PROTECT PENUMBRA TO LOVE

Q.All are true regarding pathophysiology of stroke except

a. Normal cerebral blood flow is in the range of 50 to 55 mL/100 g brain tissue/min

b. cerebral blood flow values below 10 mL/100 g/min may lead to infarction within a matter of minutes

c. Cell depolarization is not observed until blood flow drops below 10 mL/100 g/min

d. penumbra surround the zone around the central core

e. In acute period there is a swelling and softening of the tissue with evidence of mass effect

ANS.----e

An initial acute period lasts for the first 2 days after the infarction in which gross examination demonstrates what appears to be normal tissue. This is followed by a subacute period during which there is a swelling and softening of the tissue with evidence of mass effect. This subacute period (with reference to pathology) generally extends for 7 to 10 days after the infarction, with maximal edema occurring at approximately 3 to 5 days. The chronic period extends from weeks to months after the infarction. During this time the infarcted tissue evolves into an area of encephalomalacia or cystic change.

Functionally the ischemic tissue can be divided into three compartments. The infarct core representing the dead or dying tissue is at the center of the infarction. The zone around the central core may have lost electrical activity, but it has more moderate reductions in blood flow and is defined as the penumbra. With reperfusion this tissue may be salvageable, but without reperfusion it may go on to infarction . Surrounding the penumbra is tissue with mildly reduced blood flow, often called the oligemic region. This tissue is more likely to survive; however, this region too may go on to infarct if perfusion is further hemodynamically altered.