Imaging	General use and technique	Median nerve assessment	Radial nerve assessment	Ulnar nerve assessment
Magnetic resonance imaging	Fat-suppressed highly T2-weighted images demonstrate nerve pathology the best Low slice thickness: 2 mm to 3 mm in distal extremity and 4 mm to 5 mm in proximal extremity Identify anatomic abnormalities such as ganglion cysts or bony abnormalities Rule out other causes by identifying abnormalities of surrounding soft tissues Evaluate for muscle denervation Evaluate for nerve tumors	Carpal tunnel syndrome: evaluate persistent nerve distress and/or inadequate surgical release	Posterior interosseous nerve: thickened superficial head of supinator (most common entrapment point of posterior interosseous nerve), denervation of the supinator muscle Superficial radial nerve: imaging of choice for evaluation of surrounding muscle	Cubital tunnel syndrome: perform with extended elbow, shows nerve enlargement, external compression by loose bodies or space-occupying lesions, and regional inflammatory and denervation changes Guyon canal: useful for persistent symptoms with normal electromyography or tumor noted on ultrasonography
Ultrasonography	Use high-resolution (15 to 18 MHz) transducers Identify causes of entrapment such as fibrous bands, ganglion cysts, anomalous muscles, and bony abnormalities Evaluate for changes in nerve thickness (by cross-sectional area) and fascicular appearance Assessment of nerve and surrounding tissue vascularization Easy comparison to contralateral arm Dynamic testing	Carpal tunnel syndrome: assess nerve thickness within the carpal tunnel and pronator quadratus for a change greater than 2 mm	Posterior interosseous nerve: superficial nerve is easy to visualize, enlargement and hypoechogenicity of the nerve can be seen	Cubital tunnel syndrome: nerve appears enlarged and hypoechoic, loss of normal fibrillar appearance; comparison of cross section to contralateral side, shows dynamic snapping of nerve Guyon canal: shows thickened and hypoechoic nerve and ganglion cyst or accessory muscle