Level Of Maximum Compression Research Articles

Prognostic relevance of the postoperative evolution of intramedullary spinal cord changes in signal intensity on magnetic resonance imaging after anterior decompression for cervical spondylotic myelopathy

Areas of intramedullary signal intensity changes (hypointensity on T1-weighted magnetic resonance [MR] images and hyperintensity on T2-weighted MR images) in patients with cervical spondylotic myelopathy (CSM) have been described by several investigators. The role of postoperative evolution of these alterations is still not well known. A total of 47 patients underwent MR imaging before and at the end of the surgical procedure (intraoperative MR imaging [iMRI]) for cervical spine decompression and fusion using an anterior approach. Imaging was performed with a 1.5-tesla scanner integrated with the operative room (BrainSuite). Patients were followed clinically and evaluated using the Japanese Orthopaedic Association (JOA) and Nurick scales and also underwent MR imaging 3 and 6 months after surgery. Preoperative MR imaging showed an alteration (from the normal) of the intramedullary signal in 37 (78.7%) of 47 cases. In 23 cases, signal changes were altered on both T1- and T2-weighted images, and in 14 cases only on T2-weighted images. In 12 (52.2%) of the 23 cases, regression of hyperintensity on T2-weighted imaging was observed postoperatively. In 4 (17.4%) of these 23 cases, regression of hyperintensity was observed during the iMRI at the end of surgery. Residual compression on postoperative iMRI was not detected in any patients. A nonsignificant correlation was observed between postoperative expansion of the transverse diameter of the spinal cord at the level of maximal compression and the postoperative JOA score and Nurick grade. A statistically significant correlation was observed between the surgical result and the length of a patient's clinical history. A significant correlation was also observed according to the preoperative presence of intramedullary signal alteration. The best results were found in patients without spinal cord changes of signal, acceptable results were observed in the presence of changes on T2-weighted imaging only, and the worst results were observed in patients with spinal cord signal changes on both Tl- and T2-weighted imaging. Finally, a statistically significant correlation was observed between patients with postoperative spinal cord signal change regression and better outcomes. Intramedullary spinal cord changes in signal intensity in patients with CSM can be reversible (hyperintensity on T2-weighted imaging) or nonreversible (hypointensity on T1-weighted imaging). The regression of areas of hyperintensity on T2-weighted imaging is associated with a better prognosis, whereas the T1-weighted hypointensity is an expression of irreversible damage and, therefore, the worst prognosis. The preliminary experience with this patient series appears to exclude a relationship between the time of signal intensity recovery and outcome of CSM.

Cross-sectional Transverse Area and Hyperintensities on Magnetic Resonance Imaging in Relation to the Clinical Picture in Cervical Spondylotic Myelopathy

Prospective observational cohort study. To ascertain the threshold of critical spondylotic cervical cord compression and its relation to MRI-increased signal intensities. The critical degree of spinal cord compression required to induce significant clinical signs remains unknown. The study group consisted of 243 patients (mean age, 53.9 +/- 9.8 years), with spondylotic cervical spine compression. The transverse cross-sectional area of the spinal cord at the level of maximum compression was measured, while MRI hyperintensities were recorded and related to clinical status and quantified by modified JOA score (mJOA). A statistically significant difference in mJOA was shown between patients with a spinal cord sectional area of under 50 mm2 and a group of patients with a spinal cord sectional area of over 60 mm2. This difference was highly significant (P = 0.001) in a subgroup with MRI hyperintensities (187 patients, P = 0.001), whereas within the group of patients without hyperintensities this difference was not observed (P = 0.63). The critical degree of spinal cord compression needed to induce clinically significant signs was found between 50 and 60 mm2 of cross-sectional transverse area at the level of maximal compression in association with MRI hyperintensities.

A wavelet thresholding technique for local geoid and deflection of the vertical determination using a planar approximation

SUMMARY A computational scheme using the wavelet transform is employed for local geoid determination, where wavelet multiresolution analysis (MRA) is introduced as an alternative approach to the well-established fast Fourier transform (FFT). The Stokes and Vening Meinesz integrals are approximated in finite MRA subspaces. The algorithm is built using an orthogonal wavelet base function. The characteristics of the base function and its effect on the final result are investigated. Hard and soft thresholding are tested in the compression of the kernel as well as global thresholding is compared to level-wise thresholding to optimize the compression level with an acceptable accuracy. Both global and level-wise thresholding are combined in order to achieve the maximum compression level, with acceptable geoid accuracy. The compression rate depends on the degree of singularity of the kernel. In the case of Stokes, a 94 per cent compression level is achieved with 1 cm (rms) accuracy in comparison to FFT and numerical integration approaches. Due to its stronger singularity, in the case of the Vening Meinesz kernel, 97 per cent compression rate is achieved with a 0.07 arc-second (rms) accuracy. The compression percentages achieved in this study are higher than those reported in pervious studies, which shows that this algorithm is very suitable for use in local geoid determination.

Prognostic Factors Affecting the Results of the Surgery for Cervical Spondylotic Myelopathy

Study design : This retrospective study was designed to investigate and define the factors affecting the results of surgery for cervical spondylotic myelopathy. Objective: This study was performed in an attempt to investigate and define the factors affecting the results of surgery for cervical spondylotic myelopathy. Summary of the Literature Review: There have been few studies about the factors affecting the results of surgery for cervical myelopathy, including MEP (Motor evoked potential) studies and gait analysis, so we investigated the factors that affect the results of surgery for cervical myelopathy. Materials and Methods: We retrospectively studied 59 cervical spondylotic myelopathy patients who underwent operation from Nov. 1994 to Oct. 2002. We analyzed 13 prognostic factors: age, disease duration, the pre-op JOA score, the pre-op. AP canal diameter, the Pavlov ratio, disease level, the AP and lateral cord diameter, the transverse area and the compression ratio at the level of the maximal cord compression on MRI, the cord signal changes on MRI, the MEP(Motor evoked potential) and the gait analysis. The mean follow up period was 29 months. The clinical results were evaluated according to the JOA score. Statistical analysis was performed using the Pearson correlation test, ANOVA and the Kruskal-Wallis test. Results: The mean pre-op JOA score was 11.1 and the post-op. JOA score was improved to 14.7. The average recovery rate was 67%. The following factors were proved to an influence on the surgical outcomes: age and multiplicity of involvement, and the signal changes of the cord on MRI showed a negative correlation with the recovery rate. The pre-op JOA score, the mean sagittal diameter and the transverse area of the spinal cord at the level of maximum compression showed a positive correlation with the recovery rate. Spasticity on the gait analysis and central conduction block on MEP had an influence on the surgical outcomes. Conclusions: The prognostic factors affecting the results of surgery for cervical myelopathy are age, the pre-op JOA score, the disease level, the mean sagittal diameter and the transverse area of the spinal cord at the level of maximum compression, signal change of the cord on MRI, spasticity on the gait analysis and central conduction block on MEP.

Cervical spondylotic myelopathy: surgical results and factors affecting outcome with special reference to age differences.

A variety of factors may affect the surgical outcome in patients with cervical spondylotic myelopathy. The aim of this study is to analyze the prognostic factors by comparing younger and elderly patient groups on the basis of preoperative radiological and clinical data. To assess the prognostic factors after surgery had been performed, the clinical and radiological data of 64 patients who underwent expansive laminoplasty were reviewed. Patients were classified into two groups, a younger patient group (<65 yr of age; n = 29) and an elderly patient group (>/=65 yr of age; n = 35). The neurological status of the patients was assessed by use of the Japanese Orthopaedic Association scale. Radiological features were examined with computed tomographic myelography and magnetic resonance imaging. The effects of the clinical and radiological findings on neurological outcome were investigated. The preoperative and postoperative mean Japanese Orthopaedic Association scores in elderly patients were significantly lower than those in younger patients. For elderly patients, the transverse area of the spinal cord at the level of maximum compression and symptom duration were the factors that predicted an excellent recovery. In contrast, the transverse area was the only predictor of excellent recovery in younger patients. Age, preoperative Japanese Orthopaedic Association score, canal diameter, and an intensity change on the spinal cord were not predictive in either age range. The transverse area of the spinal cord may be a reliable predictor of excellent recovery in both younger and elderly patient groups. Shorter symptom duration was an important factor in the excellent recovery of elderly patients.

Cervical radiculopathy and myelopathy: when and what can surgery contribute to treatment?

Indications and timing of surgical treatment for cervical radiculopathy and myelopathy, and the long-term results for the conditions, were reviewed. Advances in spinal imaging and accumulation of clinical experience have provided some clues as to indications and timing of surgery for cervical myelopathy. Duration of myelopathy prior to surgery and the transverse area of the spinal cord at the maximum compression level were the most significant prognostic parameters for surgical outcome. Thus, when myelopathy is caused by etiological factors that are either unchangeable by nature, such as developmental canal stenosis, or progressive, such as ossification of the posterior longitudinal ligament, surgical treatment should be considered. When an etiology of myelopathy is remissible, such as soft disc herniation and listhesis, surgery may be reserved until the effects of conservative treatment are confirmed. When surgery is properly carried out, long-term surgical results are expected to be good and stable, and the natural course of myelopathy secondary to cervical spondylosis may be modified. However, little attention has been paid to the questions "When and what can surgery contribute to treatment of cervical radiculopathy?". A well-controlled clinical study including natural history should be done to provide some answers.

Can Intramedullary Signal Change on Magnetic Resonance Imaging Predict Surgical Outcome in Cervical Spondylotic Myelopathy?

A retrospective study evaluating magnetic resonance imaging, computed tomographic myelography, and clinical parameters in patients with cervical spondylotic myelopathy. To investigate whether magnetic resonance imaging can predict the surgical outcome in patients with cervical spondylotic myelopathy. No previous studies have established whether areas of high signal intensity in T2-weighted magnetic resonance images can be a predictor of surgical outcomes. Fifty patients with cervical spondylotic myelopathy were examined by magnetic resonance imaging and computed tomographic myelography before surgery and by delayed computed tomographic myelography after surgery. The correlation between the recovery rate and the clinical and imaging parameters was analyzed. The best prognostic factor was the transverse area of the spinal cord at maximum compression (correlation coefficient, R = 0.58). The presence of high signal intensity areas on T2-weighted magnetic resonance images correlated poorly with the recovery rate (R = -0.29). However, patients with multisegmental areas of high signal intensity on T2-weighted magnetic resonance images tended to have poor surgical results associated with muscle atrophy in the upper extremities. Postoperative delayed computed tomographic myelography showed that multisegmental areas of high signal intensity on T2-weighted magnetic resonance images probably represent cavitation in the central spinal cord. Patients with multisegmental areas of high signal intensity on T2-weighted magnetic resonance images tended to have poorer surgical results. However, the transverse area of the spinal cord at the level of maximum compression was a better prognostic indicator.

Magnetic resonance imaging findings in ossification of the posterior longitudinal ligament of the cervical spine.

Because of the lack of magnetic resonance (MR) signal from cortical bones, MR imaging is inadequate for diagnosing ossified lesions in the spinal canal. However, MR imaging provides important information on spinal cord morphology and associated soft-tissue abnormality. The purpose of this study is to determine the role of MR imaging in the diagnosis and treatment of patients with ossification of the posterior longitudinal ligament (OPLL) of the cervical spine. The authors reviewed MR imaging findings in 42 patients with cervical OPLL who were examined with a superconducting MR imaging system. The types of OPLL reviewed included eight cases of continuous, 21 cases of segmental, and 13 cases of the mixed type. All patients were treated surgically either by anterior (26 cases) or posterior decompression (16 cases). The T1-weighted images clearly demonstrated the spinal cord deformity caused by OPLL. Associated disc protrusion was found to be present at the maximum compression level in 60% of the patients in this series. The highest incidence of disc protrusion (81%) was found in patients with segmental OPLL. Intramedullary hyperintensity on T2*-weighted imaging was noted in 18 patients (43%). The neurological deficits observed in these 18 patients were significantly more severe than those observed in the other 24 patients. Postoperative MR imaging revealed improvement in the spinal cord deformity, although the intramedullary hyperintensity was still observed in most cases. The present study demonstrates the importance of associated disc protrusion in the development of myelopathy in patients with cervical OPLL. Magnetic resonance imaging findings may be used to help determine the actual levels of spinal cord compression and to suggest the method of surgical treatment.

Cervical spine degenerative diseases: An evaluation of clinical and imaging features in surgical decisions

In clinically severe cervical spondylosis, imaging plays a vital role in surgical decisions. A prime factor is acquired canal stenosis with cord compression. To validate this concept, the clinical and imaging features of 20 patients with spondylotic myelopathy and 24 with radiculopathy were retrospectively reviewed. All had computed tomographic myelography (CTM) as part of their clinical work-up. The patients' clinical severity was graded as mild, moderate and severe; the age, length of illness and a history of eventual surgery or otherwise were recorded. At the level of maximum compression the following parameters were obtained from the axial CTM images: surface area and ratio of the anteroposterior to the transverse diameter of the cord; subarachnoid space and vertebral canal areas. Data were statistically analysed. A significant association exists between surgery and increasing severity of symptoms (P = 0.04), and advancing age (P = 0.01). These associations hold true for myelopathy and radiculopathy. A strong association is present between surgery and the surface area of the cord (P = 0.01), being applicable to myelopathy only. The other parameters show no association with surgical decisions. It is concluded that with myelopathy a narrow cord area at the level of maximum compression, and moderate--severe functional impairment are indicators for surgical intervention.

Morphologic analysis of the cervical spinal cord, dural tube, and spinal canal by magnetic resonance imaging in normal adults and patients with cervical spondylotic myelopathy.

Transverse areas of the spinal canal, the dural tube and the spinal cord of the cervical spine of normal adults and patients with cervical spondylotic myelopathy (CSM) were analyzed by magnetic resonance imaging (MRI). Correlations of the results of MRI to clarify the pathogenesis of CSM. Relationships between the area of the spinal cord and that of the dural tube or the spinal canal have been reported, but there is no report to compare the relationships among the three in patients with CSM and normal adults. T1-weighted MR images of the cervical spine of 96 normal adults and 74 patients with CSM were evaluated by measuring the transverse areas of the three structures mentioned above in the axial plane. In normal adults, the maximal transverse area of the spinal cord was 85.8 mm2 at C4/5 and the minimal transverse areas of the dural tube and the spinal canal were 186.0 mm2 at C5/6 and 236.1 mm2 at C4, respectively. At the unaffected level of C3, the ratio of the canal to the spinal cord was significantly higher in CSM patients than in age-matched normal adults. The transverse area of the spinal cord and the ratio at the maximal compression level showed significant correlations with the severity of neurological symptoms. These results suggest that the narrow area and high ratio of the spinal canal to the spinal cord are responsible for a static factor in CSM.

Magnetic resonance imaging study on the results of surgery for cervical compression myelopathy.

The morphologic changes and signal intensity of the spinal cord on preoperative magnetic resonance images were correlated with postoperative outcomes in 74 patients undergoing decompressive cervical surgery for compressive myelopathy. The transverse area of the spinal cord on T1-weighted images at the level of maximum compression was closely correlated with the severity of myelopathy, duration of disease, and recovery rate as determined by the Japanese Orthopaedic Association score. In patients with ossification of the posterior longitudinal ligament or cervical spondylotic myelopathy, the increased intramedullary T2-weighted magnetic resonance imaging signal at the site of maximal cord compression and duration of disease significantly influenced the rate of recovery. A multiple regression equation was then developed with these three variables to predict surgical outcomes.

観血的治療を行った高令者頚髄症症例の検討

In twenty-five cases operated for cervical myelpathy above sixty years old, we examined some factors influencing on the postoperative results. But there was no good correlation between these factors and recovery of symptoms.A clinical study of computed tomographic myelography with metrizamide was perfomed in 11 patients operated for cervical myelopathy. The compression ratio at the maximam compression level in CTM was not correlated with surgical results. The patients in whom the compression ratio at the maximum compression level increased in the postoperative CTM, showed clinically good postoperative results.