Encephalomalacia:

• It may be defined as the degenerative changes of the brain. Changes comprises of demyelination, necrosis and edema.
• Degenerative changes of gray matter are known as polioencephalomalacia
• Degenerative changes of white matter are known as leukoencephalomalacia.

Etiology:

All species:

• Hepatic encephalopathy caused by alkaloid poisoning, hepatic arteriovenous anomaly, thrombosis of portal vein in horse
• Focal or diffuse lesion in axons or myelin of neuronal process
• Poisoning by organic mercurial, in some cases lead, selenium poisoning
• EHV-1 infections in horses
• Cerebellar cortical abiotrophy occurs in calves and lambs

Ruminants:

• BSE
• Plant poisons; Astralagus spp, Oxytropis spp, Swainsona spp, Vicia spp, Kochia scoparia
• Intoxication with toxin of Clostridium perfringens type D toxin
• Thiamine deficiency caused by Brackern fern poisoning, ingestion of mouldy corns and excess grain
• Sulphur toxicosis
• Antimetabolite of nicotinic acid causes encephalomalacia in sheep
• Neuronal dystrophy
• Inherited defect of Brown Swiss cattle known as weavers or degenerative myeloencephalopathy
• Swayback and enzootic ataxia caused by copper deficiency in lambs
• Prolonged parturition of calves causing cerebral hypoxia
• Ingestion of ammoniated forages
• Inherited neuronal degeneration in Angora goats

Horse:

• Feeding of mouldy corn infested with Fusarium monoliforme
• Feeding of yellow star thistle; Centaurea solstitialis
• Poisoning by bracken and horsetail causing a conditioned deficiency of thiamine
• Ischemic encephalopathy of neonatal maladjustment syndrome of foals
• EDM associated with vitamin E deficiency

Pigs:

• Mulberry heart disease
• Subclinical attacks of enterotoxemia
• Poisoning by organic arsenials and salt

Clinical Findings:

• Weakness in all four limbs
• Dullness or somnolence
• Blindness, ataxia
• Head pressing
• Circling
• Terminal coma
• In early stages of PEM in ruminants; muscle tremor, opisthotonus, nystagmus, convulsion
• In equine leukoencephalomalacia:
  • Anorexia and depression
  • Ataxia, circling, head-pressing
  • Blindness
  • Hyperaesthesia
  • Agitation, delirium, recumbency, seizures and death
  • Delayed retraction of tongue after extension
  • In hepatotoxic form, icterus, swelling of lips and nose, petechiation, abdominal breathing and cyanosis.

Diagnosis:

• Physical and neurological examination of animal including assessment of gait, reflex
• Blood test to rule out infectious causes
• PM findings:
  • Softening, cavitation and laminar necrosis of cortex may be visible

Treatment:

• PEM caused by thiamine deficiency can be corrected by administration of thiamine parenterally. Thiamine @10mg/kg, TID-QID, for cattle or small ruminants.
• If brain lesion is severe and treatment delayed, full recovery is not possible. Certain neurological signs remain within life time of affected animals.
• If there is no initial improvement, treatment course should be prolonged > 3 days.
• Reduction of cerebral edema can be attempted with administration of dexamethasone @ 1-2 mg/kg, IM or SC.
• Dietary supplementation of thiamine @3-10 mg/kg feed, for prevention of disease.
• In case of sulphur toxicosis, dietary sulphur should be reduced and drinking water containing high sulphur should be avoided.
• In case of toxicity by organic chemicals, appropriate measure for absorption of toxin should be adopted. Gastric lavage should be carried out to avoid further absorption of toxin.
• Salt intake should be reduced in case of salt poisoning.
• There is no specific therapy for equine leukoencephalomalacia. Feed infested with fungi should be removed immediately from feedlot.
• In case of agitation or delirium, sedation of animal is necessary for prevention of further injury.
• Activated charcoal and laxatives are administered to remove or flush out toxin from gastrointestinal tract.