Thyroxine-responsive unilateral forelimb lameness and generalized neuromuscular disease in four hypothyroid dogs.

Four dogs were examined because of unilateral forelimb lameness. For all dogs, results of physical examination, including complete neurologic examination, were unremarkable except for vague, intermittent signs of pain upon deep palpation of the affected limb. During electromyography, insertional activity, fibrillation potentials, and positive sharp waves were recorded symmetrically from all major muscle groups. Generalized neuromyopathy was diagnosed. All dogs were determined to be thyroid deficient, and L-thyroxine supplementation was initiated. The lameness resolved within 2 months in all dogs. During follow-up electromyography, abnormalities were not recorded from 3 of the dogs and were less severe in the fourth. Thyroxine supplementation was discontinued in 2 dogs, and lameness redeveloped. Lameness again resolved when supplementation was reinstituted.