Pathology: Metabolic and Toxic diseases of the neural system Flashcards
What are the most common lesions found in Metabolic and Toxic diseases in the neural system?
- Usually symmetrical lesions which involve specific regions of the brain or spinal cord
- The most common lesion is malacia (tissue softening)
What disease does Copper deficiency cause in Newborn or Young Lambs?
Swayback (Enzootic Ataxia)
What disease does Thiamine deficiency cause in animals (horses, ruminants and carnivores)?
Cerebrocortical Necrosis (CCN)
What causes Congenital Swayback in Newborn Lambs?
- Cu deficiency during day 100 - 120 days of gestation (important time for myelination of the cerebrum)
What are the clinical signs associated with Congenital Swayback in newborn lambs?
- Blind, unable to suckle or dead
What lesions are found in a lamb with Congenital Swayback?
- Cavitation/ gelatinous subcortical white matter of the brain
- Hydrocephalus
- Degeneration of the spinal cord: bilateral, symmetrical in the dorsolateral and ventromedial columns
What causes Delayed Swayback in Young Lambs?
- Cu deficiency at 20 days after birth (important time for myelination again)
What are the clinical signs associated with Delayed Swayback in Young lambs?
- Ataxia at 1-2 months old
What lesions are found in a lamb with Delayed Swayback?
- No gross brain lesions are visible
- Histologically: Chromatolysis of neuron nucleus
- Degeneration of the spinal cord: bilateral, symmetrical in the dorsolateral and ventromedial columns (same as congenital form)
Cerebrocortical Necrosis (CCN) can also be seen in what other diseases/ intoxications?
- Salt poisoning (water intoxication): pigs and ruminants
- Lead poisoning: ruminants
- Sulphur intoxication: ruminants
- Severe hypoxia
How can thiamine deficiency occur in the diet of horses, dogs/ cats, and foxes/mink/cats?
Horses: bracken fern poisoning (contains thiaminases)
Dogs/ cats: cooked meat diet (thiamine is heat labile)
Foxes/ mink/ cats: fish diets (rich in thiaminases)
What lesions are associated with Thiamine deficiency in carnivores?
- Multifocal haemorrhage and malacia often periventricular
What animal species is most commonly affected by Lead Poisoning, and why?
Cattle/ calves, through the ingestion of batteries, old paint, fishing weights, or contaminated feeds
What is the pathogenesis of lead poisoning?
- Lead interferes with DNA transcription, enzymes that help in the synthesis of vitamin D, and enzymes that maintain the integrity of the cell membrane.
- Anemia may result when the cell membranes of red blood cells become more fragile as the result of damage to their membranes.
- Lead alters the permeability of blood vessels and collagen synthesis causing ischemia and neuronal injury
What are the typical lesions associated with lead poisoning in cattle?
- Gross: cerebral edema
- Histopathology: endothelial degeneration with astrocytic swelling
What animals are most at risk of salt poisoning/ water intoxication?
- Pigs and cattle
Due to frozen water pipes leading to dehydration
What is the pathogenesis of salt poisoning/ water intoxication?
- Decreased water intake –> dehydration and increased plasma sodium, which moves passively into the CSF
- High sodium content in the CSF inhibits anaerobic glycolysis in the brain –> cerebral ATP production is decreased and Sodium cant be actively transported from the CSF back to the plasma
- Increased cerebral sodium creates an osmotic gradient, water follows salt into the CSF leading to edema, increased pressure and necrosis
How can salt poisoning/ water intoxication be treated?
Slow reintroduction of water
What lesion of the neural system can chronic Clostridium perfringens type D (Pulpy kidney disease) in lambs/ calves?
Focal Symmetrical Encephalomalacia: edema +/- haemorrhage in the white and grey matter, malacia and swelling of the endothelial cells
What lesion of the neural system can edema disease (STEC) cause in rapidly growing feeder pigs?
Cerebrospinal Angiopathy: widespread injury of the small arteries and arterioles, leading to edema and ischaemic injury of the tissues including the brain
Define Dysautonomia
Dysautonomia or autonomic dysfunction is a condition in which the autonomic nervous system (ANS) does not work properly
What pathological findings can be found in animals with dysautonomia?
Acute neuronal degeneration in the autonomic ganglia and CNS
What are the clinical signs associated with Dysautonomia?
- Pupillary dilation
- Megaesophagus
- Constipation
- Anorexia
- Dehydration
- Colic
What is another name for Dysautonomia in horses?
Grass Sickness
What is another name for Dysautonomia in cats?
Key-Gaskell Syndrome
What is Equine Motor Neuron Disease?
Equine motor neuron disease is a progressive, noninflammatory degeneration of motor neurons in the spinal cord and brain stem of horses
What is the cause of Equine Motor Neuron Disease?
Uncertain but a strong risk factor is associated with Vit E deficiency
What are the clinical signs associated with Equine Motor Neuron Disease?
generalized, symmetric weakness, trembling and muscle atrophy
note: ataxia is NOT a feature, in contrast to most spinal cord diseases
What lesions are associated with Equine Motor Neuron Disease?
Gross: none
Histological: degeneration and loss of motor neurons in the ventral horns of the spinal cord
What is Hepatic Encephalopathy?
Hepatic encephalopathy is a decline in brain function that occurs as a result of severe liver disease. In this condition, your liver can’t adequately remove toxins from your blood. This causes a buildup of toxins in your bloodstream, which can lead to brain damage.
What are the most common causes of hepatic Encephalopathy in Cattle and Horses?
- Ragwort poisoning
- Aflatoxin ingestion
What are the most common causes of hepatic Encephalopathy in the dog?
- Porto-systemic shunts
- Liver Cirrhosis
What are the most common causes of hepatic Encephalopathy in the Sheep?
- Copper poisoning
What lesions are associated with hepatic encephalopathy?
Gross: subtle cerebral edema (or no changes at all)
Histologically: Myelin edema (spongy vacuolation), and hypertrophy/ hyperplasia of astrocytes
