Acute, severe, diffuse neuromuscular disease is characterized by distinct neurologic signs and the primary differential diagnoses include Coonhound paralysis/acute polyradiculoneuritis, organophosphate toxicity, fulminant myasthenia gravis, botulism, tick paralysis, and polymyositis. In the case presented in this paper, history and diagnostics were used to identify acute polyradiculoneuritis as the most likely cause of clinical signs. Coonhound paralysis is an acute polyradiculoneuritis that is believed to be caused by an immune-mediated reaction to an antigen present in the saliva of a raccoon. Acute idiopathic polyradiculoneuritis is an identical syndrome except that there is no history of exposure to a raccoon. In the latter case, it is presumed that another foreign antigen is responsible for the immune response. In either case, the foreign antigen resembles the individual's own gangliosides such that antibodies formed against the foreign antigen attack both that antigen and the patient's neural tissue. The result is an acute inflammation of the ventral nerve roots and subsequent demyelination with or without axonal degeneration. This results in the clinical signs of diffuse neuromuscular disease. Treatment is supportive, including adequate cushioning, frequent turning, and feeding in an upright position. The majority of dogs will recover in weeks to several months.