Tests
1st tests to order
plain x-ray
Test
Plain x-rays in patients with degenerative lumbar stenosis typically show overgrowth of the facet joints, narrowing of the disk spaces, and osteophyte formation. Other important findings include narrowing of the anteroposterior diameter of the canal, whereas the interpedicular distance may be normal. Oblique x-ray films may show pars defect (spondylolysis).[24]
When vertebral slippage (spondylolisthesis) is present, flexion and extension views are helpful, as the presence and degree of instability may alter the surgical management.
Result
degenerative changes or spondylolisthesis
MRI (T2-weighted)
Test
MRI is the most accurate test for diagnostic and treatment planning purposes.
Sagittal images provide a panoramic view of the spinal canal, and the images of the lateral spine reveal the position of the nerve roots in the intervertebral foramina.
Gradient-echo images are usually able to distinguish compression caused by ligament from osteophyte, but CT remains superior in displaying bone.
Symptoms of lumbar stenosis characteristically are dynamic, with compression being worse when a patient stands erect or walks. Open MRI offers the possibility of studying the patient in flexion and extension, although image quality remains inferior to that obtained with closed MRI, and the relevance of this study is not yet clear.
Abnormalities are found in up to 33% of asymptomatic patients ages 50 to 70 years.[14]
MRI should generally not be ordered unless the patient has symptoms of radiculopathy or claudication. Imaging for atraumatic low back pain should be kept to a minimum unless a patient has “red flags” suggestive of infection or malignancy.
Result
compression of the neural elements and soft tissue
Tests to consider
CT myelography
Test
Although CT myelography is performed less often now that MRI is widely available, it is still occasionally necessary for patients with claustrophobia or implanted pacemakers, or in instances when a good-quality MRI cannot be obtained.
One potential advantage of myelography over MRI is the ability to study the dynamic compression of the thecal sac and nerve roots in flexion and extension. It is also a good method for the assessment of lateral recess and foraminal compression.
Complications such as seizures and arachnoiditis have largely been eliminated with the introduction of newer contrast media. The potential for spinal fluid headaches, although low, still remains.
Result
classic "hourglass" constriction of the dye column
CT spine
Test
CT is the best method of imaging for bony anatomy and is often necessary for surgical planning as well as in establishing the diagnosis.
CT accurately provides anatomic details of the lateral recesses and neural foramina, and distinguishes between neural compression with bone and thickened ligaments or disk protrusion.
The presence of spondylolysis may be more evident on CT than on MRI or plain x-ray.
In addition, when pedicle screw instrumentation is to be placed, many surgeons use axial CT to analyze pedicle diameter and medial-lateral orientation; however, MRI is usually adequate for bone measurement.
CT does not allow for high-quality imaging of neural structures or evaluation of the severity of stenosis.
Result
abnormal bony anatomy
electromyographic (EMG) walking test
Test
Patients with symptomatic neurogenic claudication from lumbar spinal stenosis demonstrate increased F latency values on EMG studies after walking, which return to baseline after sitting. It is unclear if this test is specific enough to distinguish between those with and without spinal stenosis.
Result
increased F latency values
electromyographic paraspinal mapping
Test
A sensitive method and may reflect the physiology of nerve roots better than limb EMG. It may be useful for presurgical evaluation with more equivocal clinical and radiographic findings. Routine electrophysiological tests (EMG, nerve conduction study, F-wave response, Hoffmann-reflex, somatosensory evoked potentials, motor evoked potentials) have no diagnostic value for lumbar spinal stenosis.[23]
Result
fibrillation potential and positive sharp waves in at least two levels may be seen with clinically symptomatic radiographic spinal stenosis
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