Electrical impedance myography in the diagnosis of radiculopathy.

INTRODUCTION: We sought to determine whether electrical impedance myography (EIM) could serve as a diagnostic procedure for evaluation of radiculopathy. METHODS: Twenty-seven patients with clinically and radiologically diagnosed cervical or lumbosacral radiculopathy who met a "gold standard" definition underwent EIM and standard needle electromyography (EMG) of multiple upper or lower extremity muscles. RESULTS: EIM reactance values revealed consistent reductions in the radiculopathy-affected myotomal muscles as compared with those on the unaffected side; the degree of asymmetry was associated strongly with the degree of EMG abnormality (P < 0.001). EIM had a sensitivity of 64.5% and a specificity of 77.0%; in comparison, EMG had a sensitivity of 79.7% but a specificity of 69.7%. CONCLUSIONS: These findings support the potential for EIM to serve as a new non-invasive tool to assist in diagnosis of radiculopathy; however, further refinement of the technique is needed for this specific application.

Utilizing a handheld electrode array for localized muscle impedance measurements.

INTRODUCTION: Electrical impedance myography (EIM) is a noninvasive technique used for assessment of muscle health in which a high-frequency, low-amplitude electric current is applied to the skin overlying a muscle, and the resulting surface voltage is measured. We have previously used adhesive electrodes, application of which is inconvenient. We present data using a handheld electrode array (HEA) that we devised to expedite the EIM procedure in a clinical setting. METHODS: Thirty-four healthy volunteers and 24 radiculopathy subjects underwent EIM testing using the HEA and adhesive electrodes. RESULTS: The HEA was shown to have good test-retest reproducibility, with intraclass correlation coefficients as high as 0.99. HEA data correlated strongly with data from adhesive electrodes, ρ = 0.85 in healthy volunteers (P < 0.001) and ρ = 0.75 in radiculopathy subjects (P < 0.001). CONCLUSIONS: These data support the potential use of a handheld array for performing rapid localized surface impedance measurements.