Approach to Electrodiagnostic Studies in Radiculopathy: What Referring Physicians Should Know

When patients present with radiating arm or leg pain, numbness, or weakness, one of the most valuable tools available is the electrodiagnostic study. This evaluation, which includes both nerve conduction studies (NCS) and needle electromyography (EMG), allows direct testing of the peripheral nervous system. It can confirm or rule out a diagnosis and, perhaps most importantly, help localize the source of symptoms. The true strength of electrodiagnostic testing lies in answering focused questions. It is not designed to be a general screening tool for anyone with pain or weakness. Instead, it is most helpful when the referring physician provides a specific clinical scenario to be addressed. For a trained physiatrist, it is a powerful extension of the physical examination.

What Electrodiagnostic Studies Can Reveal

NCS assess the function of sensory and motor nerves, making them especially useful in identifying conditions such as peripheral neuropathies or focal nerve entrapments. EMG evaluates muscle activity and can detect signs of denervation and reinnervation in tested muscles which allows the examiner to determine several important pieces of information that may help in the diagnosis and treatment of patients.

Beyond localization, these studies can provide valuable information about the severity and timing of a nerve injury. It can distinguish between acute and chronic changes, assess whether there is evidence of nerve recovery, and offer prognostic insight into the likelihood of functional improvement. This makes electrodiagnostic testing particularly useful not only in suspected radiculopathy but also in cases where a nerve injury is already known and the question is about extent and prognosis.

Why the Referral Question Matters

The diagnostic yield of electrodiagnostic studies is greatly improved when the referring provider asks a specific question. A referral that simply reads “rule out neuropathy” provides little direction. In contrast, asking whether a patient’s leg pain and weakness is due to an L5 radiculopathy versus a peroneal neuropathy allows the examiner to tailor the study to the patient’s presentation. Similarly, if there is a known nerve injury, the request can focus on determining how severe the injury is and whether there are signs of recovery.

When the referral is focused, the study can be designed and interpreted with the clinical context in mind. This increases the likelihood that the results will provide information that is directly useful in guiding management and maximizes the utility of the study.

A Case Example

Consider a patient who presents with pain and weakness along the outside of the leg and into the foot. This could represent either an L5 radiculopathy or a peroneal neuropathy at the knee. Both conditions can produce nearly identical symptoms, and imaging alone does not always clarify the difference. Electrodiagnostic testing can provide the answer. By evaluating muscle and nerve function at multiple levels, EMG and NCS can determine whether the problem originates from the spinal nerve root or from the peripheral nerve; a distinction makes all the difference in guiding appropriate treatment.

What Electrodiagnostic Studies Cannot Do

It is also important to understand the limitations of electrodiagnostic testing. These studies do not replace imaging, which remains the gold standard for evaluating the structural causes of symptoms. For example, a patient with electrodiagnostic evidence of an L5 radiculopathy may have compression of the nerve root from a disc herniation, or more critically, a mass pressing on the nerve. They also cannot measure pain directly, since they assess physiologic changes in nerves and muscles rather than the patient’s subjective experience. Finally, electrodiagnostic abnormalities may not yet be detectable early on in the course of a lesion (< 3-6 weeks). For these reasons, EMG and NCS should be considered complementary to imaging and physical examination rather than stand-alone diagnostic tools.

Practical Considerations for Referring Physicians

When sending a patient for an electrodiagnostic evaluation, framing the referral around a specific clinical question is important. Providing further details such as symptom onset, distribution, examination findings, and any relevant imaging results allows the study to be carefully targeted to the patient’s specific needs. Electrodiagnostic studies are “live” studies that are interpreted, adjusted, and performed actively as the study is being conducted. Having as much clinical context as possible allows the electromyographer to conduct the best study possible to assist in the diagnosis and treatment of the patient.

Why This Matters

Electrodiagnostic studies are not simply tests to confirm the presence of “nerve damage.” They are tools for localization, characterization, and prognosis. They provide actionable information that actively guides treatment and helps patients and physicians set realistic expectations.

At Desert Spine and Sports Physicians, our physiatrists approach every electrodiagnostic study with this mindset. Each evaluation is tailored to the patient’s history and examination, with the specific referral question serving as the guide. When referring physicians provide that clinical focus, the diagnostic power of electrodiagnostic testing is maximized, and both patients and providers benefit from more meaningful results.

References
Preston DC, Shapiro BE. Electromyography and Neuromuscular Disorders:
Clinical-Electrophysiologic Correlations.4th ed. Elsevier; 2021.
Dumitru D, Amato AA, Zwarts MJ. Electrodiagnostic Medicine. 2nd ed. Hanley & Belfus; 2002. Jablecki CK, et al. Evidence-based guideline: Electrodiagnostic studies in carpal tunnel syndrome. Muscle Nerve.2002;25(6):918–922.