Continuous muscle fibre activity: a case treated with acetazolamide.

A case is reported of the continuous muscle fibre activity syndrome, which includes a group of disorders characterised by sustained motor unit activity due to hyperactivity of peripheral nerve motor axons. In this patient the muscle stiffness and myokymic movements were successfully treated with acetazolamide, which acts as a membrane stabiliser either by blockade of chloride and bicarbonate membrane transport or by producing kaliuresis and raising the transmembrane potential by decreasing extracellular potassium.