Polioencephalomalacia or cerebrocortical necrosis is a neurological disease seen in ruminants for a variety of reasons. The most common being thiamine deficiency, salt toxicity, and sulfur intoxication. Animals typically present with blindness, followed by inability to stand, seizures, opisthotonos, and eventually coma. Depending on the cause, recovery is often possible as long as intervention is started early, but some animals may have residual neurologic side effects. For these animals, euthanasia is often the best option.
On post-mortem examination, the lesions within the brain can often go unnoticed. Brain swelling is sometimes evident and the gyri may become flattened and the tissue may become yellow. As the condition progresses, the tissue becomes more necrotic and will become soft and friable. Cavitation of the brain can be seen in long-standing cases. The occipital and temporal regions are most commonly affected.
In very acute cases, changes are not easily detected unless evaluated under histopathology. This will yield signs of necrotic neuronal changes. The cerebrocortical neurons are smaller with an eosinophilic cytoplasm and absent to pyknotic nuclei.
So how have anatomic pathologists come up with an ingenious way to help diagnose this condition?
A black light of course!
This is where the glowing brain comes into play. Using ultraviolet light, a brain affected by polioencephalomalacia will actually fluoresce! The necrotic tissue will actually glow when the light is passed over it. So when changes are not easily seen with the naked eye, a black light can help uncover what is actually going on. I thought this was the coolest thing!
Though using a black light does not completely confirm polioencephalomalacia (histopathology is confirmatory) it does help clinicians answers questions a bit more quickly and rule out other differential causes of disease.