Let's start neuromuscular ultrasound testing

Abstract

Neuromuscular ultrasound is useful complementary testing in conjunction with clinical evaluation and neurophysiological testing such as nerve conduction study and electromyography. Two kinds of probe frequencies are commonly used, higher frequency (15–18MHz) for the evaluation of surface regions such as nerve locating at the wrist, on the other hand, lower frequency (11–15MHz) is suitable for deeper structures such as nerve roots and sciatic nerves. To differentiate peripheral nerves from other structures, the color–Doppler technique is useful in identifying blood vessels, and also a long stretching structure can be recognized as a peripheral nerve. For quantitative evaluation, cross–sectional area (CSA) and fascicule diameter (FD) can be measured by the coronal view. In a suspected case of carpal tunnel syndrome, the ratio to compare the CSAs between at the wrist and the elbow. Evaluation of multiple nerves at the different sites enables differential diagnosis of focal vs. diffuse localization as well as axonal vs. demyelinating pathology.

For evaluation of muscles, a linear–type probe is used to check echointensity, fiber arrangement, the presence of characteristic structures intramuscularly, and involuntary movements such as fasciculations and myokymia. Muscular high echointensity may suggest inflammation and fat reposition, that are further differentiated by observing muscle fiber arrangement. Other indications of muscle ultrasound include determination of optimal sites for muscle biopsy, identification of ALS, and other muscle diseases. Muscle ultrasound can detect fasciculation, especially in bulbar muscles at least at the equivalent sensitivity as needle electromyography.