Peripheral nerve ultrasound: seeing compression before electromyography

Flattening, focal thickening, and loss of the fascicular pattern are signs high-resolution ultrasound identifies in compressive neuropathies, complementing clinical and electrophysiological assessment.

Superficial peripheral nerves — median, ulnar, radial, fibular — are particularly accessible to high-resolution ultrasound, where its spatial-resolution advantage over MRI becomes most evident.

The signs that indicate compression

The flattening ratio (largest diameter divided by smallest) is one of the most widely used parameters: at the compression point, a normally round nerve takes on a flattened, oval shape. Alongside this, the compressed nerve tends to become hypoechoic, with loss of the fascicular pattern from intraneural edema — and is often thickened just proximal to the compression point.

Practical advantages over other methods

Dynamic assessment, easy comparison with the contralateral side, no contraindications related to metal implants, and the ability to guide perineural injections in real time make ultrasound a natural complement to electromyography — not a replacement for it.