Currently, there are many imaging tests available to help specialists make the proper diagnosis of degenerative spondylolisthesis. These are the plain xray, myelography, computed tomography scanning, magnetic resonance imaging and EMG/NCV. We will describe briefly each one of them.
Plain XRAY is the easiest and most reliable means of diagnosing degenerative spondylolisthesis. Standing lateral films may detect up to 15% of slips not seen on supine films (lying flat on your back). The amount of slip may be expressed as a percentage of the total anteroposterior diameter of the rostral end plate of the subjacent vertebra. The most widely used classification scheme is that of Meyerding in which the rostral end plate of the lower vertebra is divided into fourths and the degree of slip is described as grade I (0-25%), grade II (26-50%), etc.
Determination of segmental stability may alter the treatment strategy of degenerative spondylolisthesis. The most widely accepted method is standing lateral flexion and extension radiographs, although false-negatives may be significant. Static and dynamic images under a standardized load or traction may be a more sensitive means of assessing stability.
Myelography is a useful tool in evaluation of the degree and levels of canal stenosis and may show evidence of multilevel disease not otherwise appreciated. This investigation is rarely performed nowadays as MRI scan is much more useful and non-invasive. The characteristic myelographic finding in degenerative spondylolisthesis is that of an hourglass defect at the level of the lithesis. Absence of root sleeve filling due to lateral recess stenosis may also be seen in patients with radiculopathy. Myelography with standing flexion and extension views may show dynamic canal or root impingement not visible with other imaging modalities.
Computed tomography (CT) scanning, especially postmyelographic CT, is important in evaluating the bony degenerative changes that are characteristic of this disease process. Axial images at the level of listhesis may reveal significant hypertrophy of the superior articular process of the caudal vertebra encroaching on the lateral recess in patients with radiculopathy. CT also demonstrates the more sagittal alignment of the facets often seen in degenerative spondylolisthesis.
Magnetic resonance imaging
Magnetic resonance imaging (MRI) allows for detailed imaging of the soft tissues of the spine, including the ligamentum flavum and its contribution to canal stenosis. Superior evaluation of disc degeneration or herniation is obtained with this imaging modality. The ability to obtain multiplanar views, especially sagittal images, is helpful in evaluating multilevel stenosis and may provide excellent imaging of the neuroforamen.
Adjunctive studies such as EMG/NCV may be helpful to confirm radiculopathy or rule out other causes of radicular pain such as diabetic or other peripheral neuropathies. Differential pressure studies are indicated when vascular disease is suspected.
You might also want to read: Non Operative Treatment of Degenerative Spondylolisthesis
At the London Spine Unit, we have some of the most qualified specialists to diagnose degenerative spondylolisthesis. Book an appointment to get a checkup.