Cerebrovascular disease

Willis arterial circle 85% carotic circulation (85%), vertebral circulation (15%)  a.carotis interna  a. cerebri anterior et media a. carotis comunis  a.carotis interna  a. cerebri anterior et media  a. basilaris  a. cerebri posterior a. vertebralis  a. basilaris  a. cerebri posterior a. cerebri anterior: a. cerebri anterior: frontal, parietal lobe a. cerebri media: a. cerebri media: frontal, parietal, temporal lole a. basilaris: a. basilaris: brain trunk, cerebelum, diencefalon a. cerebri posterior: a. cerebri posterior: diencefalon, okcipital lobe, temporal lobe aa. chorioideae anterior, posterior: aa. chorioideae anterior, posterior: capsula interna, brain trunk Venous system: infratentorial (brain trunk, cerebelum) follow up arterial circulation (v. jugularis int.) supratentorial (superficial, deep veins, durální siny) Cerebral circulation:

Cerebral blood flow: Function of brain - markedly dependent on delivery of glucose, brain markedly dependent on oxidative and metabolic delivery (aerobian metabolism) Brain is absolutely dependent on continuously uninterrupted oxidative metabolism for manintenance of its functional and structural integrity… Cerebral metabolic oxygen consumption (O 2 ): - 3,5 ml/100 g brain tissue / min. (50 ml/min whole brain – 20 % general consumption O 2 ) consumption of glucose : 5,5 mg/100 g brain tissue /min. (75 mg/min whole brain )

Cerebral blood flow : ml/100 g brain tissue /min., (children 2x) 800 ml/min. for the whole brain Cerebral blood flow must to be able maintain the brains avaricious appetite for oxygen. If cerebral flow is completely interrupted, consciousness is lost within less than 10 sec. There is evidence that average critical level of oxygen tension in the brain tissues, below which consciousness are lies between 15 – 20 mmHg. (CBF).. depends of MAP, ICP, viscosity of blood, diameter of artery…

Regulation of cerebral blood flow: Primary importance for life,… it is different Cerebral perfusion pressure …(CPP) - difference between (mean arterial pressure MAP) and ( intracranial pressure, ICP) CPP = MAP- ICP - normal CPP je torr, dilatation of capilaries, motion of erytrocytes - flow is directly proportional pressure and undirectly brain vascular resistance

Regulation of cerebral blood flow : Numerous reflexes and other pyhsiological mechanisms to sustain adequate levels of arterial blood pressure at he head levels of and to maintain the cerebral blood flow even when arterial pressure falls in times of stress There are also mechanisms to adjust the cerebral blood flow to changes in cereberal metabolic demand complex : - autoregulation - chemical-metabolic control - intrakranial pressure, viscosity of blood, prostaglandins - neurogenn (less important)

Regulation of the cerebral blood flow is achieved mainly by control of the tone or the degree of constriction or dilatation of the cerebral vessels This, in turn, is controleled mainly by local chemical factors, such as PaCO2, PaO2, pH, and still unrecognized factors. High PaCO 2 low PaO 2 and low pH – products of metabilic acitvity- tend to dilate the blood vessels and increase cerebral blood flow Change in opposite direction lowPaCO 2 lhigh PaO 2 and high pH constrict the vessels and decrease blood flow Cerebral blood flow is regulated through such mechanisms to maintain homeostasis of these chemical factors in the local tissue. The rates of production of these chemical factors depend on the rates of energy metabolism and cerebral blood flow is therefore, also adjusted to the cerebral metabolic rate

Consenquence of drop of cerebral blood flow : - Because of the high rate of oxygen metabolism and the lack of tissue oxygen stores, interuption of oxygen delivery to the brain causes immediate cell dysfunction and rapidly leads to cell death Oxygen delivery to the brain is defined as the product of the oxygen content of arterial blood and the cerebral blood flow Inadequate oxygen delivery (hypoxia) can result form inadequate cerebral blood flow (ischemic hypoxia), inadequate partial pressure of oxygen in arterial blood (hypoxic hypoxia) and inadequate oxygen- carrying capacity of arterial blood (anemic hypoxia) The most common cause of brain hypoxia is ischemia or inadequate cerebral blood flow The level of cerebral blood flow at which the brain begins to exhibit energy failure is fairly well defined

Reduction of cerebral blood flow below 15ml/min/100 g of tissue results in failure of electrical activity and a reduction to less than 10ml/min,/100 g of tissue results in loss of the transmembrane ionic gradient Cellular energe depletion apears to be triggering event for many of the damaging biochemical processes occuring during ischemie There are many causes of cerebral ischemia in humans, including head trauma, stroke and cardiac arrest… Cerebral ischemia may be further divided into focal and global categories In global ischemia blood supply to the entire brain is interrupted (cardiac arrest) In focal ischemia, blood supply to a particular region of the brain is interupted, ussually representing the area supplied by particular vasculature

Cerebral ischemia may also described as complete or incomplete Complete ischemia is defined as total absence of blood flow to the entire brain or region of the brain Incomplete ischemia on the other hand is defined as a severe reducion of cerebral blood flow in a focal or global pattern. Ischemia may result in reversible cell injury or may be sufficient ot cause tissue death (infarction), depending on the duration and severity of ischemia. In focal ischemia, the anatomical location and extent of ischemic damage depend on the distribution of the blood vessels whose flow is limited and on the presence of collateral circulation

Damage resulting from local ischemia commonly occurs in a graded fashion because collateral circulation partially perfuses the area surrounding the ischemic core This ischemic penumbra may receive blood flow that is inadequate to preserve normal cellular function but adequate enough to allow recovery. The concept of ischemic penembra is important because the compromised status of these areas may be improved if effective early intervention is achieved.

Cerebrovascular disease or stroke, is in general terms, a disturbance in cerebral circulation Focal neurologic disorder it may be secondary to a pathologic process within a cerabral blood vessel such as thrombosis, embolus, rupture of a vessel wall or basic vascular disease such atherosclerosis, arteritis,trauma, aneurysm, or developmental malformations. Stroke is responsible for deaths in the USA It is the third most frequent cause of death in the country The major causes of stroke in order of importance : atherosclerosis, embolism, hypertensive intracerebral hemorrhage, and ruptured saccular aneurysm

Stroke is generally accompanied by one or more associated medical problems such as hypertension, cardiac disease, elevated blood lipids, diabetes mellitus or periferal vascular disease. The severity of the stroke process is variable: - some infarcts are found on autopsy after death from unrelated causes.. - in others the stroke i sudden and dramatic, with the patient literally being „ struck down“ - in this latter form, hemiplegia and unconsciousnes may both evident

Definition: Stroke - akute status : focal or generral damage of brain functions It is consenquence of drop of cerebral blood flow Categorization: (mechanism of development): 1. Ischemic stroke 80% case, trombotic or trombembolism vascular closure 2. Hemorrhage stroke 15% case, rupture of a vessel wall 3. Subarachnoid hemorhhage 1% case, hemorhhage into the subarachnoid space 4. Developmental malformations < 1%

Risk factors : Hypertension Cardiac disease (cardiac infarct, arrhytmia) Diabetes mellitus. High cholesterol Smoking Hormonal contraceptive Alcohol Overweight Stress Age, gender, genetic factors

Stroke : categorization accorging to cause on the basis of theis course TIA (transient ischemic atack) –focal brain dysfunction, focal neurologic deficits –develop suddenly and disapper completly within 24 hours RIND (reverzible ischemic neurologic deficit) –neurologic deficits more 24 hod. –disapper completly within 2 weeks –persistent little neurologic deficits Progressive SE (strouke in evolution) - evolution of stroke is gradual though acute CS (completed stroke) - deficit is maximal at onset, with little improvement - focal ischemia of brain - persistent neurological deficit

Territorial diagnosis : -2 major arterial territory : carotic, vertebro-basilar -Affection of karotic circulation („anterior ischemia“).. hemisferal lesion: hemiparesis, hemiplegia, dysesthesia aphasia, Affection of middle cerebral artery (50%) of all brain infarcts … contralateral monoparesis or hemiparesis with greater defect on upper extremity ……occasional contralateral hemianopsia (blindness) ….. global aphasia ( if dominant hemispher is involved) ……disturbance of all functions involving speech and communication …… dysphasia

-Affection of anterior cerebral artery (3%) ….. confusion is the primary symptom …..contralateral weakness greater defect on under extremity (proximal arm may also be involved, voluntary movement of that leg impaired …mental defect, pathologic reflexes… -Affection of posterior cerebral artery (12%) - contralateral monoparesis or hemiparesis with greater defect on upper extremity -- occasional contralateral hemianopsia (blindness) -dysphasia, global aphasia…

-Affection of vertebral („anterior ischemia“) brain trunk and cereberal symptoms : vertigo, vommiting, ataxia, nystagmus, diplopia, weakness in one to four extramities, increased tendon reflexes, dysphagia, dysarthria, syncope, stupor, coma, memory disturbances, visual disturbances… -Repetitive ischemia…. „vertebro-basilarní insufficiency“… participation of compression of a. vertebralis

Complications of stroke local : edema of brain cerebral hemorrhage general : bronchopneumonia, deep venous thrombosis, pulmonary embolism urinary infection, decubitus, contracture, depressive sy, thalamic pain

Diagnosis : clinical symptoms risk factors CT angiography

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