Chiari malformation with thick occipital bone

A case of a Chiari malformation with an extraordinarily thick occipital bone is described. The thick occipital bone might make the posterior fossa narrow with consequent herniation of the cerebellar tonsils to the foramen magnum and formation of a syrinx. At dural plasty, well-developed marginal and occipital sinuses should be deliberately handled with the preservation of normal venous drainage. This case gives us the essence of the occurrence mechanisms of Chiari malformation and foramen magnum decompression.     

Emissary occipital foramen

214 skulls were studied for the present study. A small foramen in the squamous part of the occipital bone just behind foramen magnum was noticed for the passage of emissary vein in one skull only, probably connecting occipital sinus with suboccipital venous plexus.     

枕骨大孔腹侧区肿瘤手术入路的应用解剖

目的:探讨枕骨大孔区腹侧肿瘤的最佳手术入路及其应用解剖学基础.方法:在5例共10侧正常人尸头标本上模拟枕下外侧经枕髁入路逐层解剖观测毗邻结构,到达枕骨大孔腹外侧区.结果:应用此入路切除部分枕髁可满意暴露枕骨大孔腹外侧区,而对重要的血管神经损伤最小.结论:枕下远外侧入路是枕骨大孔腹侧区肿瘤的最佳手术入路.     

Bony observations of some morphological variations and anomalies of the craniovertebral region

Human skeletons (214) belonging to a South African black and white cadaver population were pooled and examined for malformations of the craniovertebral region. Four crania, presenting with various manifestations of an occipital vertebra, such as a paracondylar process, epicondylar process, hypocondylar arch, and a third condyle were identified as well as two crania showing various degrees of assimilation of the atlas to the basicranium. Of particular interest was the identification of a cloverleaf-shaped foramen magnum in a cranium of an individual with achondroplasia as well as a cranium with marked asymmetry of both foramen magnum and occipital condyles. Due to the availability of both cranium and corresponding atlanto-axial components, the clinical significance of certain aspects of craniovertebral anomalies were vividly demonstrated, such as a pseudarthrosis formed by the meeting of a paracondylar process with an epitransverse process and a dens "riding high" in the foramen magnum as a result of assimilation of the atlas.     

上、下项线间相关距离测量及临床应用研究

目的　测量完整人颅骨的上、下项线及枕骨大孔间的距离,为临床应用提供数据。 方法　在113例中国成年人正常、干燥颅骨标本上,取枕外隆突最高点、上项线上枕外隆突最高点左、右两侧旁开1 cm、2 cm各取一点,颅骨后正中线上枕外嵴中点及其左、右两侧旁开1 cm点各取一点,从上、下项线所取测量点向枕骨大孔方向作与颅骨后正中线平行的直线,用游标卡尺测量枕骨上、下项线间及上、下项线分别与枕骨大孔间的弧面、直线、垂直及水平距离。 结果　在后正中线上,上、下项线间的距离最小,直线距离为（18.11±2.99）mm、弧面距离为（19.18±2.83）mm、垂直距离为（11.11±3.44）mm、水平距离为（14.65±3.19）mm,向左、右旁开后除水平距离变小,其余各距离指标变大;枕外嵴中点到枕骨大孔后缘间两点的距离最小,直线距离为（21.73±3.35）mm、弧面距离为（22.74±3.47）mm、垂直距离为（10.69±3.44）mm、水平距离为（19.10±3.35）mm,向左、右旁开后,各距离指标变大。 结论　下项线准确定位是临床操作安全和有效的关键,以枕外隆突和上项线可以确定下项线位置,在后正中线上,下项线距上项线的垂直距离最小,为（11.11±3.44）mm。     

Growth of the foramen magnum in achondroplasia

Foramen magnum growth curves in achondroplasia and in the general population are presented. The achondroplastic foramen magnum is small at birth, and during the first year it has a severely impaired rate of growth especially in the transverse dimension. This markedly diminished growth results not only from abnormal endochondral bone growth but also because of abnormal placement and premature fusion of the synchondroses. Evaluation of the foramen magnum in achondroplasia should address absolute size of the transverse and sagittal dimensions, shape, and growth centers to determine growth potential of this area.     

寰枕关节周围韧带的显微断层解剖

目的：揭示寰枕区的显微断层解剖结构，为临床手术提供准确的解剖学数据。方法：选取8具尸体头颅标本制作颅底组织块，并将这些组织块进行塑化，然后切成连续的切片。染色后在光学显微镜下观察。结果：齿突尖主要为骨密质，齿突中下部主要为骨松质。齿突尖韧带是连接齿突尖与枕骨大孔前缘的细小索状纤维束。覆膜是坚韧的薄膜，从枕骨斜坡下降，在十字韧带的上下纵束之后，与枢椎联系紧密。硬脊膜前方为覆膜，后方为蛛网膜。硬脊膜从斜坡开始与覆膜汇合，并向下移行至枕骨大孔前缘最下方的位置分开然后各自继续向下走行，在齿突的位置和覆膜再次汇合，向下走行至枢椎椎体后分离。在齿突尖水平的位置覆膜与前方的后纵韧带汇合。结论：Barkow韧带可能并不存在，临床手术中不能将其作为识别标志。     

远外侧入路中枕髁相关解剖学参数的CT影像研究

目的 探讨正常成人枕髁相关解剖学参数的CT影像测量,为远外侧入路手术中枕髁的处理提供解剖学依据。方法 回顾性分析2018年9月-2019年3月新乡医学院第一附属医院影像资料库中335例正常成人头颈CTA影像资料,应用Mimics软件对枕髁进行三维重建后,在图像下面观标出:枕骨大孔前缘中点(A)、枕骨大孔后缘中点(B)、枕髁后缘和枕骨大孔后缘交点(C)、舌下神经管内口后缘中点(D)等定位点,分别测量枕髁两侧A、B点连线与A、C点连线的夹角(∠α),A、B点连线与A、D点连线的夹角(∠β),CD两点之间的长度,枕髁前后径长度,以及∠β和∠α差值。采用配对样本t检验比较不同侧别间上述测量指标的差异。结果 335例正常成人两侧合计检测结果:∠α为32.49°~52.18°(42.06°±3.25°)、∠β为43.62°~73.48°(58.51°±5.37°),∠β和∠α差值为7.42°~30.10°(16.45°±4.07°);CD长度为6.18~13.08(8.94±1.33)mm;枕髁前后径长度为16.12~27.71(21.57±2.17) mm。枕髁左侧、右侧∠α为42.12° ± 2.88°、42.00°±3.59°,∠β为59.37° ± 5.24°、57.66° ± 5.39°,∠β和∠α差值为17.24°±4.13°、15.66°±3.87°,CD长度为(9.14±1.39)mm、 (8.73±1.23)mm,枕髁前后径长度为(21.59±2.28)mm、(21.55±2.08)mm。不同侧别间比较:左侧∠β、∠β与∠α差值、CD长度均大于右侧,差异均有统计学意义(t=4.402、5.971、4.199,P值均＜0.05);而∠α、枕髁前后径长度不同侧别间差异均无统计学意义(P值均＞0.05)。结论 不同侧别间枕髁的相关解剖学影像测量数据存在差异;远外侧入路中,磨除从枕髁后缘至舌下神经管内口范围的骨质所暴露的视野及扩大的视角,在左侧均大于右侧。因此,对于枕骨大孔腹侧正中病变,建议从左侧开颅,可获得更大的暴露范围。     

小脑下后动脉在枕骨大孔区的解剖学研究

目的对颅后窝枕骨大孔区小脑下后动脉进行观察与测量,并探讨其临床意义。方法选取成人颅底标本15例,观察枕骨大孔区小脑下后动脉位置、走行、毗邻关系及其分布,测量相关数据并进行统计学处理。结果颅后窝枕骨大孔区小脑下后动脉左右两侧起始部外径:左侧为1.32~1.49 mm,平均(1.41±0.05)mm;右侧为1.27~1.49 mm,平均(1.39±0.07)mm,左右管径比较差异无统计学意义(P>0.05);小脑下后动脉走行呈“S”形,与第Ⅸ、Ⅹ、Ⅺ对脑神经的位置关系密切。结论小脑下后动脉在枕骨大孔区起点走行、分布具有特有的解剖特点,在临床中枕骨大孔区小脑下后动脉相关疾病的手术时应避免医源性损伤。     

Variability of Human Foramen Magnum Size

The foramen magnum is an important landmark of the skull base and is of particular interest for anthropology, anatomy, forensic medicine, and other medical fields. Despite its importance, few osteometric studies of the foramen magnum have been published so far. A total of 110 transverse and 111 sagittal diameters from Central European male and female dry specimens dating from the Pleistocene to modern times were measured, and related to sex, age, stature, ethnicity, and a possible secular trend. Only a moderate positive correlation between the transverse and the sagittal diameter of the foramen magnum was found. Surprisingly, neither sexual dimorphism, individual age‐dependency, nor a secular trend was found for either diameter. Furthermore, the relationship between the individual stature and foramen magnum diameters was weak: thus foramen magnum size cannot be used as reliable indicator for stature estimation. Further consideration of possible factors influencing the variability of human foramen magnum size shall be explored in larger and geographically more diverse samples, thus serving forensic, clinical, anatomical, and anthropological interests in this body part. Anat Rec, 2009. © 2009 Wiley‐Liss, Inc.     

内蒙古地区枕骨髁及枕骨大孔应用解剖三维数字化测量

目的 利用三维重建测量枕骨髁(OC)及枕骨大孔(FM)解剖学结构,分析OC、FM形态学特征及相对位置关系,为颅颈交界区病变的影像学诊断及外科手术入路的选择提供解剖学参数.方法 选取60例正常者的头颅和上颈椎螺旋CT扫描图像,男、女各30例,年龄20～65(48.18±16.17)岁,将数据导入Syno.Via VB10...     

颈动脉管外口及周边骨性结构的解剖特点

目的:探究颈动脉管外口及周边骨性结构的解剖结构特点.方法:选取成人颅骨,由1位口腔专业教师确定各观测点的位置后,用游标卡尺、圆规和直尺等测量颈动脉管外口的长径、短径及该口长径外侧点至茎突根部内侧点、茎乳孔内侧点、乳突尖、舌下神经管外口长径内侧点、枕髁最前点、枕骨大孔最前点和正中矢状面的最短距离,所得数据进行统计学分析....     

Absent falx cerebelli: report of a rare case

The falx cerebelli is a small crescentic fold of dura mater below the tentorium cerebelli, which projects forward into the posterior cerebellar notch. Its base is directed upwards and attached to the posterior part of the inferior surface of the tentorium cerebelli in the midline; its posterior margin is attached to the internal occipital crest and contains the occipital sinus; the apex frequently dividing into two small folds which disappear at the sides of the foramen magnum. The material of our neuroanatomic study consisted of formalin-embalmed cadavers that we had in the dissection room of our Department from cadaver donors for students education. We report a case of absence of this dura mater structure from a 91-year-old female cadaver. To our knowledge, this is the first report of absent falx cerebelli in a normal human brain. The review of the literature revealed a few reports of its multiplication.     

Hypoplastic occipital condyle and third occipital condyle: Review of their dysembryology

Disruption or embryologic derailment of the normal bony architecture of the craniovertebral junction (CVJ) may result in symptoms. As studies of the embryology and pathology of hypoplasia of the occipital condyles and third occipital condyles are lacking in the literature, the present review was performed. Standard search engines were accessed and queried for publications regarding hypoplastic occipital condyles and third occipital condyles. The literature supports the notion that occipital condyle hypoplasia and a third occipital condyle are due to malformation or persistence of the proatlas, respectively. The Pax‐1 gene is most likely involved in this process. Clinically, condylar hypoplasia may narrow the foramen magnum and lead to lateral medullary compression. Additionally, this maldevelopment can result in transient vertebral artery compression secondary to posterior subluxation of the occiput. Third occipital condyles have been associated with cervical canal stenosis, hypoplasia of the dens, transverse ligament laxity, and atlanto‐axial instability causing acute and chronic spinal cord compression. Treatment goals are focused on craniovertebral stability. A better understanding of the embryology and pathology related to CVJ anomalies is useful to the clinician treating patients presenting with these entities. Clin. Anat. 26:928–932, 2013. © 2013 Wiley Periodicals, Inc.     

Notochordal remnants in human iniencephaly suggest disturbed dorsoventral axis signaling.

Iniencephaly is a central nervous system malformation in which brain and spinal cord are not normally separated at the level of the foramen magnum. The occipital region is fastened to the back of the body at different levels. The purpose of this study of a 16-week human fetus with iniencephaly and holoprosencephaly was to examine the body axis for notochordal remnants in order to determine if an abnormality of dorsoventral axis signaling may be responsible for the development of the iniencephaly abnormality. This aspect of iniencephaly has not been described previously. Radiographic and histochemical investigations were performed. The fetus described here appeared to exhibit an abnormal notochordal course in the upper lumbar, thoracic, and cervical regions. This finding leads us to the hypothesis that iniencephaly might arise because of deviant gene expression in the embryonic period affecting the dorsoventral orientation of the body axis, anatomically indicated by the notochordal malpositions.     

枕下极外侧手术入路的解剖学研究

目的：为枕下极外侧手术入路提供解剖学基础。方法：10例成人尸体头湿标本按手术入路在手术显微镜下进行解剖和观测。结果：枕下三角是枕下极外侧入路中重要的解剖学标志，在分离移位椎动脉后，切除枕骨髁后部1／3以辨别和暴露舌下神经管，枕骨髁的磨除可显著扩大枕骨大孔前缘的暴露范围，磨除颈静脉结节对扩大斜坡中下部的暴露有重要的作用。椎动脉硬膜内段及其分支与后组脑神经有复杂的毗邻和穿行关系。结论：枕下极外侧入路尽管解剖复杂，但可在不牵拉延髓的基础上充分暴露颈延髓交界部腹侧面和外侧面的区域，达到充分暴露的枕骨髁磨除范围限于其后1／3即可.     

颅底外面枕骨基底部及周边骨性结构的测量和临床意义

目的为斜坡区肿瘤手术提供解剖资料。方法20例整颅,10例行水平切面,10例行正中矢状切面。测量切牙孔、前鼻棘、后鼻棘、枕骨大孔前端、枕髁前端、卵圆孔、破裂孔、颈动脉管外口及舌下神经管外口的内侧缘至咽结节的距离;测量卵圆孔、破裂孔、颈动脉管外口及舌下神经管外口的内侧缘至正中线的距离;测量枕骨基底部颅底外面的长径、枕骨大孔纵径(FML)、枕骨大孔前正中点与枕髁后缘连线垂直距离(AOCP)、枕髁轴径(OCA)、枕髁间距。结果切牙孔后缘、前鼻棘、后鼻棘、枕骨大孔前端、枕髁前端、卵圆孔、破裂孔、颈动脉管外口及舌下神经管外口的内侧缘至咽结节的距离分别为(mm):72.12±4.25、77.77±3.89、33.73±2.07、13.14±1.91、15.71±1.74、27.51±2.12、15.98±1.98、25.93±2.23、19.15±1.49。卵圆孔、破裂孔、颈动脉管及舌下神经管外口的内侧缘至中线的距离分别为:25.55±1.63、11.72±1.70、25.75±1.98、17.41±1.41。枕骨基底部颅底外面长径、FML、AOCP、OCA、枕髁间距分别为(mm):28.80±2.67、35.84±2.59、17.10±1.13、24.55±2.35、21.07±1.92。结论经口咽至斜坡区的手术入路中,开骨窗时安全范围是以咽结节为中心,以15mm为半径做斜坡磨除;也可以做矩形骨窗,即以咽结节为中心开一长(高)25mm×宽20mm的骨窗。     

Improvement in ventriculomegaly following cervicomedullary decompressive surgery in children with achondroplasia and foramen magnum stenosis

The role of cervicomedullary decompression (CMD) in the care of hydrocephalic achondroplastic children who present with simultaneous foramen magnum stenosis is not well understood. We sought to determine the percentage of symptomatic achondroplastic children with foramen magnum stenosis who had stabilization or improvement in ventriculomegaly following CMD. The authors retrospectively reviewed the records of pediatric patients at Cedars‐Sinai Medical Center with achondroplasia and signs of progressive ventriculomegaly who underwent CMD for symptomatic foramen magnum stenosis between the years 2000 and 2018. Clinical outcomes included changes in fontanelle characteristics, head circumference (HC) percentile, and incidence of ventriculoperitoneal (VP) shunting. Radiographic outcomes measured included changes in Evans ratio. We excluded individuals who were shunted before CMD from our study. Sixteen children presented with symptomatic foramen magnum stenosis and full anterior fontanelle or jump in the HC percentiles. Two children underwent placement of a VP shunt before decompressive surgery and were excluded from further analysis. Of the remaining 14 children who underwent CMD, 13 (93%) showed softening or flattening of their fontanelles post‐operatively. Ten of these 14 children had both pre‐ and post‐operative HC percentile records available, with 8 showing increasing HC percentiles before surgery. Seven of those eight children (88%) showed a deceleration or stabilization of HC growth velocity following decompression of the foramen magnum. Among 10 children with available pre‐ and post‐operative brain imaging, ventricular size improved in 5 (50%), stabilized in 2 (20%), and slightly increased in 3 (30%) children after decompression. Two children (14%) required a shunt despite decompression of the foramen magnum. A significant proportion of children with concomitant signs of raised intracranial pressure or findings of progressive ventriculomegaly and foramen magnum stenosis may have improvement or stabilization of these findings following CMD. CMD may decrease the need for VP shunting and its associated complications in the select group of hydrocephalic children with achondroplasia presenting with symptomatic foramen magnum stenosis.     

Computerized tomography of the foramen magnum: achondroplastic values compared to normal standards

Computerized tomographic dimensions of the foramen magnum of 63 achondroplastic individuals were compared to standards established for nonachondroplastic individuals. The size of the foramen magnum in patients with achondroplasia was small at all ages, particularly in those with serious neurologic problems. The data suggest that measurement of the foramen magnum may identify achondroplastic individuals at high risk of developing neurologic complications.