Cervical cord size in metrizamide myelography

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.

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.

Optimal positioning for cervical immobilization

STUDY OBJECTIVE

We hypothesized that optimal positioning of the head and neck to protect the spinal cord during cervical spine immobilization can be determined with reference to external landmarks. In this study we sought to determine the optimal position for cervical spine immobilization using magnetic resonance imaging (MRI) and to define this optimal position in a clinically reproducible fashion.

METHODS

Our subjects were 19 healthy adult volunteers (11 women, 8 men). In each, we positioned the head to produce various degrees of neck flexion and extension. This positioning was followed by quantitative MRI of the cervical spine.

RESULTS

The mean ratio of spinal canal and spinal cord cross-sectional areas was smallest at C6 but exceeded 2.0 at all levels from C2 to T1 (P < .05). At the C5 and C6 levels, the maximal area ratio was most consistently obtained with slight flexion (cervical-thoracic angle of 14 degrees) (P < .05). For a patient lying flat on a backboard, this corresponds to raising the occiput 2 cm. More extreme flexion or extension produced variable results.

CONCLUSION

In healthy adults, a slight degree of flexion equivalent to 2 cm of occiput elevation produces a favorable increase in spinal canal/spinal cord ration at levels C5 and C6, a region of frequent unstable spine injuries.

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.

Sagittal measurements of the cervical spine in subaxial fractures and dislocations. An analysis of two hundred and eighty-eight patients with and without neurological deficits

We analyzed three factors involved in fractures and dislocations of the cervical spine and their relation to the degree of injury of the spinal cord. The three factors were the space available for the spinal cord at the level of the injury, the sagittal diameter of the spinal canal at the uninjured levels, and the Pavlov ratio at the uninjured levels. Of the 288 patients analyzed, eighty-three had a complete injury of the spinal cord, ninety-two had an incomplete injury of the spinal cord, thirty had an isolated nerve-root injury, and eighty-three had no neurological deficit. The mean space available for the spinal cord at the level of the injury was 10.5 millimeters for the patients who had a complete injury of the spinal cord, 13.1 millimeters for those who had an incomplete injury of the spinal cord, 15.9 millimeters for those who had an isolated nerve-root injury, and 16.7 millimeters for those who had no neurological deficit. The difference between the groups was significant (p < 0.001) except for the difference between the patients who had an isolated nerve-root injury and those who had no neurological deficit. The mean sagittal diameter of the canal at the uninjured levels was 16.1 millimeters for the patients who had a complete injury of the spinal cord, 16.1 millimeters for those who had an incomplete injury of the spinal cord, 17.9 millimeters for those who had an isolated nerve-root injury, and 18.1 millimeters for those who had no neurological deficit. The difference between the patients who had a complete injury of the spinal cord and those who had an incomplete injury of the spinal cord and that between the patients who had an isolated nerve-root injury and those who had no neurological deficit were not significant (p > 0.05). However, the patients who had a complete injury of the spinal cord and those who had an incomplete injury of the spinal cord were significantly different from the patients who had an isolated nerve-root injury and those who had no neurological deficit (p < 0.001). The mean Pavlov ratio at the uninjured levels was 0.82 for the patients who had a complete injury of the spinal cord, 0.84 for those who had an incomplete injury of the spinal cord, 0.96 for those who had an isolated nerve-root injury, and 0.96 for those who had no neurological deficit.(ABSTRACT TRUNCATED AT 400 WORDS)

The effectiveness of strapping techniques in spinal immobilization

STUDY OBJECTIVES

To test the effectiveness of strapping techniques in reducing lateral motion of volunteers restrained on a backboard.

DESIGN

Randomized block experimentation.

SETTING

Medical products research and design laboratory.

PARTICIPANTS

Healthy adult volunteers with no history of head, neck, or back trauma.

INTERVENTIONS

Subjects were restrained on a wooden backboard using a control and three variations of strapping techniques. The backboard was rolled 90 degrees to the side, and lateral motion of the torso was measured.

MEASUREMENTS AND MAIN RESULTS

Nineteen subjects participated. Technique 2, which added an abdominal strap to the control technique, reduced 26% of the lateral motion.

CONCLUSION

Additional, specifically placed strapping should be added to the torso to reduce lateral motion on a backboard. Further study is needed to determine the effect of lateral motion in the spine and potential benefits of reduced motion.

Cervical Spinal Stenosis

Cervical spinal cord symptoms after a spine injury from contact sports require a more precise workup to detect cervical spinal stenosis than radiographic bone measurements alone can provide. Imaging technologies such as MRI, contrast-positive CT, and myelography more accurately identify true spinal stenosis and allow for safer return-to-play decisions.

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.

Influence of certain factors on the manifestations of the adverse effects of metrizamide myelography

Although metrizamide is now being superseded by other contrast media, the mechanisms of its side effects may be of fundamental importance. One hundred and four consecutive patients with suspected cervical cord or root lesion were studied prospectively for factors which might influence the side effects of metrizamide myelography. Elderly patients were more prone to develop mental confusion. An earlier onset of dizziness and/or vertigo was associated with the lumbar route of intrathecal injection. Perhaps surprisingly, phenobarbitone prophylaxis shortened the duration of confusion and delayed the onset of headaches. Other factors, viz. sex, excess intracranial flow of metrizamide and myelographic blockage were not shown to have a significant influence on the adverse reactions.

Quantitative analysis of the cervical spinal canal by computed tomography

Computed tomography measurements of the AP diameter, width, and cross-sectional area of the bony cervical canal were derived from cervical spine examinations of fifty-two normal adults. These quantitative parameters were then used to evaluate 80 patients with various cervical abnormalities to determine the clinical usefulness of the measurements. With the exception of spinal stenosis, quantitative cervical canal analysis was found to be of limited usefulness since normal measurements frequently occurred in the presence of significant cervical pathology.

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

Thirty-six control subjects had computer assisted myelography (CAM) using the EMI CT 5005 scanner. The normal cervical cord is elliptical, more circular at the upper and lower ends and flatter in the mid-segments. Asymptomatic cord deformities, usually mild, were present in nine subjects (25%). Four measurements, namely, sagittal diameter (APD), transverse diameter (TD), area (a) and circumference (c) were made and two more parameters calculated i.e. APD/TD ratio and circularity (= 4 pi a/c2). These control values form the basis of qualitative and quantitative assessment of cord deformity. When cord measurements are to be used, control values should be obtained for each scanner and procedures should be standardized.