Date Published: July 20, 2012
Publisher: Hindawi Publishing Corporation
Author(s): C. Green, J. Butler, S. Eustace, A. Poynton, J. M. O’Byrne.
Cervical spondylosis is a spectrum of pathology presenting as neck pain, radiculopathy, and myelopathy or all in combination. Diagnostic imaging is essential to diagnosis and preoperative planning. We discuss the modalities of imaging in common practice. We examine the use of imaging to differentiate among central, subarticular, and lateral stenosis and in the assessment of myelopathy.
Imaging modalities for cervical spondylosis aim to assist the clinician in differentiating discogenic neck pain, radiculopathy, and myelopathy. Radiological assessment helps to localise the site and level of the disease for preoperative planning when surgical intervention is required. The current modalities in common use are pain film roentgenology, magnetic resonance imaging, and computed tomography.
Modalities employed for a central assessment of the cervical spine should determine the extent and site of canal stenosis and any associated myelopathy.
The size of the cervical spinal canal is clinically important [4, 8]. The spinal canal is narrowed with central stenosis, and this can lead to cervical myelopathy. The role of the narrow cervical spine in the expression of clinical syndromes was evaluated by Edwards and LaRocca . They predicted that patients with a canal size of <10 mm had myelopathy, those with a canal size of 13 to 17 mm were less prone to myelopathy but were more prone to symptomatic cervical spondylosis, and those with a canal size of greater than 17 mm were asymptomatic . MRI studies which take into account soft tissue structures, weight-bearing, and dynamic imaging have suggested that a congenital sagittal diameter of <13 mm is a significant risk factor for development of stenosis . However, a number of authors have reported an incidence of asymptomatic stenosis of between 16 and 19% [10, 11]. With MRI scanning becoming more routinely available the best management of this group of individuals will be challenging. As well as the anatomy of spinal cord compression MRI can show the pathological spinal cord changes in cervical spondylotic myelopathy. Signal change not only indicates the presence of myelopathic change but has also been used as a predictor of outcome . Takahashi et al. were the first group to correlate a high signal on T2-weighted MR images with a poor clinical result after both operative and nonoperative management . However, controversy exists in the interpretation of signal changes in the spinal cord. This may explain why although some studies have shown similar results to Takahashi et al. other studies have not [19, 20]. Radicular symptoms can be attributed to either subarticular recess stenosis in lateral aspect of the central spinal canal or lateral stenosis at the foramina. Detailed history and examination findings are essential to interpreting the results of these scans. The distribution of radiculopathy should be localised to a nerve root. Imaging should be used to ascertain if compression of that nerve root is occurring. Where impingement is demonstrated and surgery is being considered the exact location of obstruction needs to be identified. Preoperative planning should distinguish between subarticular recess stenosis at the same level as the exiting nerve root and lateral stenosis at the foramina below. Intraoperative ultrasound has been described to be useful during central corpectomy for compressive cervical myelopathy. It is inexpensive and simple imaging modality. It is helpful in identifying the vertebral artery and the trajectory of approach . However, ossification of the posterior longitudinal ligament limits the use of this technique . Development of advanced MRI techniques such as diffusion tensor imaging has shown promise in intramedullary microarchitectural analysis with improved imaging quality and increased lesion identification when compared to conventional MRI . Metabolic neuroimaging has been described for image acquisition from the spinal cord. Findings on high-resolution 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) have been compared with clinical scores and findings on magnetic resonance imaging in patients undergoing surgery for myelopathy . FDG-PET findings correlated with preoperative scores, postoperative scores, and the rate of postoperative improvement, but they had no correlation with high-intensity intramedullary signal changes on T2-weighted images. The major limitation of this technology is the poor resolution of PET scans. Future technological advancements in PET scanning may facilitate evaluation of early spinal cord damage and provide indications for surgical intervention. Source: http://doi.org/10.1155/2012/908324