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April 2015

Sheep: Cerebrum, gray matter: polioencephalomalacia,
moderate, multifocal to coalescing



Female Cameroon sheep, 6 months, 26.5 kg


Cerebrum, gray matter: polioencephalomalacia, moderate, multifocal to coalescing


Gross lesions were restricted to the dorsal areas of the neocortex. There were bilaterally symmetrical, multifocal to coalescing areas of thinned grey matter with larger areas of yellowish discolorations. Under ultraviolet light, the discolored areas presented distinct green to blue autofluorescence.


Clinically, the animal exhibited acute recumbency, increased sensitivity to noise and touch, tremor, tonic-clonic seizures, ophisthotonus, and nystagmus.

Histology revealed multifocal, moderate disruption, vacuolation and loss of neuropil in the macroscopically yellowish areas. Increased numbers of macrophages containing pale eosinophilic, foamy cytoplasm (gitter cells) were present in the affected areas. Multifocally, perivascular moderate hemorrhage was present throughout the entire cerebrum.

The gross and histologic findings are pathognomonic for polioencephalomalacia which is commonly seen in juvenile animals. Although formerly thought of being exclusively caused by thiamine deficiency, it has been shown to be additionally caused by sulfur or lead toxicity as well as hypoxia.

Picture and Authored by:

Stefanie Binder, Department of Veterinary Pathology, Freie Universitaet Berlin, Germany