Follow-up CT myelography of severe cervical spinal cord injury

There are many reports describing gross anatomical and microscopical findings of severely injured cervical cords in autopsy of the acute and chronic state, but no morphological findings of a severe cervical spinal cord injury in a chronic state by follow-up CT myelography have been found in the literature so far. The sagittal and transverse diameters of the cervical spinal cord and subarachnoid space of 9 out of 14 severe cervical spinal cord injury patients were measured with CT myelography within 7.5 years after the trauma and their size compared with a control group which was made up of 29 patients with slight radiculopathy due to cervical spondylosis and whiplash injuries. Injured cord levels were C4 4 cases, C5 4 cases and C6 1 case. Remarkable spinal cord atrophy was recognized in the sagittal diameter from C1 to C7 and in the transverse diameter below C4 and narrowing of the cervical subarachnoid space in the sagittal diameter from C2 to C5. The significance level was set at 1-5%. From these findings, we have concluded that atrophy appeared not only in the injured segment but also the whole cervical cord after the trauma. There was less cord atrophy in a good functional prognosis than in a poor prognosis.     

Spinal cord mensuration--a comparative study on the spinal cord segments and spinal nerves in Zambian goats.

It has been known that the relative length of spinal cord and its segmental volume in domestic animals has established that the dynamics of spinal cord is directly related with the functions of the limbs and in particular to their feeding habits. Bilateral rostrocaudal measurements of spinal nerves involving their root attachment length, root emergence length, interroot length, segment length and cross sectional area were recorded on the dorsal and ventral surfaces of each segment of the spinal cords of five local healthy Zambian goats. We identified that the brachial and lumbar enlargements have involved identical number of spinal cord segments. Brachial and lumbar enlargements extended from C6 to T1 and L4 to L7. The average length of spinal cord was 59.9 cm and it extended up to caudal end of 5th sacral vertebrae. The root emergence length appeared to decrease gradually from C2 segment, which remained less variable in thoracic and lumbar segments and then receded sharply through sacral segments. The dorsal nerves entered spinal cord over a greater area than ventral because of more spinal rootlets. The greatest segment length lied in mid cervical region and then from lumbar segment it decreased sharply up to the end of sacral segments. It is concluded that these goats have a feeding habit similar to that of cattle rather than resting their forelimbs on the shrubs while nibbling the leaves as recorded in Asian goats. It also confirmed that the shrubs were more drooping along with grasses in the Gwembe Valley of Zambia.     

国人胎儿脊髓和脊柱发育的测量

对９～４１周的１９３例胎儿尸体分别就脊髓和脊柱的颈、胸、腰、骶尾各部及全长的逐月发育情况进行了测量。求得了脊髓和脊柱从胎龄３个月至出生期间８个不同月龄的发育数据。脊髓与脊柱的发育在早期较快，６个月（２１～２４周）之后逐渐减慢下来。脊髓与脊柱各部发育都不平衡。脊髓的增长率显示了从上到下渐次减少的趋势，即颈髓及胸髓较快，腰髓及骶尾髓较慢。而脊柱则是颈椎最慢，腰椎最快。由于发育速率的不同，导致二者的差额从３个月的５．７５ｍｍ增加到出生时的８５．６０ｍｍ。脊髓发育的性别差异不明显。     

Cervical spinal canal stenosis: the differences between stenosis at the lower cervical and multiple segment levels

The lower cervical segments are commonly the level responsible for cervical spondylotic myelopathy; however, we rarely encounter stenosis at the upper cervical segment in a clinical setting. We assumed that there might be some differences between the pathogenetic mechanisms underlying the development of cervical canal stenosis at different segments. We performed positional MRI in the weight-bearing position for 295 consecutive symptomatic patients. All subjects were classified into four groups (A: normal; B: C3-4 stenosis; C: C5-6 stenosis; D: two-level cervical segments stenosis, stenosis at C3-4 and C5-6). Age, sagittal cervical canal diameter, cervical intervertebral disc degeneration, cervical cord compression, and cervical mobilities were evaluated for each group. Group B showed a narrow cervical spinal canal structure at the C3 to C4 pedicle levels, while groups C and D showed narrow structures at the C4 to C6 pedicle levels in the cervical spine. Additionally, the sagittal cervical canal diameters at all pedicle levels, except C7, in group D were significantly smaller than those observed in group C. We demonstrated the differences in the pathogenetic processes for the development of cervical spinal canal stenosis between C3-4, C5-6, and two-level cervical segments stenosis. Our results suggest that the developmental morphological structure of the cervical spinal canal plays an important role in the development of cervical canal stenosis at different segments. Moreover, individuals with sagittal cervical canal diameters of less than 13 mm may be exposed to an increased risk for future development of cervical spinal canal stenosis at the upper cervical segments following stenosis at the lower cervical segments.     

Cervical spinal canal narrowing and cervical neurological injuries

Cervical spinal canal narrowing can lead to injury of the spinal cord and neurological symptoms including neck pain,headache,weakness and parasthesisas.According to previous and recent clinical researc...     

Morphological study of the spinal canal content for subarachnoid endoscopy.

STUDY DESIGN AND OBJECTIVE: This study was designed to examine the morphology of the spinal dural sac and contents, using magnetic resonance imaging in order to define the inner geometrical dimensions that confine the manoeuvre of an endoscope inserted in the lumbar region and along the thoracic and cervical spine. BACKGROUND: The morphology of the spine has been studied since the development of myelography. However, most studies have measured the diameters of the spinal cord only, not the size of the subarachnoid space. In addition, the few studies available on the subarachnoid space have focused on the cervical spine, leaving a near-complete dearth of data on the subarachnoid space dimensions along the thoracic spine. METHODS: Based on MRI images of the spine from 42 patients, the dimensions of the spinal cord, dural sac, and subarachnoid space were measured at mid-vertebral and inter-vertebral disc levels. RESULTS: It was found that at each selected transverse level, the subarachnoid space tends to be symmetrical on the right and left sides of the cord, and measures 2.5 mm on average. However, the posterior and anterior segments, measured on the mid-sagittal plane, are generally asymmetrical and vary widely in size, ranging from 1 to 5 mm. These measurements match those found in previous studies, where these are available. The coefficient of variance for the dimensions of the subarachnoid space is as high as 42.4%, while that for the dimensions of the spinal cord is 10-15%. CONCLUSIONS: The findings presented here expand our knowledge of the spinal canal's morphology, and show that an endoscope designed to travel within the subarachnoid space must be smaller than 2.5 mm in diameter.     

正常人颈脊髓矢状径MRI测量

目的 提供颈脊髓矢状径、颈椎管有效矢状径(脑脊液柱矢状径)正常参考值,筛选出较科学的评估颈脊髓病的影像学标准.方法 在120例正常人颈椎MRI片上,对各节段颈脊髓矢状径、颈椎管有效矢状径、M值(桥脑-延髓交界处矢状径)进行测量,计算脊髓矢状径与椎管有效矢状径比值,以及脊髓矢状径和M值的比值(C/M值),研究它们与性别、年龄和颈椎长度的相关性.评估脊髓矢状径与椎管有效矢状径比值和C/M值的临床应用价值.结果 脊髓矢状径、椎管有效矢状径、M值男性大于女性(P<0.05),脊髓矢状径和椎管有效矢状径比值和C/M值男女无差别(P>0.05).颈脊髓矢状径和M值随着颈椎长度的增加而增加(r=0.215,P=0.010;r=0.151,P=0.020).颈脊髓矢状径和颈椎管有效矢状径比值与年龄成呈相关(r=0.242,P<0.01),与颈椎长度无明显相关(r=0.082,P=0.200).C/M值与年龄和颈椎长度均无相关性(r=0.06,P=0.359;r=0.003,P=0.900).结论 C/M值能够很好评价颈脊髓萎缩、受压、损害的状况,它很少受到个体差异的影响,是临床评估颈脊髓疾病的良好标准之一.     

大鼠神经病理性痛早期脊髓背角Homer-1a基因的表达

目的 探讨大鼠神经病理性痛早期脊髓背角Homer-1a基因的表达.方法 健康雄性SD大鼠60只,体重200～220 g,随机分为3组(n=20):正常对照组(C组)、假手术组(S组)和慢性背根神经节压迫组(CCD组).CCD组制备CCD诱导神经病理性痛模型,分别于术前48 h(基础状态)、术后4、8、24 h时取5只大鼠,测定热痛阈,然后取术侧L4,5节段脊髓,采用实时定量PCR技术测定脊髓背角Homer-1a基因的表达水平.结果 与基础值相比,CCD组术后4、8 h时脊髓背角Homer-1a基因表达上调(P<0.01),术后24 h时降至基础值水平(P0.05),术后24 h时热痛阈降低(P<0.01).与C组和S组比较,CCD组术后4、8 h时脊髓背角Homer-1a基因表达上调,术后24 h时热痛阈降低(P<0.01).结论 大鼠神经病理性痛早期脊髓背角Homer-1a表达水平迅速而短暂的上调,可能抑制早期痛敏的发生.     

Microsurgical anatomy of dorsal root entry zone of brachial plexus

The purpose of this study was to describe microsurgical anatomy of the dorsal root entry zone (DREZ) and provide an anatomic basis for the approach of DREZ lesion in treating radiculopathy of brachial plexus avulsion injuries. We studied 100 dorsal cervical roots and DREZ/posterior horn complexes in 20 adult cadavers. At each root level the following data were recorded: widths of laminectomy, numbers of posterior rootlets, angle of the inferior rootlets with the spinal cord, and distance from posterior median sulcus to posterolateral sulcus. On cross-sectional plane, the length and width of dorsal horn and the angle between longitudinal axis of dorsal horn and sagittal plane of spinal cord were measured. The results showed that the spinal cord segment and the entry of dorsal roots from C5 to T1 were exposed clearly after laminectomy from C4 to C7. The average number of roolets of C5-T1 roots was about 7.76 and C6 has the most. From up to down, the angle from the inferior rootlet to spinal cord of C5-T1 diminished gradually. The average distance from posterior median sulcus to posterolateral sulcus was 2.95 mm. The average length, width, and angle of posterior horn were 3.47 mm, 1.346 mm, and 35.9 degrees , respectively. Our study demonstrated that the spinous process and lamina of the C4 to C7 vertebrae should be resected to expose the C5-T1 when DREZ lesions are employed to treat pain after brachial plexus avulsion. The lesion-making apparatus should be inserted at an angle of 30 degrees -40 degrees , the width of lesion should be less than 1.2 mm and the lesion depth less than 3.1 mm.     

颈椎板成形术后的脊髓扩大和后移

目的 研究反成形术后脊髓的形态学改变和疗效的相互关系。方法 对２０例颈脊髓病口才在行椎管扩大椎板成形术前后进行颈ＣＴ脊髓成像术,测量脊髓的矢状径、横径和横截面的变化。结果 颈椎板成形术后脊髓的Ｃ５水平脊髓矢状径增大约０．８ｍｍ,但横径减小约０．９ｍｍ,脊髓横截面面积增大７．４％,在Ｃ５水平脊髓向后移动２．８ｍｍ。。结论管扩大椎板成形术可使脊髓减压,而术后脊髓是否后移可能是决定椎管成形术减压效果的重     

Comparison of computerized tomography parameters of the thoracolumbar spine in normal control subjects and spinal cord injured patients

The cross-sectional area and the sagittal and transverse diameters of the spinal canal at the thoracolumbar junction were measured using high resolution thin-section computerized tomography images in 15 control subjects and 28 patients with traumatic injury to the spinal cord at the thoracolumbar junction. No significant difference between the control and study groups was found with regard to any of the three measures taken. With the exception of the sagittal canal diameter for the first lumbar vertebra, all the mean values were higher for the spinal cord injured group. The ratio of the sagittal to transverse diameter was larger for the control group; however, this difference also was not significant. These findings suggest no significant differences in the dimensions and shape of the canal at the thoracolumbar region between the spinal cord injured and control groups. In contrast to the cervical spinal canal, there appears to be no correlation between the spinal cord injury and the dimensions of the thoracolumbar spinal canal.     

Ultrasound-guided periradicular injections in the middle to lower cervical spine: an imaging study of a new approach

BACKGROUND AND OBJECTIVES: The objective of this study was to show the efficacy of ultrasound in facilitating the performance of a simulated cervical periradicular injection in cadavers. METHODS: A total of 40 ultrasound-guided examinations at 4 levels (C3 to C7) were performed on 4 embalmed cadavers. The cervical spinal nerves were located with ultrasound. First, the transverse process of each level was taken as a sonoanatomic landmark. The most lateral aspect of the transverse process of the seventh cervical vertebra was then established as the reference point. Ipsilateral distances (A, B, C, and D) between this point and each one of the transverse processes of the cervical spine up to the third vertebra were then computed. Subsequently, coronal computed tomography (CT) scans were taken to verify these distances. In a second part, a spinal needle was advanced under ultrasound guidance to the spinal nerves C5 to C8 on both sides of one cadaver. The exact placement of the needle tips was checked by CT. RESULTS: The transverse processes were identified in all cadavers. In 5 attempts, a depiction of the spinal nerves was not possible. Ultrasound and CT provided the same mean measurements of 1.1 cm, 2.1 cm, 3.1 cm, and 4.1 cm for distances A, B, C, and D, respectively. All 8 needle tips were placed within 5 mm dorsal to the spinal nerve and less than 5 mm away from the posterior tubercle of each level's transverse process, as also verified by CT. CONCLUSIONS: This preclinical study suggests that ultrasound is a useful guiding tool for periradicular injections in the cervical spine.     

Relationship of cervical spinal rootlets and the inferior vertebral notch

The anatomic features of cervical spinal rootlets from C5 to T1 and their relationships to the inferior vertebral notches were studied. Fifteen fresh cadavers were dissected and the cervical spinal cord and spinal rootlets were exposed by posterior total laminectomy. The dorsal rootlet entry zone of each spinal root was located proximal to the inferior vertebral notch, with an increasing distance from 15 mm at C5 to 28 mm at T1. The angle sustained by the rootlets to the cord decreased from 45 degrees to 89 degrees at C5 and to 23 degrees to 41 degrees at T1. Ventral rootlet exit zones shared similar arrangements and orientations, but they could not be exposed with posterior laminectomy only. Spinal rootlets of a particular cervical spinal segment may be found medial to the pedicles or through the intervertebral foramen one level above. They may be exposed by foraminotomy or partial excision of the pedicles. The inferior vertebral notch, which is the inferior border of the pedicle, is a reliable landmark for location of the rootlets. The information is useful for safe surgical manipulation and instrumentation around the pedicles, and when reimplantation of spinal nerve roots is considered for total brachial palsy.     

下颈椎椎弓根螺旋CT扫描的三维重建及测量

目的 评价应用多层螺旋CT扫描三维重建技术测量下颈椎椎弓根相关参数的可行性. 方法 8具成年男性颈椎标本经螺旋CT扫描后,把信息传送至随机工作站(Silicon Graphics O2),结合下颈椎榷弓根置钉的参数需求,进行三维重建[容积成像(VR)和多平面重组(MPR)]后测量椎弓根各个相关数据.然后对这些数据进行分析. 结果本组下颈椎椎弓根的外展角平均为42.02°±7.55°,C_7最小(35.63°±6.34°),C_4最大(46.94°±5.69°);头倾角平均为76.30°±12.01°,C_3最小(72.93°±6.57°),C,最大(81.27°±13.34°);入点至下关节缘距离平均为(11.23±1.78)mm,C_3最小[(10.54±1.25)mm],C_6最大[(12.05±1.40)mm];入点至侧块外缘距离各椎体相筹较大,平均为(2.65±1.21)mm,C_4最小[(1.69±0.81)mm],C_7最大[(3.74±0.99)mm];入点至椎体前缘距离各椎体差异较小,平均为(31.42±2.13)mm;椎弓根皮质骨高度平均为(8.43±1.30)mm,宽度半均为(5.54±1.26)mm;椎弓根松质骨高度平均为(3.69±1.19)mm,宽度平均为(2.67±1.15)mm;椎弓根皮质高度一般大于宽度,C_4内径最小,C_7内径最大. 结论 VR、MPR重建图像可满足椎弓根参数测量要求,其所测量的下颈椎椎弓根参数可满足经椎弓根手术的术前评估需求;下颈椎椎弓根变异较大.     

Stress analysis of the cervical spinal cord: Impact of the morphology of spinal cord segments on stress

Objective: Although there are several classifications for cervical myelopathy, these do not take differences between spinal cord segments into account. Moreover, there has been no report of stress analyses for individual segments to date.

Methods: By using the finite element method, we constructed 3-dimensional spinal cord models comprised of gray matter, white matter, and pia mater of the second to eighth cervical vertebrae (C2–C8). We placed compression components (disc and yellow ligament) at the front and back of these models, and applied compression to the posterior section covering 10%, 20%, 30%, or 40% of the anteroposterior diameter of each cervical spinal cord segment.

Results: Our results revealed that, under compression applied to an area covering 10%, 20%, or 30% of the anteroposterior diameter of the cervical spinal cord segment, sites of increased stress varied depending on the morphology of each cervical spinal cord segment. Under 40% compression, stress was increased in the gray matter, lateral funiculus, and posterior funiculus of all spinal cord segments, and stress differences between the segments were smaller.

Conclusion: These results indicate that, under moderate compression, sites of increased stress vary depending on the morphology of each spinal cord segment or the shape of compression components, and also that the variability of symptoms may depend on the direction of compression. However, under severe compression, the differences among the cervical spinal segments are smaller, which may facilitate diagnosis.     

The relationship between the cervical spinal canal diameter and the pathological changes in the cervical spine

A congenitally narrow cervical spinal canal has been established as an important risk factor for the development of cervical spondylotic myelopathy. However, few reports have described the mechanism underlying this risk. In this study, we investigate the relationship between cervical spinal canal narrowing and pathological changes in the cervical spine using positional magnetic resonance imaging (MRI). Two hundred and ninety-five symptomatic patients underwent cervical MRI in the weight-bearing position with dynamic motion (flexion, neutral, and extension) of the cervical spine. The sagittal cervical spinal canal diameter and cervical segmental angular motion were measured and calculated. Each segment was assessed for the extent of intervertebral disc degeneration and cervical cord compression. Based on the sagittal canal diameter, the subjects were classified into three groups: A, subjects with a congenitally narrow canal, diameter of less than 13 mm; B, subjects with a normal canal, diameter of 13–15 mm; C, subjects with a wide canal, diameter of more than 15 mm. When compared with Groups A and B, the disc degeneration grades at the C3-4, C5-6, and C6-7 segments and the cervical cord compression scores at the C3-4 and C5-6 segments showed significant differences. Additionally, when compare with Groups A and C, the disc degeneration grades at all segments, except C2-3, and the cervical cord compression scores at all segments, except C2-3, showed significant differences. With respect to the cervical kinematics, few differences in the kinematics were observed between Groups B and C, however, the kinematics in Group A was different with other two groups. In Group A, the segmental mobility at the C4-5 and C6-7 segments were significantly higher than those observed in Group B, and the segmental mobility at the C3-4 segment was significantly lower than that observed in Groups B or C. We demonstrated the unique pathological and kinematic traits of cervical spine that exist in a congenitally narrow canal. We hypothesize that kinematic trait associated with a congenitally narrow canal may greatly contribute to pathological changes in the cervical spine. Our results suggest that cervical spinal canal diameter of less than 13 mm may be associated with an increased risk for development of pathological changes in cervical intervertebral discs. Subsequently, the presence of a congenitally narrow canal can expose individuals to a greater risk of developing cervical spinal stenosis.     

Extraforaminal lumbar arterial anatomy

BACKGROUND: There are few studies carried out to reveal lumbar arterial anatomy. The studies of vascular anatomy of the lumbar zone are usually based on the angiographic imaging methods and barium injected radiographic sections of human specimens. METHODS: Upon the recent breakthroughs in the microscopic anatomic dissections, the vascular structure of this zone is examined in 16 cadavers. Arterial anatomies of the extraforaminal zones of 80 lumbar vertebral objects were studied. RESULTS: In each segment, lumbar artery, extraforaminal branches of the lumbar artery and the spinal (foraminal) branch were described. The spinal branch is originated from lumbar artery and extends as the dorsal branch. The dorsal branch is divided into 4 branches: ganglionic, transverse, ascending, and descending. Diameters of the lumbar artery, spinal, dorsal, and ganglionic branches were measured at each stage. The mean diameter of the lumbar artery was 2.7 mm, the dorsal branch was 2.0 mm, the foraminal branch was 1.9 mm, and the ganglionic branch was 1.0 mm, respectively. CONCLUSION: Knowledge of lumbar arterial anatomy is needed for carrying out a successful surgical operation and reducing complications.     

Clinicoradiologic study of cervical laminoplasty with posterolateral fusion or bone graft

STUDY DESIGN: A retrospective study of cervical expansive laminoplasty for cervical myelopathy from a clinicoradiologic perspective. OBJECTIVE: To clarify the correlation among sagittal curvature of the cervical spine, cervical range of motion, sagittal plane translation, spinal cord atrophy, and myelopathic symptoms in patients who have undergone laminoplasty. SUMMARY OF BACKGROUND DATA: Laminoplasties were developed to diminish the undesirable effects of laminectomy, which include postoperative kyphotic changes and instability. However, the superiority of laminoplasty over laminectomy remains controversial. METHODS: Fifty-one patients with cervical spondylotic myelopathy or ossification of the cervical posterior longitudinal ligament who underwent laminoplasty were radiologically assessed before and after surgery. The index of the sagittal curvature, intervertebral range of motion, listhesis, and the transverse area of the spinal cord at the site of maximal compression were measured to evaluate interrelations among those parameters and myelopathic symptoms. RESULTS: There were no patients with kyphotic curvature before surgery. The postoperative curvature tended to be less lordotic. This tendency did not adversely affect postoperative symptoms. The intervertebral range of motion was significantly decreased except at C1-C2. The final C4-C5 range of motion and the postoperative myelopathic symptoms were negatively correlated. A significant correlation was observed between the postoperative spinal cord atrophy and the final myelopathic symptoms. CONCLUSIONS: The decrease in the lordotic curvature index and the decrease in the intervertebral range of motion after laminoplasty did not cause neurologic deterioration. In the C4-C5 intervertebral segment with a high incidence of listhesis, the restriction of the C4-C5 range of motion improved the clinical myelopathic symptoms. The radiologic prognostic factors were the postoperative restriction of intervertebral range of motion in preoperatively unstable segments and the anatomic reversibility of spinal cord insult.     

Quantitative analysis of fiber tractography in cervical spondylotic myelopathy

Background contextDiffusion tensor fiber tractography is an emerging tool for the visualization of spinal cord microstructure. However, there are few quantitative analyses of the damage in the nerve fiber tracts of the myelopathic spinal cord.PurposeThe aim of this study was to develop a quantitative approach for fiber tractography analysis in cervical spondylotic myelopathy (CSM).Study design/settingProspective study on a series of patients.Materials and methodsA total of 22 volunteers were recruited with informed consent, including 15 healthy subjects and 7 CSM patients. The clinical severity of CSM was evaluated using modified Japanese Orthopedic Association (JOA) score. The microstructure of myelopathic cervical cord was analyzed using diffusion tensor imaging. Diffusion tensor imaging was performed with a 3.0-T magnetic resonance imaging scanner using pulsed gradient, spin-echo, echo-planar imaging sequence. Fiber tractography was generated via TrackVis with fractional anisotropy threshold set at 0.2 and angle threshold at 40°. Region of interest (ROI) was defined to cover C4 level only or the whole-length cervical spinal cord from C1 to C7 for analysis. The length and density of tracked nerve bundles were measured for comparison between healthy subjects and CSM patients.ResultsThe length of tracked nerve bundles significantly shortened in CSM patients compared with healthy subjects (healthy: 6.85–77.90 mm, CSM: 0.68–62.53 mm). The density of the tracked nerve bundles was also lower in CSM patients (healthy: 086±0.03, CSM: 0.80±0.06, p<.05). Although the definition of ROI covering C4 only or whole cervical cord appeared not to affect the trend of the disparity between healthy and myelopathic cervical cords, the density of the tracked nerve bundle through whole myelopathic cords was in an association with the modified JOA score in CSM cases (r=0.949, p=.015), yet not found with ROI at C4 only (r=0.316, p=.684).ConclusionsThe quantitative analysis of fiber tractography is a reliable approach to detect cervical spondylotic myelopathic lesions compared with healthy spinal cords. It could be employed to delineate the severity of CSM.     

Spinal canal size in ossification of the posterior longitudinal ligament of the cervical spine

BACKGROUND: The size of the spinal canal is a factor that contributes to the neurologic deficits associated with cervical ossification of the posterior longitudinal ligament (OPLL). METHODS: Bone-window computed tomography (CT) examinations of the cervical spine in 64 patients with cervical OPLL were reviewed. Forty-two patients underwent surgical treatment (anterior decompression: 16 patients, posterior decompression: 26 patients). The remaining 22 patients were managed conservatively. Selection of the surgical approach, anterior or posterior, was based on the longitudinal extent of cord compression. RESULTS: The mean developmental size of the spinal canal in the posterior decompression group (10.7 mm at C4) was significantly smaller than the other 2 groups. The spinal canal was narrowed by OPLL to 2.9 to 10.0 mm. The proportion of the patients showing motor deficits of the lower extremities significantly increased when the sagittal canal diameter was narrowed to less than 8 mm. CONCLUSIONS: This study demonstrates critical values of CT-determined spinal canal stenosis. Developmental size of the spinal canal and the residual anterior-posterior canal diameters resulting from OPLL spinal cord compression are important factors influencing clinical management and the neurologic state.