Limb movement sensor

Periodic limb movement disorder is scored on tibialis anterior activity. The reference method remains surface EMG, two electrodes per leg with skin preparation and gel. That is reliable and it takes time, and an electrode that comes loose in the middle of the night does not get restuck.

The movement sensor offers a different bargain: a piezoelectric housing held by a belt on the shin, nothing to prepare, nothing to stick, five seconds to fit. It detects movement of the limb rather than the muscle activity that produces it.

That nuance matters at scoring. The AASM criteria are written for EMG, and a department applying them to the letter has to stay on electrodes. For screening, ambulatory polygraphy, or a patient where EMG has already failed, the movement sensor does what is asked.

One per leg is needed to respect bilateral scoring rules. The kit of two sensors and two belts is made for that; the single-sensor kit suits unilateral montages.