantly decreased in multiplex compared with simplex autism, and HC showed a trend decrease. The rate of pyelectasis was increased and breech position decreased in the autism group. No lateral ventricle abnormalities were reported. CONCLUSIONS: This preliminary study suggests that fetal head circumference is not abnormal in autism. The preliminary findings identify a subtle disturbance in uniformity of fetal brain growth and in renal development in some autistic cases, and differences in fetal development between simplex and multiplex autism.     

A pilot study on risperidone metabolism: the role of cytochromes P450 2D6 and 3A.

BACKGROUND: The limited available information on plasma risperidone levels shows a stable relationship between daily doses of risperidone and total plasma concentration (risperidone plus its active metabolite 9-hydroxyrisperidone). The ratio between risperidone and 9-hydroxyrisperidone characterizes cytochrome P450 2D6 (CYP2D6) status. According to the manufacturer, the CYP2D6 genotype or drugs that influence CYP2D6 or other cytochrome P450 isoenzyme activity are not expected to be clinically significant. One case report suggests that CYP3A participates in the metabolism of risperidone. METHOD: A case series of 13 risperidone patients (the initial case and 12 new cases) who were genotyped for CYP2D6 were followed, and another 20 risperidone patients from a case-control study for the CYP2D6 genotype were reviewed. RESULTS: The CYP2D6 poor metabolizers, who are enzyme deficient (2/13 in the case series and 3/20 in the case-control study), did not appear to tolerate risperidone well. Drugs affecting CYP3A, in particular powerful inducers and inhibitors, resulted in at least a 2-fold decrease or increase in plasma risperidone levels. CONCLUSION: The anecdotal nature of this study is clearly a limitation. Drugs influencing CYP3A and CYP2D6 metabolic activity may significantly affect risperidone levels. Thus, plasma level monitoring of risperidone in a clinical setting may be useful, especially if patients are taking multiple medications or a CYP2D6 deficiency is suspected. New prospective studies under more controlled conditions are needed to verify these hypotheses.     

Skeletal muscle involvement in myotonic dystrophy type 2. A comparative muscle ultrasound study

This study determines the presence and extent of muscle changes in 31 myotonic dystrophy type 2 (DM2) patients detected by muscle ultrasound. Results were compared to 31 adult-onset myotonic dystrophy type 1 patients (DM1) and healthy controls. Furthermore, we tested the hypothesis that structural muscle changes correlate with age, quantitative muscle force and serum creatine kinase in both disorders. In DM2 all seven examined muscles (right masseter muscle, right and left biceps brachii, right and left forearm flexors, right rectus femoris, and left tibialis anterior muscle) showed increased mean echo intensities (p ≤ 0.001). Atrophy of the masseter muscle and rectus femoris were both found in 23% of DM2 patients. Muscle thickness was significantly more decreased in the elbow flexors in DM2 compared to DM1. Echo intensity sum score correlated positively with age in DM2 (r=0.57, p=0.001) and negatively with muscle force (r=0.36, p=0.048). We conclude that all tested muscles are affected and structurally abnormal in DM2 patients. Proximal arm muscles are more affected in DM2 compared to DM1, which corresponds to clinical findings.     

脑动静脉畸形的多普勒超声研究

本文报道经颅多普勒超声(TCD)研究29例脑动静脉畸形(AVM)的血流动力学改变,50％小型AVM供血动脉的流速正常,50％小型AVM和大中型AVM供血动脉的流速均增快;中型AVM同侧颅外颈内动脉(PICA)流速增快,大型AVM双侧PICA流速均增快。AVM切除后供血动脉流速均减慢、脉动指数(PI)增大,其中中型AVM同侧PICA流速减慢,大型AVM双侧PI-CA流速均减慢且双侧颅内非AVM供血动脉的舒张末期流速减慢和PI增大。3例大型AVM手术中或手术后发生脑血流过度灌注现象。     

Comparative study of 3D reconstruction of rat sciatic nerve microvessels using Evans blue and lead oxide

Abstract

Background:

The blood supply of peripheral nerve grafts is one of the important factors that affect nerve regeneration. Many investigators have studied how intraneural microvessels are distributed and ways to promote the angiogenesis of grafts. However, there still does not exist an ideal intraneural microvascular model. The purpose of this study was to compare the three-dimensional (3D) reconstruction of microvessels of the sciatic nerve in Sprague-Dawley (SD) rats after systemic perfusion with Evans blue (EB) or lead oxide.

Methods:

Ten adult SD rats were randomized to a fluorography group (EB) or radiography group (lead oxide). After administration of the perfusion agents, imaging information was obtained by fluorescence microscopy and micro-computed tomography (μCT). Three-dimensional reconstruction was performed, and the diameter of microvessels at a constant distance (a cross-section was taken every 1 mm), the vascular index, and volume were measured. Two-dimensional (2D) images were obtained by serial sectioning and μCT scanning using the two methods described.

Results:

In the EB group, the diameter, vascular area, and vascular index of microvessels were 11·79 ± 7·23 μm, 0.14 ± 0.05 mm², and 24·19 ± 5·03%, respectively, and in the lead oxide group 26·45 ± 11·81 μm, 0.06 ± 0.02 mm², and 10·73 ± 2·06%, respectively. Microvessels with diameters <20 μm were visualized better in the EB group than in the lead oxide group (P < 0·01). However, there was no significant difference between the groups in the visualization of microvessels with diameters 20–49 μm (P > 0·05).

Conclusions:

Both EB and lead oxide can be used for 2D study of intraneural microvessels and 3D observation after reconstruction. Lead oxide is easy to use, and though its resolution is lower than that of EB for smaller microvessels with diameters <20 μm, it is more suitable for studying a large sample volume.     

Value of 3D imaging for the study of craniofacial malformations in children.

Three-dimensional (3D) imaging was performed on 150 children with craniofacial malformations divided into three groups: craniostenosis, craniofacial dysraphism and labio-maxillo-palatine clefts arbitrarily included in a corpus of constitutional and acquired abnormalities. The authors believe that this technique is of interest not only for the management of these children, but also to understand the pathogenesis of their malformations.     

Neuropeptide FF receptors in rat brain: A quantitative light-microscopic autoradiographic study using [125I][D.Tyr1, (NMe)Phe3]NPFF

The anatomical localization of neuropeptide FF receptors was examined by in vitro autoradiography techniques in rat brain sections by using [¹²⁵I][D.Tyr¹, (NMe)Phe³]NPFF. The specific binding of [¹²⁵I][D.Tyr¹, (NMe)Phe³]NPFF reached 90% of the total binding at 0.05 nM in rat spinal cord sections. Up to 40% of the specific binding of [¹²⁵I][D.Tyr¹, (NMe)Phe³]NPFF to rat spinal cord sections was still detectable following fixation with glutaraldehyde. Afterwards, the distribution of NPFF receptors was studied by light microscopy and their densities by microdensitometry with an image analysis system. In the light microscope, [¹²⁵I][D.Tyr¹, (NMe)Phe³]NPFF labelling appeared more or less uniformly distributed over nerve-cell bodies and surrounding neuropil. High concentrations of binding sites were detected in the presubiculum, parafascicular thalamic nucleus, gracile nucleus, spinal trigeminal tract nucleus, and a number of brainstem nuclei, with virtually no labelling in the cerebellum. In several areas a rostrocaudal gradient of sites concentration was observed. Neuropeptide FF receptors are well-placed to control incoming sensory and autonomic information processing. In contrast, the more recently developed areas of the forebrain possessed low density of sites. The distribution of [¹²⁵I][D.Tyr¹, (NMe)Phe³]NPFF binding sites should suggest anatomical substrates for the actions of neuropeptide FF. © 1996 Wiley-Liss, Inc.     

A prospective study of the accuracy of Doppler ultrasound in detecting carotid artery disease.

Results are presented from a two year prospective study using a Doppler ultrasound technique for the detection of carotid disease. The patients studied presented with transient cerebral ischaemic attacks or small strokes in the carotid territory. No other form of patient selection was used. Results were compared with those from carotid and arch aortography. 86% of normal vessels and 78% of diseases vessels were correctly classified. It is concluded that this technique offers a safe and accurate screening procedure for the management of patients presenting with transient cerebral ischaemia or small strokes.     

Mapping the avian visual tectofugal pathway using 3D reconstruction

Image processing in amniotes is usually accomplished by the thalamofugal and/or tectofugal visual systems. In laterally eyed birds, the tectofugal system dominates with functions such as color and motion processing, spatial orientation, stimulus identification, and localization. This makes it a critical system for complex avian behavior. Here, the brains of chicks, Gallus gallus, were used to produce serial brain sections in either coronal, sagittal, or horizontal planes and stained with either Nissl and Gallyas silver myelin or Luxol fast blue stain and cresyl echt violet (CEV). The emerging techniques of diffusible iodine-based contrast-enhanced computed tomography (diceCT) coupled with serial histochemistry in three planes were used to generate a comprehensive three-dimensional (3D) model of the avian tectofugal visual system. This enabled the 3D reconstruction of tectofugal circuits, including the three primary neuronal projections. Specifically, major components of the system included four regions of the retina, layers of the optic tectum, subdivisions of the nucleus rotundus in the thalamus, the entopallium in the forebrain, and supplementary components connecting into or out of this major avian visual sensory system. The resulting 3D model enabled a better understanding of the structural components and connectivity of this complex system by providing a complete spatial organization that occupied several distinct brain regions. We demonstrate how pairing diceCT with traditional histochemistry is an effective means to improve the understanding of, and thereby should generate insights into, anatomical and functional properties of complicated neural pathways, and we recommend this approach to clarify enigmatic properties of these pathways.