Table 2.

Characteristic ultrasound findings of nerve and muscle disease.

Neuropathy
Focal neuropathies	Increased CSA, hypoechoic proximal to site of entrapment, decreased nerve mobility, increased intraneural vascularity
	Normal CSA cutoffs:
	Median nerve at wrist	≤10 mm2 ;or WFR of 1.4 (Fowler et al., 2014, Mhoon et al., 2012)
	Ulnar nerve at elbow	≤10 mm2 (Beekman et al., 2011)
	Radial nerve at spiral groove	≤10 mm2 (Cartwright et al., 2008)
	Fibular nerve at fibular head	≤12 mm2 (Cartwright et al., 2008)
	Tibial nerve in tarsal tunnel	≤19 mm2 for CSA within the tunnel; or within tunnel-to-proximal tunnel CSA ratio 1.0 (Tawfik et al., 2016)
Hereditary neuropathies (e.g. CMT1a)	Diffuse nerve enlargement and prominent dark fascicles
Acquired inflammatory polyneuropathies (e.g. CIDP)	Multifocal nerve enlargement outside of areas of compression
Myopathy
Muscular dystrophy	Hyperechoic muscle with attenuation of the underlying bone
Inflammatory myopathy	Although likely dependent on chronicity, the most common findings are hyperechoic muscle, normal underlying bone echo, possibly increased muscle thickness, and increased vascularity.
Motor neuron disease
Hyperechoic muscle with decreased thickness, decreased muscle echovariation; presence of fasciculations; reduction in cervical root and peripheral nerve CSA

CSA: Cross-sectional area; WFR: Wrist-to-forearm ratio; CMT1a: Charcot-Marie-Tooth type 1a; CIDP: Chronic inflammatory demyelinating polyneuropathy.