<prompt> Below what values of cerebral blood flow, Ischemia occurs in the brain?20 mL100 gmin30 mL100 gmin40 mL100 gmin50 mL100 gmin  <response>: Cerebral blood flow 20 mL100 g tissue per minute cause Ischemia without infarction unless prolonged for several hours or days. Transient ischemic attack - Patient may experience only transient symptoms, if blood flow is restored to ischemic tissue before significant infarction develops. Normal cerebral blood flow CBF - 50-55 mL100 gmin. 