In addition to nerve conduction and EMG testing, patients referred for evaluation of neuromuscular symptoms may undergo nerve or muscle ultrasound. This is a painless, noninvasive procedure that is used in conjunction with standard electrodiagnostic studies. High resolution ultrasound allows visualization of affected nerves and muscles in search for diagnostic anatomic abnormalities that may reflect various compressive or inflammatory conditions.
For example, in patients with entrapment neuropathies (e.g., carpal tunnel syndrome, ulnar neuropathy at the elbow, fibular neuropathy at the knee), ultrasound, in conjunction with clinical and electrophysiologic data, can provide confirmatory anatomic information (e.g., nerve enlargement at the site of entrapment). In patients with polyneuropathies, ultrasound of affected nerves can provide key ancillary anatomic information that can distinguish axonal from demyelinating neuropathies (e.g., cross-sectional area increased in the latter) thereby helping with diagnosis, and guiding treatment. In patients with muscle diseases of various types (dystrophies, inflammatory myopathies) ultrasound of muscles in the leg or arm can be helpful in confirming the diagnosis and even in guiding muscle biopsies. In patients with breathing problems, ultrasound can be helpful in visualizing and quantitating diaphragmatic movement during quiet breathing or after stimulation of the phrenic nerve.