Primary intra-axial leiomyosarcoma with obstructive hydrocephalus in a young dog.

A female Chihuahua dog aged 2 months had a 3-week history of progressive neurological signs (abnormal behaviour, disorientation, left-sided circling, and incessant whimpering). Necropsy revealed a primary leiomyosarcoma in the midline of the posterior thalamus with secondary obstructive hydrocephalus of the lateral ventricles. Grossly, an infiltrative, grey-white tumour had partly invaded the third ventricle. Histologically, the tumour formed hypercellular, interlacing bundles of neoplastic spindle cells with blunt-ended nuclei. Neoplastic cells were strongly immunoreactive for vimentin and both muscle-specific and alpha-smooth muscle actin; MIB-1 immunoreactivity indicated a proliferative index of up to 5%. Leiomyosarcoma should be included in the differential diagnosis for primary brain tumours and hydrocephalus in young dogs.

Polioencephalomalacia associated with the ingestion of ammonium sulphate by sheep and cattle.

In the latter part of 1991 an unusual neurological disease was recognised on several farms in England. This report describes the case histories and clinical, biochemical and pathological findings in six calves and two lambs aged from two to 44 weeks obtained from five of these farms. Laminar cerebrocortical necrosis and severe bilateral necrosis of the thalamus and/or striatum progressing to cavitation were recognised in their brains. These changes are similar to those of experimental sulphate toxicity. Morbidity rates of 16 to 48 per cent and mortality rates of 0 to 8 per cent were recorded. The affected animals did not respond to vitamin B1 treatment; the erythrocyte transketolase levels of in-contact cattle and of one untreated affected calf and one untreated lamb were within the normal range. All five farms had recently introduced a proprietary concentrate ration containing ammonium bicarbonate. After this ration was withdrawn no new cases of nervous clinical disease were observed. It is suggested that, in at least some cases, the morphology and topography of lesions may distinguish sulphate induced polioencephalomalacia from that of sporadic thiamine-dependent cerebrocortical necrosis.