Morphology and measurements of the cervical spinal cord in computer-assisted myelography

Morphometric Study of the Cervical Spinal Canal Content and the Vertebral Artery

BACKGROUND

The morphological features of the cervical spinal nerves (C1-C8), their dimensions, and their anatomical relations with the vertebral artery are important for safe spinal surgery. The aim of the present study is to give detailed morphological data of the region to avoid complications.

METHODS

Five formalin-fixed adult cadavers were studied. The cervical spinal nerves and the vertebral artery were exposed via the posterior approach, and detailed anatomy and morphometric measurements were evaluated. The following measurements were documented: angles between the spinal nerve and the spinal cord of C1 to C8, width of the C1 to C8 spinal nerves at their origin, distance of the spinal cord to the vertebral artery, number of dorsal rootlets, length of the dorsal root entry zone of C1 to C8, and distance between respective spinal nerves. Further, the average length and width of the transverse foramen were measured.

RESULTS

The average angle between the spinal cord and the spinal nerve within the vertebral canal ranged between 54 and 87 degrees and were most acute at C5 (54 degrees) compared to the rest of the cervical spinal nerves. The average width of the spinal nerves (mean ± SD), was thickest at C5 (5.7 ± 1.2 mm) and C6 (5.8 ± 0.7 mm). The average largest distance between the vertebral artery and the spinal cord was at C2 (14.3 ± 1.7 mm) and the smallest at C5 (7.3 ± 0.9 mm) and C6 (7.3 ± 2.2 mm) spinal levels. The number of dorsal rootlets was most numerous at C6 (8.25 ± 0.6) and C7 (7.25 ± 0.9). The dorsal root entry zone length was the largest at C5 (13.0 ± 1.6 mm) and C6 (13.75 ± 0.5 mm). The distance between respective spinal nerves was largest between C2 and C3 (11.8 ± 2.2) and C7 and C8 (11.5 ± 0.6).

CONCLUSION

The knowledge of detailed anatomy of the cervical spine (C1-C8) and its relations with the vertebral artery will reduce the unwanted damage to the vital structures of the region.

Heritability of cervical spinal cord structure

OBJECTIVE

Measures of spinal cord structure can be a useful phenotype to track disease severity and development; this observational study measures the hereditability of cervical spinal cord anatomy and its correlates in healthy human beings.

METHODS

Twin data from the Human Connectome Project were analyzed with semiautomated spinal cord segmentation, evaluating test-retest reliability and broad-sense heritability with an AE model. Relationships between spinal cord metrics, general physical measures, regional brain structural measures, and motor function were assessed.

RESULTS

We found that the spinal cord C2 cross-sectional area (CSA), left-right width (LRW), and anterior-posterior width (APW) are highly heritable (85%-91%). All measures were highly correlated with the brain volume, and CSA only was positively correlated with thalamic volumes (p = 0.005) but negatively correlated with the occipital cortex area (p = 0.001). LRW was correlated with the participant's height (p = 0.00027). The subjects' sex significantly influenced these metrics. Analyses of a test-retest data set confirmed validity of the approach.

CONCLUSIONS

This study provides the evidence of genetic influence on spinal cord structure. MRI metrics of cervical spinal cord anatomy are robust and not easily influenced by nonpathological environmental factors, providing a useful metric for monitoring normal development and progression of neurodegenerative disorders affecting the spinal cord, including-but not limited to-spinal cord injury and MS.

The Future of Biomechanical Spine Research: Conception and Design of a Dynamic 3D Printed Cervical Myelography Phantom

Background

Three-dimensional (3D) printing is a growing practice in the medical community for patient care and trainee education as well as production of equipment and devices. The development of functional models to replicate physiologic systems of human tissue has also been explored, although to a lesser degree. Specifically, the design of 3D printed phantoms that possess comparable biomechanical properties to human cervical vertebrae is an underdeveloped area of spine research. In order to investigate the functional uses of cervical 3D printed models for replicating the complex physiologic and biomechanical properties of the human subaxial cervical spine, our institution has created a prototype that accurately reflects these properties and provides a novel method of assessing spinal canal dimensions using simulated myelography. To our knowledge, this is the first 3D printed phantom created to study these parameters.

Materials and methods

A de-identified cervical spine computed tomography imaging file was segmented using threshold modulation in 3D Slicer software. The subaxial vertebrae (C3-C7) of the scan were individualized by separating the facet joint spaces and uncovertebral joints within the software in order to create individual stereolithography (STL) files. Each individual vertebra was printed on an Ultimaker S5 dual-extrusion printer using white “tough” polylactic acid filament. A human cadaveric subaxial cervical spine was harvested to provide a control for our experiment. Both models were assessed and compared in flexion and extension dynamic motion grossly and fluoroscopically. The maximum angles of deformation on X-ray imaging were recorded using DICOM (Digital Imaging and Communications in Medicine) viewing software. In order to compare the ability to assess canal dimensions of the models using fluoroscopic imaging, a myelography simulation was designed.

Results

The cervical phantom demonstrated excellent ability to resist deformation in flexion and extension positions, attributed to the high quality of initial segmentation. The gross and fluoroscopic dynamic movement of the phantom was analogous to the cadaver model. The myelography simulator adequately demonstrated the canal dimensions in static and dynamic positions for both models. Pertinent anatomic landmarks were able to be effectively visualized for assessment of canal measurements for sagittal and transverse dimensions.

Conclusions

By utilizing the latest technologies in DICOM segmentation and 3D printing, our institution has created the first cervical myelography phantom for biomechanical evaluation and trainee instruction. By combining new technologies with anatomical knowledge, quality 3D printing shows great promise in becoming a standard player in the future of spinal biomechanical research.

Usefulness of conventional magnetic resonance imaging, diffusion tensor imaging and neurite orientation dispersion and density imaging in evaluating postoperative function in patients with cervical spondylotic myelopathy

Objective

The objective of this study was to evaluate the usefulness of T2 high signal intensity (T2-HSI) and decreased anteroposterior diameter (APD), diffusion tensor imaging (DTI) and neurite orientation dispersion and density imaging (NODDI) in evaluating postoperative cervical cord function.

Methods

The study included 57 postoperative cervical spondylotic myelopathy patients. Clinical evaluation and functional recovery assessments were performed using the modified Japanese Orthopaedic Association (mJOA) score and recovery rate. The presence of T2-HSI and decreased APD was recorded for exploring the relevance. Spearman correlation was applied to investigate the relationships between DTI and NODDI metrics and mJOA score. Multiple comparisons of T2 signal intensity, APD and diffusion metrics were evaluated by using multiple linear regression.

Results

Only the recovery rate was significantly different between T2-HSI and non-T2-HSI (nT2-HSI) patients (χ² = 4.466, p = 0.045). Significant differences were not observed between cervical cords with and without decreased APD. Diffusion metrics, including fractional anisotropy (p = 0.0005), mean diffusivity (p = 0.0008), radial diffusivity (p = 0.0003) and intracellular volume fraction (p = 0.001), were significantly correlated with mJOA score. The ability of T2 signal intensity (p = 0.421) and APD (p = 0.420) to evaluate the postoperative function was inferior to that of fractional anisotropy (p = 0.002), mean diffusivity (p = 0.001), radial diffusivity (p = 0.001) and intracellular volume fraction (p = 0.004).

Conclusion

Conventional magnetic resonance imaging signs could be considered as a reference to make an approximate assessment, whereas DTI and NODDI could be better quantitative tools for evaluating the postoperative function and may help in interpreting residual symptoms.

The translational potential of this article

DTI and NODDI could provide reliable postoperative evaluation and analysis for cervical spondylotic myelopathy patients.

A Review of the Segmental Diameter of the Healthy Human Spinal Cord

Knowledge of the average size and variability of the human spinal cord can be of importance when treating pathological conditions in the spinal cord. Data on healthy human spinal cord morphometrics have been published for more than a century using different techniques of measurements, but unfortunately, comparison of results from different studies is difficult because of the different anatomical landmarks used as reference points along the craniocaudal axis for the measurements. The aim of this review was to compute population estimates of the transverse and anteroposterior diameter of the human spinal cord by comparing and combining previously published data on a normalized craniocaudal axis. We included 11 studies presenting measurements of spinal cord cross-sectional diameters, with a combined sample size ranging from 15 to 488 subjects, depending on spinal cord level. Based on five published studies presenting data on the lengths of the segments of the spinal cord and vertebral column, we calculated the relative positions of all spinal cord neuronal segments and vertebral bony segments and mapped measurements of spinal cord size to a normalized craniocaudal axis. This mapping resulted in better alignment between studies and allowed the calculation of weighted averages and standard deviations (SDs) along the spinal cord. These weighted averages were smoothed using a generalized additive model to yield continuous population estimates for transverse and anteroposterior diameter and associated SDs. The spinal cord had the largest transverse diameter at spinal cord neuronal segment C5 (13.3 ± 2.2), decreased to segment T8 (8.3 ± 2.1), and increased slightly again to 9.4 ± 1.5 at L3. The anteroposterior diameter showed less variation in size along the spinal cord at C5 (7.4 ± 1.6), T8 (6.3 ± 2.0), and L3 (7.5 ± 1.6). All estimates are presented in millimeters ± 2 SDs. We conclude that segmental transverse and anteroposterior diameters of the healthy human spinal cord from different published sources can be combined on a normalized craniocaudal axis and yield meaningful population estimates. These estimates could be useful in routine management of patients with neurodegenerative diseases as well as for clinical research and experimental applications aimed at surgical spinal cord repair.

The segmental morphometric properties of the horse cervical spinal cord: a study of cadaver

Although the cervical spinal cord (CSC) of the horse has particular importance in diseases of CNS, there is very little information about its segmental morphometry. The objective of the present study was to determine the morphometric features of the CSC segments in the horse and possible relationships among the morphometric features. The segmented CSC from five mature animals was used. Length, weight, diameter, and volume measurements of the segments were performed macroscopically. Lengths and diameters of segments were measured histologically, and area and volume measurements were performed using stereological methods. The length, weight, and volume of the CSC were 61.6±3.2 cm, 107.2±10.4 g, and 95.5±8.3 cm3, respectively. The length of the segments was increased from C1 to C3, while it decreased from C3 to C8. The gross section (GS), white matter (WM), grey matter (GM), dorsal horn (DH), and ventral horn (VH) had the largest cross-section areas at C8. The highest volume was found for the total segment and WM at C4, GM, DH, and VH at C7, and the central canal (CC) at C3. The data obtained not only contribute to the knowledge of the normal anatomy of the CSC but may also provide reference data for veterinary pathologists and clinicians.

The Pathogenesis of Syringomyelia: A Re-Evaluation of the Elastic-Jump Hypothesis

Syringomyelia is a disease in which fluid-filled cavities, called syrinxes, form in the spinal cord causing progressive loss of sensory and motor functions. Invasive monitoring of pressure waves in the spinal subarachnoid space implicates a hydrodynamic origin. Poor treatment outcomes have led to myriad hypotheses for its pathogenesis, which unfortunately are often based on small numbers of patients due to the relative rarity of the disease. However, only recently have models begun to appear based on the principles of mechanics. One such model is the mathematically rigorous work of Carpenter and colleagues (2003, “Pressure Wave Propagation in Fluid-Filled Co-Axial Elastic Tubes Part 1: Basic Theory,” ASME J. Biomech. Eng., 125(6), pp. 852–856; 2003, “Pressure Wave Propagation in Fluid-Filled Co-Axial Elastic Tubes Part 2: Mechanisms for the Pathogenesis of Syringomyelia,” ASME J. Biomech. Eng., 125(6), pp. 857–863). They suggested that a pressure wave due to a cough or sneeze could form a shocklike elastic jump, which when incident at a stenosis, such as a hindbrain tonsil, would generate a transient region of high pressure within the spinal cord and lead to fluid accumulation. The salient physiological parameters of this model were reviewed from the literature and the assumptions and predictions re-evaluated from a mechanical standpoint. It was found that, while the spinal geometry does allow for elastic jumps to occur, their effects are likely to be weak and subsumed by the small amount of viscous damping present in the subarachnoid space. Furthermore, the polarity of the pressure differential set up by cough-type impulses opposes the tenets of the elastic-jump hypothesis. The analysis presented here does not support the elastic-jump hypothesis or any theory reliant on cough-based pressure impulses as a mechanism for the pathogenesis of syringomyelia.

Cervical Myelopathy Due to OPLL

BACKGROUND

Concerning the relationship between morphology and clinical outcome, there have been many reports using computed tomography/myelography but not so many using axial magnetic resonance imaging (MRI) of the spinal cord. This is the first report to correlate axial cord image, intensity changes in MRI, and cord expansion pattern using intraoperative ultrasonography.

OBJECTIVE

The objectives were to correlate MRI studies, axial cord images/expansion, and changes in MRI intensity to see if there is a direct prognostic significance to these changes and to determine whether preoperative axial MRI images of the spinal cord predict recovery from compressive myelopathy.

METHODS

Posterior cervical decompressions with laminoplasty were performed in 44 patients with cervical myelopathy due to ossification of the posterior longitudinal ligament. On T2-weighted MR images, the cross-sectional shape of the cord at the level of maximal compression was categorized as boomerang, teardrop, or triangle. Additionally, with use of intraoperative ultrasonography, the expansion pattern of the cord that occurred intraoperatively was contrasted with that seen on postoperative MR images.

RESULTS

Clinical recovery rates were the worst for those with triangular, intermediate for those with boomerang, and the best for those with teardrop shape. Preoperative low T1 and high T2 signals were found in most cases with triangular cord configurations. Triangular cord configurations showed the least expansion among the three categorized spinal cords.

CONCLUSION

Patients with triangular deformity of the cord have atrophy as confirmed on MR studies where there is a low T1 and high T2 signal in the cord. Poor postoperative clinical recovery correlates with the lack of postoperative cord expansion on either MR or ultrasound evaluations. Those with either teardrop or boomerang deformities demonstrate a relatively good recovery rate.

Gross quantitative measurements of spinal cord segments in human

STUDY DESIGN

Anatomical measurement.

OBJECTIVE

To obtain quantitative anatomical data on each spinal cord segment in human, and determine the presence of correlations between the measures.

SETTING

Department of Rehabilitation Medicine, Pusan National University Hospital, Pusan, Korea.

METHODS

A total of 15 embalmed Korean adult human cadavers (13 males, two females; mean age 57.3 years) were used. The length of each cord segment was defined as the root attachment length plus the upper inter-root length. After performing a total vertebrectomy, a transverse cut was made at the approximate proximal and distal point of each segment from segment C3 to S5. Sagittal and transverse diameters at the proximal end of each segment, and cross-sectional area, height, and volume of the segment were measured.

RESULTS

The transverse diameter was largest at segment C5, and decreased progressively to segment T8. However, the sagittal diameter of each segment did not change distinctly with the segment. The cervical and lumbar enlargements were determined by the transverse diameters of the segments. Segment C5 had the largest cross-sectional area, at 75.0 mm(2). Segment T6 was the longest, averaging 22.4 mm in length. The longest segment in the cervical spinal cord was segment C5, at 15.5 mm, and segment L1 in the lumbar spinal cord. The volume was largest at segment C5, with a value of 1173.9 mm(3).

CONCLUSIONS

We found characteristic quantitative differences in the values of the parameters measured in the thoracic spinal cord compared to those measured in the cervical and lumbar or lumbosacral spinal cords. These measurements of spinal cord segments appear to provide valuable and practical standard quantitative features and may provide basic data for understanding the morphometric characteristics relevant to pathophysiologic conditions of the spinal cord.

Relationship of cervical spinal cord diameter to vertebral dimensions: a radiographic study of normal dogs

Cervical spinal cord abnormalities are often unapparent on myelographic studies, because no normal values for cervical spinal cord diameter are currently available. The purpose of this study was to establish, myelographically, the normal sagittal diameter of the cervical spinal cord in large and small breed dogs and its relationship to the sagittal diameter of the vertebral canal and sagittal height/length of the corresponding vertebral bodies. Forty-one adult dogs underwent cervical radiography and myelography. Spinal cord and vertebral canal sagittal diameter, vertebral body height at C2 to 5, body length at C3 to 5, and dorsal spine length of C2 were measured on lateral views. Ratios of spinal cord:vertebral canal diameter, spinal cord:body height, and spinal cord:body length/spine were calculated, and a normal range was determined for small and large breed dogs. The spinal cord:vertebral canal ratios showed that small breeds have a higher cervical cord-to-canal ratio than large breeds. The mean values and ranges of 14 ratios are reported. The ratios of spinal cord:body length at C2 to 4 in small breeds and spinal cord:body height at C3 to 5 in large breeds were found to be the most accurate for assessing spinal cord sagittal diameter. These normal ranges would allow quantitative and objective evaluation of the cervical spinal cord by myelography and early identification of dogs with altered spinal cord diameter, which could be further evaluated by means of alternative imaging techniques.

Cervical spinal cord--smaller than considered?

STUDY DESIGN

One hundred two patients with symptoms of cervical radiculopathy, were retrospectively analyzed and their cervical spinal cord diameters obtained.

OBJECTIVES

To measure the cervical spinal cord in vivo and to compare the findings with those previously reported in the literature.

SUMMARY OF BACKGROUND DATA

Traditionally, autopsy data have served as the linchpin of cervical cord measurements. However, several studies obtained by realtime radiographic methods have failed to confirm such measurements.

METHODS

The spinal cord was retrospectively measured in 102 patients. All patients underwent myelogram and postmyelogram computed tomographic scan. Anteroposterior and transverse diameters of the spinal cord were measured from C2 to T1 at the level of each intervertebral disc. The depth of the anterior median fissure and cross-sectional area were measured as well. Plain myelographic films were reviewed but demonstrated no findings contrary to postmyelogram computed tomographic measurements.

RESULTS

There was no statistically significant difference in the spinal cord measurements in relation to age or sex. There was an increase in the transverse diameter but not in the anteroposterior diameter in the midcervical spinal enlargement. The anteroposterior diameter decreased linearly. The transverse diameter and the cross-sectional area increased to a maximum at C5, as did the depth of the anterior median fissure. The cervical spinal cord diameter was documented to be 15-20% smaller than has commonly been determined by autopsy data.

CONCLUSIONS

Postmyelogram computed tomographic measurements are smaller than those obtained from autopsy data.

Morphologic features of the normal human cadaveric spinal cord

STUDY DESIGN

The cross-sectional area and diameter of the normal cadaveric spinal cord at each segmental level were measured, and the morphologic features were presented.

OBJECTIVES

To provide accurate anatomic descriptions and morphometric data of the human spinal cord.

SUMMARY OF BACKGROUND DATA

There is a large individual variation in human spinal cord size, and no authorized standard of measurement has been established. There have been few detailed descriptions of the normal morphologic features of the spinal cord.

METHODS

The authors measured the cross-sectional area and diameter of the spinal cord at each segment from C2 and S3 in 12 cadaveric specimens, and the morphologic features of each segment were described.

RESULTS

The relative ratio of the cross-sectional area of each segment to that of the C3 segment was similar in all the specimens examined despite a large individual variation in absolute cord size. Each segment had distinct qualitative and quantitative morphologic features.

CONCLUSIONS

The normal cross-sectional area of the spinal cord at any segment in an individual is calculable from measurements of a given single normal segment. This value appears to be an appropriate and practical standard of measurement of the normal morphologic features of the spinal cord.

Surgery on the rheumatoid cervical spine for the non-ambulant myelopathic patient-too much, too late?

BACKGROUND

Opinions differ on the timing of surgery for rheumatoid arthritis patients with atlanto-axial subluxation. Some clinicians wait for development of neurological signs; others favour prophylactic fusion and decompression. We examined the results of surgery in relation to neurological state at the time of operation.

METHODS

134 patients underwent surgery for rheumatoid involvement of the cervical spine, after development of objective signs of myelopathy. Surgical outcomes were examined prospectively in two groups-patients who were still ambulant at the time of presentation (Ranawat class III A) and patients who had lost the ability to walk (Ranawat class III B)-by means of neurological and functional grading systems in conjunction with standard measures of postoperative morbidity and mortality.

FINDINGS

58% of the ambulant patients attained Ranawat neurological grades I or II compared with only 20% of the non-ambulant patients (p<0.0001). The non-ambulant group also fared worse in terms of postoperative complication rate, length of hospital stay, functional outcome, and ultimately survival. Radiologically, the non-ambulant patients were characterised by a smaller cross-sectional spinal cord area.

INTERPRETATION

The strong likelihood of surgical complications, the poor survival, and the limited prospects for functional recovery in non-ambulant patients make a strong case for earlier surgical intervention. At a late stage of disease most patients will have irreversible cord damage.

A novel technique for laminoplasty augmentation of spinal canal area using titanium miniplate stabilization. A computerized morphometric analysis

STUDY DESIGN

Titanium miniplates are used to secure the posterior elements in the open position after expansive open-door laminoplasty. Preoperative and postoperative spinal canal dimensions are measured to assess the effectiveness of this technique.

OBJECTIVES

To develop a simple yet effective technique to stabilize the posterior elements after laminoplasty and to compare preoperative and postoperative spinal canal dimensions to accepted normal values.

SUMMARY OF BACKGROUND DATA

Expansive open-door laminoplasty has been offered as a simple alternative to laminectomy, which has been associated with postoperative kyphosis. Although the technique of laminoplasty is effective, a simple and reliable method of holding the posterior elements open has not been described.

METHODS

Ten myelopathic patients with multilevel cervical canal stenosis secondary to spondylosis or ossification of the posterior longitudinal ligament were treated with an expansive open-door laminoplasty. The posterior elements were stabilized in the open position with titanium miniplates. Computer-assisted morphometric analysis was performed on preoperative and postoperative computed tomography scans to obtain spinal canal dimensions. Plain radiographs were used to monitor construct integrity.

RESULTS

The preoperative sagittal canal diameter was 8.2 +/- 0.96 mm, and the canal area was 180.6 +/- 33.7 mm2. These dimensions increased after surgery to 16.6 +/- 1.5 mm and 321.9 +/- 29.7 mm2, respectively. The titanium miniplate constructs did not fail during the follow-up period (mean, 26.4 months), and the decompression was maintained. The single significant complication was transient C5 radiculopathy.

CONCLUSIONS

Normal canal dimensions can be reestablished with open-door laminoplasty. Achieving and maintaining an increased sagittal canal diameter is probably the most important change in anatomic parameters to facilitate neurologic recovery. The use of titanium miniplates to stabilize the posterior elements after laminoplasty is a simple, durable, and effective technique to maintain the increased sagittal diameter of the spinal canal.

Morphological analysis of the cervical spinal canal, dural tube and spinal cord in normal individuals using CT myelography

To verify the conventional concept of "developmental stenosis of the cervical spinal canal", we performed a morphological analysis of the relations of the cervical spinal canal, dural tube and spinal cord in normal individuals. The sagittal diameter, area and circularity of the three structures, and the dispersion of each parameter, were examined on axial sections of CT myelograms of 36 normal subjects. The spinal canal was narrowest at C4, followed by C5, while the spinal cord was largest at C4/5. The area and circularity of the cervical spinal cord were not significantly correlated with any parameter of the spinal canal nor with the sagittal diameter and area of the dural tube at any level examined, and the spinal cord showed less individual variation than the bony canal. Compression of the spinal cord might be expected whenever the sagittal diameter of the spinal canal is below the lower limit of normal, that is about 12 mm on plain radiographs. Thus, we concluded that the concept of "developmental stenosis of the cervical spinal canal" was reasonable and acceptable.

Assessment of the narrow cervical spinal canal: a prospective comparison of MRI, myelography and CT-myelography

This study was designed to compare the accuracy of magnetic resonance imaging (MRI), myelography and computed tomography in the assessment of degenerative cervical spinal stenosis. We prospectively examined a total of 75 spinal segments in 18 patients with suspected cervical spinal canal stenosis, using sagittal spin-echo and axial gradient-echo sequences generated by a 1.5 Tesla imager, conventional myelography, and computed tomography with intrathecal contrast medium (CT-myelography). The degree of stenosis was often overestimated using MRI. This error was most prominent in cases of severe stenosis but was significant with minor to moderate stenosis. In these cases, the clinical consequences of such an overestimation can be serious, because treatment is misdirected. The error is probably caused by pulsation of the cerebrospinal fluid and truncation artefact (Gibbs phenomenon). MRI at 1.5 Tesla is thus frequently inadequate for diagnostic assessment of degenerative cervical spinal stenosis. Myelography and myelographic CT are still useful for decisions on operative treatment, especially in cases of moderate stenosis. This may, however, not apply to imagers operating at 0.5 Tesla as below.

Myelography, CT, and MRI of the spinal canal in patients with myelopathy: a prospective study

A prospective study including myelography, CT, and MRI was performed on 36 patients with clinical signs of myelopathy. Evoked potentials and spinal fluid examinations were also carried out. Based on our findings, the patients could be classified as suffering from cryptogenic myelopathy (n = 12), multiple sclerosis (n = 6), spinal stenosis (n = 6), or miscellaneous myelopathies (n = 12). The diameter of the spinal cord was normal in the 2 first groups of patients and of same magnitude evaluated by myelography and CT, while MRI constantly gave higher figures. In only four of the patients important new information was added by CT and MRI (syringomyelia, myelitis, lipomatosis) compared with myelography, although a more precise visualization was often provided. Further diagnostic progress in patients with myelopathy of undetermined etiology may be obtained by including supplementary MRI of the brain disclosing multiple sclerosis in several cases.

Dynamics of the spinal cord: an analysis of functional myelography by CT scan

The antero-posterior movement of the spinal cord with flexion and extension of the neck was analyzed in order to clarify the mechanism of spinal cord compression in cases with postoperative spinal deformity, and to contribute to the improvement of the surgical methods of conventional laminectomy. The control subjects were 47 cases without cervico-thoracic neurological symptoms, who underwent CT myelography in flexion and extension of the neck; the cervical spinal cord was examined in 27 of these cases and the thoracic cord in the other 20. CT myelography was also carried out in 16 patients with cervical myelopathy and in 5 patients after posterior decompression surgery (suspension laminotomy). CT sections in flexion and extension of the neck were analyzed for 1) change of configuration of the dura mater and the spinal cord, and 2) antero-posterior shift of the spinal cord in the subarachnoid space. In the control subjects, the configuration of the dura mater was slightly flattened at C5/6, C6 and C6/7 in extension of the neck. The cervical spinal cord shifted anteriorly in flexion and posteriorly in extension of the neck, and was flattened at the midcervical level in flexion in the control subjects. There was a statistically significant correlation between the location of the spinal cord and the adjacent intervertebral angles at the levels of C4, C5 and C6. These results were compared with the results from the 16 patients with cervical myelopathy and 5 patients after suspension laminotomy.(ABSTRACT TRUNCATED AT 250 WORDS)

Some dynamic factors in compressive deformity of the cervical spinal cord

An investigation into the relative elastic and non-elastic components of compressive deformity of the cervical spinal cord has been made. Sixteen patients were examined by computed myelography with the neck flexed and extended, and one fresh specimen of a human spinal cord was studied under reversible transverse compression with the specimen in a stretched and shortened state. In conditions of transverse compression cord tissue undergoes an alteration in viscoelastic properties, manifesting itself as reduced expansion of the compressed segment as the cord shortens, which in some cases is independent of whether the agent is seen to actually contact the cord. The presence of degenerative changes in cord substance probably accentuates this alteration in mechanical properties.

Computed tomography in cervical spondylotic myelopathy and radiculopathy: visualisation of structures, myelographic comparison, cord measurements and clinical utility

Sixty-nine patients with cervical spondylotic myelopathy (CSM), radiculopathy (CSR), or both (CSMR) were studied with computed tomography (CT). Computer-assisted myelography (CAM) accurately determines the site and nature of spondylotic protrusions and provides good visualisation of the subarachnoid space and cord deformities even in areas with dilute metrizamide. However, excessive vertebral movement and bulging ligamenta flava with their effects on cord deformity, so easily visualised in myelograms, are completely or partially missed. In the assessment of CSM, metrizamide myelography (MM) followed by CAM should be performed, particularly when the myelographic images are unsatisfactory due to contrast dilution or blockage, when cord compression cannot be ascertained with MM and when cord atrophy is suspected. In CSR, the diagnostic information from MM and CAM is comparable. The diagnostic criteria in CAM are, however, less direct and since MM is adequate in uncomplicated cases, CAM is generally not necessary. The APD, APD/TD ratio, area and circularity are sensitive indices of cord deformity and the first two should be used more often to assist visual assessment of cord deformity. The relation between cord parameters and treatment response is better reflected in CSM cases managed conservatively and the results suggest that the degree of cord deformity is helpful in determining the outcome and hence the choice between surgical and conservative treatment. In plain CT, the osteophytes and calcified discs are adequately visualised and canal dimensions measured with accuracy, but the cervical cord and roots cannot be properly assessed and the diagnosis of CSM or CSR cannot be ascertained. At present, its role in cervical spondylosis is therefore limited.