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Expanded Use of EMG-NCV Helps Guide Treatment of Lower Extremity Neuromuscular Disorders

This once-popular test is again being recommended as a cost-effective alternative for the diagnosis of lower extremity nerve complaints.
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Although the most common complaints of patients seeking chiropractic evaluation are low back pain, neck pain, and headache, many patients present with extremity complaints—weakness, numbness, burning, tingling and sciatica. The differential diagnosis of lower extremity pain includes several neuropathic conditions, including radiculopathies, plexopathies, entrapment neuropathies, and sensorimotor polyneuropathies.

The role of electrodiagnostic testing (EDX), including electromyography (EMG) and nerve condition velocity (NCV), has been well established for all of these conditions, and it is considered the gold standard for diagnosing both radiculopathies and sensorimotor polyneuropathies.1-5 Unfortunately, this test appears to be underutilized. Instead, physicians refer most patients for computerized tomography (CT) or expensive magnetic resonance imaging (MRI) scans that, in our opinion, do not accurately diagnose the cause of the patient’s symptoms or provide the physiologic information with which to guide his or her treatment.

We hypothesized that digitized plain x-ray examination and needle EMG-NCV testing, both performed in our clinic, would allow accurate and immediate diagnosis of all extremity complaints in a cost-effective manner. Furthermore, immediate treatment could be initiated for all conditions based on the EDX findings.

Study Overview

In the chiropractic/health and wellness clinic, we initiated a comprehensive neuropathy treatment program in 2011 based on the results of a convenience study of 551 patients with the ReBuilder electrical system.6  This device is registered with the Food and Drug Administration as a 510(k) pre-amendment version of a TENS unit but delivers 2 simultaneous signals (1 to nerves and 1 to muscles) at low frequency (7.83 Hz).

The nerve signal imitates the natural waveform of a healthy neuron and is designed to allow time for repolarization. The signals are delivered via cutaneous electrodes on the feet or through a conductive solution in a split-compartment water bath. Because the signal travels from foot to foot, the lower spinal cord, legs, and pelvis are recruited. The study showed that pain scores decreased significantly within 10 days of treatment (P<0.0001) and that quality of life was improved in 91% of patients after 1 month.6

We performed lower extremity EMG-NCV studies in 208 consecutive patients in order to guide their treatment plans. This report details the clinical and electrodiagnostic findings in this group of patients with lower extremity symptoms and correlates the clinical impressions at the initial examination to the later electrodiagnoses.

Although the initial visit included medical and chiropractic evaluations, a complete neuropathy evaluation was not performed, and diagnostic codes were assigned based on the screening evaluations (Table 1). In addition, data analyses included a comparison of the clinical diagnosis at the time of initial screening examination with those determined by EDX.

Patient Population

Every patient who presented to our clinic had an initial history and physical examination by both the chiropractic and medical staff. Frequently, the examination was performed by both the physician (or physician assistant) and chiropractor concomitantly—both for enhancement of information sharing and to save time for the patients and clinicians.

From February 2010 to February 2013, 403 consecutive patients with upper and/or lower extremity pain that was thought to be neuropathic after the initial examination underwent EMG and NCV testing. This paper is a report of the findings of only those patients with lower extremity signs and symptoms; the upper extremity study is in process.

All needle EMG-NCV studies were performed by a single board-certified electrodiagnostician in a climate-
controlled environment in our clinic. Both studies were performed on the same day, and interpretation of the studies followed the guidelines proposed by Bromberg and Brownell.1

Results

EMG-NCV findings revealed the following: Of the 208 patients, 10% had isolated sensorimotor peripheral neuropathy (PN), 40% had isolated radiculopathy (RAD), 46% had both RAD and PN, and 4% had neither condition (Table 2). There was no difference in the severity of symptoms in patients with PN alone (mild, moderate, or severe) and in those with combined PN and RAD. Muscle denervation was present in half of the patients with RAD alone and in a third of the patients with isolated PN (P<0.05).

One or more toxic conditions were identified in 61% of the 117 patients with PN. Diabetes or elevated HbA1C was present in 22% of patients, and other toxic conditions were found in 39% of patients, the most common being cancer with chemotherapy (14%) and medications reported to be neurotoxic (17%). In an additional 31 patients (26%), a toxin was not identified in the patient’s history but a “toxic-metabolic” condition was diagnosed by EMG-NCV (Table 3).

When PN was present (117 patients) the following nerve involvement was noted: tibial 80%, peroneal 82%, and sural 66%.  All 3 nerves were involved in 40% of the PN patients (Table 4). Superficial saphenous nerves were also studied but involvement was rare (only 5 patients).

Based on the initial examination (prior to EMG-NCV testing), the presence and type of neuropathy was correctly identified in only 51% of patients. When RAD alone was documented, the diagnoses were correct 70% of the time. With PN alone or with RAD, the accuracy was 40% and 45%, respectively. None of the 8 patients with a completely normal EMG-NCV had an accurate diagnosis (Table 5).

Discussion

All patients in our facility had a complete chiropractic and medical evaluation at their screening evaluation. When neuropathy was suspected, a subsequent evaluation included an assessment of the patient’s Michigan Neuropathy Score,7 a detailed assessment of sensory and motor changes in the extremities, and extensive testing of vibratory sensation and reflexes.8,9

We also performed a peripheral vascular examination, including ankle/brachial index and duplex examination (Doppler and echo) when arterial insufficiency was suspected. We did not use the monofilament test. We have, however, added an assessment of skin temperatures at the proximal calf, mid-calf, and dorsum of the foot because skin temperature drops with normal arterial scans are common in neuropathy.10

Last updated on: November 10, 2016
First published on: October 31, 2016
Continue Reading:
Application of Acupuncture to Treat Low Back Pain
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