Steroid-responsive electromyographic abnormalities in polymyalgia rheumatica.

Prior to definitive diagnosis, electrodiagnostic studies are often requested in patients with polymyalgia rheumatica to evaluate complaints of muscle aching, tenderness, and weakness. These studies are generally normal, although rare reports of electromyographic abnormalities in polymyalgia rheumatica exist. Two patients with polymyalgia rheumatica and electrodiagnostic findings consistent with diffuse denervation are described. Following steroid treatment, both patients experienced impressive clinical and electromyographic improvement. To explain this improvement, we hypothesize a steroid-responsive microvascular arteritis resulting in ischemic damage to axons of motor nerve terminal branches.