Normal ascent of the conus medullaris: a post-mortem foetal MRI study

Abstract

Objectives: The position of the conus medullaris is considered abnormal if it ends below lumbar vertebrae three (L3) at birth. We used magnetic resonance imaging (MRI) to measure the position of the conus in post-mortem foetuses, to investigate the timing of normal ascent.

Methods: The position of the conus in 84 post-mortem foetuses (mean gestation 26.3 weeks; range 14–41 weeks) was identified using 3D MRI datasets. A numerical scale was used for vertebral levels, from 1 (S2) to 15 (T12).

Results: There was significant ascent of the conus medullaris with increasing gestation. At 20 weeks gestation, an estimated 84.2% (95% confidence interval (CI): 72.9, 93.2%) of foetuses have a conus position of L4/5 or higher, but only 22.8% (95% CI 11.7, 34.9%) at L3 or higher. By 26 weeks, an estimated 50.7% (95% CI 34.1, 67.5) will have reached L3, and 94.8% (95% CI 87.0, 98.5%) reach L3 by 40 weeks.

Conclusion: There is regular ascent of the conus throughout foetal life. Although growth for each individual foetus may be non-linear, most foetuses have a conus level within the normal adult range by 33 weeks gestation.     

Evidence for, and nature of, the tonic inhibitory influence of habenulointerpeduncular pathways upon cerebral dopaminergic transmission in the rat

The potential role of the habenula in the transsynaptic regulation of the activity of ascending dopaminergic systems has been investigated in the rat by studying the effect of an acute interruption of impulse traffic in the diencephalic conduction system (stria medullaris-habenula-fasciculus retroflexus) and of pharmacological manipulation of various neurotransmitter systems in the interpeduncular nucleus on dopamine metabolism in several dopaminergic projection fields. The bilateral infusion of tetrodotoxin into the fasciculus retroflexus (which conveys the habenulointerpeduncular tract) of conscious rats markedly increased homovanillic acid levels and dopamine synthesis and utilization in the medial prefrontal cortex, nucleus accumbens, olfactory tubercle and striatum. Similar changes in dopamine metabolism were observed in these areas after bilateral infusion of tetrodotoxin into the stria medullaris (which conveys most of the afferents to the habenula). Infusion of atropine (0.4-1 micrograms) into the interpeduncular nucleus increased homovanillic acid concentrations and dopamine utilization in the medial prefrontal cortex and nucleus accumbens but not in the olfactory tubercle and striatum. Moreover, intra-interpeduncular injection of oxotremorine (17 micrograms) antagonized the increase in dopamine utilization in the nucleus accumbens (but not in the olfactory tubercle) induced by an intrafasciculus retroflexus infusion of tetrodotoxin. Local infusion of naloxone (20 micrograms) into the interpeduncular nucleus increased homovanillic acid concentrations in the nucleus accumbens and olfactory tubercle but not in the medial prefrontal cortex and striatum. In contrast, intra-interpeduncular nucleus infusion of the substance P antagonist D-Arg1, D-Pro2, D-Trp7,9, Leu11-substance P or of substance P antiserum failed to alter homovanillic acid levels in the 4 dopamine-rich areas investigated. Finally, intraraphé medianus (but not intraraphé dorsalis) infusion of muscimol (25 ng) moderately increased dopamine synthesis in the nucleus accumbens and striatum. The present findings suggest that the habenulointerpeduncular pathways exert a tonic inhibitory influence on mesocortical, mesolimbic and mesostriatal dopaminergic neurons. Cholinergic and/or opioid peptidergic neurons coursing through the fasciculus retroflexus as well as ascending serotonergic neurons originating in the raphé medianus could take part in this inhibitory control of ascending dopaminergic neurons.     

The spinal cord and its membranes

The spinal cord is 45 cm long in the adult. In the early fetus, it extends the length of the vertebral canal; differential growth results in its termination at L3 in the newborn. In the adult it terminates, as the conus medullaris, at the disc between L1 and L2, although there is a range from T12 to L3. Inferiorly, the nerve roots form the cauda equina, while the lower end of the cord is attached by the filum terminale, of pia mater, to the coccyx. The dural sac terminates usually at the second segment of the sacrum. The cord receives its arterial supply from the anterior and posterior spinal arteries, which descend from the foramen magnum. They are reinforced serially via the intervertebral foramina from segmental vessels, especially the arteria magna. The three layers of the meninges are the dura mater, arachnoid mater and pia mater. The cerebrospinal fluid is contained within the subarachnoid space. The epidural space contains fat, blood vessels, lymphatics and the nerve roots.     

Giant lumbar spinal schwannoma: a case report and literature review

We report a case of a 40-year-old female patient admitted to the hospital due to lumbar pain that spread to both legs and was associated with weakness of the lower extremities. Magnetic resonance imaging revealed an intradural - extramedullary tumor at the level of the T12 - L2 vertebra. The lesion was over 7 cm in greatest diameter and compressed the conus medullaris. The patient underwent surgery to remove the entire tumor. Postoperative pathology confirmed the diagnosis of schwannoma. The symptoms resolved almost completely without significant complications.     

圆锥马尾部室管膜瘤的诊断与治疗

目的:探讨圆锥马尾部室管膜瘤的诊断及手术治疗特点。方法:分析13例经手术治疗的圆锥马尾部室管膜瘤患者的临床表现、影像学特征和手术治疗疗效。结果:13例患者中MRI对圆锥马尾部室管膜瘤作出定性诊断的占53.8%。全组患者均行手术治疗,获肿瘤全切除10例,次全肿瘤切除3例。术后所有患者症状体和体征均明显改善。结论:圆锥马尾部室管膜瘤的MRI术前定性有一定困难,需与星形胶质细胞瘤、神经鞘瘤及胆脂瘤等鉴别。显微手术技术的应用和肿瘤全切除是获得满意疗效的关键。     

Radiologic and histopathologic findings in a rare case of complex occult spinal dysraphism with association of a lumbar fibrolipoma, neurenteric cyst and tethered cord syndrome

We present the case of a 60-year-old farmer who reported non-specific back pains for the past 30 years. Increasing paralysis of the left leg led to hospitalization. A complex occult spinal dysraphism comprising a fibrolipoma of the conus medullaris, an neurenteric cyst, and a tethered cord syndrome was diagnosed and operated on. The radiological and histological findings are demonstrated. Received 19 March 1997; Revision received 18 July 1997; Accepted 3 September 1997     

芋螺毒素研究进展

芋螺毒素是含约１０－３０个氨基酸残基的小肽，大多富含二硫键，可分为α－，μ，ω－，δ－，芋螺睡眠肽，加压素，惊厥剂等。已确定四十余个毒素的序列，对４个有代表性的芋螺肽进行了溶液构象分析和构效关系的研究。本文介绍了芋螺毒素研究历史。综述了国外对甚至芋螺毒素的构效关系研究的结果及应用研究情况。     

Projections of the zona incerta in the cat, with stimulation controls.

In eight cats single electrolytic lesions were placed in the zona incerta, and resultant fiber degeneration studies were made. In seven additional cats, stimulating electrodes were chronically implanted bilaterally into the zona incerta, H₂ (lenticular fasciculus), or H (prerubral) fields of Forel. The animals were placed in a two-compartment shuttle box, and a routinely established procedure of subthalamic stimulation was instituted. When the sensory (nociceptive) or motor manifestations and reactions were established, small lesions were made through both poles of the electrodes. The brains were studied by silver techniques for degenerating axons and terminals. Findings in the latter group of animals with physiologic substrates, compared to those in the first group, indicated that the zona incerta contains at least two major physiologic-anatomic components with differential fiber projections. The first component is a medial zona incerta proper or caudalis, paleospinothalamic, nociceptive-conducting system which causes typical escape responses. Its unequivocal projections are to the nucleus of the H₁ field, posterior and dorsal hypothalamus, part of the intralaminar system, ventromedial and ventralis anterior nuclei, nucleus reuniens, reticular nucleus, pulvinar, posterior nucleus, central gray, red nucleus, and the central tegmental tract. The second constitutent concerns pyramidal-extrapyramidal motor type responses that arise with avoidance reactions from other portions of the zona incerta. In these cases there is heavy projection to the caudate, entopenduncular, globus pallidus, and putamen nuclei. In contrast, degeneration from the nociceptive part of the zona incerta or H₂ and H fields to these nuclei is minimal.     

青少年特发性脊柱侧凸大弯度患者脊髓圆锥位置的MRI研究

目的探讨青少年特发性脊柱侧凸(AIS)患者的脊髓圆锥位置及其与患者年龄、性别、侧凸严重程度和侧凸模式之间的关系。方法对202名 Cobb 角40°以上的 AIS 患者和52名对照组青少年进行腰椎 MRI 扫描,在矢状面自旋回波 T1WI 序列图像上,观测脊髓圆锥末端的位置,并根据圆锥末端与相邻的椎体的上、中、下1/3和椎间盘的对应关系进行定位。结果 AIS 组和对照组青少年的圆锥位置范围分别为 T_(12)中1/3～L_(2/3)椎间盘和 T_(12)下1/3～L_2下1/3,平均位置则均为 L_1下1/3水平。两组间圆锥位置分布无统计学差异。这两组青少年的圆锥位置不受年龄和性别的影响。在AIS 组内,圆锥位置与侧凸的严重程度和侧凸模式无显著相关性。结论 AIS 患者的圆锥位置分布与对照组相当,圆锥位置不受年龄、性别、侧凸严重程度和侧凸模式等影响。这提示,圆锥位置的改变不能用于对 AIS 的发病及进展的研究。     

Correlative studies of axonal spheroids and Lafora-like bodies in aged dogs

Summary The gracile nucleus and conus medullaris, the sites of predilection for spheroids and Lafora-like bodies, were examined light and electron microscopically in 91 dogs ranging from 1 month to 19 years of age. The number of both structures showed a tendency to increase with age. Spheroids have already been found in younger dogs before the appearance of Lafora-like bodies. In the aged dog, intra-spheroidal Lafora-like bodies were occasionally observed. Correlative studies may yield clues on the pathogenesis of aging phenomena in the CNS.