Descriptive study of the differences in the level of the conus medullaris in four different age groups

In performing neuraxial procedures, knowledge of the location of the conus medullaris in patients of all ages is important. The aim of this study was to determine the location of conus medullaris in a sample of newborn/infant cadavers and sagittal MRIs of children, adolescents, and young adults. The subjects of both the samples were subdivided into four developmental stages. No statistical difference was seen between the three older age groups (P > 0.05). A significant difference was evident when the newborn/infant stage was compared with the other, older stages (P < 0.001 for all comparisons). In the newborn/infant group the spinal cord terminated most frequently at the level of L2/L3 (16%). In the childhood stage, the spinal cord terminated at the levels of T12/L1 and the lower third of L1 (21%). In the adolescent population, it was most often found at the level of the middle third of L1 and L1/L2 (19%). Finally, in the young adult group, the spinal cord terminated at the level of L1/L2 (25%). This study confirmed the different level of spinal cord termination between newborns/infants less than one‐year‐old and subjects older than one year. In this sample the conus medullaris was not found caudal to the L3 vertebral body, which is more cranial than the prescribed level of needle insertion recommended for lumbar neuraxial procedures. It is recommended that the exact level of spinal cord termination should be determined prior to attempting lumbar neuraxial procedures in newborns or infants. Clin. Anat. 28:638–644, 2015. © 2015 Wiley Periodicals, Inc.     

What is the true location of Jacoby's line?

We investigated 60 cadavers to examine the accurate location of conus medullaris, lower end of dura mater, and intercrestal line (Jacoby's line). Jacoby's line was established using the method described by Jacoby GW (1899). Then the intersection of this line and vertical line through the spinous processes was marked by a fine nail. After a laminectomy was performed to expose the spinal cord, spinal level of the conus medullaris, the lower end of dura mater, and Jacoby's line were examined, and marked and recorded these locations of nailing. In 2 of 48 cases (2.1%), Jacoby's line passed through the level superior to 3rd lumber vertebra (L3). The Conus medullaris was at the level beneath L3 in 2 of 57 cases (3.5%). And lower end of dura mater was located beneath the superior margin of S3 in 1 of 28 cases (3.6%). When Jacoby's line is used as a guide-point, the site for subarachnoid puncture is established in the L3-4 interspinous space. But when we consider the risk of spinal cord injury cannot be completely excluded, in case that conus medullaris is located inferior to L3 in 3.5% of cases. Conseqently, it should be important to avoid performing subarachnoid puncture at L2-3 or higher lumbar vertebral level especially in the elderly.     

An investigation of the conus medullaris termination level during the period of fetal development to adulthood.

The spinal cord fills the length of the vertebral canal at the early period of intrauterine term. It is reported to extend to the level of the third lumbar vertebra at birth, because the vertebral column is growing more rapidly in the longitudinal direction than the spinal cord. The present investigation aimed to determine the changes in the termination level of conus medullaris (TLCM) from fetus to adulthood in a total of 285 individuals who had no defects in the central or peripheral nervous system, and were obtained from our Faculties of Medicine and Konya Maternity Hospital between 1992-1995. The age distribution was as follows: 36 fetuses, 20 prematures and 50 neonates, 51 children aged 1 to 7 years and 128 adults aged 15 to 68 years. In this study, for fetuses, prematures, neonates and children the TLCM was determined using ultrasonography. In addition, microdissection was used in fetuses to confirm the results obtained from the above technique. Also, magnetic resonance imaging was used in adults. During fetal life the end of the conus altered its levels from S5 to L3 vertebrae. The tip of the conus medullaris of the prematures and neonates ranged from L1 to L3 vertebrae. The tip of the conus medullaris in the children lay between the Th12 and L3 vertebrae, and in the adults it was between the Th12 and L2 vertebrae. There were slight differences between the prematures and neonates in terms of the TLCM. We concluded that there are differences in the TLCM between the age groups and therefore, especially in prematures and infants the determination of the tip of conus medullaris might be important for preventing postoperative neurological complications.     

Anatomical relationship and positions of the lumbar and sacral segments of the spinal cord according to the vertebral bodies and the spinal roots

Segments of the spinal cord generally do not correspond to the respective vertebral level and there are many anatomical variations in terms of the segment and the level of vertebra. The aim of this study is to investigate the variations and levels of lumbar and sacral spinal cord segments with reference to the axilla of the T11, T12, and L1 spinal nerve roots and adjacent vertebrae. Morphometric measurements were made on 16 formalin fixed adult cadaveric spinal cords. We observed termination of the spinal cord between the axilla of the L1 and L2 spinal nerve roots in 15 specimens (93.8%). In all cadavers the emergence of the T11, T12, and the L1 spinal nerve roots was at the level of the lower one‐third of the same vertebral body. In 15 specimens (93.8%), the beginning of the lumbar spinal cord segment was found to be above the T11 spinal nerve root axilla and corresponded to the upper one‐third of the T11 vertebral body. The beginning of the sacral spinal cord segment occurred above the L1 spinal nerve root axilla and corresponded to the upper one‐third of the L1 vertebral body. The results of this study showed that when the conus medullaris is located at the L1–L2 level, the beginning of the lumbar spinal cord segment always corresponds to the body of T11 vertebra. This study provides detailed information about the correspondence of the spinal cord segments with reference to the axilla of the spinal nerve roots. Clin. Anat. 27:227–233, 2014. © 2013 Wiley Periodicals, Inc.     

Radiographic and Magnetic Resonance Imaging Identification of Thoracolumbar Spine Variants with Implications for the Positioning of the Conus Medullaris in Rhesus Macaques

The anatomy of the vertebral column in mammals may differ between species and between subjects of the same species, especially with regards to the composition of the thoracolumbar spine. We investigated, using several noninvasive imaging techniques, the thoracolumbar spine of a total of 44 adult rhesus macaques of both genders. Radiographic examination of the vertebral column showed a predominant spine phenotype with 12 rib‐bearing thoracic vertebrae and 7 lumbar vertebrae without ribs in 82% of subjects, whereas a subset of subjects demonstrated 13 rib‐bearing thoracic vertebrae and 6 lumbar vertebrae without ribs. Computer tomography studies of the thoraco‐lumbar spine in two cases with a pair of supernumerary ribs showed facet joints between the most caudal pair of ribs and the associated vertebra, supporting a thoracic phenotype. Magnetic resonance imaging (MRI) studies were used to determine the relationship between the lumbosacral spinal cord and the vertebral column. The length of the conus medullaris portion of the spinal cord was 1.5 ± 0.3 vertebral units, and its rostral and caudal positions in the spinal canal were at 2.0 ± 0.3 and 3.6 ± 0.4 vertebral units below the thoracolumbar junction, respectively (n = 44). The presence of a set of supernumerary ribs did not affect the length or craniocaudal position of the conus medullaris, and subjects with13 rib‐bearing vertebrae may from a functional or spine surgical perspective be considered as exhibiting12 thoracic vertebrae and an L1 vertebra with ribs. Anat Rec, 300:300–308, 2017. © 2016 Wiley Periodicals, Inc.     

Which spinal levels are identified by palpation of the iliac crests and the posterior superior iliac spines?

The line joining the superior aspect of the iliac crests posteriorly (the intercristal line) is commonly stated to cross the midline at the L4 or L4-5 spinal level on imaging. This study aimed to assess the spinal level identified through palpation of surface anatomy (iliac crests and posterior superior iliac spines) in adults and the level of agreement compared with the intercristal line identified through imaging. The study participants included consecutive adult patients undergoing prone fluoroscopically guided spinal injections for chronic low back pain at the Royal Orthopaedic Hospital, Birmingham, between April and July 2004. Prior to fluoroscopic imaging, each patient's surface anatomy was palpated by two examiners and lines created to form the palpated intercristal line and the posterior superior iliac spine line. Following imaging, the mid-line spinal levels identified by these palpated lines were recorded and the level of agreement (kappa coefficient) with the intercristal line formed by imaging of the iliac crests was assessed. The results showed that although the L4 or L4-5 spinal levels were identified on imaging of the intercristal line in 86.7% of 75 patients (49 female), the intercristal line formed through palpation tended to identify higher levels; the L3 or L3-4 spinal levels in 77.3% of cases and more commonly in females than in males (85.7 vs. 61.5%) and in patients with higher body mass indices. The level of agreement between the two lines was poor (kappa = 0.05). The posterior superior iliac spine line identified the S2 spinous process in 51% and the S1 in 44% of 60 (45 female) patients. The results suggest that formation of the intercristal line by palpation of the iliac crests identifies different spinal levels to those identified by imaging and that both methods should be regarded as different instruments. In the clinical situation, it may be more appropriate to consider that palpation of the intercristal line is a guide for identifying the L3 or L3-4 spinal levels rather than the L4 or L4-5 levels, particularly in females and patients with higher body mass indices.     

A single re-implanted ventral root exerts neurotropic effects over multiple spinal cord segments in the adult rat

Spinal cord injuries, particularly traumatic injuries to the conus medullaris and cauda equina, are typically complex and involve multiple segmental levels. Implantation of avulsed ventral roots into the spinal cord as a repair strategy has been shown to be neuroprotective and promote axonal regeneration by spinal cord neurons into an implanted root. However, it is not well known over what distance in the spinal cord an implanted ventral root can exert its neurotropic effect. Here, we investigated whether an avulsed L6 ventral root acutely implanted into the rat spinal cord after a four level (L5–S2) unilateral ventral root avulsion injury may exert neurotropic effects on autonomic and motor neurons over multiple spinal cord segments at 6 weeks postoperatively. Using retrograde labeling techniques and stereological quantification methods, we demonstrate that autonomic and motor neurons from all four lesioned spinal cord segments, spanning more than an 8 mm rostro-caudal distance, reinnervated the one implanted root. The rostro-caudal distribution suggested a gradient of neurotropism, where the axotomized neurons closest to the implanted site had the highest probability of root reinnervation. These results suggest that implantation of a single ventral root may provide neurotropic effects to injured neurons at the site of lesion as well as in the adjacent spinal cord segments. Our findings may be of translational research interest for the development of surgical repair strategies after multi-level conus medullaris and cauda equina injuries, in which fewer ventral roots than spinal cord segments may be available for implantation.     

腹腔镜辅助下腰椎骨折前路减压内固定术

目的探讨在腹腔镜辅助下，经腹膜后腰肌间隙人路的小切口对腰椎爆裂性骨折椎管减压、植骨、内固定手术的可行性。方法13例腰椎爆裂性骨折，在腹腔镜辅助下经腹膜后腰肌间隙入路，应用腹腔镜、自制手术器械，进行椎体爆裂性骨折并脊髓圆锥、马尾神经压迫症病例的椎管减压、植骨、内固定手术。结果全部病例切口Ⅰ期愈合，椎管内骨块清除彻底。椎管减压充分，植骨块融合良好，内固定器无松动；1例L4椎体爆裂性骨折、马尾神经受压病例同时还伴有T6骨折、完全性截瘫，术后脊髓功能未恢复；4例圆锥、马尾神经受压，术后功能基本恢复。结论腹腔镜辅助下经腹膜后腰肌间隙人路的小切口腰椎手术，可以完成椎体爆裂性骨折并脊髓圆锥、马尾神经压迫症的椎管减压、植骨、内固定术。     

The relationship between the lumbosacral enlargement and the conus medullaris during the period of fetal development and adulthood

The spinal cord is situated within the vertebral canal by the third month of intrauterine life. The spinal cord possesses two symmetrical enlargements, which constitute the segments of the plexuses the cervical enlargement for the brachial plexus and the lumbosacral enlargement for the lumbar and sacral plexus. In our study, we aimed to investigate the relationship between the termination level of the lumbosacral enlargement (TLLE) and that of the conus medullaris (TLCM) during the period of fetal development and adulthood. We used a total of 75 cases 25 fetuses (male 16, female 9) whose crown-rump length ranged between 90–190 mm, 25 premature and full-term neonates (male 17, female 8) whose post-menstrual ages ranged between 33–55 weeks, and 25 adults (male 12, female 13) aged between 22–72 years. The dissection technique for fetuses, ultrasonography for premature and full-term newborns, and magnetic resonance imaging (MRI) for adults were used to determine lumbosacral enlargement and TLCM. The differences between the TLCM and the termination level of the largest part of the transverse diameter of the lumbosacral enlargement were investigated. The differences between the TLLE and TLCM were found in different ratios from the period of fetal development to adulthood. Therefore, during medical treatment and surgical procedures this should be taken into account to avoid complications.     

Bronchogenic cyst of the conus medullaris with spinal cord tethering: a case report and review of the literature

Bronchogenic cysts (BCs) are congenital malformations that originate from remnants of the primitive foregut. Intraspinal BCs, especially those of the conus medullaris are rare with only one case reported until now. To date, a bronchogenic cyst with spinal cord tethering has not been previously reported. We reviewed the clinical course of a 44-year-old woman, who presented with low back pain and leg weaknesss as well as sphincter disturbance. Magnetic resonance imaging showed an intradural oval mass located at the conus medullaris. A tethered cord was also observed, as well as a dermal sinus tract. The mass was totally removed after an L3-L4 laminectomy without detethering during operation. Pathologic examination confirmed the diagnosis of bronchogenic cyst. By six months after treatment, the patient had experienced nearly complete recovery. The review of literature indicated that detethering was performed in most reported cases of neurenteric cysts with spinal cord tethering, and one of six patients was diagnosed with a postoperative recurrence. The co-existence of bronchogenic cyst and a tethered spinal cord would imply associated developmental errors in embryogenesis. It is worth noting that whether detethering is necessary after the cyst removal.     

Reimplantation of avulsed lumbosacral ventral roots in the rat ameliorates injury-induced degeneration of primary afferent axon collaterals in the spinal dorsal columns

Injuries to the cauda equina/conus medullaris portion of the spinal cord can result in motor, sensory, and autonomic dysfunction, and neuropathic pain. In rats, unilateral avulsion of the motor efferents from the lumbosacral spinal cord results in at-level allodynia, along with a corresponding glial and inflammatory response in the dorsal horn of the spinal cord segments immediately rostral to the lesion. Here, we investigated the fate of intramedullary primary sensory projections following a motor efferent lesion. The lumbosacral (L6 and S1) ventral roots were unilaterally avulsed from the rat spinal cord (VRA; n=9). A second experimental group had the avulsed roots acutely reimplanted into the lateral funiculus (Imp; n=5), as this neural repair strategy is neuroprotective, and promotes the functional reinnervation of peripheral targets. A laminectomy-only group served as controls (Lam; n=7). At 8 weeks post-lesion, immunohistochemical examination showed a 42% reduction (P<0.001) in the number of RT97-positive axons in the ascending tracts of the dorsal funiculus of the L4-5 spinal segment in VRA rats. Evidence for degenerating myelin was also present. Reimplantation of the avulsed roots ameliorated axon and myelin degeneration. Axons in the descending dorsal corticospinal tract were unaffected in all groups, suggesting a specificity of this lesion for spinal primary sensory afferents. These results show for the first time that a lesion restricted to motor roots can induce the degeneration of intramedullary sensory afferents. Importantly, reimplantation of the lesioned motor roots ameliorated sensory axon degeneration. These data further support the therapeutic potential for reimplantation of avulsed ventral roots following trauma to the cauda equina/conus medullaris.     

Spinal dysraphism: genetic relation to neural tube malformations.

The families of 207 index patients treated for spinal dysraphism at The Hospital for Sick Children were studied to discover whether the condition was aetiologically related to the classical neural tube malformation--spina bifida cystica and anencephaly. The index patients had all had a tethered conus medullaris and one or more of a variety of anomalies of the spinal cord, vertebrae, or skin overlying the vertebral column. Of 364 sibs of index patients, 9 had an encephaly and 6 spina bifida cystica, a pro-proportion of 4.12%. This approximates to the proportion of sibs affected by neural tube malformations in the London region when the index patients themselves have spina bifida or anencephaly. It is, therefore, appropriate that the mothers of children with spinal dysraphism should be offered prenatal screening for neural tube malformations.     

The vertebral level of origin of spinal nerves in the rat

Several dissections were performed to determine the level of spinal cord termination and the vertebral level at which the dorsal and ventral roots of spinal nerves C1-S4 emerged from the spinal cord in the rat. These levels of emergence were then compared to the level of exit from the vertebral canal. The dissections demonstrated that the effect of differential growth between spinal cord and vertebral column begins in the lower cervical region and becomes progressively more pronounced throughout thoracic and lumbar levels. The disparity between the vertebral level of emergence of spinal roots from the spinal cord and their level of exit via intervertebral foramina was found to be considerably larger than was previously reported by Greene ('68). It was further noted that the spinal cord terminated at the level of the intervertebral disc between the third and fourth lumbar vertebrae, not between the fourth and fifth lumbar vertebrae as reported by Greene ('68).     

Clinical relevance of conus medullaris and dural sac termination level with special reference to sacral hiatus apex: anatomical and MRI radiologic study

The aim of this study was to determine the vertebral level and variations in the position of the termination of both conus medullaris (CMT) and dural sac (DST) with special reference to the apex of the sacral hiatus (SHA) using magnetic resonance (MR) images and human cadavers. Different measurements were made on 200 MR sagittal T1- and T2-weighted lumbosacral images and 60 formalin-fixed adult human cadavers. The linear distances between the CMT, DST and SHA, the anteroposterior diameter at SHA, delete length and thickness of the sacrococcygeal membrane were also measured. These measurements were correlated with age and sex. In the MRI study, the mean vertebral level of CMT and its highest incidence were seen at the lower third of L1 (L1L) in male patients and at the L1-2 disc in female patients; that of DST was observed at the upper third of S2 (S2U) in male patients and the middle third of S2 (S2M) in female patients and the mean vertebral level of the SHA was noted at the middle third of S4 (S4M) in both males and females with no significant age or sex differences (P < 0.05). In the cadaveric specimens, the mean vertebral levels of CMT, DST and SHA were seen at L1L, S2M and S4U, respectively in both male and female specimens, with no sex difference. Also in the MRI study, all linear distances in the male patients were significantly different (P < 0.05) from those in female patients with exception of the thickness of SCM and the AP diameter at SHA. Accurate knowledge of these levels and the distances in-between are important for safe and successful spinal and caudal anaesthesia.     

An investigation of the conus medullaris and filum terminale variations in human fetuses

The morphologic structure of the conus medullaris and filum terminale was investigated by dissection in 123 human fetuses, obtained from Selçuk University, Faculty of Medicine and Maternity hospital of Konya between 1992–1995. In 78 fetuses, the conus medullaris and filum terminale had a normal morphologic aspect, whereas there was a slight depression or groove formation in the closure region of the caudal neuropore in 45 fetuses. In 15 fetuses, important malformations of the cranium and vertebral column were observed. The morphologic aspects of the conus medullaris in 30 fetuses were abnormal in shape and position, among them 24 fetuses had an abnormal filum terminale (grooved, depressed, thickened or duplicated) whereas it was normal in 6. Deficiency of closure of the caudal neuropore was considered to have a negative effect on the fetal development of the filum terminale.     

Observations on the giraffe central nervous system related to the corticospinal tract,motor cortex and spinal cord: What difference does a long neck make?

The mammalian corticospinal tract is known to contain axons that travel from the cerebral cortex to various levels of the spinal cord and its main function is thought to be the mediation of voluntary movement. The current study describes neuroanatomy related to the corticospinal tract of the giraffe. This animal presents a specific morphology that may present challenges to this neural pathway in terms of the metabolism required for correct functioning and maintenance of potentially very long axons. The spinal cord of the giraffe can be up to 2.6 m long and forms the conus medullaris at the level of the sacral vertebrae. Primary motor cortex was found in a location typical of that of other ungulates, and the cytoarchitectonic appearance of this cortical area was similar to that previously reported for sheep, despite the potential distance that the axons emanating from the layer 5 gigantopyramidal neurons must travel. A typically mammalian dorsal striatopallidal complex was transected by a strongly coalesced internal capsule passing through to the pons and forming clearly identifiable but somewhat flattened (in a dorsoventral plane) pyramidal tracts. These tracts terminated in a spinal cord that exhibited no unique anatomical features related to its length. Our results, at least at the level of organization investigated herein, show that the corticospinal tract of the giraffe resembled that of a typical ungulate.     

Spinal dural sac termination and internal filum terminale fusion

Surgery for tethered spinal cord caused by thickened filum terminale (FT) is frequently performed through S1 laminectomy based on the assumption that the internal FT (FTi) fuses with dura mater at S2 vertebral level. Literature on specific study for the site of its fusion and dural sac (DS) termination was rather limited. Moreover, there is no large anatomical study in Asian population. To determine the anatomy, examination of the FTi fusion site, as well as the region at which DS ended, was undertaken. From 80 embalmed cadavers, the majority of FTi fusion occurred at, or below, S1/S2 disk space (62.5%) which was less frequent than previous reports (70%–90%). In addition, there was 11.3% of the fila that fused above S1. Regarding the DS termination, it was found at, or below, S1/S2 disk space in 76.3% with one subject (1.3%) at L5/S1 disk space. With modest differences compared with non-Asian cadaveric data, our results offer pertinent information to surgeons performing tethered cord release. One ought to keep in mind that small, but not negligible, percentage of FTi can fuse with dura mater above S1 level; hence, more rostral laminectomy at L5 may be required. Clin. Anat. 33:558–561, 2020. © 2019 Wiley Periodicals, Inc.     

髂嵴连线和肋架下缘连线在椎体或椎间隙中定位的作用及意义

目的　探讨髂嵴连线和肋架下缘连线作为定位椎体或椎间隙的可行性。 方法　216例正常成人,其中男98 例,女118 例,年龄 18～94 岁。均行胸腰骶椎立位X片和MR SE序列矢状位片,测定脊髓圆锥、髂嵴连线和肋架下缘对应的脊椎位置,并利用Reimanm方法进行量化,所得结果经统计学处理。 结果　脊髓圆锥、髂嵴连线和肋架下缘连线对应的脊椎位置分别为L1下三分之一（29.72±2.032）、L4~5（16.11±1.192）和L2~3（24.69±1.909）,且后两者男女之间差别有统计学意义,肋架下缘对应的脊椎位置与年龄之间存在相关性。 结论　立位时,髂嵴连线对应的脊椎位置绝大部分为L4~5或L4,肋架下缘对应脊椎位置集中分布于L2~3,两者均能用于定位椎间隙的序数;两者结合定位可更好的减少操作风险。     

The central canal of the human spinal cord: a computerised 3-D study

Knowledge of the structure and function of the central canal of the human spinal cord is important in understanding the pathogenesis of syringomyelia. Analysis of the morphology of the central canal is difficult using isolated histological sections. A 3-dimensional reconstruction technique using digitised histological sections was therefore developed to visualise the morphology of the central canal. The technique was used to study the canal in the conus medullaris and filum terminale of 1 sheep and 4 human spinal cords. A variety of morphological features were demonstrated including canal duplication, a terminal ventricle and openings from the canal lumen into the subarachnoid space. The findings suggest the possibility of a functionally important fluid communication in the caudal spinal cord which may have a sink function.     

Anaplastic Ependymoma of the Spinal Cord in Childhood A Case Report

We report a 6-year-old girl with anaplastic ependymoma probably originating in the region of the conus medullaris and probably spreading retrogradely to the region of the interventricular foramen (Monro) through the cere-brospinal fluid (CSF). Since ependymoma of the spinal cord rarely occurs in children, and retrograde spreading is extremely rare, the histological features and mechanism of metastasis of the tumor are discussed.