Neuro Flashcards
What are the main goals of a neurological examination?
Detect the presence of neurological disease, determine the location of the lesion
What aspects of a neurological exam must be performed in ruminants
Mentation/level of consciousness
Cranial nerve function
Posture
Gait and placing in ambulatory animals
Spinal reflexes in recumbent animals
Rectum, bladder, anus, and tail function
What is the brain functionally divided into for a neuro exam?
Forebrain, cerebellum, brain stem
Generalized lower motor neuron signs are due to disease of what
Peripheral nerve, neuromuscular junction, or muscle
What are the components of the forebrain?
Telencephalon (cerebrum) and diencephalon (thalamus and associated structures)
What signs are typical of a forebrain lesion?
Altered mentation, seizures, postural reaction deficits, facial hypoexthesia, loss of vision, compulsive pacing, circling, dorsomedial strabismus, dysphagia, alterations in behavior (head pressing, yawning, biting)
With lateralizing forebrain disease, where do clinical signs occur relative to the lesion? What is the exception to this rule?
Contralateral to the lesion; exception is circling- towards the lesion
What are differentials for forebrain disease?
Polioencephalomalacia, lead toxicity, salt/water intoxication, nonprotein nitrogen poisoning, vitamin A deficiency, bacterial, viral, protozoal infection, trauma, metabolic, congenital (hydrocephalus) etc.
Which disorders can cause polioencephalomalacia?
Thiamine deficiency, sulfur toxicity, lead toxicity, salt/water intoxication
What are causes of disturbed thiamine metabolism?
Increased rumen bacterial thiaminase activity, production or ingestion of inactive thiamin analogs (amprolium), impaired absorption, ingestion of thiaminases, increased excretion
What are sources of sulfur in ruminant diets?
Molasses, beet, corn, cruciferous crops, high protein forage, alfalfa
What group of animals are most likely to develop polioencephalomalacia?
Calves and lambs <18 months and kids 2-6 months
Which herds are more likely to develop a polioencephalomalacia outbreak?
Those on feedlots with high carb, low roughage diets
How does high sulfur lead to polioencephalomalacia?
Depletes ATP leading to symmetrical laminar cortical necrosis
What clinical signs are associated with polioencephalomalacia?
Central blindness (normal PLR), staggering gait, wandering, opisthotonus and dorsomedial strabismus
Can develop brain stem dysfunction with advanced disease
How is polioencephalomalacia diagnosed?
History, clinical signs, dietary sulfur level, CSF analysis with mononuclear pleocytosis, moderate protein elevation, and xanthochromia, response to thiamine supplementation
How is polioencephalomalacia treated?
Parenteral thiamine, removal of dietary sulfur source, supportive care
What is the prognosis of polioencephalomalacia?
Good if animal isn’t recumbent yet
Severely affected animals can recover but still have signs
How is polioencephalomalacia prevented?
Dietary management, adaptation to high-concentrate rations, analysis of sulfur levels in feed and water
Which animals is lead toxicity most common in?
2-6 month old beef cows
What diet promotes the absorption of lead?
Milk based diets
How does lead cause polioencephalomalacia?
Crosses the BBB and concentrates in the brain, causes microvascular damage, cell death, cerebral edema, neurotransmitter dysfunction, and decreased glucose uptake
What clinical signs are associated with lead toxicity polioencephalomalacia?
Forebrain dysfunction with GI signs
How is lead poisoning diagnosed?
CBC with nucleated RBCs and basophilic stippling, whole blood lead levels can be used for acute disease, urinary lead levels following chelation therapy can be used for chronic disease
How is lead toxicity treated?
Removal of sources of lead, administer calcium disodium EDTA, supportive care, thiamine administration
What is the prognosis for lead toxicity?
Fair providing aggressive treatment is initiated early
What group of animals most commonly gets salt/water intoxication?
Range cattle, feeder calves, and lambs
What are potential causes of salt/water intoxication?
Overeating with oral electrolytes, ingestion of brackish or contaminated water, restricted access to water, hot weather
What are the characteristic lesions of salt/water toxicity?
Laminar cerebrocortical necrosis and edema
What clinical signs are associated with salt/water toxicity?
Forebrain disease, colic, fluid filled rumen, diarrhea, IV hemolysis and hemoglobinuria
How is salt/water toxicity diagnosed?
History, ratio of CSF sodium to serum sodium >1 is suggestive, CSF sodium concentration >200meq/L is suggestive
How do you replace a water deficit in ruminants without causing water toxicity?
Use sodium containing fluids (no dextrose!), provide small amounts of fresh water frequently, replace fluids slowly over 1-2 days
What is the prognosis for salt/water intoxication?
Fair if treated early
Which animals are predisposed to vitamin A deficiency?
Growing ruminants on drylot or feedlot
Which feeds are naturally low in vitamin A?
Cereal grain, beet pulp and cottonseed hulls
How are vitamin A levels in feed affected by prolonged storage?
They decline over time
How does vitamin A deficiency damage the brain?
Causes thickening of dura mater resulting in diminished CSF absorption and hydrocephalus
What kind of blindness does vitamin A deficiency cause?
Night blindness, PLRs will be absent
Vitamin A is necessary for retina function, deficiency can also lead to bony remodeling and stenosis of optic foramen
What clinical signs are associated with vitamin A deficiency?
Forebrain disease, blindness, anorexia, ill-thrift, diarrhea, pneumonia
How is vitamin A deficiency diagnosed?
Assay of vitamin A and carotene in plasma and feed
How is vitamin A deficiency treated?
With vitamin A supplementation
Describe the transmission and progression of rabies
Inoculation from bite -> incubation for 3w-6m -> virus travels up peripheral nerves to CNS -> rapidly progressive neuro signs and death
What are the clinical forms of rabies?
Cerebral (furious), brain stem (dumb), spinal cord (paralytic)
What are common clinical signs of rabies?
Excessive salivation, behavioral changes (aggressiveness), hyperesthesia, pharyngeal paresis/paralysis, flaccid limb paresis/paralysis
How is rabies diagnosed?
No antemortem test; fluorescent antibody testing on fresh brain tissue
How is rabies prevented?
Inactivated vaccine for ruminants, vaccinate/eradicate wildlife
Which animals are prone to bacterial meningoencephalitis/brain abscess?
Neonatal and weanling cattle, sheep, and goats