Aetiology and pathogenesis of congenital torticollis and head scoliosis in the equine foetus.

In 214 cases of severe dystocia in mares, of which 141 (66 per cent) were Draught horses, deviation of the head and neck, with or without torticollis, malformed head and limbs were found to be the cause of dystocia. No evidence of a genetic lethal factor was found and torticollis was often combined with scoliosis of the head and, frequently, with malformation of one or more limbs. This is considered evidence of a common aetiology and pathogenesis of the syndrome of malformation. The malformations were found to be associated with an increased incidence of caudal and, particularly, transverse presentations. These findings are presented as evidence to support the hypothesis that, during the second half of pregnancy, the narrow tip of the uterine horns provides only limited space for the developing cranial half of the foetus. The surprisingly rapid and complete anatomical and functional recovery of severe malformations of the bones of the neck, head and limbs of surviving foals, born by caesarian section, is taken as further evidence that these malformations have no genetic basis, but originate from unfavourable intrauterine conditions.