Congenital hydrocephalus in three sheep: Clinical, electroencephalographic and pathological features

The clinical, electroencephalographic and neuro-pathological features of three cases (cases 1, 2 and 3) of congenital hydrocephalus in sheep were described. The observed neurological signs reflected damage in the telencephalon and brain stem. The electroencephalogram performed in case 1 and case 2 showed different patterns: symmetric and synchronous high-voltage slow-activity in case 1, and low-voltage slow-activity in case 2. By the postmortem examination, in all the animals, dilatation of the ventricular system, especially of the lateral ventricles, associated with a glial reaction surrounding the dilated ventricles was observed. Only in case 3, a monolateral meningeal thickening at the left cerebellopontine angle seemed to be responsible for the obstructive hydrocephalus. In the other two brains (case 1 and 2), no potential anatomical cause for the hydrocephalus were detected, even if, in case 2, a compensatory form was not excluded due to the moderate hypoplasia of the cerebrum and the presence of the non-suppurative inflammation. The results of this work provide a contribution to the EEG characterisation in ovine hydrocephalus cases; nevertheless further multidisciplinary studies of a larger number of sheep could permit to better characterise the EEG pattern in ovine hydrocephalus cases.