Laryngeal paralysis-polyneuropathy complex in young Dalmatians.

Clinical, morphologic, and morphometric findings are reported in 14 young Dalmatians with laryngeal paralysis. Neurologic signs, including megaesophagus, were observed in 13 of 14 dogs. Electromyographic abnormalities included fibrillation potentials and positive sharp waves in laryngeal, esophageal, facial, and distal appendicular muscles. Neurogenic atrophy was detected in intrinsic laryngeal and appendicular skeletal muscles. A diffuse, generalized polyneuropathy, dominated by axonal degeneration, was observed in recurrent laryngeal and appendicular peripheral nerves. Results of quantitative studies, using single teased fiber and cross-sectional nerve preparations, indicated that changes were more severe in distal parts of peripheral nerves, with preferential loss of medium sized (5.5 to 8 microns) and large-caliber (8.5 to 12 microns) myelinated nerve fibers. Ultrastructural alterations were observed in myelinated and unmyelinated nerve fibers. The term laryngeal paralysis-polyneuropathy complex is proposed for this apparent dying-back disorder, which is clinically, electrophysiologically, and pathologically different from laryngeal paralysis in young Bouvier des Flandres and Siberian Huskies. Prognosis for Dalmatians with laryngeal paralysis-polyneuropathy complex is guarded to poor. The condition is believed to be inherited.