How to Diagnose and Treat Neuromuscular Diseases: "The Weak, Trembling Horse"

1. Introduction
Disease states affecting the lower motor neuron (LMN), neuromuscular junction, or muscles can result in vague clinical signs of weakness and trembling that make these diseases difficult to distinguish from one another as well as from non-neuromuscular problems such as electrolyte disturbances, colic, or pain. Early recognition of neuromuscular disease is important in rapid diagnosis and early, appropriate treatment. Clinical signs in acute cases often include trembling, tachycardia, unwillingness to stand still, an abnormal stance (elephant on a ball), repeated attempts to lie down, and prolonged periods of recumbency. There are several disease processes that have been recognized in the horse that result in these signs either acutely or chronically. This summary describes these diseases and presents a stepwise process that practitioners can use to differentiate the diseases from each other as well as from more common causes of weakness and trembling. In addition, this summary reviews diagnostic and therapeutic options. [...]