Neurology

Question 1

How many dogs with portosystemic shunts display neurologic signs?

Answer 1

95%

Question 2

Name 4 neurologic signs of hepatic encephalopathy

Answer 2

Decreased ability to learn, behavioral changes, head pressing, seizures, blindness

Question 3

Are neurologic signs more common when shunts insert cranial to or caudal to the liver

Answer 3

Caudal

Question 4

Name 3 endotoxins thought to be involved in the development of hepatic encephalopathy

Answer 4

Ammonia, amino acids (tryptophan), GABA, mercaptans

Question 5

Hyperammonemia has been documented in young Irish Wolfhounds due to what deficiency?

Answer 5

Deficiency in urea cycle enzymes

Question 6

What neurologic signs can be seen in hypothyroid dogs?

Answer 6

Acute or chronic, progressive central vestibular signs

Question 7

Name 4 clinical signs of myxedema coma in dogs

Answer 7

Mentation changes due to brain edema, hypothermia without shivering, non-pitting skin edema, bradycardia

Question 8

Name 3 mild CNS signs noted in cats with hyperthyroidism

Answer 8

Hyperactivity, changes in sleep/wake cycles, aggression, obtundation

Question 9

How large are pituitary tumors before they result in neurologic signs?

Answer 9

Typically >1 to 1.5cm diameter

Question 10

Pituitary tumors result in neurologic signs in what percent of dogs before or after diagnosis of hyperadrenocorticism?

Answer 10

15-30%

Question 11

Name 4 neurologic signs of a pituitary macroadenoma

Answer 11

Obtundation, pacing, circling, disorientation, ataxia, seizures

Question 12

How does persistent hypoglycemia results in neurologic damage?

Answer 12

Leads to vasoconstriction and hypoxia

Question 13

Name two tumors capable of resulting in hypoglycemia

Answer 13

Insulinoma, leiomyosarcoma

Question 14

What drug can be used to treat insulin producing tumors because it inhibits insulin secretion, stimulates production of glucose by the liver, and inhibits uptake of glucose by cells?

Answer 14

Diazoxide

Question 15

What role does thiamine play in the body?

Answer 15

Essential cofactor for carbohydrate metabolism - essential for utilization of pyruvic acid in the TCA cycle and pentose phosphate pathway. Absence of thiamine leads to excessive lactic acid buildup as anaerobic metabolism occurs

Question 16

How can thiamine deficiency result in dogs and cats?

Answer 16

Fed meats preserved with sulfur dioxide, thiaminase-containing raw fish

Question 17

What are the histopathologic findings associated with thiamine deficiency?

Answer 17

Polioencephalomalacia

Question 18

Name 3 clinical signs of thiamine deficiency

Answer 18

Vestibular signs, spastic cervical ventroflexion in cats, vision loss, mydriasis without pupil light reflexes, incoordination, ataxia, and seizures

Question 19

How does hypocalcemia alter membrane excitability?

Answer 19

Increases it

Question 20

Name 3 neurologic signs of hypocalcemia

Answer 20

Facial rubbing, stiffness, muscle twitching, nervousness, tetany, and seizures

Question 21

Severe hyponatremia results in what changes to the brain?

Answer 21

Cerebral edema, diffuse encephalopathy

Question 22

Rapid correction of hyponatremia can result in what histopathologic changes in the brain? How long after correction do these signs manifest?

Answer 22

Central pontine myelinolysis; occurs 48 hours to days after correction

Question 23

When correcting hyponatremia, the serum sodium concentration should not rise by more than ____ in 24 hours?

Answer 23

10 mEq/L

Question 24

Acute hypernatremia can cause what changes to the brain?

Answer 24

Decrease in brain volume from osmotic shifts, leading to vascular rupture and focal hemorrhage

Question 25

In chronic hypernatremia, the brain adjusts to hypertonicity by producing what substance?

Answer 25

Idiogenic osmoles

Question 26

Rapid correction of hypernatremia results in what changes to the brain?

Answer 26

Cerebral edema

Question 27

T4 stimulates mitochondrial respiratory activity, thereby leading to ATP production. In hypothyroidism, how does ATP deficiency affect peripheral nerves?

Answer 27

Impairs the function of the Na/K pump, leading to decreased axonal transport ==> leads to axonal degeneration and demyelination

Question 28

List 3 neurologic signs of hypothyroidism

Answer 28

Weakness, muscle atrophy, laryngeal paralysis, megaesophagus facial paralysis, peripheral vestibular signs

Question 29

What hormonal disease causes fibrotic myopathy and polyneuropathy?

Answer 29

Hyperadrenocorticism

Question 30

Name 3 clinical signs of fibrotic myopathy

Answer 30

Stiff, stilted gain, difficulty flexing the limbs, generalized muscle atrophy

Question 31

Name 3 signs of diabetic polyneuropathy in cats

Answer 31

Plantigrade stance, difficulty jumping, CP deficits, decreased tendon reflexes, muscle atrophy

Question 32

Name two feline diseases that may result in hypokalemia

Answer 32

CKD, hyperaldosteronism

Question 33

What is the reticular activating system and what is it responsible for?

Answer 33

Network of nuclei in the brainstem. Activate the cerebral cortex to maintain consciousness

Question 34

What is the function of the cerebrum?

Answer 34

Integrates sensory info, plans motor activity, responsible for emotion and memory

Question 35

Diffuse, bilateral forebrain lesions will result in stupor/coma. How will they affect movement and reflexes?

Answer 35

Tetraparesis, postural deficits are present. Reflexes are normal but vision is absent

Question 36

Lesions of the rostral brainstem will result in stupor/coma. How will they affect movement and reflexes?

Answer 36

Bilateral lesions will cause tetraparesis, unilateral lesions will cause hemiparesis. Postural deficits present. Reflexes are exaggerated with increased extensor tone

Question 37

Name 3 brainstem reflexes

Answer 37

Pupil size/symmetry and response to light. Physiologic nystagmus. Dazzle reflex. Palpebral reflex

Question 38

If a patient has unilateral mydriasis with no pupillary response to light, where is the lesion located?

Answer 38

Cranial nerve III

Question 39

If a patient has unilateral mydriasis AND ventrolateral strabismus with no response to light, where is the lesion located?

Answer 39

Midbrain

Question 40

Describe Cheyne-Stokes breathing

Answer 40

Alternating hypernea and apnea

Question 41

Describe apneusis. Where is the lesion located

Answer 41

Breathing raises for a full inspiratory period with otherwise normal breathing. Pontine lesions

Question 42

What equation describes cranial perfusion pressure (CPP)

Answer 42

CPP = MAP - ICP

Question 43

Describe the Cushing's reflex

Answer 43

If ICP rises, the MAP increases to maintain CPP. Systemic hypertension triggers the baroflex, leading to bradycardia

Question 44

Name 3 causes of hepatic encephalopathy

Answer 44

A = acute, fulminant liver disease B = bypass (portosystemic shunts) C = cirrhosis (cirrhotic liver, portal hypertension, acquired shunting)

Question 45

Acute, fulminant liver disease can result in hepatic encephalopathy by what pathologic change?

Answer 45

Cytotoxic brain edema. Can lead to intracranial hypertension and brain herniation

Question 46

What causes cytotoxic brain edema?

Answer 46

Failure of ion pumps, so no sodium efflux occurs. Water shifts to the intracellular space to maintain iso-osmotic state => edema. BBB is intact

Question 47

What causes vasogenic edema?

Answer 47

Disruption of the BBB, which triggers a cascade of inflammatory and vasoactive mediators. Often causes by tumors

Question 48

Chronic hepatic disease can result in hepatic encephalopathy by what pathologic change?

Answer 48

Alzheimer type II astrocytosis - astrocytes change structure and function. Very minimal brain edema

Question 49

Name 2 non-hepatic causes of hyperammonemia

Answer 49

Vitamin B12 deficiency. Arginine deficiency in cats

Question 50

Name 3 sources of ammonia in the body

Answer 50

Bacteria breakdown of proteins, urease bacterial breakdown of urea, intestinal breakdown of glutamine

Question 51

Which form of ammonia is absorbed from the gut (NH3 or NH4+)?

Answer 51

NH3

Question 52

In the periportal hepatocytes, ammonia is converted into _____ via the _____ pathway

Answer 52

Urea, urea cycle

Question 53

How does arginine deficiency in cats lead to hyperammonemia?

Answer 53

Arginine is an important component of the urea cycle. Without it, ammonia cannot be converted into urea. Essential amino acid in cats

Question 54

How does ammonia affect glutamate in the brain?

Answer 54

Ammonia is added to glutamate (a major neurotransmitter) to form glutamine. Glutamine is taken up by astrocytes and is osmotically active, leading to edema formation

Question 55

What hepatic synthetic parameter is NOT affected by PSS?

Answer 55

Bilirubin (hyperbilirubinemia is not a feature of congenital PSS)

Question 56

What is the major excitatory neurotransmitter?

Answer 56

Glutamate

Question 57

What is the major inhibitory neurotransmitter?

Answer 57

GABA

Question 58

Name two catecholamine based neurotransmitters

Answer 58

Dopamine, norepinephrine

Question 59

What type of amino acids are precursors to catecholamines?

Answer 59

Aromatic amino acids: phenylalanine, tyrosine, tryptophan

Question 60

Aromatic amino acids are usually removed by the liver. How do they contribute to hepatic encephalopathy

Answer 60

Can build up and become false neurotransmitters

Question 61

What amino acids may be decreased with liver failure?

Answer 61

Branched chain amino acids: leucine, valine, isoleucine

Question 62

How does lactulose reduce hyperammonemia?

Answer 62

Broken down into acid byproducts in the gut. The acidity traps NH3 in the NH4 form, which is not absorbed

Question 63

How do antibiotics reduce hyperammonemia?

Answer 63

Reduce the number of urease producing bacteria

Question 64

What is dialysis disequilibrium syndrome?

Answer 64

A rapid decline in peripheral osmolality results from dialysis => cerebral edema => increased ICP

Question 65

What is kernicterus?

Answer 65

Deposition of bilirubin in the grey matter and spinal cord => neuronal degeneration