Encephalopathy with idiopathic hyperammonaemia and Alzheimer type II astrocytes in Equidae

Abstract

Summary In 3 mature female horses of varying breeds, episodes of colic and depression for 1–4 days preceded an encephalopathic disorder with maniacal behaviour, anxiety, profuse sweating and, in one case, terminal opisthotonus. Blood ammonia levels were elevated approximately 10‐fold. At necropsy, there were gastrointestinal serosal and mesenteric haemorrhages. Histologically, all 3 cases revealed diffuse Alzheimer type II astrocytes in the cerebral grey matter. Alzheimer type II astrocytes were glial fibrillary acidic protein (GFAP) negative or only weakly positive, weakly S‐100 positive, and vimentin negative. In the absence of primary hepatic and/or renal lesions, an increase in intestinal ammonia absorption due to ileus or increased ammonia production by colonic bacteria is hypothesised.

Hepatic Encephalopathy Associated With Hepatic Lipidosis in Llamas (Lama glama)

“…The neurologic signs reported in this study are consistent with those previously reported in llamas diagnosed with hepatic lipidosis 17 and suspected to be associated with hepatic encephalopathy in horses, 10 cattle, 4 and sheep.…”

“…Our findings are consistent with staining patterns for glial fibrillary acid protein and S100 protein reported in horses with idiopathic hyperammonemia. 10 Additional studies including serum blood ammonia levels and more thorough and systematic examination of brain sections would potentially allow for statistical evaluation of lesion predominance and distribution and for correlations among signalment, clinical signs, biochemical abnormalities, underlying disease, and histopathologic lesions. Transmission electron microscopy and development of an immunohistochemical protocol for glutamate synthetase in llamas may allow for confirmation of glutamine accumulation within llama Alzheimer type II cells.…”

Clostridium sordelli Infection as a Suspected Cause of Transient Hyperammonemia in an Adult Horse

“…Similar cases of hyperammonemia of unknown origin have also been described in humans and dogs. [12][13][14][15][16] Several similarities between the horse reported in this study and other equine patients were found with regard to history, clinical findings, and laboratory abnormalities. A postmortem examination was performed on 4 of the previously reported horses and showed similar findings.…”

“…To the authors' knowledge, 7 similar cases of equine idiopathic hyperammonemia have been reported in the relevant veterinary literature to date. 1,11,12 These cases were thought to be associated with possible gastrointestinal disorders resulting in hyperammonemia without marked evidence of liver disease. Similar cases of hyperammonemia of unknown origin have also been described in humans and dogs.…”

Potential complications in equine colic surgery

“…Auch sind idiopathische Hyperammoniämien beschrieben, welche ev. in Zusammenhang mit einer Clostridieninfektion stehen (Hasel et al 1999, Wilkins et al 2003. Symptome weisen auf eine Beeinträchti-gung der Grosshirnfunktion hin und beinhalten progressive Apathie, Somnolenz oder Stupor, Kreiswandern und Kopfpressen.…”