Nervous system pathology 4

Question 1

Define hernitation

Answer 1

When something comes out of the area where it is normally placed and crushes against the spinal cord, brain or nerves

Question 2

Name and describe the two types of intervertebral disc herniation

Answer 2

Hansen type 1: Extrusion of degenerated disc material

Hansen type 2: Protrusion without rupture of the annulus fibrosus

Question 3

What is meant by coup and contre-coup?

Answer 3

• Coup: traumatic lesion just beneath the site of impact

- Contre-coup: on the opposite side

Question 4

Describe impact on the skull/brain and the effect this has on the site of impact and on the opposite side

Answer 4

If there is impact the brain will follow, even if the skull stops, the brain will continue to more (inertia) because it is unable to stop itself, the only way to stop it is by pulling on the vessels attached to the brain which causes haemorrhage in the exact opposite place to where the trauma occurred (e.g. to the skull)

Question 5

Describe the effect of acceleration-deceleration injuries, or injuries by fall, at the site of impact and on the opposite side

Answer 5

• Caused by the sudden stop (deceleration or negative acceleration) of the head
• At the site of impact (impact site), cutaneous and cortical haemorrhages can be seen but are minimal
• At the diametrically opposite site (controlateral haemorrhage site), intensity of lesions is much more pronounced with consistent cortical haemorrhages

Question 6

Describe the effects of deformation or injury by blow on the site of impact and on the contralateral side

Answer 6

• Caused by a kinetic energy delivered with higher velocity at the impact point
• Kinetic energy transforms into deformation of the skull or fracture
• Large contusion and lacerations extending deeply into the neuroparenchyma at the impact site
• Contralateral haemorrhages are mild or not present

Question 7

Accumulation of fluid in the ventricles is termed?

Answer 7

Hydrocephalus

Question 8

On a PM what would be an indicator of immediate death following an impact lesions?

Answer 8

Any impact on the midline injuries would lead to death immediately
Any impact to the brainstem

Question 9

Describe the features of acute spinal cord contusion due to a vertebral fracture

Answer 9

Haemorrhage, axonal damage and gliotic and inflammatory reaction

Question 10

What are some general features of abnormal development in the CNS?

Answer 10

• Congenital malformations are structural abnormalities of prenatal origin present at birth
• Long period of development, starting early during embryogenesis
• Higher severity when acting early (first third) during gestation
• Environmental factors (viruses, toxic compounds, vitamin deficiencies, etc..) act often together with genetic mutations

Question 11

Name two conditions caused by neural tube closure defects

Answer 11

Cranium bifida

Spina bifida

Question 12

Malformation of the caudal fossa leads to which conditions?

Answer 12

• Cerebellar agenesis

- Cerebellar hyperplasia and dysplasia

Question 13

Name 3 conditions cause by abnormalities of the CSF

Answer 13

• Hydrocephalus
• Hydromyelia
• Syringomyelia

Question 14

What causes spina bifida?

Answer 14

Failure of development of the vertebral arch of the spine (lumbar)

Question 15

What is anecephaly?

Answer 15

Lack of brain development

Question 16

What is holoprosencephaly?

Answer 16

Lack of development of the cerebral hemisphere

Question 17

Define hydrocephalus

Answer 17

Increase in volume of CSF (water in the brain)

Question 18

What is communicating hydrocephalus

Answer 18

Bilateral and symmetrical dilation without detectable lesions (toy breed)

Question 19

Define syringomyelia

Answer 19

Fluid-filled (CSF) cavity within the spinal cord following rupture of the ependymal covering

Question 20

Define syringobulbia

Answer 20

Similar to syringomyelia but also involves the brainstem

Question 21

Define hydromyelia

Answer 21

Fluid-filled (CSF) cavity within the spinal cord, lined by a continuous layer of ependyma

Question 22

Define Encephalomalacia

Answer 22

The softening or loss of brain tissue after cerebral infarction, cerebral ischemia, infection, craniocerebral trauma, or other injury.

Question 23

Describe the lesion distribution pattern in metabolic/toxic CNS lesions

Answer 23

Symmetrically affecting specific areas

Question 24

Describe the histopathological presentations of metabolic/toxic CNS lesions

Answer 24

• Malacia (polio- or leuko-)
• Specific cell necrosis
• Spongy change

Question 25

What is the clinical hallmark of metabolic/toxic CNS lesions

Answer 25

Acute to subacute onset of progressively worsening neurological dysfunctions

Question 26

How are acute corticocerebral necrosis lesions characterised?

Answer 26

Oedema (spongy state) and red hypoxic neurons affecting specific laminae of the cerebral cortex (laminar necrosis) -> swollen brain

Question 27

How are chronic corticocerebral necrosis lesions characterised?

Answer 27

Cavitation of the affected cortex, gitter cell proliferation, glial scar formation

Question 28

What are two suspected causative agents of corticocerebral necrosis?

Answer 28

Sulphur intoxication and thiamine deficiency

Question 29

Focal symmetrical encephalomalacia affects which spp?

Answer 29

Sheep Cattle Pigs

Question 30

Describe the pathogenesis of Focal symmetrical encephalomalacia

Answer 30

Alterations in intestinal environment due to sudden diet changes (e.g. sudden feeding of large amounts of grain) -> inadequate ruminal flora for digestion of starch -> undigested starch passes into intestine and acts as a substrate for bacteria, promoting C. perfringens type D growth and proliferation Glucose in environment is low due to poor digestion of feed -> decreased glucose stimulates Epsilon exotoxin production -> facilitates its own absorption through the intestinal mucosa -> endothelial damage and increased vascular permeability (especially in lungs and brain) -> vasogenic brain oedema -> hypoxic-ischemic necrosis

Question 31

What is the cause of swayback?

Answer 31

Congenital copper deficiency in lambs

Question 32

What is the progression of sway back disease?

Answer 32

Animal are blind and ataxic -> severe incoordination -> immobility -> death

Question 33

How does swayback appear grossly?

Answer 33

Ventricular distension due to bilateral symmetrical rarefaction of the periventricular grey matter

Question 34

Describe the pathogenesis of hepatic encephalopathy

Answer 34

The detoxifying role of astrocytes (ammonia removal) is overwhelmed by increased haematic concentration -> metabolized to glutamine -> cytotoxic oedema (astrocyte cell swelling)

Question 35

What is the main histological finding for hepatic encephalopathy?

Answer 35

Severe spongy state of the white matter