Circulatory Disturbances and Traumatic Injuries of the Nervous System

Question 1

what is cerebrovascular disease?

Answer 1

stroke: any abnormality in the brain resulting from a pathologic process of the blood vessels

hallmark: sudden loss of neurologic function

Question 2

you take a phone call from a client with an 8 year old dog that has acute onset of neurologic signs. they are not progressing. what is your first differential?

Answer 2

stroke

Question 3

thrombosis and infarction

Answer 3

• infarction less common in animals compared to humans (diet- atherosclerosis)
• outcome depends on type and size of obstructed vessel, rapid onset of ischemia, vulnerability of the area of brain or spinal cord

Question 4

what conditions could pre-dispose a patient to thrombosis or infarction?

Answer 4

atherosclerosis: causes in dogs include hypothyroidism, diabetes mellitus, hypercholesterolemia

Question 5

what cell types are most susceptible to hypoxia?

Answer 5

neurons > oligodendrocytes > astrocytes > microglia > vascular endothelial cell

Question 6

what cell is most susceptible to hypoxia?

Answer 6

neurons

Question 7

ischemic infarcts

Answer 7

• vascular (artery/arterioles) obstruction: thrombus or thromboembolism
• gross lesion: well circumscribed area of yellow to tan discoloration and softening (malacia)
• grey matter more susceptible (neurons in there)
• with chronicity: see cavitation if large region or injury

Question 8

what is the gross lesion of ischemic infarcts?

Answer 8

• these are vascular obstructions
• see well circumscribed area of tan to yellow discoloration = malacia

Question 9

what are the 2 types of infarcts?

Answer 9

1. ischemic
2. hemorrhagic

Question 10

hemorrhagic infarcts

Answer 10

• vascular damage/rupture leading to leakage of RBCs
• venous thrombosis
• gross lesion: regional area of parenchymal hemorrhage

Question 11

chronic infarcts leads to

Answer 11

cavitation

Question 12

fibrocartilaginous emboli (FCE)

Answer 12

• common in dogs, uncommon in other species
• peracute (usually lateralized) spinal signs without pain
• exact mechanism unknown: herniation of degenerative disk material (nucleus pulposus) Hansen type 1 –> vasculature –> occlusive emboli –> ischemic injury

Question 13

what is the proposed pathogenesis of fibrocartilaginous emboli?

Answer 13

exact mechanism unknown: herniation of degenerative disk material (nucleus pulposus) Hansen type 1 –> vasculature –> occlusive emboli –> ischemic injury

Question 14

fibrocartilaginous emboli is common in what species

Answer 14

dogs

Question 15

edema

Answer 15

excess fluid accumulation in the CNS parenchyma: can be associated with most disease processes

Question 16

what are the 3 types of cerebral edema?

Answer 16

1. vasogenic edema: most common
2. cytotoxic edema
3. interstitial edema

Question 17

vasogenic edema

Answer 17

• most common
• disruption of BBB
• increased vascular permeability = ECF accumulation
• white matter most affected (spongiosis)
• common causes: trauma, neoplasia, inflammation and some toxic/metabolic conditions

Question 18

what are common causes of cerebral edema?

Answer 18

trauma, neoplasia, inflammation

Question 19

what cells are most affected by vasogenic edema?

Answer 19

white matter

Question 20

cytotoxic edema

Answer 20

• altered cellular metabolism = intracellular fluid accumulation
• low O2 = interference with ATP dependent Na K pumps in cell membrane
• swelling of neurons, glial and endothelial cells (grey and white matter affected)
• common causes: hypoxia, neoplasia, toxic/metabolic conditions (ex salt poisoning in pigs, hepatic encephalopathy)

Question 21

what causes cytotoxic edema?

Answer 21

• altered cellular metabolism = intracellular fluid accumulation
• low O2 = interference with ATP dependent Na K pumps in cell membrane

Question 22

what are common causes of cytotoxic edema?

Answer 22

hypoxia, neoplasia, toxic/metabolic conditions (ex salt poisoning in pigs, hepatic encephalopathy)

Question 23

what is the unique cell type seen with hepatic encephalopathy?

Answer 23

alzheimer type 2 astrocytes

Question 24

what are the gross lesions with edema?

Answer 24

• flattened gyri and shallow sulci
• clear, watery fluid in leptomeninges
• posterior shifting of brain: ie herniation thru foramen magnum
• white matter may be soft, wet, pale yellow

Question 24

interstitial edema (hydrostatic)

Answer 24

- accumulation of fluid in the periventricular white matter associated with increased ventricular pressure (see with bad hydrocephalus or hydromyelia)

Question 25

what bacteria causes focal symmetrical encephalomalacia?

Answer 25

clostridium perfringens type D (epsilon toxin)

Question 26

pathogenesis of Clostridium perfringens type D

Answer 26

- degeneration of vascular endothelial tight junctions = swelling and rupture of perivascular astrocyte processes = leakage of fluid and increased intracerebral pressure = parenchymal necrosis systemic: see leakage of fluid in all sorts of places: abdomen, cardiac, pulmonary edema, petechiation

Question 27

what is the classic animal for clostridium perfringens type D?

Answer 27

sheep and goats subacute and chronic cause FSE, acute and peracute is protein rich fluid around blood vessels brain involvement uncommon in goats and cattle. in these species with chronic issues, would see colitis

Question 28

what is the big concern with edema

Answer 28

herniation

Question 29

where can the brain herniate?

Answer 29

1. thru foramen magnum (foramenal herniation) 2. under tentorium cerebelli (transtentorial herniation) 3. under the falx cerebri (falcine herniation) 4. thru a defect in the skull (ex trauma/fracture)

Question 30

transtentorial herniation

Answer 30

when the brain herniates under the tentorium cerebelli

Question 31

traumatic injury of the nervous system

Answer 31

- external trauma: forces external to body. HBC, kicks, falls, gunshots, bites - internal injury: intrinsic physical disturbances. disc extrusion, vertebral abscesses, neoplasia, congenital malformation - less frequent in animals than in humans: not exposed to trauma causing situations as commonly. anatomic differences: brain volume to cranium volume ration is less in animals

Question 32

what trauma patients are susceptible to what 2 phases of injury?

Answer 32

1. primary injury: direct trauma or forces acting on brain 2. secondary injury: series of events that lead to continued injury to neurons/glial cells (ie days after)

Question 33

primary injury with TBIs

Answer 33

- direct trauma: fractures, hemorrhages, edema, direct injury to parenchyma - forces acting on brain: acceleration, deceleration, rotational forces

Question 34

acceleration/deceleration and rotational forces cause what types of damage to the brain?

Answer 34

acceleration/deceleration: superficial grey matter (hemorrhages, contusion, tearing of neuronal tissue) rotational: deeper white matter (causing concussive injuries and axonal damage)

Question 35

secondary injury with TBIs

Answer 35

series of events that lead to continued injury to neurons/glial cells major mediators: oxygen free radicals, excitatory amino acids, nitric oxides

Question 36

what are the 2 big types of brain trauma?

Answer 36

1. concussion: diffuse but transient brain injury associated with temporary loss of consciousness. typically no lesions and minimal microscopic lesions. uncommon in animals 2. contusion: focal brain injury which may result in unconsciousness. usually grossly detectable and superficial area of brain hemorrhage. often associated with a skull fracture

Question 37

what is a concussion?

Answer 37

diffuse but transient brain injury associated with temporary loss of consciousness. typically no lesions and minimal microscopic lesions. uncommon in animals

Question 38

what is a contusion?

Answer 38

focal brain injury which may result in unconsciousness. usually grossly detectable and superficial area of brain hemorrhage. often associated with a skull fracture

Question 39

contusions are often associated with

Answer 39

skull fractures

Question 40

T/F: concussions typically have no gross lesions

Answer 40

true

Question 41

what are the gross lesions of a contusion?

Answer 41

superficial area of brain hemorrhage, often associated with skull fracture

Question 42

hemorrhage can be seen with a wide variety of causes, what are some examples of these

Answer 42

1. TRAUMA most common 2. DIC 3. damage to vessels/vasculitis (virus, septic, immune, neoplasia, etc

Question 43

what is the most common site to see damage to following brain trauma?

Answer 43

subarachnoid hemorrhage

Question 44

what is the common site of traumatic brain injury in. horses?

Answer 44

they rear and fall over on their back, break the basisphenoid bone displaced bone lacerates large vessels at base of brain hemorrhage becomes the dominant lesion

Question 45

what is the dominant lesion of TBI in horses? what is this from?

Answer 45

hemorrhage is the dominant lesion, from fracture of the basisphenoid bone from rearing over backward

Question 46

what factor will determine the degree of spinal cord injury?

Answer 46

amount of space between spinal cord and vertebral canal is important

Question 47

where is the extradural space the greatest?

Answer 47

cervical vertebral column, cranial thoracic and caudal lumbar region = spinal cord compression less likely intercapital ligaments (T2-T10): lower incidence of intervertebral disc extrusion in this region

Question 48

major mechanisms of spinal cord injury

Answer 48

1. contusion: focal hemorrhage associated with fracture, luxation, subluxation or disc herniation 2. compression: extramedullary pressures (disc herniation, neoplasia, fracture, malformation

Question 49

what are examples of compression of the spinal cord?

Answer 49

extramedullary pressures: disc herniation, vertebral and meningeal neoplasia, vertebral fracture/subluxation, vertebral malformation

Question 50

microscopic lesions of spinal cord trauma

Answer 50

- hemorrhage (more prominent in grey matter) - axonal/myelin degeneration at site of compression - degeneration of axon and myelin sheath distal to site of injury (Wallerian degeneration)

Question 51

acute spinal cord compression

Answer 51

- direct mechanical injury to spinal cord (contusion) - hypoxia: caused by injury to vessels, compression of vessels, release of NTs - ex: hansen type 1 intervertebral disc extrusion

Question 52

hansen type 1 intervertebral disc extrusion is an example of what spinal cord injury?

Answer 52

acute spinal cord compression

Question 53

what is an example of acute spinal cord compression?

Answer 53

hansen type 1 intervertebral disc extrusion

Question 54

hansen type 1 disc extrusion

Answer 54

- acute extrusion of nucleus pulposus thru annulus fibrosus and into canal - usually associated with "chondroid" degeneration/metaplasia of nucleus pulposus" genetically programmed and starts early (6 mo) - chondrodystrophic breeds of dogs - lesions: degenerative, chalky white mineralization of nucleus pulposus

Question 55

hansen type 1 disc extrusion is usually associated with

Answer 55

chondroid degeneration/metaplasia of nucleus pulposus: genetically programmed and starts early (6 mo)

Question 56

in what breeds do we see hansen type 1 disc extrusion in?

Answer 56

chondrodystrophic breeds

Question 57

chronic spinal cord compression

Answer 57

- direct but slowly developing injury to cord - low grade hypoxia due to compression of vessels: reduced perfusion, vascular stasis, increased hydrostatic pressure leads to edema ex: hansen type 2 intervertebral disc protrusion, cervical vertebral stenotic myelopathy (wobblers)

Question 58

what are examples of chronic spinal cord progression?

Answer 58

1. hansen type 2 intervertebral disc protrusion 2. cervical vertebral stenotic myelopathy (wobblers)

Question 59

1. hansen type 2 intervertebral disc protrusion 2. cervical vertebral stenotic myelopathy (wobblers) these are both examples of

Answer 59

chronic spinal cord compression

Question 60

what is wobbler's syndrome and what does it lead to?

Answer 60

chronic spinal cord compression: cervical vertebral stenotic myelopathy. low grade hypoxia due to compression of vessels reduced perfusion, vascular stasis, increased hydrostatic pressure leading to edema

Question 61

hansen type 2 disc protrusion

Answer 61

- bulging of disc material into vertebral canal - associated with "fibrous degeneration" of annlus (usually begins around 8-10 years of age) - more common in non-chondrodystrophic dogs

Question 62

when does hansen type 2 disc protrusion begin?

Answer 62

8-10 years of age

Question 63

a severe complication of spinal cord compression often leading to euthanasia is

Answer 63

ascending/descending hemorrhagic myelomalacia seen more with type 1 IVDD 12-24 hours after injury dog seems to be doing better and then crashes. get hemorrhage and necrosis that ascends up. unsure on pathogenesis

Question 64

ascending/descending hemorrhagic myelomalacia

Answer 64

spinal cord compression consequence that is severe; acute and chronic lesions can result in these. more common with type 1 IVDD, 12-24 hours after injury

Question 65

cervical vertebral stenotic myelopathy "wobblers syndrom"

Answer 65

- horses and large breed dogs - osseous: young adults: vertebral malformations often associated with degeneration of facet joints (osteochondrosis dissecans) - disc-associated: adult dogs born with congenital vertebral canal stenosis

Question 66

what are the 2 types of wobblers syndrome?

Answer 66

- osseous: young adults: vertebral malformations often associated with degeneration of facet joints (osteochondrosis dissecans) - disc-associated: adult dogs born with congenital vertebral canal stenosis: prone to cord compression bc of smaller extradural space. C5-C6, C6-C7

Question 67

what are the 2 characterizations of wobblers syndrome used in horses?

Answer 67

1. static: >1 year of age, compression regardless of neck position. C5-C6 and C6-C7 2. dynamic: usually 8-18 months of age. flexed neck: C3-C4, C4-C5

Question 68

what is a necessary diagnostic for wobblers syndrome?

Answer 68

myelogram: actually see if you are getting compression