When should an electromyogram or nerve conduction velocities be ordered for a patient with low back pain?
An EMG is obtained in a patient with low back pain who has signs and symptoms of a radiculopathy if this information will change your approach. MRI imaging has largely replaced the need for EMG/NCV, especially in patients who have radicular symptoms/signs that correlate with the MRI findings. However, in complex cases, where the etiology of lower extremity pain or weakness is unclear despite careful neurologic exam and imaging, EMG/NCV studies can be of value. The EMG is usually performed at least 3 weeks after the onset of symptoms to accurately assess for potential muscle denervation. The results of EMG are helpful only when combined with the clinical presentation, physical examination, and radiographic tests (MRIs). Laminectomy or microdiscectomy has the greatest likelihood of improving symptoms if the physical examination, EMG, and radiographic studies all agree on the anatomic location of the disc compressing the nerve root.