Horner's syndrome in large animals.

The sympathetic nervous innervation of the head was surgically transected in the horse, cow, sheep and goat. The site of transection was preganglionic in all 4 species and ganglionic-postganglionic in 2 additional horses. The Horner's syndrome, manifested as a result of the iatrogenic lesion, varied with the species. Ptosis was the most constant sign in all species. Unilateral sweating over the face and proximal neck, particularly at the base of the ear, was the most prominent feature in the horse. The cow revealed distension of vasculature and cutaneous heat of the pinna, and a reduced production of beads of sweat over the nostril on the affected side. The goat and sheep exhibited little more than slight ptosis of the upper eyelid of the affected side as the most prominent sign. The ophthalmologic manifestations of Horner's syndrome seen in these large animals were not readily apparent and could easily be overlooked upon clinical examination.