Lumbar spinal stenosis remains a vexing imaging and diagnostic problem that complicates efforts to plan effective therapy, a Cleveland radiologist said at an RSNA refresher course.
Little correlation exists between symptoms and morphology revealed by various imaging modalities. Structural findings often appear more severe than the symptoms would indicate. No controlled studies have demonstrated the superiority of one imaging modality over another. Conservative therapy often works as well as surgery, though outcomes with either approach remain discouraging, said Dr. Michael Modic of the Cleveland Clinic Foundation.
Lumbar spinal stenosis occurs in two forms: acquired and developmental. Acquired often results from degeneration, spondylosis, iatrogenic causes, or trauma. Developmental spinal stenosis may be idiopathic, hereditary or the result of a genetic disturbance.
With developmental stenosis, the narrowing tends to be more uniform and involve multiple levels of the spinal column, said Modic, whereas acquired stenosis usually is more focal. In younger patients, pain is the more common. Sensory disturbance predominates in older patients.
Weakness, voiding disturbances, claudication, relief of discomfort on bending, and worsening of discomfort with downhill walking are other common clinical findings.
The medical literature provides no universal agreement about what constitutes narrowing of the spinal canal, said Modic. However, most experts would agree that sagittal narrowing to less than 12-20 mm, lateral narrowing to less than 20-30 mm, and a pedicle length of greater than 3-10 mm would point to a diagnosis of spinal stenosis.
With respect to treatment, the literature provides a discouraging picture, said Modic. Once patients become symptomatic, they rarely get better. In virtually all cases, the condition is progressive. Medical treatment leads to some symptomatic improvement in up to 30% of patients, and surgery results in some improvement in about 50-55% of cases. Surgery tends to work best for patients who have severe, highly symptomatic stenoses.
The major objective of imaging studies is to provide the surgeon with as much information as possible.
"The radiologist has to identify and characterize the morphology of the stenosis in great detail and identify and characterize changes in morphology," said Modic. "We don't know why patients hurt, and we don't know how morphologic findings on imaging studies correlate with patient symptoms. I'm really sympathetic with the surgeon's plight."
