Motor callosal disconnection in early relapsing-remitting multiple sclerosis

In relapsing-remitting multiple sclerosis (RRMS) the corpus callosum (CC) is often and early affected by macroscopic lesions when investigated by conventional MRI. We sought to determine to which extent microstructural and effective disconnection of the CC are already present in RRMS patients at the earliest stages of the disease prior to evidence of macroscopic CC lesion. We compared 16 very early RRMS patients (median expanded disability status scale (EDSS), 1.5; range, 0-2.0) to an age-matched group of healthy controls and focused analysis to the motor CC, i.e. that part of the CC relaying interhemispheric motor information. A combined functional magnetic resonance imaging/diffusion tensor imaging fiber-tracking procedure was applied to identify the callosal motor fibers (CMFs) connecting the hand areas of the primary motor cortices of the two hemispheres. Fractional anisotropy (FA) within the motor CC (FA-CC) assessed the CMF microstructural integrity. Bifocal paired transcranial magnetic stimulation (TMS) tested short-interval interhemispheric inhibition (S-IHI), an established measure of CMF effective connectivity. FA-CC and S-IHI were significantly reduced in early RRMS compared to healthy controls. Furthermore, a significant linear correlation between microstructure (FA-CC) and function (S-IHI) in the controls was broken down in the patients. These abnormalities were obtained in the absence of macroscopic CMF lesion in conventional MRI, and whilst motor hand/arm function in the nine-hole-peg test and corticospinal conduction time were normal. Findings suggest that reductions in FA and S-IHI may serve as surrogate markers of motor callosal disconnection at the earliest stages of RRMS prior to development of macroscopic lesion.     

Retinal input influences the size and corticocortical connectivity of visual cortex during postnatal development in the ferret

Retinal input plays an important role in the specification of topographically organized circuits and neuronal response properties, but the mechanism and timing of this effect is not known in most species. A system that shows dramatic dependence on retinal influences is the interhemispheric connection through the corpus callosum. Using ferrets, we analyzed the extent to which development of the visual callosal pattern depends on retinal influences, and explored the period during which these influences are required for normal pattern formation. We studied the mature callosal patterns in normal ferrets and in ferrets bilaterally enucleated (BE) at postnatal day 7 (P7) or P20. Callosal patterns were revealed in tangential sections from unfolded and flattened brains following multiple injections of horseradish peroxidase in the opposite hemisphere. We also estimated the effect of enucleation on the surface areas of striate and extrastriate visual cortex by using magnetic resonance imaging (MRI) data from intact brains. In BEP7 ferrets we found that the pattern of callosal connections was highly anomalous and the sizes of both striate and extrastriate visual cortex were significantly reduced. In contrast, enucleation at P20 had no significant effect on the callosal pattern, but it still caused a reduction in the size of striate and extrastriate visual cortex. Finally, retinal deafferentation had no significant effect on the number of visual callosal neurons. These results indicate that the critical period during which the eyes influence the development of callosal patterns, but not the size of visual cortex, ends by P20 in the ferret.     

前纵裂入路显微手术治疗鞍结节脑膜瘤

目的:探讨前纵裂入路切除鞍结节脑膜瘤的手术技术以及安全性有效性,特别关注术后视力的变化。方法:回顾性分析新疆医科大学第一附属医院神经外科2005年1月～2010年12月连续收治的21例前纵裂入路切除鞍结节脑膜瘤患者的临床资料。前纵裂分离时在显微镜高倍放大视野下锐性逆向分离,且要分离足够开,从大脑前动脉膝部至蝶骨平台,必要时可同时在第一间隙和第四间隙操作切除突入三脑室底的肿瘤,而不牵拉视交叉和三脑室底。肿瘤切除从中线开始,先分离阻断肿瘤基底部血供,蛛网膜内瘤内分块切除减压,分离肿瘤和神经之间的蛛网膜界限,依次分离视力较差侧、视交叉、视力较好侧,最后分离垂体柄以及脚尖窝的肿瘤,注意保护蛛网膜界限完整。评价术前、术后视力变化以及肿瘤是否全切。结果:随访3个月～58个月,肿瘤全切19例(SimpsonⅡ级),1例复发。2例大部切除。21例病人中,视力好转15例,没有变化5例,1例恶化。2例额叶静脉梗塞性出血。结论:尽管病例数较少,随访时间也较短,本研究结果基本可以说明前纵裂入路切除鞍结节脑膜瘤是安全有效地。     

Low Anterior Interhemispheric Approach – A Narrow Corridor to Aneurysms of the Anterior Communicating Artery

Summary. Summary. Background: Many approaches for clipping anterior communicating artery (ACoA) aneurysms are reported in the literature. We describe here a new approach called “low anterior interhemispheric approach” for clipping of ACoA aneurysms. Materials and Methods: A low anterior interhemispheric approach utilizing a unilateral frontal craniotomy flap with minimal unilateral frontal lobe retraction was used in treating four patients harboring an unruptured ACoA aneurysm. The approach axis is directed to the ACoA area itself with minimal exposure to the anterior cerebral vessels. Findings: In all patients, complete neck clipping was possible with minimal brain retraction, without vascular damage and preserved olfaction. Interpretation: This approach is preferred on anatomical grounds for cases of unruptured small and medium sized ACoA aneurysms projecting anteriorly or posteriorly because the anterior communicating artery complex area can be fully visualized with minimal manipulation of the frontal lobes and anterior cerebral arteries.     

Basic Connectivity of the Cerebral Cortex and some Considerations on the Corpus Callosum

SCHÜZ, A. Basic connectivity of the cerebral cortex and some considerations on the corpus callosum. NEUROSCI BIOBEHAV REV 20(4)567–570, 1996.—Studies on the connectivity of the cerebral cortex have lent strong support to the idea that the cortex is an associative network in which information is stored by way of Hebbian cell assemblies. One of the main arguments for this is the elaborated system of cortico-cortical long-range connections which allows distant regions of the cortex to interact. Part of this system is the corpus callosum, which is responsible for the co-operation of the two cortical hemispheres. The following points are interesting with regard to interhemispheric co-operation: (1) the callosal system includes fewer neurons than the system of intrahemispheric long-range connections; (2) the mirror image activity induced by the callosal system may be advantageous for the ignition of cell assemblies; (3) the fibres of the corpus callosum differ considerably in thickness, which may be considered as anatomical evidence for more direct co-operation of the two hemispheres in some tasks rather than in others; and (4) a complex relationship between brain size and fibre thickness becomes evident in the corpus callosum, in which only some fibres seem to compensate for the longer conduction times in larger brains. Copyright © 1996 Elsevier Science Ltd.     

Exploratory data analysis reveals visuovisual interhemispheric transfer in functional magnetic resonance imaging.

We used an exploratory data analysis approach to detect interhemispheric processing of complex visual stimuli in functional magnetic resonance imaging (fMRI). A crossed-uncrossed visual field paradigm was used to elicit interhemispheric transfer of picture/word information. Under the uncrossed (control) condition, the stimuli were presented to the preferential hemispheres (pictures to the left visual field/right hemisphere and words to the right visual field/left hemisphere). Under the crossed condition, the visual field presentation was switched in order to elicit increased interhemispheric processing. Fuzzy cluster analysis revealed significantly more crossed activity in cortical areas near the splenium of the corpus callosum. As expected, examination of the activation revealed smaller responses in perisplenial regions (relative to visual responses in the medial extrastriate regions). The exploratory results were compared with those obtained from parametric and masked analyses. The findings confirm that fMRI can be used to detect interhemispheric transfer of picture/word information. The activation was optimally characterized using exploratory data analysis.     

Bilateral cerebral metabolic alterations following lesion of the ventromedial thalamic nucleus: mapping by the 14C-deoxyglucose method in conscious rats

The functional role of the ventromedial thalamic nucleus (VM) was investigated by means of the quantitative autoradiographic 14C-deoxyglucose method. Local cerebral glucose utilization (LCGU) was measured bilaterally in 53 discrete brain areas of conscious rats 1 week and 1 month following electrolytic lesion of the VM. There was no difference observed in the LCGU values between the two groups of lesioned animals. In the VM-lesioned rats glucose consumption was decreased in several ipsilateral (pre-frontal, frontal, cingulate, sensorimotor, visual) and in some contralateral (cingulate, sensorimotor, visual) cortical areas. Furthermore, LCGU values were depressed bilaterally in the striatum, hippocampus, dentate gyrus, substantia nigra compacta, superficial layers of the superior colliculus, oculomotor complex, and cerebellar dentate nuclei. Glucose utilization was diminished also in the deep layers of the superior colliculus and in the fastigial nucleus ipsilateral to the lesion. Within the thalamus, glucose metabolism was decreased in several nuclei either bilaterally (reticular, intralaminar, paralamellar mediodorsal) or ipsilaterally (lateroposterior, ventrobasal, ventrolateral, ventroanterior, and medioventral) to the lesion. A significant correlation between the percentage of injured VM and the regional metabolic depression was demonstrated in the areas displaying the most pronounced decrease in LCGU. These results support a widespread influence of the VM on brain function extending beyond the limits of purely motor systems and reveal the consequences of a unilateral lesion of the thalamus on metabolic activity in several contralateral structures.     

显微外科治疗前交通动脉瘤手术入路的选择及疗效分析

目的探讨显微外科标准翼点入路、纵裂入路和翼点纵裂联合入路治疗前交通动脉瘤的疗效,以及显微手术入路选择的原则。方法回顾性分析2012年1月~2015年6月保定市第二医院神经外科收治的78例前交通动脉瘤患者的临床资料和手术效果,术前均行头颅CTA或DSA检查确诊。疾病早期显微手术经翼点入路夹闭动脉瘤39例,经纵裂入路34例,联合入路5例。结果根据患者出院后6个月时的格拉斯哥预后量表(GOS)评分评估手术疗效,经翼点入路手术的患者中预后良好者29例,经纵裂入路患者中预后良好者25例,联合入路的5例患者均预后良好。结论早期显微手术经翼点入路、经纵裂入路及联合入路治疗前交通动脉瘤均有效且预后良好。根据不同的动脉瘤瘤体指向,合理地选择手术入路是手术成功的基础。