29.CNS pathophys

Question 1

4 ventricles or fluid filled cavities in CNS

Answer 1

1. lateral ventricles (one within ea hemisphere)–foramina2. third ventricle (diencephalon)–mesencephalic aqueduct3. fourth ventricle (ventral to cerebellum)–lateral apertures into subarachnoid spacechoroid plexus makes CSF

Question 2

3 layers of connective tissue surrounding brain and spinal cord

Answer 2

1. pia mater–intimate contact with parenchyma–subarachnoid space (CSF)2. arachnoid–lies in contact with outermost layer–subdural (blood vessels)3. dura mater–outer layer

Question 3

epidural space

Answer 3

space surrounding dura in the area of the spinal cord; fat is stored hereno such space exists in the calvarium (dura is next to skull)

Question 4

most common area of brain herniation

Answer 4

caudally–tentorium –foramen magnum

Question 5

resting membrane potential of neuronal cell body

Answer 5

-80 mV depol w rapid Na channel influxdepol w closing Na channel and opening K channel to allow for efflux of K out

Question 6

myelin characteristics

Answer 6

fatty, insulationproduced by oligodendrocytesallows fast rapid efficient conduction over long distancesinterrupted by nodes of ranvier which are UNmyelinated

Question 7

pressure auto regulation of CNS

Answer 7

perfusion should remain constant despite fluctuations btwn MAP 50-160 mm Hgbrain vasodilates during hypotensionbrain vasoconstricts during hypertensionmyogenic mx of smooth muscle cells

Question 8

metabolic auto regulation of CNS

Answer 8

astrocytes detect chemical changes–extremely sensitive to PaCO21 mm Hg change PaCO2 changes cerebral perfusion 5%sense incr PaCO2 –>vasodilation–>incr intracranial vol/P (risk herniation)sense decr PaCO2–>vasoconstriction->decr intracranial vol/P (may cause ischemic damage)

Question 9

define Cushings reflex

Answer 9

bradycardia w hypertensionduring marked peripheral hypotension, bodies response is to vasoconstrictor but damages organs (ie. kidneys). Systemic hypertension causes reflex bradycardia

Question 10

T/Fblood flow is more affected by changes in PaO2 within the physiologic range

Answer 10

FALSE blood flow is LESS affected by changes in PaO2 within a physiologic rangebut if PaO2 is severely low (50 mm Hg), vasodilation to increase perfusion in CNSMajority of regulation is under control of PaCO2 unless oxygenation status is severely decreased

Question 11

how is cerebral blood flow determined

Answer 11

cerebral blood flow depends on cerebral perfusion pressure (CPP)CPP = MAP-ICP

Question 12

marked peripheral hypotension may do what to cerebral perfusion pressure

Answer 12

reduce cerebral perfusion pressure

Question 13

marked elevation in intracranial pressure may do what to cerebral perfusion pressure

Answer 13

reduce cerebral perfusion pressure

Question 14

brain –heart syndrome

Answer 14

during peripheral hypotension and vasoconstriction (Cushings reflex hypertension w reflex bradycardia)sustained release of catecholamines may result in myocardial ischemia and arrhythmias (brain-heart syndrome)

Question 15

normal intracranial pressures

Answer 15

8-15 mm Hgminimal intracranial compliance to adjust (one compensatory mx is CSF and blood flow) fig 29-3 page 376

Question 16

how much does a durotomy decreases intracranial pressure

Answer 16

durotomy 65%craniotomy 15%

Question 17

what compromises the BBB

Answer 17

–endothelial cell and astrocyte processes tight junctions–basal lamina–pericytes–perivascular microglia**selectively permeable: depends on size, lipophilicity, ionization

Question 18

antibiotics with good penetration into CNS

Answer 18

–3rd generation cephalosporins–fluoroquinolones–metronidazole–sulfonamides//trimethoprim–chloramphenicolCCFMS

Question 19

antibiotics that penetration BBB with inflammation present

Answer 19

–tetracyclines (doxy/minocycline)–erythromycin–penicillins–rifampinPERT

Question 20

POOR antibiotic penetration into CNS

Answer 20

–1st and 2nd generation cephalosporins–aminoglycosides–clindamycin–vancomycinVCCA

Question 21

T/Fthe meninges and choroid plexus do NOT have a BBB

Answer 21

TRUEthe meninges and choroid plexus do NOT have a BBBtherefor they can undergo inflammatory responses similar to those in peripheral tissue

Question 22

immune system of CNS

Answer 22

immunologically privileged –complex molecules for lymphocyte activation (B7)–cell adhesion molecules–perivascular macrophages (antigen presenting cells)–microglial cells (phagocytic, resident cells)

Question 23

neuronal stem cells are a type of adult stem cellwhere does neurogenesis occur within the brain

Answer 23

1. OLFACTORY system/subventricular zone2. dentate gyrus of the HIPPOCAMPUS

Question 24

contusion leading to primary and secondary damage

Answer 24

(contusions more common in spinal cord due to dynamic nature)1. primary mechanical damage–in the brain contusion leads to focal and diffuse changes2. secondary injury–series of biochemical and metabolic changes causing neuronal and glial cell death which may lasts for weeks (acute hemorrhage–>multi located cavitations with apoptosis (gray matter)–>central cavitation with apoptosis (white matter), wallerian degeneration and cell death

Question 25

hypothesis why GCC are avoided and potentially deleterious for patients with acute spinal cord injury

Answer 25

CNS response to injury is one that internally depresses lymphocyte and monocyte numbers for several days after injurythat is accompanied by endogenous release of ACTH and catecholamines which can damage distant organs “CNS injury induced immunodepression”GCC may enhance this affect and be potentially deleterious

Question 26

clinical signs of compressive injury depends on…

Answer 26

speedsizedurationlocationseverity

Question 27

pathological changes associated with compression injury

Answer 27

demyelinationvasogenic edema (favors white matter)axonal degenerationneuronal necrosiswith chronic compressions–necrosis/apoptosis of glial cells

Question 28

role of oligodendrocytes

Answer 28

produce and maintain myelin sheath

Question 29

hypothesis of worsening or clinic deterioration seen after decompressive surgery

Answer 29

1. mechanical insult from surgery2. reperfusion injury

Question 30

Is gray matter or white matter affected more with thomboembolic disease

Answer 30

gray matter dz includes: FCE (nucleus pulposus), feline ischemic encephalopathy (Cuterebra vasotoxin), thrombotic “stroke”, septic or neoplastic emboli

Question 31

most common tumors to metastasize to the CNS

Answer 31

HSAmelanomascarcinomas

Question 32

difference btwn cytotoxic and vasogenic edema

Answer 32

cytotoxic–intracellular fluid from failure of ion pumps from ischemic/hypoxic injury; most pronounced in astrocytesvasogenic–extracellular fluid from increased vascular permeability along white matter; like interstitial edemacytotoxic edema is best treated by alleviating inciting causevasogenic edema responds well to GCC

Question 33

types of IVDD

Answer 33

most common cause of myelopathy in dogs1. nucleus has progressive decr in proteoglycan (dehydrates) and replaced with mineral; seen in chondrodystrophic; acute compression with tear in annulus2. nucleus dehydrates and replaced with fibrinoid tissue; chronic wear and tear of annulus with compression3. peracute type 1; low volume, high velocity’ acute non compressive nucleus pulpous extrusions

Question 34

T/FContusive effect, rather than compression, is probably responsible for most of the observe clinical signs after acute IVDD

Answer 34

TRUE

Question 35

T/Fneurons/axon damage is likely irreversibleoligodendrocytes/astrocyte damage can be regenerated

Answer 35

TRUE

Question 36

define hydrocephalus, hydromyelia, syringomelia

Answer 36

hydrocephalus–fluid accumulation in ventricleshydromyelia–fluid accumulation in spinal cordsyringomyelia–fluid within spinal cord parenchyma