Magnetic resonance imaging vs. electrodiagnostic root compromise in lumbar spinal stenosis: a masked controlled study

The high false-positive rate of magnetic resonance imaging (MRI) makes it a less-than-reliable tool for evaluating clinically significant stenosis. Finding MRI changes that correlate with electrodiagnostic abnormalities might lead to more successful treatment decision making. The purpose of this study was to identify MRI changes that correlate with neurologic abnormalities measured by electrodiagnosis in patients with spinal stenosis.

One hundred fifty persons with and without back pain between the ages of 55 and 79 yrs participated in this prospective, blinded, controlled study. Exclusion criteria included previous spine surgery or known neuropathy. Needle electromyography of the limb, nerve conduction studies, including peroneal F-wave and tibial H-wave, and noncontrast lumbo-sacral spine MRI were completed. A codified physical medicine and rehabilitation history and physical examination was completed to differentiate symptomatic lumbar stenosis patients from asymptomatic controls. The relationship between lumbar MRI measurements and extremity electromyography findings was studied.

MRI measurements did not differ significantly with respect to extremity needle electromyography findings in the entire population or in patients with clinical signs of lumbar stenosis. In the entire population, an absent tibial H-wave corresponded to the interfacet ligament distance at L5-S1 and anterior to posterior canal size at L4-5. In patients clinically evaluated as having lumbar stenosis, peroneal F-wave latency correlated with anteroposterior canal size at L4-5 and interfacet ligament and anterior to posterior lateral recess narrowing at L5-S1. In patients with clinical signs and symptoms of lumbar stenosis, limb electromyography findings did not correlate with MRI measurements, although H-wave and F-wave testing correlated with relevant locations of stenosis.

Needle electromyography does not differentiate patients with symptomatic mild or moderate lumbar stenosis. However, H-wave and F-wave correlated to specific anatomical changes on MRI in this patient population.