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CNS Ischemia Path
McDonald Neuro Ischemia Path M2T2
16
Medical
Graduate
12/30/2010

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Cards

Term
General causes of dec delivery of oxygen to the brain
Definition
  • fxnal hypoxia: low partial pressure of O2
  • impaired O2 carrying capacity of the blood
  • inhib of O2 use by the tissue
  • ischemia due to dec perfusion or obstruction of large or small blood vessels
Term
Consequences of Reduced Blood Flow
Definition
  • amount of collarteral circ
  • duration of ischemia
  • magnitude of rapidity of the reduction of blood flow
  • these factors will determine
    • antamoic site of lesion
    • size of lesion
    • clinical deficit
Term
2 types of acute ischemia
Definition
  • global cerebral ischemia
    • results form a general dec in cerebral perfusion such as in cardiac arrest, shock, marked hypotension, asphyxia
  • Focal cerebral ischemia
    • cessation of blood flow to localized areas of the brain due to large or small blood vessel disease
Term
Vulnerability of CNS cells
Definition
  • Neurons: most sensitive to hypoxia
  • oligodendroglia: also sensitive
  • astrocytes: also sensitive
  • there are differences in regional blood flow and cellular metabolic requirements
Term
Global Ischemia
Definition
  • the outcome depends on severity of insult
  • MINOR ISCHEMIA: result in trasient confusion with  no morpho or fxn derangements but at times can cause perm damage w/ permanent clinical deficits
  • more SEVERE ISCHEMIA: result in variety of clinical and morph changes, many devastating
  • widespread neuronal death
    • if pt survives permanent deficits
    • severe neuro impair, remain in deep coma
  • BRAIN DEATH: evidence of diffuse cortical injury: flat EEG w/ brainstem damage, no resp drive, no reflexes, no cerebral perfusion
  • RESPIRATOR BRAIN: necrosis, edema, widespread destruction of brain due to recurrent cycles of edema and vasocompression --> autolysis & soft brain which prevents its fixation if formalin (on resp for long time - swell, inc in kids)
Term
Morph of Cerebral Ischemia
Definition
  • swollen brain
  • wide gyri
  • narrow sulci
  • possible herniation (bc of swelling)
  • ischemia and hemorrhage assoc w/ herniation
Term
Microscopic features of ischemic injury
Definition
  • Early Stage: 12-24hrs after injury produces neuronal cell change causing red nerons - cells undergo vacuolization and eosinophilia of cyto ultimately resulting in pyknosis & karyorrhexis
    • pyramidal cells of hippocampus & purkinje cells of cerebellum partic susceptible to global ischemia. eventually nphils infiltrate
  • subacute changes: 24 hrs -2w includes necrosis infiltration of mphags, vascular prolif, reactive gliosis
  • Repair: after 2 wk removal of necro tissue, loss of org cell structures & gliosis --> uneven destruction of the neocortex w/ preserve of some areas and involv of others called: psuedolaminar necrosis
Term
Focal Cerebral Ischemia
Definition
  • Cerebral arterial occlusion caused by thrombotic occlusions arising from aterosclerosis
  • most common sites of primary thrombosis --> infarc are: CAROTID BIFURCATION, ORIGIN OF MCA & BASILAR A
  • occlusion caused by anterograde progression of the thrombus or frag and subsequent embolization
  • assoc w/ systemic dz: DM & HTN
Term

Focal Ischemia due to vasc Inflam

 

Definition
  • arteritis: small and large vessel inflam - syphilis, TB, immunosuppressed
  • PAN & collagen vasc dz: inv cerebral vessels-->single or mult infarcts
  • primary angiitis of CNS: inv small to med sized parenchymal & subarachnoid vessels w/ infilt by chronic inflam & giant cells
  • hypercoag states: PCV, sickle cell
  • dissect aneurysm of extracranial A, esp in neck
  • drug abuse: partic stim like meth & cocain, heroin
Term
CADASIL
Definition
  • Cerebral Autosomal Dominant Arteriopathy w/ subcortical infarcts & leukoencephalopathy
  • Assoc w/ mut in Notch 3
  • characterized by recurrent strokes and dementia
  • abnorm of white matter & concentric narrow of adventitia and media of leptomeningeal arteries
  • rare hereditary form of stroke
Term
emboli
Definition
  • much more common cause of ischemia and infarct
    • cardiac mural thrombi
    • MI
    • valv dz
    • Afib
    • cartoid artery atherosclerosis
    • fat, air, tumor emboli
  • area of distribution of the MCA, direct extensionof Int Carotid A,
  • emboli lodge at bifurcation of arteries
  • location of embolus cant be ID'd at autopsy bc lysis
  • fat emboli:fracture of long bones w/ release of bone marrow & fat occur in MVA, widespread white matter hemorrhage & generalized cerebral dysfxn
  • air emboli: penetrating injury to cervical vessels, IV injection of air, divers, sex
  • tumor emboli many sarcomas and some CA can emboli
Term
asphyxiation
Definition
  • suffocation
    • air cant get in
    • entrapment/env: inadequate O2, autopsy alone will not give COD
    • smother: occlude ext airway, minimal autopsy findings
    • choke: occlusion int airway
      • nat: epiglottitis, homicidal: movement of gag, Accident: inhale food, foreing obj
    • positional asphyxia: usu accident, drugs/alc, trapped in position which impair breath, congestion cyanosis, petechiae
    • traumatic asphyxia: heavy weight compresses chest/upper abd, congestion petechia, BURKING, overlaying - baby sleep w/ parents
    • mech asphyxia: compression of body
    • suffocating gases: displace O2
  • strangulation
    • hanging, ligature strangulation, manual strangulation
  • chemical asphyxiation
Term
carbon monoxide
Definition
  • colorless, odorless, tasteless -
  • compete w/ o2 for binding sites on o2 carrying proteins.
  •  cherry red discolors of tissues.
  •  necrosis of globus pallidus, cerebral cortex, hippocampus
Term
hydrogen cyanide
Definition
  • produces cell hypoxia by competing w/ ferric iron atom of intracell cytochrome oxidase
  • seen in suicides gas chambers
  • death is not usu instantaneous
  • smell of almonds
  • burns of gastric mucosa
  • pink discolorationof tissues
Term
hydorgen sulfide
Definition
  • produced by fermentation of organic matter
  • found in sewers and cesspools
  • low doses have rotten egg smell
  • high doses paralyze olfactory nerves
  • high doses cause rapid death
Term
suffocating gases
Definition
  • gases displace oxygen from the atmosphere
  • carbon dioxide and methane most common
  • reduction of atmosphereic O2 in less than 25% causes unconsciousness in seconds and death in minutes
  • no specific autopsy findings
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