Circulatory Disorders and Trauma in the CNS Flashcards
Terms
stroke/cerebrovascular accident (CVA) Hypoxia Ischemia Infarct Cerebral emboli Thrombosis Hemorrhage Blood brain barrier Brain herniation
Hypoxia
a decreased amount of oxygen in perfused tissue regardless of the blood pressure. Hypoxia can lead to capillary dilation, vascular stagnation and consequent ischemia.
Ischemia
a decrease in blood supply. this may be local, involving one area of the brain secondary to narrowed vessels, or it may be generalized, due to decreased systemic blood pressure.
Cerebral emboli
refers to occlusion of a vessel by any material (fragments of a clot, vegetations from heart valves, or other fragment material) *transported through the circulation from a distant site. Cerebral emboli are commonly the result of carotid or cerebral vessel thrombi or rarely atherosclerotic plaque material that breaks off from the vessel wall and lodges distally. Many emboli arrive in cerebral vessels from the systemic circulation and most of them probably arise from thrombi in the carotid arteries. Clinically, embolic occlusions are usually sudden events and are the most common cause of cerebral infarction.
thrombosis
occlusion of a vessel IN SITU. it is usually secondary to the formation of a blood clot in the intima of an intra- or extra cranial artery which has already been damaged by atherosclerosis. Clinically, cerebral thrombosis often develops gradually and may be preceded by one or more transient episodes of neurological deficit.
Hemorrhage
usually associated with hypertension and the consequent damage to small intraparenchymal arterioles. The most common sites are basal nuclei, cerebellum and pons.
Blood-brain barrier
the brain endothelial cells have tight junctions between them to restrict this movement. In addition, the endothelial cells possess transport mechanisms that only allow selected types of molecules to cross into the brain and back into the vascular system. this is to protect the brain from imbibing excess fluids that would result in increased intracranial pressure and its consequence, brain herniation.
cerebrovascular accident (CVA)/stroke
the sudden onset of focal neurologic deficit without regard for etiology.
The 3rd leading cause of death in the US.
Majority are between 40-80
MEN are affected more often than women
most cases are due to embolism or spontaneous, massive hemorrhage.
most frequent neurologic disease.
42% recurrance
3 categories of cerebrovascular accident
73% infarcts (mainly due to hypoxia or ischemia – THROMBOEMBOLISM)
19% intraparenchymal hemorrhages (most commonly secondary to HYPERTENSION)
7% subarachnoid hemorrhages (most commonly due to rupture of saccular ANEURYSMS)
Infarcts
necrosis of tissue secondary to ischemia/hypoxia. However, some strokes are transient and reversible and do not result in infarcts. Conversely, cerebral infarcts are seen in patients without clinical stroke syndrome. (small, in non-critical locations/masked by debilitation of other clinical conditions)
cause major morbidity and mortality
Transient ischemic attacks TIA
patients with severe atherosclerosis of carotid or cerebral vessels often display transient hemiparesis or loss of speech days or weeks prior to a stroke.
Pathological presentation of infarcts
- the gyro are widened and gray/dark due to emdema and vascular congestion/stasis
- the necrotic tissue is soft to touch.
- significant atrophy (loss of tissue) at certain lobe area
- infarcts are often distributed distant to the place of atherosclerosis due to the diminished blood supply.
the most common cause of Cerebral Infarcts
thromboembolism!!!!!!
Arteriosclerosis
means hardening of arteries.
includes:
atherosclerosis
arteriolosclerosis
Atherosclerosis
due to hyperlipidemia
in large and medium sized arteries
atherosclerosis (with or without thrombi) leads to major INFARCTS and/or multiple small infarcts.
ateriolosclerosis
“micro aneurysms” cause small HEMORRHAGES and massive hemorrhages
Intraparenchymal hemorrhage
non-traumatic brain hemorrhage, may be massive or multiple and small. usually seen in people with HYPERTENSION
Multiple small hemorrhages are seen in a variety of conditions, including fat embolism, air embolic, thrombocytopenia, arsenic poisoning, malaria, or leukemia.
Increasingly, brain hemorrhages are seen in Alzheimer patients who have brittle cerebral blood vessels secondary to amyloid deposition.
Presentation of intraparenchymal hemorrhage
thickening of the walls of the arterioles =lipohyalinosis
developing of micro aneurysms as a result of hyalinosis of the arterioles. these aneurysm can then rupture and produce hypertensive hemorrhage.
Subarachnoid Hemorrhage
NONTRAUMATIC subarachnoid hemorrhage is most commonly due to rupture of a saccular aneurysm.
The most common cause of subarachnoid hemorrhage is trauma.
Causes of SAH
-Aneurysms
congenital or berry aneurysms
atherosclerotic aneurysms
-Vascular malformations
can cause CVA as wellsaccular or berry aneurysm
associated with hypertension, but there is no cause-effect relationship known between these two entities. also associated with smoking.
- 90% found in the anterior portion of the arterial circle (of willis)
- the most common location is at the juncture of the anterior communicating artery with the anterior cerebral arteries.
Leakage of blood from aneurysms into the subarachnoid space sometimes causes severe spasm of other subarachnoid vessels and consequent infarcts due to the release of vasoconstriction chemicals from the necrotic blood.
3 ways of aneurysm presentation
- subarachnoid hemorrhage with attendant meningeal signs and vascular spasm (most common)
- intracranial hemorrhage following rupture into brain parenchyma often associated with rapid death
- expanding intracranial masses which compress the hypothalamus and the optic chiasm (infrequent) mimicking pituitary tumors.
Trauma to the CNS causes…
epidural hemorrhage
SUBDURAL HEMORRHAGE
subarachnoid hemorrhage
intraparenchymal hemorrhage
Depending on the magnitude and the anatomic site of injury, trauma may cause any combination of the hemorrhages above.
Brain Herniation
herniation refers to a pathologic process whereby an organ/tissue or structure is displaced from its normal position into another nearby location through a pre0existing normal opening or an opening which has developed pathologically.
Epidural hemorrhage
almost always results from laceration of the middle meningeal artery close to its point of entry into the skull through the foramen spinosum.
30min lucid interval followed by rapid loss of consciousness with contralateral hemiparesis and dilated, fixed pupil on the ipsilateral side.
15-22% fatal head injuries
Subdural hemorrhage
hematoma
50% fatal head injuries
more common in males.
most common source: rupture of cortical veins
