Signalment:5-year-old, female, Spanish-Boer cross goat (Capra hircus)

This animal was noted to be acutely disoriented, visually impaired, and intermittently down and twitching. It responded immediately to empirical tr-eatment, but never completely recovered full neurological function and was euthanized two months later.

Gross Description:  

The brain appeared somewhat shrunken on removal from the cranial vault. The cerebral cortex was thinned and discolored, especially in the occipital-parietal region, with areas of clefting and separation from the underlying white matter noted. 

Histopathologic Description:

Sections of occipital-parietal cortex are examined. Each slide contains tissue from the affected animal as well as location-matched cortex from an age-matched control goat. The latter is essentially normal brain for comparison purposes. In the former, there is focally extensive laminar loss of cortical grey matter, significantly di-minishing cortical thickness. Although occasional neuronal cells remain present, residual cellularity consists primarily of large, reactive (gemistocytic) astrocytes, activated microglial cells, and phag-ocytically active macrophages (Gitter cells). Capillary structures are prominent with somewhat swollen endothelium, both in grey matter and in collapsed, redundant leptomeninges present in the expanded subarachnoid space. Abundant, phagocytically active macrophages are also noted in the latter. The white matter appears slightly hypercellular, probably due to a mild reactive astrocytosis also present in this region. Infrequent pyknotic cells, probably representing necrotic oligodendroglia, are seen due to axonal die back. Mild perivascular lymphocytic cuffing is noted in white matter in some sections.

Morphologic Diagnosis:  

1) Subtotal laminar cortical necrosis and collapse, severe, with marked extensive residual reactive gliosis, vacuolization and patchy regions of parenchymal se-paration/clefting, with areas of tissue dropout and meningeal collapse 2) Patchy, mild perivascular lymphocytic cuffing, subjacent white matter, mild (some sections)

Lab Results:  



Polioencephalomalacia (PEM)

Contributor Comment:  

The microscopic findings are consistent with po-lioencephalomalacia (PEM). This is a morphological term used to describe necrosis with softening (malacia) in grey matter of the brain. The condition is described in a surprisingly wide range of domestic animals, both ruminant and carnivores, as well as some non-domestic species.9 Wernicke`s encephalopathy is the equivalent human disease, which is classically associated with chronic alcoholism. Cattle, sheep and goats are commonly affected ruminants, although a variety of other species are also susceptible. Clinical manifestations of the disease are variable, with animals often presenting with facial twitching, teeth grinding, sal-ivation, blindness, seizures and opisthotonus.8 The condition affects primarily young animals, and sheep and goats, as a rule, have a shorter course with fewer survivors. The syndrome is not always fatal; mortality rates are reported at 50-90%, although surviving animals typically have significant neurological deficits, including visual impairment and stupor.4 Disease is seen worldwide and is responsible for important economic losses in many countries. The condition is more commonly seen in goats under intensive management conditions when fed more grain concentrate to encourage accelerated growth.7 PEM was recognized as a clinical and pathological entity long before specific pathogeneses had been discovered. Originally applied as a diagnosis to cattle and sheep losses in Colorado, the mor-phological designation of cerebrocortical malacia was subsequently used sy-nonymously for the specific entity of thiamine deficiency disease. However; it is now known that many cases of PEM in ruminants cannot be ascribed to thiamine deficiency.2,3,6 There is often a lack of changes in thiamine concentration in ruminal fluid, tissue and blood in affected animals. Furthermore, there has been a failure to induce the disease by ex-perimentally created deficiencies. The most compelling argument for thiamine`s role in PEM had been that administration of it in clinical cases, especially to those early in the disease course, often resulted in recovery. However, this is now believed to be related to improved energy metabolism in the impaired brain, regardless of the inciting cause.5, 6, 7

Currently, it is believed that PEM in ruminants can involve a wide range of pathogeneses, including toxic, metabolic, dietary/nutritional and even infectious events. In addition to thiamine deficiency, some of the specific causes of polioencephalomalacia in ruminants include sulfur poisoning, lead poisoning, salt poisoning (water deprivation), ad-ministration of levamisol or thiamine analogues such as amprolium, ingestion of thiaminase rich plants, and infection with bovine herpesvirus.2

Gross pathological changes are often striking, with the parietal-occipital cortex being most prominently affected. In acute cases, brains may have a swollen appearance and palpable softness, with flattening of gyri and narrowing of sulci. With more prolonged survival, as in this case, there is marked thinning or, in some areas, complete absence of friable, necrotic appearing grey matter, with zones of clefting/separation from underlying white matter visible.8 The subarachnoid space is widened, and brains often appear smaller or shrunken. Areas of cerebrocortical necrosis (CCN) can be identified by autoflourescence under UV light, as a consequence of degraded lipoidal material within macrophages or high molecular weight collagen-like material. Although blood pyruvate levels may be elevated,4 other serum biochemical analysis is variable and is generally of little value in disease diagnosis.

As previously noted, the animal in question responded favorably to thiamine administration upon onset of signs, but continued to have significant neurological and visual deficits after stabilization.

JPC Diagnosis:  

Brain, cerebral cortex:vNecrosis, laminar, multifocal to coalescing, with reactive gliosis.

Conference Comment:  

The contributor provides an excellent review of po-lioencephalomalacia, and the aged-matched control provided on the slide increases the teaching / learning value of this case. In ruminants, polioencephalomalacia is usually limited to the cerebrocortical grey matter and has a laminar pattern of distribution, often being referred to as "laminar cortical necrosis." The lesion in ruminants discussed above shares similarities with salt poisoning in swine and has been documented in cases of lead poisoning in cattle as mentioned in WSC Case 3 of this conference. It is most often a disease of young animals, although older animals may be affected sporadically.

Lesions of PEM vary in severity, depending on various factors such as species, age and duration.1 Lesions are more severe grossly obvious in animals that survive for a period of time. The cerebral cortex often demonstrates superficial, laminar pallor which will trace the grey-white matter junction and may be most prominent in the gyri. Lesions are bilaterally symmetrical and are apparently more consistent in the caudal cerebral hemispheres. The distribution appears to be related to the area supplied by the middle cerebral artery.1

Cerebrum, goat: Adjacent to necrotic areas, small numbers of glial cells abut neurons. (HE, 400X). (Photo courtesy of: Division of Laboratory Animal Resources (DLAR) University of Pittsburgh,

There is some slide variation in the severity of lesions in this case, but in general, it is representative of the classic microscopic lesions of PEM. Polioencephalomalacia

does not have a specific etiology, as discussed above, but is often directly or indirectly linked to a deficiency in thiamine. Sulfur-containing compounds have also been implicated in some cases of PEM.There is some question regarding the observed tissue autoflourescence in cases of PEM with some references stating it may originate from substances in mitochondria as

opposed to ceroid-lipofuscin pigments.10


1. Cantile C, Youssef SNervous system. In: Maxie MG, ed. Jubb, Kennedy, and Palmer's Pathology of Domestic Animals. 6th ed. Vol 1. St. Louis, MO: Elsevier; 2016:309-312.

2. Fabiano JF de Sant'Ana, Claudio SL Barros.  Polioencephalomalacia in ruminants in Brazil. Braz J Vet Pathol. 2010; 3(1):70-79.

3. Gould DH, Polioencephalomalacia. J. Animal Science. 1998;76: 309-314.

4. Koestner A, Jones TC. The Nervous System. In: Jones TC, Hunt RD, King NW ed. Veterinary Pathology. 6th ed. Philadelphia: Williams & Wilkins; 1997: 1272-1274.

5. Najarnexhad V, Aslani MR, Balali-Mood Mehdi. The therapeutic potential of thiamine for treatment of experimentally induced subacute lead poisoning in sheep. Comp Clin Patho. 2010; 19:69-73.

6. Niles GA, Morgan SE, Edwards WC, The relationship between sulfur, thiamine and polioencephalomalacia – a review. Bovine Practice. 2002; 36: 93-99.

7. Smith MC, Sherman DM ed. Goat Medicine. 2nd ed. Ames, IA:Wiley Blackwell; 2009: 222-226 .

8. Sullivan ND. The Nervous System. In: Jubb KVF, Kennedy PC, Palmer N eds. Pathology of Domestic Animals 3rd ed. Vol 1. New York: Academic Press, Inc.; 1985: 251-256. 

9. Summers BA, Cummings JF, de Lahunta A. Veterinary Neuropathology. New York: Mosby; 1995:277-280.

10. Zachary JF. Nervous System. In: McGavin MD, Zachary JF, eds. Pathologic Basis of Veterinary Disease. 5th ed. St. Louis, MO: Mosby Elsevier; 2012:851.

Click the slide to view.

4-1. Cerebrum, goat.

4-1_1. Cerebrum, goat.

4-2. Cerebrum, goat.

4-3. Cerebrum, goat.

4-4. Cerebrum, goat.

4-5. Cerebrum, goat.

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