Polioencephalomalacia

Question 1

What is polioencephalomalacia?

Answer 1

neurological disorder commonly seen in ruminants caused by a thiamine deficiency

(also seen with excess sulfur, lead, or sodium intake)

Question 2

What are 5 predisposing factors for the development of polioencephalomalacia in ruminants?

Answer 2

1. high concentrate feeds
2. high grain intake can promote proliferation of thiaminase-producing bacteria
3. ingestion of plant thiaminases or thiamine analogs - bracken fern!
4. feed with corn or sugar cane byproducts
5. rations with added sulfate to limit intake

Question 3

What are the most common signs associated with acute polioencephalomalacia?

Answer 3

• blindness
• seizures
• recumbency

Question 4

What initial signs are indicative of subacute polioencephalomalacia?

Answer 4

• decreased appetite
• twitching (ears and face)
• separation from the herd
• holding head up in an elevated position
• staggering, hypermetric gait

Question 5

What 2 classic later signs are indicative of subacute encephalomalacia? What else is seen?

Answer 5

1. cortical blindness - absent menace, intact PLR and palpebral reflex
2. head pressing

dorsomedial strabismus, teeth grinding, opisthotonus

Question 6

What are some differentials for polioencephalomalacia?

Answer 6

• listeriosis
• nervous coccidiosis
• salt toxicity
• meningoencephalitis
• rabies
• vitamin A deficiency
• pregnancy toxicity (sheep)

Question 7

What are some pre-mortem diagnostics used for polioencephalomalacia?

Answer 7

• blood thiamine levels
• transketolase activity

unreliable, not available in many labs

Question 8

What is a classic post-mortem finding in cases of polioencephalomalacia? What else may be seen?

Answer 8

brain tissue fluoresces under UV light

• gryal flattening
• brain swelling
• cerebrocortical neuronal necrosis
• cortical spongiosis
• cavitation of cortical tissue
• nultifocal vascular necrosis, hemorrhage, and necrosis in deep gray matter

Question 9

What treatment is recommended for cases of polioencephalomalacia? If cerebral edema is present?

Answer 9

thiamine 10-20 mg/kg IM or SQ TID —> expect improvement within 1-3 days (animals with advanced disease may continue to show significant neurologic impairment after treatment

dexamethasone 1-2 mg/kg

Question 10

How can polioencephalomalacia be prevented?

Answer 10

• thiamine supplementation in feed
• supply forage
• investigate environment for sources of thiaminases or excessive sulfur levels