Inherited congenital myoclonus of polled Hereford calves (so-called neuraxial oedema): a clinical, pathological and biochemical study.

Thirty-four newborn polled Hereford and polled Hereford cross calves affected with a condition previously described as neuraxial oedema and six normal calves were examined. None of the affected calves were seen to stand after birth and when first examined the calves were in lateral recumbency, with extension and crossing of the hindlimbs. All the affected calves were bright and alert, could lift their heads and apparently could see and hear. When the calves were encouraged to stand spontaneous and stimulus-responsive myoclonic extensor spasms, with whole body rigidity, were consistently observed. Thirty-two of the affected calves had macroscopic lesions in the coxae. No significant pathological or biochemical lesions were observed in the central nervous system of any of the calves. The water content of the cerebellum did not differ between normal and affected calves. As oedema of the central nervous system is not a feature of this condition it is more appropriate to describe it as inherited congenital myoclonus.